Inside the vault: A rare glimpse of NASA’s otherworldly treasures

Ron Bastien holds an aerogel tile that flew into the tail of a comet, captured dust particles, and survived to tell the tale.

HOUSTON, Tex.—Building 31 on the campus of Johnson Space Center lacks the Tower of London’s majesty and history. No Queen’s Guard stand outside. But this drab, 1960s-era building is nonetheless where NASA keeps the crown jewels of its exploration program. Inside various clean rooms, curators watch over meteorites from Mars and the asteroid belt, cosmic dust, samples of the solar wind, comet particles, and, of course, hundreds of kilograms of Moon rocks.

In late December, Ars spent a day visiting these collections, including the rarely accessed Genesis Lab. While our request for a Moon rock keepsake was sadly rebuffed, we nonetheless got a VIP tour of every astromaterial NASA has collected from other bodies in the Solar System and beyond. With Senior Space Editor Eric Berger providing the words and Senior Technology Editor Lee Hutchinson capturing the photos, we can now offer an unprecedented look at how NASA protects its rarest and most valuable off-world samples.

Antarctic meteorites

To start, we wanted to see the famous Mars rock.

Before entering NASA’s meteorite lab, we had patiently removed our wedding rings and then donned booties, a surgeon’s cap, and a white gown. From the changing room, we moved into a small chamber for an air shower to remove loose particles from ourselves—it felt a bit like one of those hurricane “simulators” at an amusement park. Finally, we walked into a brightly lit, sterile room where NASA keeps asteroids that scientists collect in Antarctica.

The collection houses about 20,000 rocks, but the most famous of those rocks is ALH84001. Sometime around 16 million years ago, a large meteorite or asteroid 0.5 to 1 km across or larger struck the Martian surface and blasted some rocks into space at a speed greater than the red planet’s escape velocity. One of them flew through space until about 13,000 years ago when it crashed into Antarctica. A team of scientists funded by the National Science Foundation found it during the winter of 1984, although they didn’t know it had come from Mars at the time.

Americans weren’t the first people to realize that Antarctica was the best place in the world to find meteorites. Japanese researchers had been traveling there to collect them since the 1960s. When University of Pittsburgh geologist William Cassidy learned of their successful discovery of all kinds of meteorites in 1973, he convinced the National Science Foundation to fund US expeditions. By 1976, Americans were joining the Japanese scientists in the field; the NASA lab was created two years later to house the samples.

Although the flux of meteorites into Antarctica is no different from anywhere else in the world, the continent has an arid, cold environment with few people, helping meteorites stay intact. The geography helps as well. As massive sheets of ice flow away from the South Pole, they run up against the Transantarctic Mountains, a tall range running 3,500 km across the continent. The ice increasing in thickness as it piles up against the mountains, meteorites fall onto the wide, flat polar region and are swept up in this flow, which turns upward upon reaching the mountains.

“As this ice turns up, the right combination of elevation and temperature creates an ablation zone for the ice, and the meteorites stay behind,” explained Kevin Righter, a planetary scientist and the Antarctic meteorite curator. “There are areas on the ridge with incredible concentrations of meteorites.”

The rocks are kept frozen until they reach the lab in Houston. This prevents further rusting and alteration of minerals that can occur at higher temperatures. Once in the lab, scientists thaw the rocks in a warm, dry environment that rapidly carries the moisture away. Afterward the rocks are kept inside nitrogen cabinets to prevent further oxidation.

About a decade after scientists found ALH84001, they realized it and about a dozen others like it almost certainly came from Mars, because it contained traces of gas just like those in the Martian atmosphere.

This led to an unexpected surge of interest in the lab. As Johnson Space Center’s Dave McKay and other scientists examined the rock, they found tiny, odd features that resembled worm-like fossils. Upon this basis, the group published a 1996 article in the journal Science in which they claimed to have found evidence of ancient life on Mars. Overnight, the Antarctic meteorite lab became one of the hottest places in the world. Scientists and journalists alike clambered to get inside.

