By sampling some of the oldest rock in the solar system, the osiris-rex mission could revise the story of the origins of life.
On a brisk day in February, 2004, Dante Lauretta, an assistant professor of planetary science at the University of Arizona, got a call from Michael Drake, the head of the school’s Lunar and Planetary Laboratory. “I have Lockheed Martin in my office,” Drake said. “They want to fly a spacecraft to an asteroid and bring back a sample. Are you in?”
The two men met that evening with Steve Price, then a director of business development for Lockheed Martin Space, on the patio of a hotel bar in Tucson. Over drinks, they scribbled ideas on cocktail napkins. Price explained that the company’s engineers had developed technology that would allow a spacecraft about the size of a mail truck to rendezvous with a near-Earth asteroid, then enter a hummingbird-like mode and “kiss” its surface. The craft’s “beak” would be an unfolding eleven-foot-long mechanism with a cannister on its end, which would kick up material with a little blast of nitrogen. The spacecraft would stow this bounty in a protective capsule, fly back home, and then parachute it to Earth.
Asteroids interest researchers for many reasons. Because most predate the existence of the Earth, they harbor clues about the solar system’s long history. They often contain valuable industrial elements, such as cobalt and platinum, which are getting harder to find terrestrially. In the future, they might provide astronauts with fuel, oxygen, water, and construction material. And they can also pose a threat: in 2004, astronomers discovered that an asteroid named Apophis had an almost three-per-cent chance of striking Earth in 2029, conceivably killing millions. (It’s now projected to miss us by around twenty thousand miles—the equivalent of a round-trip flight from New York to Sydney.)
Although there is no life on asteroids that we know of, biochemists are interested in them, too. At some point in the Earth’s history, chemistry became biology: simpler molecules reacted with prebiotic molecules, and these in turn combined to create DNA, RNA, proteins, and other components of life. The precise conditions that caused this are impossible to determine, because eons of upheaval, including plate tectonics, have left the geologic record of Earth’s distant past incomplete. But asteroids—the building blocks of planets, frozen in time billions of years ago—offer chemical snapshots of what our planet was like before life existed. By crashing to Earth as meteors, they have also added to the planet’s chemical complexity. Many scientists now think that important chemical components of life weren’t cooked up on Earth but delivered, by asteroids, from the larger cauldron of the early solar system. Analyzing a sample retrieved from an asteroid could shed light on where biochemistry came from.
A month before Lauretta, Drake, and Price met for drinks, a NASA spacecraft named Stardust had visited a comet, Wild 2, and collected a single milligram of material—a snowflake’s worth. The craft would soon return it to Earth for analysis. The mission Price was describing could collect a pound of asteroid or more—enough for researchers to analyze for centuries. Still, Lauretta was hesitant. It would take years to get a mission approved; even if it launched, success wasn’t assured. Lauretta’s adviser in graduate school had been a scientist on Mars Observer, a NASA spacecraft designed to orbit the red planet and study its geology, atmosphere, and climate. The mission promised to break new scientific pathways and make careers. But in 1993, just as the spacecraft was about to enter orbit around Mars, it vanished, never to be heard from again. (NASA suspects a fuel-line rupture.)
At thirty-three, Lauretta was busy chasing tenure, not asteroids. He needed to write papers about astrobiology, not proposals for space missions. Yet what if they really could reach the asteroid and mine it? It would be an extraordinary accomplishment—like reaching back in time to gather a shovelful of primordial Earth. Lauretta and Drake talked it over, and arrived at a compromise. While Lauretta built his scientific career, Drake—a pioneer in the field of planetary science and a veteran of multiple NASA projects—would lead the mission “up and out,” shepherding the spacecraft from a bar in Tucson to deep space. Once the craft was spaceborne, Lauretta would bring it “down and in,” working as principal investigator to direct the study of the asteroid, handle the “kiss,” and the return of the material back to Earth. The process might take a decade. But it could also rewrite the story of life on Earth.
The early solar system was a chaotic place. Giant planets migrated, disrupting the accretion of Mars, building the asteroid belt, and then scattering some of it. A planet-sized object named Theia collided with the newly formed Earth, flooding its surface in a sea of magma and creating the moon. Prolonged fusillades of asteroids bombarded the planet. Eventually, Earth cooled and oceans emerged, spotted with volcanic island chains and deep-sea hydrothermal vents. Lightning storms rolled around the globe, and ultraviolet radiation rained down in the absence of an ozone layer. Several hundred million years later, life appears in the geologic record.
