75 years on from the atomic bombing of Hiroshima, more than 13,000 nuclear warheads are still scattered across the world from silos in Montana to isolated corners of European airbases and even to the ocean depths where ballistic missile submarines lurk as a deterrent nearly impossible to detect. Hiroshima was the first of two atomic bombings in 1945 and it involved a 15-kiloton device while the weapon used in the attack on Nagasaki three days later had a 22 kiloton yield. Modern nuclear warheads are far more powerful with the U.S. Trident missile yielding a 455 kiloton warhead while Russia’s SS ICBM has an 800 kiloton yield. Together, the United States and Russia possess more than 90 percent of the world’s nuclear weapons with a stockpile of 8,000 between them, according to the Federation of American Scientists. Active and inactive warheads in military custody are included in that total but it excludes strategic warheads currently deployed at bases for heavy bombers and on intercontinental ballistic missiles.
Even though 8,000 seems like an awfully large number (which it is), it represents a huge reduction on the number of warheads in existence at the height of the Cold War. This infographic shows how stockpiles evolved, particularly when various arms limitation treaties are taken into account. The number of warheads fell significantly in the wake of the Intermediate-Range Nuclear Forces Treaty which was signed by the U.S. and USSR in 1987 at a time when both countries possessed more than 60,000 nuclear weapons. The trend towards disarmament continued after the Berlin Wall came down and accelerated when the Soviet Union collapsed. Despite the decline, it isn’t all good news as states are now modernizing their existing stockpiles, adding new types, new delivery systems and committing to possessing the weapons long-term.
Developments in Washington D.C. have added to those worries with the Trump administration leaving the Intermediate-Range Nuclear Forces Treaty and now threatening to pull out of New START. That agreement limits the U.S. and Russia to 1,550 deployed nuclear missiles each. The reason cited by President Trump is that China has to be part of any such agreements in the future and so far, Beijing has categorically ruled out any participation. The treaty will expire in February, weeks after the presidential inauguration. Trump has already abandoned the Iran nuclear accord and he recently took the U.S. out of the Open Skies Treaty, blaming Russia for a lack of compliance.
Earth orbits the sun like a ship sailing in circles around its anchor. But what if someone — or something — cut that ship loose? Unbound from any star or solar system, what would become of a tiny world flying helplessly and heedlessly through interstellar space? What happens when a planet goes rogue?
Scientists suspect that billions of free-floating or "rogue" planets may exist in the Milky Way, but so far only a handful of candidates have turned up among the 4,000-or-so worlds discovered beyond our solar system. Most of these potential rogue planets appear to be enormous, measuring anywhere from two to 40 times the mass of Jupiter (one Jupiter is equivalent to about 300 Earths). But now, astronomers believe they’ve detected a rogue world like no other: a tiny, free-floating planet, roughly the mass of Earth, gallivanting through the gut of the Milky Way.
This discovery, reported today (Oct. 29) in the Astrophysical Journal Letters, may mark the smallest rogue planet ever detected, and it could help prove a long-standing cosmic theory. According to the study authors, this little world could be the first real evidence that free-floating, Earth-sized planets may be some of the most common objects in the galaxy.
"The odds of detecting such a low-mass object are extremely low," lead study author Przemek Mroz, a postdoctoral scholar at the California Institute of Technology, told Live Science in an email. "Either we were very lucky, or such objects are very common in the Milky Way. They may be as common as stars."
Most exoplanets in our galaxy are visible only because of their host stars. In a literal sense, stars provide the light that allows astronomers to directly observe alien worlds. When a planet is too small or too distant to be seen directly, scientists can still detect it from the slight gravitational pull it exerts on its host star (called the radial velocity method) or by the flickering that occurs when a planet passes in front of the star’s Earth-facing side (the transit method).
Rogue planets, by definition, have no star to light their way — or to light a telescope’s way to them. Instead, detecting rogue planets involves a facet of Einstein’s theory of general relativity known as gravitational lensing. Through this phenomenon, a planet (or even more massive object) acts as a cosmic magnifying glass that temporarily bends the light of objects behind it from Earth’s perspective.
"If a massive object passes between an Earth-based observer and a distant source star, its gravity may deflect and focus light from the source," Mroz explained in a statement. "The observer will measure a short brightening of the source star."