Today, with NASA rovers scrambling all over the surface of Mars, one might think finding new Martian rocks in Antarctica, where they have been exposed to Earth’s atmosphere for thousands of years, would not be scientifically useful. That view is wrong, Righter said.

In addition to its Mars rocks, NASA has hundreds of meteorites from the large asteroid Vesta, and some they believe come from other bodies in the asteroid belt. There are also meteorites from the Moon, and Righter said these offer a valuable diversity compared to our sampling at the six lunar landing sites. Then there are a few dozen "oddball" meteorites, which scientists cannot trace. Could one of them have originated on Venus or Mercury? It’s possible, Righter said. The discovery of new, interesting meteorites is why scientists return to Antarctica every November.“Martian meteorites are still of great interest,” he explained. “We’ve gotten a lot of great information about Mars from the rovers, and a lot of the emphasis has been on finding rock evidence of flowing water, volatiles, and things that might relate to life. However when we collect Mars rocks here on Earth, there’s not a lot of evidence for those kinds of processes in the meteorites. So we think we might be missing a significant portion of the rock diversity on Mars in our current collection. If we actually found a piece of sedimentary rock from Mars there are so many kinds of measurements you could make in labs on Earth compared to what we can do with robotic missions.”

As for ALH84001, Righter retrieved the bagged meteorite in short order. “This is it,” he said, setting it onto a scale. “You can see it’s a big hunk of rock.” It was a big hunk of rock. Shortly after the watershed paper inScience, a majority of the scientific community came up with other, seemingly more plausible explanations for the small fossil-like tunnels. The rock is lifeless today and probably always has been.

Still, the search goes on. If the Universe is going to bring chunks of other worlds to Earth, the least we can do is go and pick them up.

Comets and stardust

It stood on a table, right there in front of us. Eleven years ago, this tennis racquet-shaped tray of 132 tiles, each filled with aerogel, flew through the coma of Comet Wild 2. Passing within 240 miles of the nucleus, it captured tiny bits of a comet for the first time. The Stardust spacecraft then safely returned to Earth in 2006. Now, nearly a decade later, researchers are still carefully inspecting each tile to find and collect dust particles that became embedded in the aerogel.

The aerogel itself is kind of a magical substance. It looks like frozen smoke. With a density 1,000 times less than glass, it is essentially air. And yet it is perfect for stopping dust particles smaller than a grain of sand, traveling six times the speed of a rifle bullet. The particles create tracks through the aerogel before stopping, yet don't end up being destroyed.

Ron Bastien, manager of the Stardust lab, held one of the tiles up for inspection during our visit. “If you look closely at this, that line running down through it, that’s an impact where a small particle hit that aerogel and traveled down through it,” he said. “If you look down at the bottom of that track there would be a particle.” More accurately, this is a particle from a comet now hundreds of millions of miles away.

Dozens of research groups have examined the cometary material. To their surprise, they found that comets formed under both icy and white-hot conditions. Scientists had understood the ice of comets formed at the frigid edge of the Solar System beyond Neptune, but now they realized that the rocky cores formed much closer to the Sun.

They know this because some of the particles collected by Stardust were white and irregularly shaped. These Calcium Aluminum Inclusions are believed to have formed very near the surface of the Sun at the fiery inception of the Solar System. They are among the most ancient materials in the Solar System at 4.56 billion years old. And now scientists had found them in comets that traveled to Pluto and beyond. This gave scientists further confidence that, in studying comets further, they were truly looking at time capsules that could tell them much about how the Solar System formed.

Because the aerogel tray was only exposed to the comet for a relatively short period of time, the Stardust mission performed double duty by carrying a second tray of tiles.