The alphabet of life is sometimes called CHNOPS: carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. These chemicals bonded variously to form water, lipids, simple sugars, and other precursor compounds for living things. But no one knows for sure how life happened, and the event has so far proved impossible to replicate from scratch in a laboratory. In 1953, Stanley Miller and Harold Urey, two chemists at the University of Chicago, published the results of an experiment that Miller had run attempting to simulate the process. They sealed hydrogen, water, methane, and ammonia in a closed system, heated it slightly, and applied electrical sparks. After a week, a dark goo appeared in the apparatus. They analyzed it and found that it contained several of the amino-acid building blocks used to create proteins. This advanced greatly the hypothesis of “homegrown synthesis.” In the most widely accepted version of the story, CHNOPS atoms in the primordial soup coalesced into nucleobases, the fundamental components of genetic material, and amino acids, which linked to form proteins, setting the stage for cellular life. Lipids formed cell membranes, and sugars offered energy and became part of RNA, a precursor of DNA that stored genetic information and replicated itself. “Once Darwinian evolution is in motion and life has sufficient information-carrying capacity to be inventive, life just goes,” Gerald Joyce, the president of the Salk Institute for Biological Studies, in California, told me.
The “exogenous-delivery” hypothesis is an alternative to homegrown synthesis. It posits that sustained salvos of asteroids and comets rich in prebiotic compounds crashed into the early Earth, contributing to the origins of life. Daniel Glavin, the senior scientist for sample return at NASA’s Goddard Space Flight Center, told me that, in recent decades, scientists have concluded that the atmosphere of early Earth was not actually conducive to making organic compounds. (Although Miller and Urey postulated an ammonia- and methane-rich atmosphere, planetary scientists now believe that it was mostly carbon dioxide with a bit of nitrogen.) “Regardless of the conditions of Earth, this stuff was coming in no matter what, delivering chemical building blocks—it’s almost a guarantee,” Glavin said. “It doesn’t matter what the earlier atmosphere was like.”
In 1969, a two-hundred-and-twenty-pound meteorite broke apart and slammed across a swath of farmland near the town of Murchison, in Victoria, Australia. Cosmochemists found it to be rich in prebiotic compounds and water-bearing minerals. More recently, Yasuhiro Oba of Hokkaido University in Japan, Glavin, and others used new techniques to re-analyze fragments of the Murchison meteorite. In the samples, they discovered a diverse suite of nucleobases—molecules which, on Earth, are involved in the storage and transmission of genetic information. “We can debate whether or not there would have been enough of these compounds delivered,” Glavin said. “I guess that's a fair question. But nobody debates the fact that asteroids and comets would have delivered at least some of them.”
When Lauretta met with Drake and Price in the Tucson bar, he looked the part of a NASA engineer—his hair short and neat, his shirt starched. But his history was turbulent. Lauretta grew up with a single mother in a single-wide trailer in the Arizona desert; his father, an addict, left when he was twelve. The first in his family to go to college, Lauretta paid his way as a short-order cook. At the University of Arizona he triple-majored in physics, math, and Japanese and was a devoted Deadhead. Long-haired and draped in tie-dye, he was determined to explore the outer reaches of consciousness.
Lauretta spent the summer before his fifth year of college cooking at a dive bar near Lake Tahoe and sleeping in a Volkswagen bus parked in a national forest. But he “wanted to test the limits of everything, to see how far into the wild I could go,” he writes, in his forthcoming memoir “The Asteroid Hunter.” One day, he saw an ad in the student paper: it read, “If you want to expand your universe and get paid for it too, do we have the job for you!” It was for the NASA Space Grant research fellowships, a multi-university program aiming to bring promising young scientists into the world of space. Lauretta responded, NASAand the University of Arizona accepted, and he soon joined SETI, the Search for Extraterrestrial Intelligence, where he wrote a computer program that could convert the spectral fingerprints of chemical reactions into a mathematical language that aliens might understand. The following year, he entered graduate school.
He earned his Ph.D. in 1997. Two years later, astronomers who were part of a joint NASA-Air Force-M.I.T. research program discovered a mountain-sized object moving closer to the Earth. Researchers determined that its odds of colliding with us were one in twenty-seven hundred—a little less than those of a professional golfer hitting a hole in one. They also concluded that the asteroid, later named Bennu, was likely a carbon-rich rubble pile. It had been part of a much larger asteroid that was formed near the beginning of the solar system, before a cataclysmic collision with another asteroid broke it apart. Bennu emerged from the shattered remains and was later hurled into an orbit near Earth. To scientists at NASA, it seemed like a good candidate for an exploratory mission.
But not right away. In the three years following their cocktail conversation, Drake and Lauretta wrote two book-length proposals for a small sample-return mission they called OSIRIS (Origins, Spectral Interpretation, Resource Identification, Security); NASA rejected them as being too expensive. They wrote a third proposal, in 2008, this time doubling the cost but increasing the spacecraft’s payload of science instruments. To reflect the larger scope of the mission, they appended “Regolith Explorer” to its name, calling it OSIRIS-REx. In December, 2009, Lauretta got a call from NASA. “Congratulations!” the voice on the other end said: OSIRIS-REx had been selected for further development. But a problem struck Lauretta right away. “Why aren’t you calling Mike?”