An artist’s impression of a gravitational microlensing event by a free-floating, or rogue, planet. In microlensing, gravity from an object causes the light from a background source to bend, an astronomical phenomenon that shows up as distortions in images taken from Earth.
An artist’s impression of a gravitational microlensing event by a free-floating, or rogue, planet. In microlensing, gravity from an object causes the light from a background source to bend, an astronomical phenomenon that shows up as distortions in images taken from Earth.
The smaller that light-bending object is, the briefer the star’s perceived brightening will be. While a planet several times the mass of Jupiter might create a brightening effect that lasts a few days, a measly planet the mass of Earth will brighten the source star for only a few hours, or less, the researchers said. This exceptionally rare occurrence is called "microlensing."
"Chances of observing microlensing are extremely slim," Mroz added in the statement. "If we observed only one source star, we would have to wait almost a million years to see the source being microlensed."
Fortunately, Mroz and his colleagues weren’t observing just one star for their study — they were watching hundreds of millions of them. Using observations from the Optical Gravitational Lensing Experiment (OGLE), a star survey based at the University of Warsaw in Poland that has turned up at least 17 exoplanets since 1992, the team stared into the center of the Milky Way, looking for any signs of microlensing.
In June 2016, they witnessed the shortest microlensing event ever seen. The star in question, located roughly 27,000 light-years away in the densest part of the galaxy, brightened for just 42 minutes. Calculations showed that the offending object was not bound to any star within 8 astronomical units (AU, or eight times the average distance from Earth to the sun), suggesting it was almost certainly a tiny planet on the run, ejected from its home solar system after a brush with a much more massive object.
Depending on how far away the planet is from the source star (it’s impossible to tell with current technology), the rogue world is likely between one-half and one Earth mass. In either case, this roaming world would be the lowest-mass rogue planet ever detected. According to Mroz, that’s a "huge milestone" for the science of planet formation.
"Theories of planet formation have predicted that the majority of free-floating planets should be of Earth mass or smaller, but this is the first time that we could find such a low-mass planet," Mroz said. "It’s really amazing that Einstein’s theory allows us to detect a tiny piece of rock floating in the galaxy."
Many more tiny pieces of rock may soon follow, study co-author Radek Poleski of the University of Warsaw told Live Science. Future planet-hunting telescopes, like NASA’s Nancy Grace Roman Space Telescope (slated to launch in the mid-2020s), will be much more sensitive to the galaxy’s teensiest microlensing events than the nearly 30-year-old OGLE experiment is, Poleski said. If orphan planets of roughly Earth’s mass are indeed some of the most common denizens of the galaxy, it shouldn’t be long before many more of them turn up.
Scientists have detected a series of saltwater lakes beneath the glaciers of Mars’ southern ice cap. The researchers believe the liquid in these lakes doesn’t freeze and become solid, despite the low temperatures of Mars’ glaciers, due to their extremely high concentrations of salt.
The Mars Express spacecraft, which has been surveying the planet since 2005, had previously detected signs of a subglacial lake basin on Mars’ south pole, but it was unclear whether the lake was liquid or what it contained.
The southern ice cap of Mars, April 17, 2000.NASA/JPL
To find out, a group of Italian, German, and Australian researchers applied a radio-echo technique that Earth satellites use to detect subsurface lakes in Antarctica. They scanned the area multiple times from 2010 to 2019, then published their results in the journal Nature Astronomy on Monday.
The analysis confirmed the liquid-water nature of Mars’ underground lake, as well as its extreme saltiness. What’s more, the researchers say, they uncovered "a more extensive, complex scenario with ubiquitous water patches surrounding the subglacial lake."
The discovery offers yet another possible habitat for life to persist on Mars.
Ancient life may have retreated to underground lakes
Scientists think the Martian surface was once rich with rivers, lakes, and seas, but all the surface water evaporated as a flow of particles from the sun stripped away the planet’s atmosphere. Earth’s strong magnetic field, by contrast, has allowed it to hold onto its atmosphere and its surface water.
On Mars, any microbial life that might have existed on the surface could have migrated underground as water disappeared — perhaps to lakes like the ones beneath the red planet’s south pole.
In July, NASA launched its nuclear-powered Mars Perseverance rover, which is set to search for signs of ancient life on the planet’s surface and prepare Martian rock samples for a future mission that would return them to Earth. The rover is expected to land on Mars on February 18, 2021.
