Do microbes live elsewhere in our solar system? Signs point to yes….
The Atacama Desert in Chile is one of the most arid and uninhabitable places on earth. Decades can pass without any rainfall. Yet researchers have managed to find life there: microbes. This discovery has inspired hope that there may perhaps be life on Mars.
Uninhabitable The international research team found a number of bacteria in the bone-dry soil. Contrary to other species of bacteria, though, these single-celled organisms seemed to be inactive. For quite some time, they were assumed to be dead or perhaps dying bacteria that had been carried there by the wind from other places. However, subsequent research showed that they are specialised bacteria that survive in a form of deep sleep when there is a lack of water. When it rains, they awaken and begin to divide actively.
Chance of rain: 1 in a 1,000 When the researchers first arrived at the desert in 2015, something unusual happened. It began to rain. This exceptional occurrence led to an explosion of biological activity. Using sterile spoons and surgical precision, soil samples were taken at various depths. Near the surface, Geodermatophilaceae and Rubrobacter bacteria were found with a resistance to dehydration and UV radiation. At deeper levels, where saline levels were higher, so-called halophile (‘salt-loving’) microbes such as Betaproteobacteria were encountered.
Mars Researchers think that these micro-organisms may well be able to sleep for hundreds or even thousands of years. The conditions closely resemble the planet Mars. Although conditions there are currently arid and cold, this situation was not always the case. Billions of years ago, Mars had small oceans and lakes that may have hosted early life forms. These life forms perhaps adapted themselves to current conditions on Mars.
Water Frozen lakes are known to exist on Mars, while recent research suggests that there may even be snowfall. This fact means that circumstances exist in which humidity on Mars could increase. As the research in the Atacama Desert has shown, moisture could revive the microbes. To this end, the team would like to conduct research in Don Juan Pond on Antarctica. Since the shallow lake has a salinity of 40%, it does not even freeze over at −50°C.
Saturn’s icy moon Mars is not the only place in our solar system where life could exist. There are any number of places where moisture can be found. Austrian and German researchers have used laboratory experiments to show that there could be microbes living on Saturn’s icy moon Enceladus. Cassini, the American spacecraft which explored the planets, showed that there were geysers spewing methane into the atmosphere from a subterranean ocean. According to the researchers, this methane gas possibly is being produced by micro-organisms. They mimicked the circumstances in this ocean within the laboratory. The methane-producing archaea Methanothermococcus okinawensis, found on earth in extremely hot water near deep-sea hydrothermal vents, would easily be able to live in these circumstances.
Social distancing Apollo 11 style, how calm and collected they were! In 1969, no one knew if they’d bring home from the moon a bacterium or virus that could infect the world. If they can do three weeks, we can do two at home.
The headlines in the wake of Apollo 11 could have been very, very different.
It would have been the ultimate contingency of Apollo 11: What if the astronauts returning home unleashed upon Earth something dangerous and foreign to science — moon germs?
Before Apollo 11 set out, NASA couldn’t be positive that, if bits of dust or potential microorganisms got loose back home, life on Earth would be safe. Needless to say, accidentally setting a lunar plague loose on the inhabitants of Earth would have erased all the good publicity garnered by accomplishing the moon landing in the first place. Just in case, in addition to the protections they were establishing to make sure the moon rocks remained free of terrestrial contamination, NASA decided to establish a three-week quarantine for the crew of Apollo 11.ADVERTISING
“Initially, NASA thought that all they really needed was a clean room to handle the packaging of the lunar samples in a vacuum,” Judith Hayes, chief of NASA’s biomedical research and environmental sciences division, told Space.com. “They started really wrapping their head around this, is my understanding. They said, ‘We’ve really never done this before, so we’re not really sure,’ even though I think most of the scientists didn’t firmly believe that there might be a risk.”
The quarantine was treated all along as a better-safe-than-sorry operation. The day before Apollo 11 splashed down, support staff had already entered quarantine in Houston to prepare for the crew’s arrival, and The New York Times reported: “Twelve men are in absolute quarantine here because of something that probably does not exist.”
The problem was, though, if that threat turned out to be a reality, things would get very ugly. “The quarantine program was created out of an abundance of caution,” Jason Schwartz, a historian of medicine at the Yale School of Public Health, told Space.com. “You had a very, very small risk of something that could be very, very, very significant.”
When the Apollo missions were launching, public health professionals had generally moved on from crude tools like quarantines, he said. “By the 1960s, we were really in the golden age of vaccines and immunizations,” Schwartz said, particularly for diseases like polio, measles and mumps. “There was great optimism that the war against infectious diseases was being won,” and he said that could have contributed to a fear of backsliding if Apollo went very wrong.
And the prospect of moon germs also mirrored a real public health concern at the time, of novel pathogens that the population had never had a chance to build an immunity to. It’s a fear that remains with us today, which was sparked at the time by, for example, new influenza strains popping up on occasion. If something nasty hitched a ride back from the moon, it would have been the epitome of a novel pathogen. And, it would have driven doctors and public health practitioners way beyond their comfort zone.
“This was a different story than most public health efforts at the time, because typically, when we think about treatments, antibiotics, vaccines, quarantines, we’re thinking about known viruses or bacteria with distinct symptoms, distinct modes of transmission that we know about and we can apply that knowledge to figure out how to tailor the public health response,” Schwartz said. “In this case, it was responding to an unknowable, responding to a very slim but still nonzero uncertainty. How do you tailor a public health response when you’re not sure what exactly you’re concerned about or what it looks like or how it might affect humans at all?”
In the absence of any precisely honed tools to combat the potential threat, NASA used the blunt approach of a quarantine. The details of the plan were based on tackling a disease like the plague, according to a 1999 oral history given by Charles Berry, who was in charge of medical operations during Apollo.
The quarantine procedures began three weeks before launch, when the astronauts went into isolation to reduce the odds they would catch anything that NASA would later need to identify as terrestrial or lunar. For Apollo 11, Berry said, the prelaunch quarantine was nearly derailed by President Richard Nixon, who wanted to eat dinner with the crew the evening before launch. It was Berry’s job to explain why that simply wasn’t an option — the closest he said he believed he ever came to being fired.
“If [the astronauts] came down with anything, whatever it was, a cough, a sniffle, or anything else, we were going to have to prove that it didn’t come from the moon,” Berry told the interviewer. “So I think it would be pretty stupid to let somebody just walk into that situation. It would have been a total breakdown of the program.”
Nixon shooed off and quarantine preserved, the trio of astronauts climbed aboard their rocket and blasted off on the historic journey. As they wrapped up their time on the moon, Neil Armstrong and Buzz Aldrin abandoned some of their equipment, including their boot covers, in part to reduce the odds they would bring back any lunar threats. The 21-day quarantine clock began ticking as soon as the pair stepped off the moon and closed the hatch on the lunar module.
They rejoined their colleague, Michael Collins, and headed back to Earth, splashing down in the Pacific Ocean on July 24. But the astronauts still had more than two weeks of quarantine left, and NASA had decided it wasn’t safe to simply hoist the newly returned command module onto the aircraft carrier sent to fetch the astronauts.
The rescue crew had to send a swimmer to the spacecraft to open the hatch and throw in biological isolation garments for the astronauts to put on — spacesuits for Earth use only, essentially, with tightly woven fabric that would contain particles; rubber gloves; and a built-in breathing system.
That made splashdown the biggest weakness in the quarantine system, as Collins has said in interviews looking back at the mission. “When you open that hatch, we had stuff come into the air, without any question about it,” Berry said in his oral history. “You know, if it had been lunar plague, I don’t know what would have happened. I didn’t believe we were going to have lunar plague, but I couldn’t go on the basis that we weren’t.”
Once the astronauts had donned their isolation suits, they climbed on board the ship sent to rescue them, then into the Mobile Quarantine Facility, a trailer NASA had converted to house them. The crew spent 2.5 days in the trailer as they sailed to port in Hawaii, then boarded a plane to Houston. Back in NASA’s astronaut headquarters, the trailer was connected to the Lunar Receiving Laboratory, a special facility the agency had built at what is now the Johnson Space Center.
The building included quarantine quarters as well as lab space for preparing and studying moon rocks. The crew section was large enough to hold more than 100 people if something went very wrong, Hayes said, and included a kitchen, a lounge, a library and a collection of surgical and medical examination rooms.Advertisement
“It was, I think, quite comfortable,” Hayes said. “Talking to the crews from back then and the flight surgeon, they did say that — you know, it wasn’t bad. After spending time in a capsule, being in the quarantine facility was quite comfortable.” Armstrong even celebrated his birthday in the quarantine building.
The crew and about 20 companions waited out the rest of the quarantine period in the facility, without particular concerns about the possibility they were infected. “I got the impression that … the [astronauts] were not worried,” Hayes said. “They had daily exams from their flight surgeons … they were being carefully watched by the flight surgeons and the scientists in the quarantine.” Scientists were also monitoring mice that had been exposed to lunar samples in case they showed signs of distress, but all did well.
But by the end of the 21 days, newspapers reported that the astronauts were ready to get back to exploring Earth. “I’m ready any time they want to open that door,” Aldrin said according to The New York Times. “Take my blood. Marvelous idea. Why didn’t I think of that sooner?” the paper reported Collins said when it transpired that a blood test would shorten quarantine by a few hours.
NASA had planned to institute the quarantine for Apollo 11, 12, 13 and 14, then reevaluate the situation. The Apollo 13 quarantine was canceled after the crewmembers were forced to skip the moon landing maneuver. During the first couple years of studying moon rocks in terrestrial labs, occasional lapses in safety protocols also sent scientists into observation or quarantine.Advertisement
But after Apollo 14, NASA decided that Earth was safe from lunar bugs. The lunar receiving lab’s sample-processing side remained active until a new building was constructed and the moon rocks were moved out. Then, the building was turned over to NASA’s life sciences division, which is how Hayes ended up spending decades working in its labs and uncovering its history.