Drake, Lauretta learned, had been hospitalized with liver failure. After recovering, he returned to work and got a liver transplant, but he died in 2011. “Up and out” now fell to Lauretta—a scientist with little experience as a manager. The spacecraft was still under construction, and to come to grips with the billion-dollar project Lauretta crammed engineering textbooks. A government shutdown slowed the effort, as did Russia’s 2014 annexation of Ukraine’s Crimea, which cost OSIRIS-REx its Russian-made rocket engine. Even on the launchpad, the mission wasn’t certain. Days before launch, a nearby SpaceX rocket exploded, disrupting the OSIRIS-REx cooling system and nearly destroying its spacecraft.
Still, the mission launched on September 8, 2016. It took the spacecraft more than two years to cover the roughly two billion kilometres to Bennu. Up close, the asteroid itself proved challenging. The OSIRIS-REx team had correctly predicted its shape, direction of rotation, and polar orientation, but had misjudged its surface. “We had made the case to NASA that there was only one boulder, maybe ten metres across, on the surface of the asteroid,” Lauretta told me in 2018, the day after the craft’s arrival. But Bennu turned out to be a more rugged place. As the bird-shaped spacecraft swooped around the asteroid, it discovered a post-apocalyptic landscape—a tiny world in ruin.
For a year, the spacecraft circled Bennu, studying it remotely, while Lauretta and the team debated landing sites. Eventually, they selected a site designated Nightingale, in the northern hemisphere. It was a relatively fresh crater in a cold part of the asteroid, and featured large quantities of the fine-grained material perfect for the sample collector. But Nightingale wasn’t the safest site on Bennu; its most prominent feature was what the researchers called Mount Doom, a building-size boulder past which the craft would have to navigate.
After another ten months of study, on October 20, 2020, Lockheed Martin Space mission operations in Denver, Colorado, sent a command sequence to OSIRIS-REx. It took about eighteen minutes for the signal to travel to the other side of the sun. When it arrived, the truck-sized hummingbird tilted its solar-panel wings and extended its beak. Piloting itself, it inched downward and flew past Mount Doom, toward Nightingale. The surface was too rough for the craft to measure its altitude using its lasers; instead, the onboard computer worked optically, taking photos and studying the pixels to figure out where and how high it was. At what it believed to be sixteen feet above the surface, it sent a message to Earth: the “hazard probability” was zero per cent.
The collector pressed into the asteroid, burrowing in by an inch, then two. No one knew what the consistency of the surface would be. In mission control, people gasped as the beak continued into the surface, which turned out to be soft. The collector landed, and kept landing, reaching a depth of about a foot and a half before its backaway thrusters fired and stopped its descent. “We were basically plowing the collection head through a bunch of material,” Rich Burns, the mission’s project manager, recalled.
The beak withdrew. The team soon found that a flap inside the sample collector was wedged open by small rocks—a parting gift from Bennu. They had no choice but to stow the collector inside its return capsule that way. The wedged flap prevented the team from accurately measuring the mass of their sample, but they estimated it to be more than half a pound of material—enough for scientists to analyze in perpetuity. They completed some more observations. Then, in May, 2021, they turned the spacecraft around and set its course for Earth.
OSIRIS-REx allowed NASA to revise its odds of a collision with Bennu. Researchers can now say that it has a one-in-seventeen-hundred-and-fifty chance of striking Earth between 2135 and 2300—slightly more likely than a pro golfer hitting a hole in one. Through up-close imaging and spectrographic studies, they also know that water once flowed on Bennu’s parent body, and that the asteroid presently contains organic compounds. The only way to learn which ones will be to study them on Earth.
The mission has already been transformative through its discovery, on the asteroid, of minerals like the ones found at hydrothermal vents on Earth. Hundreds of millions of years ago, before Bennu broke away from its parent body, kilometre-scale reservoirs of carbonated fluids percolated in its interior. “It looks a lot like the rocks we’re getting from the mid-ocean ridge—from the alkaline hydrothermal vents,” Lauretta said, of the picture painted by the findings. “We think that those environments were key sites for the origin of life on Earth.” On this planet, he went on, it’s impossible to tell what kinds of basic chemical compounds those environments produced, because they’ve been “contaminated with life.” On Bennu, they haven’t been.
In 2020, a Japanese mission called Hayabusa 2 returned to Earth with around five grams of material from the asteroid Ryugu. The sample was scientifically valuable, but “they are limited to tens of milligrams worth of material for organic analysis,” Lauretta told me. “I’m willing to give ten grams of Bennu just to do the sugar chemistry alone—that’s still only something like five per cent of our sample.” Among other things, scientists will look for such building blocks as nucleobases or amino acids; in particular, they’ll be curious to see if they grew into chains in space. An “amazing discovery,” Lauretta said, would be a peptide (two amino acids or more bonded together) or a nucleic acid (a molecule with a nucleobase, a sugar, and phosphate). Such large compounds are likely to be a very small fraction of the sample’s total organic molecular inventory. “The additional mass is really going to help us here,” he said.