An artist’s illustration shows NASA’s Perseverance rover and Ingenuity helicopter on Mars.NASA/JPL-Caltech
"Is there life out there? We have, for 20 years, learned about the environment of Mars and are ready to ask that," NASA Administrator Thomas Zurbuchen said during a broadcast of the rover’s launch. "For the first time in decades, [an] astrobiology mission? We’re ready for it."
The moon is littered with patches of hidden water, NASA researchers have discovered.
That’s great news for the agency’s plans to send astronauts back to the moon, set up a permanent base there, and eventually use it as a stopping point on the way to Mars.
Those ambitions hinge on the ability to mine water ice on the moon and break it down into oxygen and hydrogen to make rocket fuel. Since it’s extremely costly and difficult to launch enough fuel off of Earth to get astronauts to Mars, water on the moon will likely play a critical role in kickstarting a new era of human deep-space exploration.
"You start making gas stations in space. This really starts cutting your dependence on bringing all that fuel from Earth," Angel Abbud-Madrid, director of the Center for Space Resources at the Colorado School of Mines, previously told Business Insider. "That’s really been what’s holding us back from deep-space exploration."
Artist’s concept of astronauts and human habitats on Mars.
Until now, NASA hadn’t known how much water could be available on the moon, or how easy it would be to mine. But two papers published in the journal Nature Astronomy on Monday make the future of lunar ice mining much brighter.
One of the studies confirmed the presence of molecular water in the moon’s surface dust for the first time. The other identified tens of billions of small, cold regions in shadows across the moon where the sun never shines and ice sits comfortably on the surface.
"Both, in different ways, would seem to indicate that there’s more water available on the lunar surface than we’ve been thinking even recently," Leslie Gertsch, a geological engineer at the Missouri University of Science and Technology, and who was not involved in the studies, told Business Insider. "Whether it’s mineable or not is another question."
A space plane detected lunar H2O for the first time
Experts had long thought the moon wouldn’t be a safe place for water, since it has no atmosphere to shield its surface from the sun’s radiation.
But scientists and their spacecraft have been picking up telltale signs of lunar water for the last three decades. First, they found hydrogen lingering over the poles. Then traces of water appeared in lunar-rock samples from the Apollo missions. Later, the Cassini spacecraft picked up signals for water as it glanced at the moon on its way to Saturn.
But there was always a possibility that none of those discoveries were actually water as we know it — H2O — instead of a compound called hydroxyl (OH).
Researchers tend to use the word "water" to describe both compounds, but the oxygen and hydrogen molecules that make up hydroxyl form a much stronger chemical bond than those in H2O.
"If we wanted to extract hydroxyl from a soil to use it for a resource, it would take a lot more energy to break that apart, to create other things like breathable oxygen or water to drink for the astronauts," Casey Honniball, a postdoctoral fellow at NASA’s Goddard Space Flight Center, said in a press briefing. "But with molecular water, if we have that on the moon and we can extract it, that makes it an easier process to get it to other compounds that we would want to use."
To find out whether the moon harbors molecular water or hydroxyl, Honniball hopped on a space plane.
NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA)NASA
The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a converted Boeing 747 souped up with a 2.7-meter telescope and the ability to fly into the stratosphere. That’s high enough to avoid the atmosphere’s distortion of infrared signals from the moon.
Honniball spent around nine hours in the plane, flying about 40,000 feet above the Earth. She detected the wavelengths of H2O and, surprisingly, they came from a sunlit part of the moon.
That means the water molecules are probably embedded in glass beads that make up about 30% of the lunar soil. Those likely protect H2O from the vaporizing powers of the sun.
Honniball doesn’t know if glass across the entire moon contains water — it could be specific to the region she studied. Either way, though, water molecules embedded in glass beads would not be easy to mine.
"There’s a reason why high-level nuclear waste is planned to be put into glass," Gertsch said. "Glass does not let stuff out easily."
Until now, the best known caches of lunar water are those in the large, permanently shadowed regions at the poles — the coldest spots ever measured in our solar system.
But in digging through thousands of photos from NASA’s Lunar Reconnaissance Orbiter, a group of researchers found smaller regions of permanent shadow littering the moon’s surface.
Paul Hayne, a planetary scientist at the University of Colorado Boulder who led the study, likened the discovery to the process of "turning over a rock and finding all the gazillions of insects that skitter away." He estimates that there are tens of billions of these "micro cold traps" surrounding the moon’s poles.