Now, her department has moved out as well. “I was the last one to shut the lights out and lock the door when we moved out of the Lunar Receiving Lab, and now it sits empty,” Hayes said.
According to NASA spokesperson Noah Michelsohn, the building is slated for demolition, with a new sample-processing facility due to be built before the asteroid missions OSIRIS-REx and Hayabusa2 bring back new, precious space rocks starting late next year. Hayes said she wishes she had appreciated the facility more when she first joined NASA, since it tells such a compelling story about the Apollo program and of spaceflight in general.
“It’s kind of amazing, all the things they thought of and pulled together to do this,” Hayes said. “I imagine when we go back to the moon, we’ll have to do some similar things, not necessarily for the crew but handling samples and the experiments that’ll be done.”
Buddy_Nath / PixabayTuesday, March 17, 2020 6:10 AM UTC
Being able to see comets is not as anticipated compared to seeing meteor showers, which occur at least once every month by a different group of meteorites. Now, experts believe one particular comet, the Atlas comet, will shine as bright as the moon when it approaches the sun.
Express reports that the comet, which is also referred to as C/2019 Y4, is expected to shine brightly when it gets closer to the Sun. The comet is currently within the vicinity of Mars’ orbit and is expected to go nearer by the latter part of May. By this time, ATLAS will be 0.25 astronomical units away from the Sun, but the distance will shorten the closer it gets.
When ATLAS approaches the Sun, scientists believe that the comet will shine as bright as a waxing crescent moon. According to the Space Weather website, “The comet is about as bright as an 8th or 9th magnitude star. That’s too dim to see with the naked eye but consider this: The comet is hundreds of times bigger than astronomers predicted when it was discovered 4 months ago…” and that by May when the comet is closer to the Sun, the comet will be as bright as a 1st magnitude star or a waxing crescent moon.
For those who already want to see a glimpse of ATLAS before May, astronomers or space enthusiasts will already be able to see the comet with a mid-sized backyard telescope. It is also encouraged to observe the comet as it gets brighter the closer it gets to the Sun and look out for possible outbursts that may happen in the coming weeks due to the volatile material within the comet getting exposed by the increasing sunlight.
Although comets are usually observed, there is a possibility that a comet may decide to strike Earth instead of passing by it. Asteroid and comet expert Dr. Steve Chesley previously revealed what makes a comet dangerous, especially if ever it decides to strike. Dr. Chesley noted how comets usually were seen as a bad omen all throughout history and explained that because comets move faster than asteroids, they will cause more damage.
Aside from the speed, the size of the comet is also a concern, as Dr. Chesley revealed that comets coming from deep space would most likely be much larger.
Should we be searching for post-biological aliens?
In a new paper published in The International Journal of Astrobiology, Joseph Gale from The Hebrew University of Jerusalem and co-authors make the point that recent advances in artificial intelligence (AI)—particularly in pattern recognition and self-learning—will likely result in a paradigm shift in the search for extraterrestrial intelligent life.
While futurist Ray Kurzweil predicted 15 years ago that the singularity—the time when the abilities of a computer overtake the abilities of the human brain—will occur in about 2045, Gale and his co-authors believe this event may be much more imminent, especially with the advent of quantum computing. It’s already been four years since the program AlphaGO, fortified with neural networks and learning modes, defeated Lee Sedol, the Go world champion. The strategy game StarCraft II may be the next to have a machine as reigning champion.
If we look at the calculating capacity of computers and compare it to the number of neurons in the human brain, the singularity could be reached as soon as the early 2020s. However, a human brain is “wired” differently than a computer, and that may be the reason why certain tasks that are simple for us are still quite challenging for today’s AI. Also, the size of the brain or the number of neurons don’t equate to intelligence. For example, whales and elephants have more than double the number of neurons in their brain, but are not more intelligent than humans.
The authors don’t know when the singularity will come, but come it will. When this occurs, the end of the human race might very well be upon us, they say, citing a 2014 prediction by the late Stephen Hawking. According to Kurzweil, humans may then be fully replaced by AI, or by some hybrid of humans and machines.
What will this mean for astrobiology? Not much, if we’re searching only for microbial extraterrestrial life. But it might have a drastic impact on the search for extraterrestrial intelligent life (SETI). If other civilizations are similar to ours but older, we would expect that they already moved beyond the singularity. So they wouldn’t necessarily be located on a planet in the so-called habitable zone. As the authors point out, such civilizations might prefer locations with little electronic noise in a dry and cold environment, perhaps in space, where they could use superconductivity for computing and quantum entanglement as a means of communication.
I think it also is still unclear whether there is something special enough about the human brain’s ability to process information that casts doubt on whether AI can surpass our abilities in all relevant areas, especially in achieving consciousness. Might there be something unique to biological brains after millions and millions of years of evolution that computers cannot achieve? If not, the authors are correct that reaching the singularity could be humanity’s greatest and last advance.
Buried inside data that NASA’s iconic Voyager 2 spacecraft gathered at Uranus more than 30 years ago is the signature of a massive bubble that may have stolen a blob of the planet’s gassy atmosphere.
That’s according to scientists who analyzed archived Voyager 2 observations of the magnetic field around Uranus. These measurements had been studied before, but only using a relatively coarse view. In the new research, scientists instead looked at those measurements every two seconds. That detail showed what had previously been missed: an abrupt zigzag in the magnetic field readings that lasted just one minute of the spacecraft’s 45-hour journey past Uranus.ADVERTISING
The tiny wobble in the Voyager 2 data represents something much larger since the spacecraft was flying so fast. Specifically, the scientists behind the new research believe the zigzag marks a plasmoid, a type of structure that wasn’t understood particularly well at the time of the flyby in January 1986.
But by now, plasmoids have earned scientists’ respect. A plasmoid is a massive bubble of plasma, which is a soup of charged particles. Plasmoids can break off from the tip of the sleeve of magnetism surrounding a planet like a teardrop.
Scientists have studied these structures at Earth and nearby planets, but never at Uranus or its neighbor Neptune, since Voyager 2 is the only spacecraft to date ever to visit those planets.
Scientists want to know about plasmoids because these structures can pull charged particles out of a planet’s atmosphere and fling them into space. And if you change a planet’s atmosphere, you change the planet itself. And Uranus’ situation is particularly complicated because the planet rotates on its side and its magnetic field is skewed from both that axis and the plane all the planets lie in.
Because Voyager 2 flew straight through this plasmoid, scientists could use the archived data to measure the structure, which they believe was about 250,000 miles (400,000 kilometers) across and could have stretched 127,000 miles (204,000 km) long, according to a NASA statement.
Ideally, scientists would piece together more observations of Uranus’ magnetic field, enough to better understand how this phenomenon has shaped the planet over time. But that will require another spacecraft visit the strange sideways world.
The research is described in a paper published in August in the journal Geophysical Review Letters. NASA announced the finding on Wednesday (March 25).
March 24, 2020: No one knows how big the icy core of Comet ATLAS (C/2019 Y4) might be–possibly no wider than a few kilometers. One thing’s for sure, though, the comet’s atmosphere is huge. New images from amateur astronomers around the world show that ATLAS’s gaseous envelope has ballooned in diameter to ~720,000 km–about half as wide as the sun.
“Comet ATLAS’s coma (atmosphere) is approximately 15 arcminutes in diameter,” reports Michael Jäger of Weißenkirchen, Austria, who took the picture, above, on March 18th. “Its newly-formed tail is about the same size.”
Other astronomers are getting similar results. 15 arcminutes = a quarter of a degree. Given Comet ATLAS’s distance of 1.1 AU on March 18th, that angle corresponds to a physical size of 720,000 km.
On the scale of big things in the solar system, Comet ATLAS falls somewhere between the sun (1,392,000 km diameter) and Jupiter (139,820 km). It’s not unusual for comets to grow so large. While their icy solid cores are typically mere kilometers in diameter, they can spew prodigious amounts of gas and dust into space, filling enormous volumes. In the fall of 2007, Comet 17P/Holmes partially exploded and, for a while, had an atmosphere even larger than the sun. The Great Comet of 1811 also had a sun-sized coma. Whether Comet ATLAS will eventually rival those behemoths of the past remains to be seen.
Right now, Comet ATLAS is certainly the biggest green thing in the Solar System. Its verdant hue comes from diatomic carbon, C2, a molecule commonly found in comets. Gaseous C2 emits a beautiful green glow in the near-vacuum of space.
Currently, Comet ATLAS is shining like an 8th magnitude star–invisible to the unaided eye but an easy target for backyard telescopes. The comet is brightening rapidly as it comes closer to Earth and the sun. By late May it could rival Venus in the evening twilight sky. Stay tuned!
Are we in danger of being erased from the universe? Here we look at the factors that could doom humanity: natural disasters, human-triggered cataclysms, willful self-destruction, and greater forces directed against us.
We’ve had a good run of it. In the 500,000 years Homo sapiens has roamed the land we’ve built cities, created complex languages, and sent robotic scouts to other planets. It’s difficult to imagine it all coming to an end. Yet 99 percent of all species that ever lived have gone extinct, including every one of our hominid ancestors. In 1983, British cosmologist Brandon Carter framed the “Doomsday argument,” a statistical way to judge when we might join them. If humans were to survive a long time and spread through the galaxy, then the total number of people who will ever live might number in the trillions. By pure odds, it’s unlikely that we would be among the very first hundredth of a percent of all those people. Or turn the argument around: How likely is it that this generation will be the one unlucky one? Something like one fifth of all the people who have ever lived are alive today. The odds of being one of the people to witness doomsday are highest when there is the largest number of witnesses around—so now is not such an improbable time.
Human activity is severely disrupting almost all life on the planet, which surely doesn’t help matters. The current rate of extinctions is, by some estimates, 10,000 times the average in the fossil record. At present, we may worry about snail darters and red squirrels in abstract terms. But the next statistic on the list could be us.