At 4:42 A.M. Mountain Time on September 24th, a guillotine-like system on the OSIRIS-REx spacecraft severed the cable that tethered it to its sample capsule, and a spring-like mechanism pushed the capsule away. The main spacecraft fired its thrusters and set a course for the asteroid Apophis. OSIRIS-REx was no more; it was now officially OSIRIS-APEX. (“It’s outta there!” Lauretta texted me.) Meanwhile, the flying-saucer-shaped capsule sped toward home at more than twenty-seven thousand miles an hour, then slammed into Earth’s atmosphere just over San Francisco. Lauretta was also midair, in a Bell 206 helicopter, one of four aircraft racing toward the expected recovery site in Utah, at the Dugway Proving Ground—one of the most isolated Army installations in the United States.
On board, Lauretta adjusted his headset. It was so noisy on the helicopter that he had trouble hearing the radio traffic about the capsule. “One hundred thousand feet,” a voice said. The capsule, heated by the atmosphere to more than five thousand degrees Fahrenheit, crossed the state of California in less than two seconds.
“Do we have drogue?” Lauretta asked. “They have not called drogue,” came the reply. A drogue chute should have deployed to stabilize the capsule and pull out the main parachute. But it looked like it hadn’t, and the spacecraft was tumbling. “Sixty thousand feet,” the voice said. Still no drogue. Lauretta began mentally preparing for the worst-case scenario: a crash landing, after which he’d pick bits of Bennu from the Utah sand. Whatever happened, he told himself, he would climb from the helicopter and remain composed.
At recovery-operations command, the team watched the main video screen. Then Anjani Polit, the mission-implementation systems engineer, pointed at something in the video. The room was silent, searching for what she saw, and then the crowd erupted.
“Main chute detected,” a voice on Lauretta’s headset announced. Hearing this, he burst into tears. Shortly after 9 A.M., Lauretta climbed from the helicopter, tools in hand. The silhouettes of desert mountains ranged in all directions. The charred capsule—his life’s work—sat lonely in shrub-speckled sand.
Tethered to a helicopter, the capsule was flown to Dugway; there, in a clean room, a team in protective suits stripped away its heat shield and back shell, revealing the sample cannister—a cylindrical container roughly the size of the wheel of a car. They sealed the cannister in a series of four protective bags, then put the bags in a large metal crate filled with continuously flowing nitrogen—an inert gas that would keep the sample pristine, even on Earth. The next morning, the crate was loaded onto an Air Force C-17 cargo plane, bound for a newly built laboratory at the Johnson Space Center, in Houston, where NASAalso preserves the Apollo moon rocks. “We fly some pretty weird stuff,” a member of the flight crew told me. “But this is pretty cool.” Lauretta boarded last, after various scientists and officials had posed for photos in front of the box. He hadn’t slept well the night before, but seemed wired. “I won’t relax until I see the sample,” he said.
In Houston, a ten-vehicle convoy, including a police escort, brought the sample to Johnson Space Center’s Building 31. Nicole Lunning, the curation lead at the facility, watched along with a team of engineers, material scientists, geologists, and biologists as the Lockheed crew rolled in the metal crate and its nitrogen tanks. “It’s like we’ve been doing all this training for a marathon, and now we’re going to start running it,” she told me.
The Bennu clean room at Johnson gleamed with silver pipes and panelling. At its center were two large windowed aluminum boxes, each about five feet wide. Lockheed Martin and NASA personnel dressed in full-body protective garb unpacked the cannister from its layers of prophylactic bagging, then loaded it into one box’s airlock; they inserted their forearms into the box’s manipulation gloves, interlacing their fingers to tighten the fit. Then, using the gloves, they started to disassemble the cannister, coördinating their movements with a series of carefully rehearsed hand gestures that they could discern even while masked and hooded. Lauretta watched from outside the room as the team removed and discarded the cannister’s fixtures, the hands in the box pointing to its parts in a kind of pantomime. Finally, a team member turned his palms upward, raising them slightly. It was time. In unison, four hands lifted the cannister’s lid. Outside the room, the NASA scientists gasped. Fine black dust coated the lid’s interior.
At last, Lauretta got gowned and masked, then entered the clean room himself. Wide-eyed, he walked slowly up to the box to get a closer look. Then, behind his mask, he smiled. The cannister brimmed with asteroid. It was a message from the dawn of the solar system. The next step was to decipher it. ♦
https://www.newyorker.com/science/elements/how-nasa-brought-an-asteroid-to-earth