Hayne’s team did not look for water in these regions, but previous research already confirmed the presence of water ice in the large shadows on the poles.
"If there’s water in these larger cold traps, then there should be water in the smaller ones too," Hayne told Business Insider.
This means that mining machines could theoretically stay in the sunlight — and avoid extreme freezing temperatures — while dredging ice from micro traps.
"You could go to a place in these polar regions and stand in the sunlight and bend over, or use a tool to extract water from one of these much smaller shadows that’s much more accessible," Hayne said.
All in all, Hayne’s team estimates that shadowed cold-trap regions cover about 0.15% of the moon’s surface.
If these micro cold traps are filled with water, that would make moon mining easier, since they extend away from the poles and it’s easier to land a spacecraft near the moon’s equator.
But Gertsch warned that big questions about lunar ice remain. Although both of these discoveries are "enticing," she said, we can’t really know the nature of the lunar ground until "we go up there and mess around."
NASA is sending a water-hunting rover to the moon’s South Pole
An illustration of NASA’s Volatiles Investigating Polar Exploration Rover (VIPER) on the surface of the moon.NASA Ames/Daniel Rutter
To investigate lunar water up close, NASA is preparing to launch a drill and mass-measuring instrument to the moon’s South Pole in 2022. Once there, it will try to harvest water ice.
Then in 2023, NASA aims to launch the VIPER (short for Volatiles Investigating Polar Exploration Rover), which will trundle over rocky terrain, drilling into sections of moon ice and soil for analysis. Over the course of its 100-day lifespan, the rover’s main goal is to collect data for NASA to map out the moon’s water resources.
An illustration shows Astrobotic’s Griffin lunar lander deploying a ramp on the moon’s surface.Astrobotic
Given their more accessible locations, Hayne’s micro cold traps could be ideal targets for these missions.
Honniball’s team, meanwhile, has requested 72 more hours on the SOFIA plane for further lunar observations.
But if NASA really wants to set up a moon-mining operation, it will have a lot more work to do.
"It takes more than one rover," Gertsch said. "You can’t just send one prospector on a donkey out into the mountains and expect to design a mine from that."
[I've been watching some videos of the Tesla turbine and began asking myself: How does this thing actually work? The answer will astound and amaze you. And to think that this thing was invented in 1909 and has … until now … not had a practical use! It was originally invented to be used as a steam engine. Don't knock steam power … nuclear submarines and aircraft carriers function on STEAM POWER generated by heat from nuclear power! So a nuclear powered submarine is really a STEAM POWERED submarine! Ditto for an aircraft carrier! Gasoline engines killed the possibilities of this engine. However, look very carefully at this video describing how this little turbine works and you'll be amazed by the unbelievable sophistication of the thinking of this man long before the age of computers, etc. How he even conceived of such a complex idea leaves me astounded! Watch the description carefully. Then they also have a tiny Tesla turbine which they run and you see it in action. What makes this little machine even more INCREDIBLE, is its speed of rotation, and even more amazingly, the faster it turns … THE MORE POWER IT GENERATES AND THE FASTER IT WANTS TO GO! Tesla, in his time found that it went so fast that it broke any known metal or alloy he could find!!! In the video, it spins up to an incredible 80,000 RPM!!! But this little machine has other features. It is reversible. It can run equally efficiently both forwards and backwards! Even more astounding, you can reverse it completely and use it as a pump! I find it hard to believe that there are no uses for it. This turbine is beyond imagination. Watch this short video and let it blow your mind! Jan]
[I'm not a big fan of Hawking, but I think some of his thoughts are well worth pondering. AI does not bother me, because we control AI. Take special note of his prediction that Nuclear Fusion is the greatest and best technology. I have been well aware, and am a firm supporter of nuclear energy and nuclear power. It is a fantastic creation with unmatched benefits. Jan]
The late physicist Stephen Hawking’s last writings predict that a breed of superhumans will take over, having used genetic engineering to surpass their fellow beings.