1. Asteroid impact Once a disaster scenario gets the cheesy Hollywood treatment, it’s hard to take it seriously. But there is no question that a cosmic interloper will hit Earth, and we won’t have to wait millions of years for it to happen. In 1908 a 200-foot-wide comet fragment slammed into the atmosphere and exploded over the Tunguska region in Siberia, Russia, with nearly 1,000 times the energy of the atomic bomb dropped on Hiroshima. Astronomers estimate similar-sized events occur every one to three centuries. Benny Peiser, an anthropologist-cum-pessimist at Liverpool John Moores University in England, claims that impacts have repeatedly disrupted human civilization. As an example, he says one killed 10,000 people in the Chinese city of Chi’ing-yang in 1490. Many scientists question his interpretations: Impacts are most likely to occur over the ocean, and small ones that happen over land are most likely to affect unpopulated areas. But with big asteroids, it doesn’t matter much where they land. Objects more than a half-mile wide—which strike Earth every 250,000 years or so—would touch off firestorms followed by global cooling from dust kicked up by the impact. Humans would likely survive, but civilization might not. An asteroid five miles wide would cause major extinctions, like the one that may have marked the end of the age of dinosaurs. For a real chill, look to the Kuiper belt, a zone just beyond Neptune that contains roughly 100,000 ice-balls more than 50 miles in diameter. The Kuiper belt sends a steady rain of small comets earthward. If one of the big ones headed right for us, that would be it for pretty much all higher forms of life, even cockroaches.
2. Gamma-ray burst If you could watch the sky with gamma-ray vision, you might think you were being stalked by cosmic paparazzi. Once a day or so, you would see a bright flash appear, briefly outshine everything else, then vanish. These gamma-ray bursts, astrophysicists recently learned, originate in distant galaxies and are unfathomably powerful—as much as 10 quadrillion (a one followed by 16 zeros) times as energetic as the sun. The bursts probably result from the merging of two collapsed stars. Before the cataclysmal event, such a double star might be almost completely undetectable, so we’d likely have no advance notice if one is lurking nearby. Once the burst begins, however, there would be no missing its fury. At a distance of 1,000 light-years—farther than most of the stars you can see on a clear night—it would appear about as bright as the sun. Earth’s atmosphere would initially protect us from most of the burst’s deadly X rays and gamma rays, but at a cost. The potent radiation would cook the atmosphere, creating nitrogen oxides that would destroy the ozone layer. Without the ozone layer, ultraviolet rays from the sun would reach the surface at nearly full force, causing skin cancer and, more seriously, killing off the tiny photosynthetic plankton in the ocean that provide oxygen to the atmosphere and bolster the bottom of the food chain. All the gamma-ray bursts observed so far have been extremely distant, which implies the events are rare. Scientists understand so little about these explosions, however, that it’s difficult to estimate the likelihood of one detonating in our galactic neighborhood.
3. Collapse of the vacuum In the book Cat’s Cradle, Kurt Vonnegut popularized the idea of “ice-nine,” a form of water that is far more stable than the ordinary kind, so it is solid at room temperature. Unleash a bit of it, and suddenly all water on Earth transforms to ice-nine and freezes solid. Ice-nine was a satirical invention, but an abrupt, disastrous phase transition is a possibility. Very early in the history of the universe, according to a leading cosmological model, empty space was full of energy. This state of affairs, called a false vacuum, was highly precarious. A new, more stable kind of vacuum appeared and, like ice-nine, it quickly took over. This transition unleashed a tremendous amount of energy and caused a brief runaway expansion of the cosmos. It is possible that another, even more stable kind of vacuum exists, however. As the universe expands and cools, tiny bubbles of this new kind of vacuum might appear and spread at nearly the speed of light. The laws of physics would change in their wake, and a blast of energy would dash everything to bits. “It makes for a beautiful story, but it’s not very likely,” says Piet Hut of the Institute for Advanced Studies in Princeton, New Jersey. He says he worries more about threats that scientists are more certain of—such as rogue black holes.
4. Rogue black holes Our galaxy is full of black holes, collapsed stellar corpses just a dozen miles wide. How full? Tough question. After all, they’re called black holes for a reason. Their gravity is so strong they swallow everything, even the light that might betray their presence. David Bennett of Notre Dame University in Indiana managed to spot two black holes recently by the way they distorted and amplified the light of ordinary, more distant stars. Based on such observations, and even more on theoretical arguments, researchers guesstimate there are about 10 million black holes in the Milky Way. These objects orbit just like other stars, meaning that it is not terribly likely that one is headed our way. But if a normal star were moving toward us, we’d know it. With a black hole there is little warning. A few decades before a close encounter, at most, astronomers would observe a strange perturbation in the orbits of the outer planets. As the effect grew larger, it would be possible to make increasingly precise estimates of the location and mass of the interloper. The black hole wouldn’t have to come all that close to Earth to bring ruin; just passing through the solar system would distort all of the planets’ orbits. Earth might get drawn into an elliptical path that would cause extreme climate swings, or it might be ejected from the solar system and go hurtling to a frigid fate in deep space.
5. Giant solar flares Solar flares—more properly known as coronal mass ejections—are enormous magnetic outbursts on the sun that bombard Earth with a torrent of high-speed subatomic particles. Earth’s atmosphere and magnetic field negate the potentially lethal effects of ordinary flares. But while looking through old astronomical records, Bradley Schaefer of Yale University found evidence that some perfectly normal-looking, sunlike stars can brighten briefly by up to a factor of 20. Schaefer believes these stellar flickers are caused by superflares, millions of times more powerful than their common cousins. Within a few hours, a superflare on the sun could fry Earth and begin disintegrating the ozone layer (see #2). Although there is persuasive evidence that our sun doesn’t engage in such excess, scientists don’t know why superflares happen at all, or whether our sun could exhibit milder but still disruptive behavior. And while too much solar activity could be deadly, too little of it is problematic as well. Sallie Baliunas at the Harvard-Smithsonian Center for Astrophysics says many solar-type stars pass through extended quiescent periods, during which they become nearly 1 percent dimmer. That might not sound like much, but a similar downturn in the sun could send us into another ice age. Baliunas cites evidence that decreased solar activity contributed to 17 of the 19 major cold episodes on Earth in the last 10,000 years.
6. Reversal of Earth’s magnetic field Every few hundred thousand years Earth’s magnetic field dwindles almost to nothing for perhaps a century, then gradually reappears with the north and south poles flipped. The last such reversal was 780,000 years ago, so we may be overdue. Worse, the strength of our magnetic field has decreased about 5 percent in the past century. Why worry in an age when GPS has made compasses obsolete? Well, the magnetic field deflects particle storms and cosmic rays from the sun, as well as even more energetic subatomic particles from deep space. Without magnetic protection, these particles would strike Earth’s atmosphere, eroding the already beleaguered ozone layer (see #5). Also, many creatures navigate by magnetic reckoning. A magnetic reversal might cause serious ecological mischief. One big caveat: “There are no identifiable fossil effects from previous flips,” says Sten Odenwald of the NASA Goddard Space Flight Center. “This is most curious.” Still, a disaster that kills a quarter of the population, like the Black Plague in Europe, would hardly register as a blip in fossil records.
7. Flood-basalt volcanism In 1783, the Laki volcano in Iceland erupted, spitting out three cubic miles of lava. Floods, ash, and fumes wiped out 9,000 people and 80 percent of the livestock. The ensuing starvation killed a quarter of Iceland’s population. Atmospheric dust caused winter temperatures to plunge by 9 degrees in the newly independent United States. And that was just a baby’s burp compared with what the Earth can do. Sixty-five million years ago, a plume of hot rock from the mantle burst through the crust in what is now India. Eruptions raged century after century, ultimately unleashing a quarter-million cubic miles of lava—the Laki eruption 100,000 times over. Some scientists still blame the Indian outburst, not an asteroid, for the death of the dinosaurs. An earlier, even larger event in Siberia occurred just about the time of the Permian-Triassic extinction, the most thorough extermination known to paleontology. At that time 95 percent of all species were wiped out.
Sulfurous volcanic gases produce acid rains. Chlorine-bearing compounds present yet another threat to the fragile ozone layer—a noxious brew all around. While they are causing short-term destruction, volcanoes also release carbon dioxide that yields long-term greenhouse-effect warming.The last big pulse of flood-basalt volcanism built the Columbia River plateau about 17 million years ago. We’re ripe for another.
8. Global epidemics If Earth doesn’t do us in, our fellow organisms might be up to the task. Germs and people have always coexisted, but occasionally the balance gets out of whack. The Black Plague killed one European in four during the 14th century; influenza took at least 20 million lives between 1918 and 1919; the AIDS epidemic has produced a similar death toll and is still going strong. From 1980 to 1992, reports the Centers for Disease Control and Prevention, mortality from infectious disease in the United States rose 58 percent. Old diseases such as cholera and measles have developed new resistance to antibiotics. Intensive agriculture and land development is bringing humans closer to animal pathogens. International travel means diseases can spread faster than ever. Michael Osterholm, an infectious disease expert who recently left the Minnesota Department of Health, described the situation as “like trying to swim against the current of a raging river.” The grimmest possibility would be the emergence of a strain that spreads so fast we are caught off guard or that resists all chemical means of control, perhaps as a result of our stirring of the ecological pot. About 12,000 years ago, a sudden wave of mammal extinctions swept through the Americas. Ross MacPhee of the American Museum of Natural History argues the culprit was extremely virulent disease, which humans helped transport as they migrated into the New World.
9. Global warming The Earth is getting warmer, and scientists mostly agree that humans bear some blame. It’s easy to see how global warming could flood cities and ruin harvests. More recently, researchers like Paul Epstein of Harvard Medical School have raised the alarm that a balmier planet could also assist the spread of infectious disease by providing a more suitable climate for parasites and spreading the range of tropical pathogens (see #8). That could include crop diseases which, combined with substantial climate shifts, might cause famine. Effects could be even more dramatic. At present, atmospheric gases trap enough heat close to the surface to keep things comfortable. Increase the global temperature a bit, however, and there could be a bad feedback effect, with water evaporating faster, freeing water vapor (a potent greenhouse gas), which traps more heat, which drives carbon dioxide from the rocks, which drives temperatures still higher. Earth could end up much like Venus, where the high on a typical day is 900 degrees Fahrenheit. It would probably take a lot of warming to initiate such a runaway greenhouse effect, but scientists have no clue where exactly the tipping point lies.
