Bringing it All Back Home

NASA just retrieved a half-pound sample of a potentially hazardous asteroid. It's the latest in a series of grand projects to drag the heavens down to Earth.

Through most of history, there was an unbreakable rule about studying the heavens: You can look, but you can’t touch.

Ancient cultures widely regarded the rarefied world up there as fundamentally separate from the crappy one down here. Aristotle formalized this idea when he postulated that the cosmic realm is composed of “aether” (αἰθήρ), an immutable fifth element. His aether was fundamentally separate from the mundane, corruptible elements of the terrestrial realm: earth, fire, air, and water.

One of the great intellectual leaps of the modern scientific era has been the realization that there is no such separation between high and low, pure and impure. All of the universe is composed of the exact same kinds of atoms, obeying the exact same physical laws. Even so, knowing intellectually that “we are made of star-stuff” (as Carl Sagan famously intoned) is a lot different than physically grabbing a chunk of the heavens and bringing it down to us.

Which is exactly what the OSIRIS-REx spacecraft did.

After a seven-year journey, OSIRIS-REx released a 46-kilogram (101-pound) capsule, filled with rocks and dust collected from asteroid Bennu, and sent it on a path toward Earth. On the morning of September 24, the capsule burned a white-hot streak through the atmosphere, popped out its parachutes, and plummeted to the ground at the U.S. Department of Defense's Utah Test and Training Range.

Scientists at NASA’s Johnson Space Center are now methodically opening the cannister and retrieving pieces of Bennu, an asteroid whose orbit sometimes brings it perilously close to Earth. Those samples will help us understand how the solar system formed, and how our planet got its water and other elements crucial for life. The technology behind OSIRIS-REx could help deflect a dangerous asteroid if the need arises.

Above all, the spacecraft has further erased the barrier between us and the rest of the cosmos. Sure, we can no longer look to the heavens in search of perfection — but we can still reach upward to learn more, to become smarter and more capable versions of ourselves.

Snatch-and-Grab Heists in Space

OSIRIS-REx is just the latest step in a half-century-long quest to reach out and touch beyond our planet. The methods have varied widely, but the motivation is consistent. Sometimes direct physical evidence is the best (or only) way to explore space.

Here is a quick rundown of the out-of-this-world places we have touched before.

• Touching the Moon. The first mission to bring back samples from outer space was also the most dramatic. In 1969, after Neil Armstrong and Buzz Aldrin made history as the first humans to set foot on the Moon, they made history again by transporting 21.6 kilograms (47.6 pounds) of lunar rocks, dust, and core samples with them on their return to Earth. All together, the six Apollo missions that landed on the Moon collected 382 kilograms (842 pounds) of lunar material, still by far the largest haul of space-stuff.

  
  A year later, in 1970, the Soviet Luna 16 lander made history again, albeit with much less fanfare. The mission is mostly remembered, if at all, as a minor coda to the failed Soviet efforts to send cosmonauts to the Moon. But Luna 16 actually marked an important beginning: It was the first robotic spacecraft to bring back samples from beyond. Ever since Apollo 17 in 1972, every sample-return mission has similiarly been carried out by machines, not humans.

• Touching orbital debris. Talk about an anticlimax! After the end of the space race to the Moon, the next round of sample-return missions didn’t go beyond low-Earth orbit, and their job was to pick up the trash. NASA’s Long Duration Exposure Facility (LDEF), launched in 1985, and the Soviet Orbital Debris Collector (ODC), which flew in 1996-1997, were designed to sweet up natural and artificial particles in orbit, to analyze them and to study the hazards flying around up there. LDEF focused on damage caused by the debris. ODC collected bits of orbiting material and created the first census of the heavens immediate above Earth’s atmosphere.