Hawking delivers a grave warning on the importance of regulating AI, noting that “in the future AI could develop a will of its own, a will that is in conflict with ours.” A possible arms race over autonomous-weapons should be stopped before it can start, he writes, asking what would happen if a crash similar to the 2010 stock market Flash Crash happened with weapons. He continues:
In short, the advent of super-intelligent AI would be either the best or the worst thing ever to happen to humanity. The real risk with AI isn’t malice, but competence. A super-intelligent AI will be extremely good at accomplishing its goals, and if those goals aren’t aligned with ours we’re in trouble. You’re probably not an evil ant-hater who steps on ants out of malice, but if you’re in charge of a hydroelectric green-energy project and there’s an anthill in the region to be flooded, too bad for the ants. Let’s not place humanity in the position of those ants.
Earth’s Bleak Future, Gene Editing, and Superhumans
The bad news: At some point in the next 1,000 years, nuclear war or environmental calamity will “cripple Earth.” However, by then, “our ingenious race will have found a way to slip the surly bonds of Earth and will therefore survive the disaster.” The Earth’s other species probably won’t make it, though.
The humans who do escape Earth will probably be new “superhumans” who have used gene editing technology like CRISPR to outpace others. They’ll do so by defying laws against genetic engineering, improving their memories, disease resistance, and life expectancy, he says
Hawking seems curiously enthusiastic about this final point, writing, “There is no time to wait for Darwinian evolution to make us more intelligent and better natured.”
Once such superhumans appear, there are going to be significant political problems with the unimproved humans, who won’t be able to compete. Presumably, they will die out, or become unimportant. Instead, there will be a race of self-designing beings who are improving themselves at an ever-increasing rate. If the human race manages to redesign itself, it will probably spread out and colonise other planets and stars.
Intelligent Life in Space
Hawking acknowledges there are various explanations for why intelligent life hasn’t been found or has not visited Earth. His predictions here aren’t so bold, but his preferred explanation is that humans have “overlooked” forms of intelligent life that are out there.
Does God Exist?
No, Hawking says.
The question is, is the way the universe began chosen by God for reasons we can’t understand, or was it determined by a law of science? I believe the second. If you like, you can call the laws of science “God”, but it wouldn’t be a personal God that you would meet and put questions to.
The Biggest Threats to Earth
Threat number one one is an asteroid collision, like the one that killed the dinosaurs. However, “we have no defense” against that, Hawking writes. More immediately: climate change. “A rise in ocean temperature would melt the ice caps and cause the release of large amounts of carbon dioxide,” Hawking writes. “Both effects could make our climate like that of Venus with a temperature of 250C.”
The Best Idea Humanity Could Implement
Nuclear fusion power. That would give us clean energy with no pollution or global warming.
Over the next few decades, Elon Musk is hoping to send 42,000 satellites to space.
He is hoping those satellites bring high-speed internet to every corner of the world— from the rainforest to Antarctica.
But experts worry that the number of satellites could have a major impact on our planet.
Their bright reflections are already blocking the views of astronomers looking for deadly asteroids. If enough of them become disabled, which is already happening, they could also block off space travel for decades.
You’re looking at 60 satellites hurtling into the sky. And over the next few decades, Elon Musk is hoping to send 42,000 of these satellites to space, 15 times the number of operational satellites in orbit today. It’s part of Starlink, the expansive constellation from Musk and SpaceX that hopes to bring the world low-latency high-speed internet, promising no more buffering and nearly instantaneous internet in every corner of the world. But experts worry it may come at a hefty cost for space exploration.
Nearly half of the world’s population does not have access to the internet, because most internet options require an extensive track of costly underground cables, leaving many rural locations offline. And while satellite internet can reach those areas…
Dave Mosher: Traditional satellite internet is provided by a bus-sized spacecraft that is launched 22,236 miles into space in orbit around Earth.
Narrator: That distance means the satellite can reach places that cables can’t. But since that one satellite is meant to service a lot of people, its data capability is limited, which then limits connection speeds. And that signal has to travel a long way, creating a lot of lag. This is where Elon Musk and SpaceX come in.
Mosher: Starlink is a globe-encircling network of internet-beaming satellites that is trying to get you online no matter where you are in the world.
Narrator: And there’s a rather persuading element for SpaceX as well.
Mosher: Elon Musk has said he’s just trying to grab a small percentage of a trillion-dollar-a-year telecommunications industry around the world. If SpaceX can pull this off, the company could net about $30 to $50 billion a year.