10. Ecosystem collapse Images of slaughtered elephants and burning rain forests capture people’s attention, but the big problem—the overall loss of biodiversity—is a lot less visible and a lot more serious. Billions of years of evolution have produced a world in which every organism’s welfare is intertwined with that of countless other species. A recent study of Isle Royale National Park in Lake Superior offers an example. Snowy winters encourage wolves to hunt in larger packs, so they kill more moose. The decline in moose population allows more balsam fir saplings to live. The fir trees pull carbon dioxide out of the atmosphere, which in turn influences the climate. It’s all connected. To meet the demands of the growing population, we are clearing land for housing and agriculture, replacing diverse wild plants with just a few varieties of crops, transporting plants and animals, and introducing new chemicals into the environment. At least 30,000 species vanish every year from human activity, which means we are living in the midst of one of the greatest mass extinctions in Earth’s history. Stephen Kellert, a social ecologist at Yale University, sees a number of ways people might upset the delicate checks and balances in the global ecology. New patterns of disease might emerge (see #8), he says, or pollinating insects might become extinct, leading to widespread crop failure. Or as with the wolves of Isle Royale, the consequences might be something we’d never think of, until it’s too late.
11. Biotech disaster While we are extinguishing natural species, we’re also creating new ones through genetic engineering. Genetically modified crops can be hardier, tastier, and more nutritious. Engineered microbes might ease our health problems. And gene therapy offers an elusive promise of fixing fundamental defects in our DNA. Then there are the possible downsides. Although there is no evidence indicating genetically modified foods are unsafe, there are signs that the genes from modified plants can leak out and find their way into other species. Engineered crops might also foster insecticide resistance. Longtime skeptics like Jeremy Rifkin worry that the resulting superweeds and superpests could further destabilize the stressed global ecosystem (see #9). Altered microbes might prove to be unexpectedly difficult to control. Scariest of all is the possibility of the deliberate misuse of biotechnology. A terrorist group or rogue nation might decide that anthrax isn’t nasty enough and then try to put together, say, an airborne version of the Ebola virus. Now there’s a showstopper.
12. Particle accelerator mishap Theodore Kaczynski, better known as the Unabomber, raved that a particle accelerator experiment could set off a chain reaction that would destroy the world. Surprisingly, many sober-minded physicists have had the same thought. Normally their anxieties come up during private meetings, amidst much scribbling on the backs of used envelopes. Recently the question went public when London’s Sunday Times reported that the Relativistic Heavy Ion Collider (RHIC) on Long Island, New York, might create a subatomic black hole that would slowly nibble away our planet. Alternately, it might create exotic bits of altered matter, called strangelets, that would obliterate whatever ordinary matter they met. To assuage RHIC’s jittery neighbors, the lab’s director convened a panel that rejected both scenarios as pretty much impossible. Just for good measure, the panel also dismissed the possibility that RHIC would trigger a phase transition in the cosmic vacuum energy (see #3). These kinds of reassurances follow the tradition of the 1942 “LA-602” report, a once-classified document that explained why the detonation of the first atomic bomb almost surely would not set the atmosphere on fire. The RHIC physicists did not, however, reject the fundamental possibility of the disasters. They argued that their machine isn’t nearly powerful enough to make a black hole or destabilize the vacuum. Oh, well. We can always build a bigger accelerator.
13. Nanotechnology disaster Before you’ve even gotten the keyboard dirty, your home computer is obsolete, largely because of incredibly rapid progress in miniaturizing circuits on silicon chips. Engineers are using the same technology to build crude, atomic-scale machines, inventing a new field as they go called nanotechnology. Within a few decades, maybe sooner, it should be possible to build microscopic robots that can assemble and replicate themselves. They might perform surgery from inside a patient, build any desired product from simple raw materials, or explore other worlds. All well and good if the technology works as intended. Then again, consider what K. Eric Drexler of the Foresight Institute calls the “grey goo problem” in his book Engines of Creation, a cult favorite among the nanotech set. After an industrial accident, he writes, bacteria-sized machines, “could spread like blowing pollen, replicate swiftly, and reduce the biosphere to dust in a matter of days.” And Drexler is actually a strong proponent of the technology. More pessimistic souls, such as Bill Joy, a cofounder of Sun Microsystems, envision nano-machines as the perfect precision military or terrorist tools.
14. Environmental toxins From Donora, Pennsylvania, to Bhopal, India, modern history abounds with frightening examples of the dangers of industrial pollutants. But the poisoning continues. In major cities around the world, the air is thick with diesel particulates, which the National Institutes of Health now considers a carcinogen. Heavy metals from industrial smokestacks circle the globe, even settling in the pristine snows of Antarctica. Intensive use of pesticides in farming guarantees runoff into rivers and lakes. In high doses, dioxins can disrupt fetal development and impair reproductive function—and dioxins are everywhere. Your house may contain polyvinyl chloride pipes, wallpaper, and siding, which belch dioxins if they catch fire or are incinerated. There are also the unknown risks to think about. Every year NIH adds to its list of cancer-causing substances—the number is up to 218. Theo Colburn of the World Wildlife Fund argues that dioxins and other, similar chlorine-bearing compounds mimic the effects of human hormones well enough that they could seriously reduce fertility. Many other scientists dispute her evidence, but if she’s right, our chemical garbage could ultimately threaten our survival.
15. Global war Together, the United States and Russia still have almost 19,000 active nuclear warheads. Nuclear war seems unlikely today, but a dozen years ago the demise of the Soviet Union also seemed rather unlikely. Political situations evolve; the bombs remain deadly. There is also the possibility of an accidental nuclear exchange. And a ballistic missile defense system, given current technology, will catch only a handful of stray missiles—assuming it works at all. Other types of weaponry could have global effects as well. Japan began experimenting with biological weapons after World War I, and both the United States and the Soviet Union experimented with killer germs during the cold war. Compared with atomic bombs, bioweapons are cheap, simple to produce, and easy to conceal. They are also hard to control, although that unpredictability could appeal to a terrorist organization. John Leslie, a philosopher at the University of Guelph in Ontario, points out that genetic engineering might permit the creation of “ethnic” biological weapons that are tailored to attack primarily one ethnic group (see #11).
16. Robots take over People create smart robots, which turn against us and take over the world. Yawn. We’ve seen this in movies, TV, and comic books for decades. After all these years, look around and still—no smart robots. Yet Hans Moravec, one of the founders of the robotics department of Carnegie Mellon University, remains a believer. By 2040, he predicts, machines will match human intelligence, and perhaps human consciousness. Then they’ll get even better. He envisions an eventual symbiotic relationship between human and machine, with the two merging into “postbiologicals” capable of vastly expanding their intellectual power. Marvin Minsky, an artificial-intelligence expert at MIT, foresees a similar future: People will download their brains into computer-enhanced mechanical surrogates and log into nearly boundless files of information and experience. Whether this counts as the end of humanity or the next stage in evolution depends on your point of view. Minsky’s vision might sound vaguely familiar. After the first virtual-reality machines hit the marketplace around 1989, feverish journalists hailed them as electronic LSD, trippy illusion machines that might entice the user in and then never let him out. Sociologists fretted that our culture, maybe even our species, would whither away. When the actual experience of virtual reality turned out to be more like trying to play Pac-Man with a bowling ball taped to your head, the talk died down. To his credit, Minsky recognizes that the merger of human and machine lies quite a few years away.
17. Mass insanity While physical health has improved in most parts of the world over the past century, mental health is getting worse. The World Health Organization estimates that 500 million people around the world suffer from a psychological disorder. By 2020, depression will likely be the second leading cause of death and lost productivity, right behind cardiovascular disease. Increasing human life spans may actually intensify the problem, because people have more years to experience the loneliness and infirmity of old age. Americans over 65 already are disproportionately likely to commit suicide. Gregory Stock, a biophysicist at the University of California at Los Angeles, believes medical science will soon allow people to live to be 200 or older. If such an extended life span becomes common, it will pose unfathomable social and psychological challenges. Perhaps 200 years of accumulated sensations will overload the human brain, leading to a new kind of insanity or fostering the spread of doomsday cults, determined to reclaim life’s endpoint. Perhaps the current trends of depression and suicide among the elderly will continue. One possible solution—promoting a certain kind of mental well-being with psychoactive drugs such as Prozac—heads into uncharted waters. Researchers have no good data on the long-term effects of taking these medicines.
A Greater Force Is Directed Against Us
18. Alien invasion At the SETI Institute in Mountain View, California, a cadre of dedicated scientists sifts through radio static in search of a telltale signal from an alien civilization. So far, nothing. Now suppose the long-sought message arrives. Not only do the aliens exist, they are about to stop by for a visit. And then . . . any science-fiction devotee can tell you what could go wrong. But the history of human exploration and exploitation suggests the most likely danger is not direct conflict. Aliens might want resources from our solar system (Earth’s oceans, perhaps, full of hydrogen for refilling a fusion-powered spacecraft) and swat us aside if we get in the way, as we might dismiss mosquitoes or beetles stirred up by the logging of a rain forest. Aliens might unwittingly import pests with a taste for human flesh, much as Dutch colonists reaching Mauritius brought cats, rats, and pigs that quickly did away with the dodo. Or aliens might accidentally upset our planet or solar system while carrying out some grandiose interstellar construction project. The late physicist Gerard O’Neill speculated that contact with extraterrestrial visitors could also be socially disastrous. “Advanced western civilization has had a destructive effect on all primitive civilizations it has come in contact with, even in those cases where every attempt was made to protect and guard the primitive civilization,” he said in a 1979 interview. “I don’t see any reason why the same thing would not happen to us.”