During the long flight to and from Comet Wild 2, the spacecraft exposed this second tray to collect interstellar dust. Unlike the profusion of comet particles, scientists only expected to collect a few of the tiny interstellar particles, about a micron in size, coming into the Solar System at odd angles. So after the spacecraft returned to Earth, the scientists asked for help finding them.

They set up an automated scanning microscope in the Stardust lab to capture images of the entire interstellar collector, and scientists invited the public—“dusters”—to help find particle tracks in individual tiles through theStardust@Home project.

In August, 2014, they announced that they had found seven interstellar dust particles, the first samples of dust from stars outside of the Solar System. Dusters had found two of the particles. Even now, scientists are only beginning to understand the nature of these particles, some of which are “fluffy” like snowflakes and may have come from a supernova explosion millions of years ago.

Genesis

We had been suiting up for the better part of half an hour when Judith Allton paused to ask us a question: “I forgot to ask you guys, do you need a restroom break?” Fortunately, we didn’t.

NASA keeps some of its most sensitive samples in the “Genesis” lab, which has the most rigorous cleanliness protocols of any facility at the space center. The Genesis lab houses particles from the solar wind, essentially tiny bits of the Sun which hold clues about the composition of the solar nebula at the time when the planets formed.

That morning we had been instructed to not wear wedding rings, nor scented deodorant. In the anteroom we had donned gloves, booties, and hair nets. In the “gowning” room, we had put on masks, full-body polyester suits, head covers, boots over the body suit and booties, and a second pair of gloves. Also, they’d taken my notepad and given me “clean” paper—once inside I’d receive a clean Sharpie pen. Nor did our photography equipment escape the cleanroom regime: we had to spend several minutes rubbing down cameras and lenses and tripods with alcohol wipes until the scientists were satisfied that the devices were reasonably dust-free.

After this entire process, we asked if the lab gets a lot of visitors. “I don’t take people in,” Allton, the lab's curator, said. “You guys are special. The main reason is, people are dirty.”

In 2001 NASA’s Genesis spacecraft launched into space and traveled to the L1 Lagrange point, where the gravity between Earth and the Sun cancel one another out. For more than two years, the spacecraft’s arrays collected ions flowing from the outer layer of the Sun. Wafers made of various high-purity materials, including aluminium, sapphire, silicon, germanium, gold, and diamond-like amorphous carbon, were designed to collect different types of solar wind.

It was hoped the spacecraft would collect billions of solar particles, equal in weight to a few grains of salt, before flying back to Earth. But during the final phase of its return, the spacecraft’s parachute system failed, and it crashed into the Utah desert at a catastrophic speed of 300 kph.

It could have been game over. For most experiments it would have been game over. But the solar wind particles were embedded some 40 to 100 nanometers below the surface. The team of researchers, including Allton, found they could salvage some of those particles if they carefully cleaned the bits of wafers that survived the collision with Earth. “We had envisioned that we would get the whole panel back here in one piece, under a nitrogen purge,” Allton said. “Well, that’s not what we ended up with.”

So the scientists adapted. Inside the brightly lit, clean room, Carla Gonzalez showed us how by turning a flow of ultrapure water onto a sample wafer spinning at several thousand rpm. Over the course of 15 minutes, she used the water to clean terrestrial dirt and spacecraft debris from the wafer. This process left no solvents behind. In the decade since Genesis returned to Earth, Allton, Gonzalez, and others have cleaned and classified more than 2,000 samples, many of which are now available to scientists for research.

This processing has worked. Scientists have met most of the mission’s research objectives, including making the surprising discovery that the Sun is richer in oxygen-16, the most common isotope, than the Earth. This discrepancy has led scientists to study how this oxygen got stripped away from the Sun during its first few million years of existence, which in turn has led to new insights about the nature and development of the early Solar System.

As we neared the end of our tour in the impeccably clean laboratory, Gonzalez removed the sample wafer from the ultrapure water. I asked if it was now so clean we could eat off of it. “I suppose so,” Allton said. “But it would break my heart if you did.”