Narrator: Musk and SpaceX president Gwynne Shotwell say that much money could single-handedly fund the development of Starlink, Starship, and SpaceX’s Mars-launch infrastructure. As of early October, SpaceX has launched more than 700 satellites into orbit, with a plan to release a total of 12,000 over the next five years, half of them by the end of 2024. And Musk wants to add another 30,000 to that, coming to a total of 42,000 satellites circling Earth. All of these satellites will also be much closer, anywhere from 200 to 400 miles above the planet in low-Earth orbit.
Mosher: This reduces the connection delay that is found with traditional internet satellite.
Narrator: Once in orbit, these Starlink satellites will be constantly on the move, which is why so many are necessary.
Mosher: The problem is you have to have many satellites orbiting to make up for the fact that you can’t stay in one spot above the Earth. Because you need several satellites overhead at any one time to cover many users.
Narrator: Every satellite will connect with several others via laser beams, creating something like the network’s backbone. And to actually bring this internet into your home, you’ll need to get a pizza-sized antenna. This phased-array antenna can aim its beam at whatever satellite is overhead, which will maintain an internet signal in your home. But this scheme isn’t without problems. Starlink satellites are bright. They reflect the sunlight and shine it back towards Earth, so they end up looking like bright moving stars. As cool as it may look, that comes with problems.
Mosher: Starlink satellites are most visible in the night sky right before dawn and right after dusk, which is the exact time that astronomers are hunting for near-Earth objects or asteroids, objects that could hit Earth and possibly harm us.
Narrator: And as more satellites go up, so does the likelihood that they’ll interfere with astronomers’ views.
Mosher: If Starlink continues to be a problem for these type of sky surveys, we may not have as much notice as we want to detect a near-Earth object and thwart it and prevent it from hitting Earth.
Narrator: Beyond detecting deadly asteroids, the wall of satellites could also obstruct the search for new planets or even black holes.
Mosher: SpaceX realized it had to do something, and it did. It created what’s called a DarkSat, which is a satellite that has all of its shiny parts coated in a very black, dark material.
Narrator: It also tried adding visors to shield those shiny parts from the ground. But unless the satellites are cloaked like a spaceship in "Star Trek," technology that does not exist, none of this will fully solve the problem. And even if it did, there is a much bigger issue at hand.
Mosher: There’s a concern about space debris, because when you have so many satellites in the closest, tightest, densest orbits around Earth, there’s a higher chance that those satellites could collide with each other or with other satellites.
Narrator: Those crashes would create clouds of debris that can orbit the Earth for years, decades, or even centuries.
Mosher: And that debris can then disable or cause other satellites to crash into each other, creating even more debris, and this problem spirals out of control in an effect called the Kessler syndrome. And if we reach that, then essentially space is too unsafe to access.
Narrator: To be clear, the risk of a runaway Kessler syndrome is very low.
Mosher: But the potential impacts of that are so high that scientists are working very hard to control such an event from ever happening.
Narrator: SpaceX has said its satellites can automatically move out of the way to avoid collisions. But dozens of SpaceX satellites are already disabled and can’t move at all, posing a potential threat. And those concerned with SpaceX’s plans are lobbying the FCC to rein in the company and more strictly regulate low-Earth orbit. And that could make it more expensive and harder to deploy the planned 42,000 satellites. But it doesn’t stop at Starlink.
Amazon’s Kuiper project, OneWeb, China’s Hongyan, and other projects are looking to challenge SpaceX by launching their own global networks of hundreds or thousands of satellites. If they all got their way with little to no regulation, we could end up with 100,000 satellites encasing our planet within the next 10 years, dramatically increasing the risk of blocking off space for everyone.
Bennu is shaped like a three-dimensional diamond and seemingly smooth from far away. OSIRIS-REx is in the foreground of this artist’s replication. The spacecraft will gather a sample from Bennu next week. (NASA/Goddard/University of Arizona)
From telescopes on Earth, Bennu’s surface appears smooth. That’s one of the reasons why NASA picked the asteroid as a destination for its OSIRIS-REx spacecraft. But in 2018, when OSIRIS-REx approached the asteroid, scientists discovered that Bennu’s surface was covered with massive boulders. It turns out those boulders moved a lot over the last few hundred thousand years, according to recent research.
“When you think of small asteroids, you’d think they aren’t very dynamic because they have no atmosphere or volcanic activity. But Bennu is so small and its gravity is so weak that material can move around much more easily than on a planet,” said Dr. Erica Jawin, a postdoctoral fellow in the Department of Mineral Sciences at the Smithsonian’s National Museum of Natural History and the study’s lead author.