19. Divine intervention Judaism has the Book of Daniel; Christianity has the Book of Revelation; Islam has the coming of the Mahdi; Zoroastrianism has the countdown to the arrival of the third son of Zoroaster. The stories and their interpretations vary widely, but the underlying concept is similar: God intervenes in the world, bringing history to an end and ushering in a new moral order. Apocalyptic thinking runs at least back to Egyptian mythology and right up to Heaven’s Gate and Y2K mania. More worrisome, to the nonbelievers at least, are the doomsday cults that prefer to take holy retribution into their own hands. In 1995, members of the Aum Shinri Kyo sect unleashed sarin nerve gas in a Tokyo subway station, killing 12 people and injuring more than 5,000. Had things gone as intended, the death toll would have been hundreds of times greater. A more determined group armed with a more lethal weapon—nuclear, biological, nanotechnological even—could have done far more damage.
20. Someone wakes up and realizes it was all a dream Are we living a shadow existence that only fools us into thinking it is real? This age-old philosophical question still reverberates through cultural thought, from the writings of William S. Burrows to the cinematic mind games of The Matrix. Hut of the Institute of Advanced Studies sees an analogy to the danger of the collapse of the vacuum. Just as our empty space might not be the true, most stable form of the vacuum, what we call reality might not be the true, most stable form of existence. In the fourth century B.C., Taoist philosopher Chuang Tzu framed the question in more poetic terms. He described a vivid dream. In it, he was a butterfly who had no awareness of his existence as a person. When he awoke, he asked: “Was I before Chuang Tzu who dreamt about being a butterfly, or am I now a butterfly who dreams about being Chuang Tzu?”
You probably think about viruses only when you’re sick, but there’s a group of microbiologists who want to change that. In fact, they want you to consider the possibility that viruses may be found in space.
Now this grim prospect has started to look a little bit more likely following the revelation that killer viruses could survive out there in the endless void. Huge fight broke out between relatives at toddler’s inquest A human would last less than 20 seconds in the cold and empty vacuum of space – the time it would take to use up all the oxygen in the body.
The lack of atmosphere would cause gas bubbles to form in the blood and other fluids, blowing the person up into a balloon before they die from decompression.
But viruses are very hardy and could be living everywhere in the universe including other planets, moons and even the void of space, Nasa scientists suspect. If we find viruses on Mars, it’s a fair bet to assume other lifeforms existed there too.
Now a team of scientists are calling on space agencies to look for them in liquid samples from Saturn and Jupiter’s moons as well as rocks from Mars. If we manage to detect viruses in these samples, it could prove if they really can survive in space and allow us to identify just how much risk they pose to our species.
Biologist Prof Stedman, from Portland State University in the United States, said: ‘More than a century has passed since the discovery of the first viruses. ‘Entering the second century of virology we can finally start focusing beyond our own planet.’ If a space explorer contracted a space virus or one found its way to Earth, the results could be devastating because humanity will have no resistance to it.
In a recent review, published online Jan. 10 in the journal Astrobiology, a trio of scientists from the U.S. and Japan posited that viruses may be spread across interplanetary space. Those researchers want to convince astrobiologists to devote more time looking for these curious molecular machines.
A virion — the form a virus takes outside of a host — consists of genetic material encapsulated in a protein shell. Some viruses also have an outer lipid layer called an envelope. One way to think of a virion is as a seed or a spore, the authors wrote.
Viruses straddle the definition of life. They lack the machinery to reproduce on their own, so they must infect a host cell and hijack its machinery. This has led to decades of debate over whether viruses should technically be considered living.
But for the review authors, viruses’ reproductive methods are enough. Indeed, “when one considers the whole virus replication cycle, it comes close to NASA’s working definition of life: ‘a self-sustaining chemical system capable of Darwinian evolution,'” the review said.
Semantics aside, if scientists were to identify a virus in space — on a meteor, perhaps — very few people would claim the discovery was not evidence of life in space, the authors wrote.
So why aren’t scientists prowling the Martian surface, the lakes of Titan or the geysers of Enceladus for evidence of these tiny “life-forms”?
In part, it’s because the technology to do so is still in development, said senior review author Kenneth Stedman, a professor of biology at Portland State University. Currently, scientists are searching for chemical signatures they can use to identify viruses in the fossil record. But if they can’t find viruses in really old rocks on Earth, they won’t be able to do it in really old rocks on Mars or Titan, he said.
Viruses are not metabolically active on their own, so they produce few by-products. Lipids in the envelopes are the current front-runner for a virus biomarker, since these compounds can survive for hundreds of millions of years, Stedman told Live Science. But scientist have yet to establish that these molecules are unique to viruses, and don’t exist in any cellular organism as well.
Currently, scientists can identify viruses by looking at the structure of their shells using electron microscopes. But it isn’t possible to strap these high-powered machines onto a Mars rover, yet. And given the diversity of virus forms on Earth, Stedman said that he doubts scientists would even recognize the shape of an alien virus.
Here on Earth, viruses form a crucial part of life, Stedman said. For one, viruses are everywhere. The oceans alone contain an estimated 10^31 individual virions. That’s about 1 million times more than estimates of the number of stars in the observable universe. And viruses are integral in most of the nutrient cycles on our planet.
What’s more, viruses and cells have been coevolving basically since life arose on the planet, Stedman said. Cells evolving to resist their viral invaders give rise to new forms and behaviors. And viruses shepherd genes between unrelated cells in what scientists call horizontal gene transfer. While this process has precipitated tremendous diversity of life on Earth, it muddies the water for researchers tracking viral evolution. “If there’s any water in the mud, you’re in luck,” Stedman said.
Scientists do know that viruses use both RNA and DNA, in single- and double-stranded forms, to code their genetic information, Stedman said. All known cellular life uses double-stranded DNA, so some scientists think that viruses may be remnants of ancient life-forms that predate the development of DNA.
This is all to say that “life on Earth would be very different if there were no viruses,” Stedman said.
Scientists are currently skilled in identifying only cellular life. In addition to helping scientists learn more about our own origins, devising ways to identify viruses is good practice for recognizing other, novel forms of life we might encounter, according to Stedman. Keeping an open mind when looking for life is crucial, as many environments are quite different than Earth.
“What is life? Are viruses alive? If we find viruses [in space], is it indicative of life? And would this be life as we know it or life as we don’t know it?” Stedman asked. “We’re hoping to get people thinking about these types of definitions.”
Sagittarius A*, the supermassive black hole at the centre of the Milky Way, isn’t exactly rowdy. It’s not classified as an active galactic nucleus – one of those galactic cores that glow exceedingly brightly as they feast on copious amounts of material from the surrounding space.
However, the brightness of our galaxy’s centre does fluctuate a little across the electromagnetic spectrum on a daily basis. Astronomers have now confirmed that, over the last few years, Sgr A*’s most energetic X-ray flares have been increasing.
The paper has been accepted in the journal Astronomy & Astrophysics, and is already available on arXiv while it undergoes the peer review process. The results support the conclusions of earlier studies that have found our galactic centre is indeed getting restless.
Specifically, a team of French and Belgian researchers led by astrophysicist Enmanuelle Mossoux of the University of Liège in Belgium continued their work from a 2017 paper that found the rate of bright flares had increased threefold from 31 August 2014.
The earlier work – also co-authored by Mossoux – studied X-ray data on Sgr A* from the XMM-Newton, Chandra and Swift observatories collected between 1999 and 2015. They detected 107 flares in total. Not only were the brightest X-ray flares increasing after August 2014, the faintest ones had decreased from August 2013.
To find out if these trends have continued, Mossoux and colleagues collected and analysed the data from all three telescopes between 2016 and 2018. They detected 14 more flares to add to the previous data for a total of 121.
Then, they analysed all the flares, using the previous methods, and revised methods to determine the flare rate and distribution. These found that one of the earlier conclusions was incorrect – there was no decrease in the rate of faint flares; these remained pretty steady over the period covered by the data.
“However, this did not change our global result: a change in flaring rate is found for the brightest and most energetic flares at the same date as was found in the previous section,” the researchers wrote in their paper.
Although these studies both only refer to X-ray flaring, they’re not the only hint in recent times that something is up with Sgr A*. Last year, the black hole flared 75 times its usual brightness in near-infrared – the brightest we’ve ever observed it in those wavelengths.
The team analysing the near-infrared observations had a dataset of 133 nights from 2003; and last year, they found three nights on which Sgr A* near-infrared activity was elevated. They said in their paper that this was “unprecedented compared to the historical data.”
(Don’t worry, Sgr A* is 26,000 light-years away. The big bad black hole can’t get you.)
Mossoux and her team have also checked to see if the 2019 activity is consistent with their recent findings. They analysed the Swift data from 2019, and found four bright flares, the largest number ever observed in a single campaign, confirming that the black hole is not settling down.
Additionally, XMM Newton and Chandra data from 2019 – due for release this year – could reveal even more about the peculiar X-ray activity, and what might be causing it – whether it’s accretion, or something else, such as the tidal disruption of passing asteroids.
Observations across other wavelengths could reveal more information too. Continued observations in the near-infrared, and radio wave observations, could help us figure out what’s making Sgr A* stir.
The lander will continue its low-frequency radio astronomy observations, but a new plan has been formulated for the Yutu 2 rover, which has already provided insights into the composition of the surface and what lies below.
Li Chunlai, deputy director of the National Astronomical Observatories of China (NAOC), told the state-run news outlet CCTV+ that the Yutu 2 team are targeting distant areas.
Yutu 2 has been driving across an area covered in ejecta from impact craters, but reaching new ground would be insightful.
“If it can enter a basalt zone, maybe we can better understand [the] distribution and structure of ejecta from meteorite impacts,” Li said. “The distance may be 1.8 kilometers [1.1 miles]. I think it may take another one year for the rover to walk out of the ejecta-covered area.”