• Touching the Sun. To be clear, nobody has landed a spacecraft on the surface of the Sun and grabbed a fistful of plama. Fortunately, there is no need to go there, because the Sun naturally comes to us. The solar wind — a constant stream of particles billowing out from the Sun’s outer layer, the corona — blows past Earth and out past all the other planets. In 2001 NASA launched the Genesis spacecraft, equipped with five collector arrays that flew in space for nearly three years, absorbing particles from the solar wind.

  All went well until Genesis delivered its Sun-infused plates back to Earth: The capsule’s parachute failed to open and it crash landed in Utah on September 8, 2004. Heartbroken researchers still managed to reassemble the remains and analyze a tiny sample of solar material.

• Touching a comet. Collecting and retrieving a piece of comet is an exceptionally challenging proposition even by space-heist standards, since much of a comet consists of frozen gas that evaporates with even the slightest kiss of heat. The Stardust spacecraft got around the problem by not attempting to collect a comet sample directly. Instead, it flew near Comet Wild 2 and allowed particles from the comet to fly into marshmallow-like sheets of aerogel aboard the spacecraft. Then Stardust swung around and returned its payload to Earth.

  The aerogel collectors trapped thousands of comet particles (about 1 milligram total), along with at least seven bits of interstellar dust. That’s right: We have grabbed pieces of other star systems and brought them home.

• Touching an(other) asteroid. OSIRIS-REx was not the first spacecraft to retrieve samples from an asteroid. That honor goes to Japan’s Hayabusa (“Falcon”) spacecraft, which visited asteroid Itokawa and returned to Earth in 2010. Due to technical glitches, Hayabusa came home carrying just 1 microgram of asteroid material, barely enough to support any meaningful analysis.

  The Japan Aerospace Exploration Agency (JAXA) tried again in with a sequel, Hayabusa-2, which completed its mission a decade later. The second spacecraft not only got its sample — 5 grams of asteroid Ryugu — it also dropped three small landers that hopped across the low-g surface, taking measurements and sending back spectacular landscape photos.

The Next Celestial Land-Grabs

There are a lot more reach-out-and-touch missions in the works. Next year, JAXA will launch the Martian Moons eXploration (MMX) mission to Mars’s potato-shaped inner moon, Phobos. Is Phobos a captured asteroid? A chunk of the Red Planet that was blasted into orbit by an ancient impact? MMX will bring back samples that should answer those questions.

In 2025, China’s Tianwen-2 will set off for a peculiar little object called Kamoʻoalewa, which orbits the Sun in tandem with Earth, behaving like a “quasi-moon.” One theory is that Kamoʻoalewa was created from material torn off from our own Moon after it was struck by an asteroid. Tianwen-2 will attempt to anchor itself to Kamoʻoalewa, collect rocks from its surface, and then ferry them to Earth for analysis.

And NASA is collaborating with the European Space Agency on the greatest sample-return effort of all: collecting pieces of Mars and transporting them to us. The grand goal here is to find out if life ever existed on Mars, or if it even persists there today in some form. Decades of searches using robotic probes have provided nothing more than ambiguous hints. The search for subtle traces of Martian life is simply too difficult. It requires the full power of the best laboratories on Earth.

The Mars Sample Return project is currently in trouble because of its huge and growing price tag, possibly as high as $11 billion according to a recent audit. The reason it is so expensive is because it is insanely ambitious. Landing safely on Mars is hard enough, but then the mission requires gathering samples; loading them into a rocket; shooting the rocket into orbit around Mars; meeting up with another, orbiting spacecraft; transfering the samples; launching the orbiter toward Earth; and ferrying the samples to a gentle touchdown. (Not to mention protecting the Mars samples to make sure they don’t contaminate Earth, or vice versa.)

The current plan is to have Mars samples in scientists’ eager hands in the early 2030s. If the engineers can pull it off, the Mars Sample Return mission will mark the first time that humans have touched another planet and brought back the proof. And if those Mars samples contain evidence of life, it would be another shocking moment of cosmic equalization: It would show that the universe is alive up there, just as it is down here.