Bennu spun out of the asteroid belt millions of years ago and now circles the sun between Earth and Mars, much closer than its original location in the asteroid belt. Because the asteroid currently has an orbit near Earth’s, it is easier to sample it than any asteroid in the main belt. By modeling how Bennu’s boulders moved in the past, Jawin can predict where rocks in OSIRIS-REx’s sample might have come from on the asteroid’s surface. Knowing those rocks’ origins will help scientists learn more about the composition of objects in the solar system and asteroid belt.
“Asteroids are always gravitationally interacting and essentially sharing material. Earth gets meteorites from asteroids and asteroids also get meteorites from other asteroids,” said Dr. Tim McCoy, Curator of Meteorites at the museum and a co-author on the study.
A moving history
Bennu’s rocks move depending on the asteroid’s rotation rate, which can change based on how the asteroid absorbs and radiates thermal energy from the Sun. (NASA/Goddard/University of Arizona)
Bennu is shaped like a three-dimensional diamond. It is relatively small for an asteroid — only about a third of a mile wide at its equator. But its surface is geologically active.
Rocks on Bennu’s surface move so easily because the asteroid’s gravity is very weak. Because of the weak gravity, rotational forces can move the rocks. This is what causes boulders and rocks to move about or potentially fly into space.
“As Bennu rotates, its surface absorbs thermal energy from the Sun. It then radiates that heat back into space as the asteroid rotates. This provides a torque on the asteroid, which affects how quickly the asteroid rotates and over time can change the orbit of the asteroid. This effect also may have caused Bennu to leave the asteroid belt and come closer to Earth,” said Jawin.
Studying Bennu’s pristine rocks could reveal what material exists in the outer solar system. And that material could yield information about the composition of primordial Earth.
“On Earth, we’ve had life for potentially billions of years. Everything has been processed so much. In order to really understand how life started, you really need to go somewhere where there’s no life yet,” said Jawin.
Since Earth has an atmosphere and active plate tectonics, its oldest rocks are weathered or have been pushed deep into the mantle. So, researchers often use meteorites to learn more about both ancient Earth’s and the solar system’s composition.
“Meteorites have been described as the poor man’s space probe, because they are constantly coming to Earth. Just picking them up, we can learn about our solar system and its history,” said McCoy. “But at the same time, we’re trying to figure out what the entire asteroid belt and early solar system looked like from these bits and pieces.”
Examining Bennu’s rocks will give McCoy and his colleagues more tools, helping them trace meteorites in the museum’s collection back to the asteroid belt.
What happens next
Meteorites in the Smithsonian’s National Meteorite Collection are found all over the world. The collection has over 45,000 specimens from over 16,800 meteorites. (Jeremy Snyder, Smithsonian)
Once the rock sample from Bennu finally reaches Earth in three years on September 24, 2023, part of it will be loaned to McCoy’s Smithsonian team. There, McCoy and Jawin will analyze it to see if any meteorites currently in the Smithsonian’s National Meteorite Collection have similar compositions. If there’s a match, it could suggest that the object is related to Bennu or it was part of another asteroid in the region where Bennu came from.
“Most meteorites in our collection came from asteroids at some point, but we’ve only been able to link a very small fraction of the meteorites in our collection to their parent asteroids. If you just pick up a meteorite on the ground, you don’t know how long it’s been sitting there. So, it’s likely not in pristine condition,” said Jawin. “The OSIRIS-REx mission will give us pristine samples to compare to our collection and bridge that gap.”
McCoy also suspects the Bennu sample could yield rocks unlike anything on Earth, complicating what scientists know about the geology of the solar system.
“Every few years, we find a new kind of meteorite so it’s very possible that Bennu also has new kinds of rocks we don’t have in our collection. It’s possible we’ll get something entirely new,” said McCoy. These new rocks could maybe decode some of the collection’s more enigmatic meteorites.
The meteorite collection exists not only for scientists currently seeking to understand the solar system, but also for future scientists conducting experiments yet to be invented. Part of the Bennu sample will immediately be sealed for the foreseeable future, saved for the future as technology advances.
“We will be able to use tools and equipment that haven’t been invented yet to ask questions we haven’t even thought of yet. But because we have those samples, we’ll be able to answer those questions,” said McCoy. “Think of it as the gift that keeps on giving.”