The resilient rover, which has far exceeded its design life time of three months, or three lunar days, would need to greatly boost its average drive distances to reach the area, however.
Yutu 2 has averaged 88 feet (26.7 meters) per lunar day for the 15 days so far, it would need to start covering around 492 feet (150 m) per day.
Even if Yutu 2 does not reach this area, the rover will further contribute to our understanding of the lunar surface and subsurface with its science payloads, Ian Crawford, professor of planetary science and astrobiology at Birkbeck College, University of London, told Space.com in an email.
He adds however that the “extreme slowness of these small rovers is a strong argument for a human return to the moon.”
“The Apollo 17 astronauts traversed about 35 kilometers (22 miles) in three days, which was actually only about 22 hours of Extra Vehicular Activity time,” Crawford notes.
China is planning a lunar sample return mission, Chang’e 5, for later this year. Subsequent missions are expected to target the lunar south pole before potential crewed missions in the 2030s.
NASA meantime is developing its Artemis program to return astronauts to the moon by 2024 to 2028.
For years, amateur astronomers have been waiting for a bright, naked-eye comet to pass by Earth — and finally, such an object may have arrived.
The possible celestial showpiece is known as Comet ATLAS, or C/2019 Y4. When it was discovered on Dec. 28, 2019, it was quite faint, but since then, it has been brightening so rapidly that astronomers have high hopes for the spectacle it could put on. But given the tricky nature of comets, skywatchers are also being cautious not to get their hopes up, knowing that the comet may fizzle out.ADVERTISING
It’s been awhile since a comet gave skywatchers a good show, particularly in the Northern Hemisphere. In March 2013, Comet PanSTARRS was visible right after sunset, albeit low in the western sky. But although it briefly attained first magnitude with a short, bright tail, its low altitude and a bright, twilight sky detracted from what otherwise would have been a much more prominent object. Comet Lovejoy in 2011 and Comet McNaught in 2007 both evolved into stunning objects, but unfortunately, when at their best, were visible only from the Southern Hemisphere.
It has now been nearly a quarter of a century since we have been treated to a spectacularly bright comet: Comet Hale-Bopp passed by during the spring of 1997 and Comet Hyakutake did so exactly one year earlier. Both were truly “great” comets, very bright and fantastically structured; in very dark conditions, Hyakutake’s tail appeared to stretch more than halfway across the sky.
So now, after a “comet drought,” Comet ATLAS may finally enliven the evening skies of early spring. Or then again, maybe not.
When astronomers first spotted Comet ATLAS in December, it was in Ursa Major and was an exceedingly faint object, close to 20th magnitude. That’s about 398,000 times dimmer than stars that are on the threshold of naked-eye visibility. At the time, it was 273 million miles (439 million kilometers) from the sun.
But comets typically brighten as they approach the sun, and at its closest, on May 31, Comet ATLAS will be just 23.5 million miles (37.8 million km) from the sun. Such a prodigious change in solar distance would typically cause a comet to increase in luminosity by almost 11 magnitudes, enough to make ATLAS easily visible in a small telescope or a pair of good binoculars, although quite frankly nothing really to write home about.
Except, since its discovery, the comet has been brightening at an almost unprecedented speed. As of March 17, ATLAS was already magnitude +8.5, over 600 times brighter than forecast. As a result, great expectations are buzzing for this icy lump of cosmic detritus, with hopes it could become a stupendously bright object by the end of May.
A famous lineage
Another factor buoying hopes for ATLAS as a potential dazzler is that its orbit is nearly identical to that of the so-called Great Comet of 1844.
Like the 1844 comet, ATLAS follows a trajectory that would require 6,000 years per orbit and take it to beyond the outer reaches of the solar system, roughly 57 billion miles (92 billion km) from the sun. Probably in the far-distant past, a much larger comet occupied this same orbit, but fragmented into several pieces — including the 1844 comet and ATLAS — upon rounding the sun.
But any comparison is dangerous. The 1844 comet was not discovered until shortly after perihelion, so we have no knowledge of its brightness behavior beforehand. But that information is currently all we know about ATLAS, and we won’t be able to see the object after it reaches the sun.
And let’s not forget some of the comets of the past that seemingly had “glory” written all over them, only to utterly fail to live up to expectations: Comet ISON in 2013, Comet Austin in 1990 and Comet Kohoutek in 1974.
So what’s ahead?
John Bortle, who has observed hundreds of comets and is a well-known expert in the field, got his first look at Comet ATLAS through 15 x 70 binoculars on Sunday night (March 15). And he’s stumped, he wrote. “For the first time in many years I am left at a bit of a loss as to what honestly worthy advice I can offer would-be observers. I really don’t know quite what to make of this object.”
The head (or coma) of Comet ATLAS is big, albeit “very faint and ghostly,” Bortle said, which doesn’t make sense. “If it’s a truly significant visitor, it should be considerably sharper in appearance. Instead we see, at best, a quite modestly condensed object with only a pinpoint stellar feature near its heart.”
The unpredictability of comets is an old story. Astronomers use special formulas to try to anticipate how bright a comet will get. Unfortunately, comets’ individual behavior and characteristics can be as varied as people: No two are alike.
Now, here is the conundrum regarding Comet ATLAS: Until a couple of weeks ago, it was brightening at an astounding rate. That brightening has slowed somewhat, but it is still an impossible rate of brightening to maintain. Were ATLAS to continue to brighten at this rate all the way to its closest approach to the sun at the end of May, it would end up rivaling the planet Venus in brightness!
“We should expect the rate of increase to slow again,” Carl Hergenrother, an assiduous comet observer based in Arizona, said. “This is where it gets tricky for predicting just how bright it will get.” Right now, no one can predict how long it will continue to quickly brighten and how dramatically that brightening will slow.
Where to look and what to expect
The only thing left to do is to track Comet ATLAS in the days and weeks ahead. Fortunately, its path in March and April will be very favorable for Northern Hemisphere observers, as it will be circumpolar and always remain above the horizon. As darkness falls, it will be positioned more than halfway up in the north-northwest sky. Right now, the comet is in western Ursa Major, and it will shift into the boundaries of Camelopardalis the Giraffe — a rather dim, shapeless star pattern — by March 29. There it will stay, right on through the month of April.Advertisement
As to how bright Comet ATLAS will get, that’s anybody’s guess. It might become faintly visible to the naked eye under dark sky conditions by mid- or late April. By mid-May, when it disappears into the bright evening twilight, perhaps it will have brightened to second magnitude — about as bright as Polaris, the North Star.
Whether ATLAS continues to overperform and shines even brighter, develops a significant tail or suddenly stops brightening altogether and remains very faint and ghostly are all unknown right now. We’ll just have to wait and see.
“It’s going to be fun the next few weeks watching Comet ATLAS develop (and provide a nice distraction from the current state of the world), Hergenrother wrote. “Here’s to good health and clear skies!”
A cannonball that a Japanese spacecraft fired at an asteroid is shedding light on the most common type of asteroid in the solar system, a new study reports.
Carbonaceous, or C-type, space rocks make up about three-quarters of known asteroids. Previous research suggests that they are relics of the early solar system that contain troves of primordial material from the nebula that gave birth to the sun and its planets about 4.6 billion years ago. This makes research into these carbon-rich asteroids essential to understanding planetary formation.
In 2018, Hayabusa2 arrived at Ryugu to scan it from orbit and deploy multiple rovers on the boulder-covered asteroid. Scientists found that Ryugu is likely a loosely packed, very porous pile of rubble, about 50% empty space.
To shed light on Ryugu’s composition and structure, Hayabusu2 shot a 4.4-lb. (2 kilograms) copper cannonball a bit larger than a tennis ball at about 4,475 mph (7,200 km/h) at the asteroid. The impact carved out an artificial crater that exposed pristine material under Ryugu’s surface for remote analysis and blasted out a plume of ejected material. Hayabusa2’s cameras recorded the evolution of this plume in detail.
The number and size of craters that pockmark asteroids such as Ryugu can help scientists estimate the age and properties of asteroid surfaces. These analyses are based on models of how such craters form, and data from artificial impacts like that on Ryugu can help test those models.
The cannonball, dubbed the Small Carry-on Impactor (SCI), blasted out a crater about 47.5 feet (14.5 m) wide with an elevated rim and a central conical pit about 10 feet (3 m) wide and 2 feet (0.6 m) deep.
“I was so surprised that the SCI crater was so large,” study lead author Masahiko Arakawa, a planetary scientist at Kobe University in Japan, told Space.com. The crater was about seven times larger than what might be expected from a comparable scenario on Earth, he added.
The artificial crater was semicircular in shape, and the curtain of ejected material was asymmetrical. Both of these details suggest that there was a large boulder buried near the impact site, the researchers said. This conclusion matches the rubble-pile picture that scientists already had of Ryugu.Click here for more Space.com videos…Watch Asteroid Debris Fly During Japan’s Hayabusa2’s 2nd TouchdownVolume 0% PLAY SOUND
Features of the artificial crater and the plume suggested that the growth of a crater was limited mostly by the asteroid’s gravity and not by the strength of the space rock’s surface. This, in turn, suggested that Ryugu has a relatively weak surface, one only about as strong as loose sand, which is consistent with recent findings that Ryugu is made of porous, fragile material.
These new findings suggest that Ryugu’s surface is about 8.9 million years old, while other models suggested that the asteroid’s surface might be up to about 158 million years old. All in all, while Ryugu is made of materials up to 4.6 billion years old, the asteroid might have coalesced from the remains of other broken-apart asteroids only about 10 million years ago, Arakawa said.
The scientists detailed their findings online Thursday (March 19) in the journal Science.
The asteroid Ryugu has a texture that is highly porous, new images from a Japanese space reveal.
“It is something like freeze-[dried] coffee,” planetary scientist Tatsuaki Okada of the Japanese Aerospace Exploration Agency explained to Science News.
Ryugu’s heat map shows that it’s about 50 percent porous, meaning half of it is holes, Okada and colleagues report. Even most of the asteroid’s large boulders appear porous.
The Hayabusa2 spacecraft measured the maximum temperatures during one full rotation of the asteroid Ryugu and found that most of the asteroid stays cool. (T. Okada et al/Nature 2020 ) (T. Okada et al/Nature 2020)
Science News reports the airiness of the rock’s texture fits with the idea that Ryugu is essentially a chunk of rubble created from the breakup of a larger mass about 700 million years ago.
“This might be common for the asteroids and even for planetesimals in the early solar system,” Okada says.
The researchers reported their observations Monday in the journal Nature.
While the scorching planet Mercury might not be the first place you’d think to look for ice, the MESSENGER mission confirmed in 2012 that the planet closest to the Sun does indeed hold water ice in the permanently-shadowed craters around its poles. But now a new study regarding Mercury’s ice provides even more counter-intuitive details about how this ice is formed. Scientists say heat likely helps create some of the ice.
Brant Jones, a researcher in Georgia Tech’s School of Chemistry and Biochemistry and the study’s first author, said this isn’t some strange, crazy idea. While it’s a bit complicated, it’s mostly just basic chemistry.
The planet’s extreme daytime heat combined with the super-cold (minus 200-degree Celsius) temperatures in the permanently shadowed craters might be acting like an “ice-making chemistry lab.”
“There is a surprising amount of ice on Mercury and significantly more than on the Moon,” Brant told Universe Today.
The process for creating ice on Mercury is similar to what happens on the Moon. Back in 2009, scientists determined electrically charged particles from the Sun’s solar wind were interacting with the oxygen present in some dust grains on the lunar surface to produce hydroxyl. Hydroxyl (OH) is just one atom of hydrogen with an oxygen atom, instead of the two hydrogen atoms found in water.
Brant worked with other scientists, including colleague Thomas Orlando, also from Georgia Tech, to refine the understanding of that process. In 2018, they published a paper that showed that while this process on the Moon produced significant amounts of hydroxyls, it produced very little molecular water.
“Though the solar wind was suggested as a potential source term in the 2009 observations of water on the Moon,” Orlando said via email, “the mechanisms were never really identified. We modeled this for the Moon but the importance was not as significant on the Moon due to the overall much lower temperatures.”
But they knew this process could also take place on asteroids, Mercury or any other surface that is bombarded by the solar wind.
“In order to create molecular water, you need one more ingredient, and that is heat,” said Brant.
Daytime temperatures on Mercury can reach 400 degrees Celsius, or 750 degrees Fahrenheit.
Minerals in Mercury’s surface soil contain what are called hydroxyl groups. The extreme heat from the Sun helps to free up these hydroxyl groups then energizes them to smash into each other to produce water molecules and hydrogen that lift off from the surface and drift around the planet.
Some water molecules are broken down by sunlight and dissipate. But other molecules land near Mercury’s poles in deep, dark craters that are shielded from the Sun. The molecules get trapped there and become a part of the growing, permanent glacial ice housed in the shadows.
“It’s a little like the song Hotel California. The water molecules can check in to the shadows but they can never leave,” said Orlando in a press release.
“The total amount that we postulate that would become ice is 1013 kilograms (10,000,000,000,000 kg or 11,023,110,000 tons) over a period of about 3 million years,” Jones said. “The process could easily account for up to 10 percent of Mercury’s total ice.”
The data used for their study comes from the MESSENGER spacecraft, which orbited Mercury between 2011 and 2015, studying the planet’s chemical composition, geology, and magnetic field. MESSENGER’s findings of polar ice corroborated previous signatures for ice picked up years earlier by Earth-based radar.
Mariner 10 was the first spacecraft sent to the planet Mercury; the first mission to explore two planets during a single mission; the first to use a gravity assist to change its flight path; the first to return to its target after an initial encounter; and the first to use the solar wind as a major means of spacecraft orientation during flight. But what did it capture with its two onboard cameras?
During its flyby of Venus, Mariner 10 discovered evidence of rotating clouds and a very weak magnetic field. Using a near-ultraviolet filter, it photographed Venus’s chevron clouds and performed other atmospheric studies.
The spacecraft flew past Mercury three times. Owing to the geometry of its orbit – its orbital period was almost exactly twice Mercury’s – the same side of Mercury was sunlit each time, so it was only able to map 40–45% of Mercury’s surface, taking over 2,800 photos. It revealed a more or less Moon-like surface. It thus contributed enormously to our understanding of Mercury, whose surface had not been successfully resolved through telescopic observation. The regions mapped included most or all of the Shakespeare, Beethoven, Kuiper, Michelangelo, Tolstoj, and Discovery quadrangles, half of Bach and Victoria quadrangles, and small portions of Solitudo Persephones (later Neruda), Liguria (later Raditladi), and Borealis quadrangles.
Mariner 10 also discovered that Mercury has a tenuous atmosphere consisting primarily of helium, as well as a magnetic field and a large iron-rich core. Its radiometer readings suggested that Mercury has a night time temperature of −183 °C (−297 °F) and maximum daytime temperatures of 187 °C (369 °F).
Planning for MESSENGER, a spacecraft that surveyed Mercury until 2015, relied extensively on data and information collected by Mariner 10.
On February 6, 2018, at 2045 UTC, the first Falcon Heavy was launched into space. It contained a very special payload- a Tesla Roadster with Starman.
But where is this vehicle? The current location is 203,837,502 miles (328,044,762 km, 2.193 AU, 18.24 light minutes) from Earth, moving toward Earth at a speed of 18,756 mi/h (30,184 km/h, 8.38 km/s).
The car is 90,671,738 miles (145,922,063 km, 0.975 AU, 8.11 light minutes) from Mars, moving toward the planet at a speed of 9,603 mi/h (15,454 km/h, 4.29 km/s).
The car is 149,430,277 miles (240,484,795 km, 1.608 AU, 13.37 light minutes) light minutes from the Sun, moving away from the star at a speed of 6,842 mi/h (11,011 km/h, 3.06 km/s).
The car has exceeded its 36,000 mile warranty 29,614.4 times while driving around the Sun, (1,066,119,513 miles, 1,715,753,572 km, 11.47 AU) moving at a speed of 46,644 mi/h (75,066 km/h, 20.85 km/s). The orbital period is about 557 days.
It has achieved a fuel economy of 8,461.3 miles per gallon (3,597.3 km/liter, 0.02780 liters/100 km), assuming 126,000 gallons of fuel.
If the battery was still working, Starman has listened to Space Oddity208,809 times since he launched in one ear, and to Is there Life On Mars?281,362 times in his other ear.
Starman has completed about 1.380 orbits around the Sun since launch.
A telescope about 48,145 ft (14,675 m) in diameter would be required to resolve the Upper stage from Earth. A smaller one could see him as an unresolved dot, about 92.6 ft (28.2 m) in diameter, in ideal conditions.
The vehicle has traveled far enough to drive all of the world’s roads 47.2 times.
It has been 2 years, 1 month, 9 days, 8 hours, 49 minutes and 33 seconds since launch.
We’re used to thinking of possible homes for life on watery worlds orbiting stars like the sun, but a new research paper has found a new potential habitat: a rocky planet orbiting just past the event horizon of a rapidly spinning supermassive black hole.
The exotic forces around that black hole are able to warm up the planet just right, but the scenario comes with a catch: the planet must orbit at nearly the speed of light.
Habitat for humanity
We don’t know all the possible places that life could arise in our universe, because so far we only have one example: us. And while scientists (and sci-fi authors) enjoy thinking about all sorts of exotic arrangements and possibilities for lifeforms, for serious searches of extraterrestrial intelligence, our best bet is to use our own circumstances as a template, hunting for life that isn’t too dissimilar to what we find on Earth.
From that, we can draw two extremely broad requirements. One, life like our own requires liquid water. Water is the most common molecule in the universe, composed of hydrogen (element No. 1 when it comes to abundance in the cosmos) and oxygen (the byproduct of fusion reactions inside stars like our sun, making it also very common). But that water is usually either vaporized into a plasma (and hence very bad for life) or locked down in its solid, frozen state as ice (also not very good for life).
The liquid stuff is harder to come by, and requires a source of heat that isn’t so hot that water just evaporates. We’ve found this perfect balance in only two kinds of locations: the so-called “habitable zone” of stars, a band of orbits where the light output it just right; and buried underneath the icy crusts of certain moons of the outer planets in our solar system, where tidal heating generates the necessary energy.
But just raw heat isn’t enough. Life is a complex process that uses energy to do interesting things (like move around, eat and reproduce). All those processes are not perfectly efficient, so they generate waste heat. This waste heat must be dumped safely away from the environment; otherwise, you end up with nightmare greenhouse scenarios, with temperatures escalating to uncontrolled levels and killing off any life that got started.
On the Earth, we dump our waste heat into the vacuum of space itself in the form of infrared radiation. This contrast, between a source of energy and a place to put all the waste, enables life to flourish on our home planet, and presumably any other planet with a similar setup.
At first glance, black holes appear to be the least inviting homes for any potential lifeforms. After all, they are objects made of pure gravity, pulling in anything that gets too close beneath their event horizons, shutting them off from further contact with the rest of the universe forever. Nothing, not even light, can escape their gravitational maw.
Black holes don’t give off light themselves — they’re black, after all — but that inescapable gravity can provide a surprise, unique to them throughout the cosmos.
Permeating the universe is something called the cosmic microwave background (CMB). The CMB is the leftover radiation from when the universe was just a baby, only 380,000 years old. It is, by far, the greatest source of radiation in the entire cosmos, easily swamping all the stars and galaxies by many orders of magnitude. The reason you don’t see it is that it’s primarily in the microwave region of the electromagnetic spectrum (hence the name).
In other words, the CMB is cold, with a temperature just about 3 degrees above absolute zero.
But as that CMB light falls into a black hole, it becomes blueshifted, bumped to higher and higher energies from the extreme gravity. Just before it hits the event horizon, CMB light can gain so much energy that it shifts into infrared, visible and even ultraviolet portions of the spectrum.
In other words, near a black hole, the CMB stops being cold, and gets very, very hot.
What’s more, if the black hole is spinning, it’s able to focus the light into a narrow beam, making the CMB appear as a single spot on the sky. Kind of like a sun.Click here for more Space.com videos…Search for Alien Life – Decades of Earth Observations a KeyVolume 0% PLAY SOUND
So if you’re able to get close enough to a black hole, you’ll find yourself surprisingly warm, and if you’re a planet, you might just find your water ice converted into liquid water oceans — a potential home for life.
But for life to thrive, it also needs a heat sink, which can handily be provided by the black hole itself. Close to the black hole, gravitational distortions enlarge the appearance of the event horizon, swelling it far larger than you might naively think.
Close enough to the black hole (say, at a radius less than 1% above the event horizon), the hot CMB shrinks to fill only a small disk, while the event horizon swells to cover 40% of the sky. If your planet is rotating, you then have a “sun” and a “night” — and life has everything it needs to do its business.
But orbits at this radius are usually extremely unstable, prone to just falling all the way into the terrible blackness itself. Recently, a team of researchers published an analysis in The Astrophysical Journal, exploring this scenario to see if there was any way to stabilize the situation.
And they found a way to make it work. If the black hole is big, at least 1.6×108 times the mass of the sun, and rapidly spinning, then it hosts a “habitable zone” just barely above the event horizon, where the CMB light peaks in the UV part of the spectrum — hot, but not terrible. Any closer and the planet would be destroyed by extreme gravitational forces, and any farther and the CMB would be too cold. But in that narrow band? Just right.
Though this scenario is possible, it wouldn’t be very pretty. The planet would have to orbit at nearly the speed of light, experiencing a time dilation factor of thousands — meaning that for every second that goes by on that world, hours would slide by for us. And who knows if a planet could even find its way that close to a black hole while still surviving.
Still, the work shows that we have to keep our minds open when it comes to potential homes for life, up to and including some of the most terrible environments in the universe.
Astronomers are getting closer to discovering the elusive and mysterious Planet Nine after 139 “minor planets” were discovered past Neptune’s orbit.
These objects, ones “that were not previously published,” are not officially planets or comets, but rather space objects that orbit the Sun. In total, the discovery is five percent of the trans-Neptunian object (TNO) population, bringing the number to approximately 3,000, according to a statement accompanying the study.
“Pluto, the best-known TNO, is 40 times farther away from the sun than Earth is, and the TNOs found using the [Dark Energy Survey] data range from 30 to 90 times Earth’s distance from the sun,” the statement reads. “Some of these objects are on extremely long-distance orbits that will carry them far beyond Pluto.”
Artist’s illustration of Planet Nine, a hypothetical world that some scientists think lurks undiscovered in the far outer solar system. (R. Hurt (IPAC)/Caltech)
The researchers used data from the DES between 2013 and 2017, which uses a 520-megapixel Dark Energy Camera. It is on the Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory in Chile.
There were 7 billion DES-detected dots that the researchers started with, a list that was condensed to 22 million “transient” objects and then eventually, approximately 400 objects that were observed over six separate nights.
“We have this list of candidates, and then we have to make sure that our candidates are actually real things,” the study’s lead author, Pedro Bernardinelli, said in the statement.
The objects range between 30 and 90 astronomical units from the sun. One astronomical unit is the equivalent of 93 million miles or the distance between the Earth and the sun.
“Dedicated TNO surveys have a way of seeing the object move, and it’s easy to track them down,” Bernardinelli added. “One of the key things we did in this paper was figure out a way to recover those movements.”
It’s expected that the discovery could play a role in further searches for TNOs, notably the infamous Planet 9.
“There are lots of ideas about giant planets that used to be in the solar system and aren’t there anymore, or planets that are far away and massive but too faint for us to have noticed yet,” the study’s co-author Gary Bernstein said. “Making the catalog is the fun discovery part. Then, when you create this resource, you can compare what you did find to what somebody’s theory said you should find.”
A hypothetical planet that has been described as “the solar system’s missing link,” Planet 9 (also known as Planet X) has been part of the lexicon for several years, first mentioned in 2014. It was brought up again in 2016, when Caltech astrophysicists Mike Brown and Konstantin Batygin first wrote about it.
In October 2017, Batygin said that there are “five different lines of observational evidence” that point to the existence of Planet Nine.
The five lines of evidence are:
Six known objects in the Kuiper Belt, all of which have elliptical orbits that point in the same direction.
The orbits of the objects are all tilted the same way; 30 degrees “downward.”
Computer simulations that show there are more objects “tilted with respect to the solar plane.”
Planet Nine could be responsible for the tilt of the planets in our solar system; the plane of the planet’s orbit is tilted about 6 degrees compared to the Sun’s equator.
Some objects from the Kuiper Belt orbit in the opposite direction from everything else in the solar system.
“No other model can explain the weirdness of these high-inclination orbits,” Batygin said at the time. “It turns out that Planet Nine provides a natural avenue for their generation. These things have been twisted out of the solar system plane with help from Planet 9 and then scattered inward by Neptune.”
In October 2017, NASA released a statement saying that Planet 9 might be 20 times further from the Sun than Neptune is, going so far as to say “it is now harder to imagine our solar system without a Planet 9 than with one.”
Some researchers have suggested the mysterious planet may be hiding behind Neptune and it may take up to 1,000 years before it’s actually found.
Two studies published in March 2019 offered support of its existence, however, a separate study published in September 2019 suggested the theoretical object may not be a giant planet hiding behind Neptune — but rather a primordial black hole.
A study published in January 2019 suggested that some of the farthest celestial bodies in our planetary system aren’t being impacted by this yet-to-be-discovered planet, but rather another mysterious object deep in the echoes of space.
65 million years ago, a large asteroid collided with Earth near present-day Chicxulub, Mexico. The impact was a climactic event that likely contributed to dinosaur extinction. Today, Earth remains vulnerable to asteroid collisions.
In recent history, space rocks have landed in The United States, Russia, and elsewhere. In the event of a potential asteroid collision, NASA has developed several options for dealing with the threat. Researchers at NASA’s Center for Near Earth Object Studies and Jet Propulsion Laboratory have proposed using blunt force, weaponized deflection or a theoretical tool called a gravity tractor to deflect impact. In addition to developing contingency plans, NASA scientists are also searching the sky for future asteroid threats.
Although an asteroid of that size would be rare — NASA estimates a one-mile-wide asteroid only hits the Earth once every one million years — the two agencies have performed multiple test runs to ensure we’d be prepared.
“It’s not a matter of if, but when, we will deal with such a situation,” said astrophysicist Thomas Zurbuchen.
Astronomers suggest microbes might hitch lifts on interstellar asteroids.
Could the Earth be a life-exporting planet? That’s the curious question examined in a recent paper written by Harvard University astronomers Amir Siraj and Abraham Loeb.
The researchers take a novel twist on the controversial notion of panspermia – the idea, propelled into the mainstream in the early 1970s by astronomers Fred Hoyle and Chandra Wickramasinghe, that life might have started on Earth through microbes arriving from space.
The theory is generally discounted, although eminent astrophysicists such as Stephen Hawking conceded it was at least possible, and a major paper published in 2018 revived the topic big-time.
In their paper, Siraj and Loeb reverse the standard assumption about the direction of the microbial journey and ask whether it is possible to that at some point Earth-evolved bacteria could have been propelled away from the planet, possibly to be deposited somewhere else in the Milky Way.
To examine the idea, they fed several bits of evidence, and a few reasonable assumptions, into a computer and let the numbers run.
First and foremost, they rely on evidence from several studies that confirm the existence of airborne microbial colonies as high as 77 kilometres above the surface of the planet. The authors note that “the abundance of microbes in the upper atmosphere is poorly constrained”, so the density of life in the upper reaches remains largely guesswork.
Also unknown at this point is whether bacteria colonies persist above 100 kilometres up.
In the absence of any extraterrestrial versions of dirt-sampling spacecraft such as Japan’s Hayabusa asteroid-lander, the only viable transport methods for shipping microbes out of Earth’s atmosphere, the researchers say, are long-period comets and interstellar objects.
The comets, they note, “can easily be ejected from the Solar System by gravitational interactions with planets due to their low gravitational binding energies and planet-crossing orbits”. Interstellar objects are new to the scenario, their existence well demonstrated by the recent discoveries of ‘Oumuamua and 2I/Borisov – both high-speed big lumps of rock that entered the solar system from elsewhere.
At particular speeds and particular angles, they calculate, both comets and asteroids could come close enough to Earth to “graze” its upper atmosphere before being flung out of the Solar System with the aid of a gravitational slingshot generated by the close encounter.
During such an interaction, the objects would inevitably plough through the airborne bacterial colonies – the researchers cite Bacillus subtilis, Deinococcus radiodurans, Escheria coli, and Paracoccus denitrificans as the most likely candidates.
Sufficient numbers of the newly gathered passengers, the modelling shows, would survive the g-forces of the slingshot acceleration and the friction-induced heating caused by leaving the atmosphere.
Siraj and Loeb calculate that across the life of Earth, between one and 10 comets and between one and 50 interstellar objects have come close enough to graze the atmosphere.
Previous research has shown that bacteria could easily survive on board an asteroid or comet in interstellar space – lapsing into suspended animation if necessary – and could just as easily survive the enormous pressure caused by their transport smacking into a planet.
Thus, the researchers conclude that although much more research is needed – particularly into the make-up and distribution of microbes in the upper atmosphere – the idea of panspermia beginning on this planet and heading outwards is “realistic”.
The truth of the matter might never be known, of course, at least for several centuries; but it is at least possible that somewhere many light years hence there is a corner of a distant solar system that is forever Earth.