And today, a rover is expected to land on Mars, carrying empty canisters to fill with soil for its return to Earth someday, in what would be the first-ever sample return from another planet.
Scientists have wanted a piece of Mars for years. Not in the form of meteorites that fall to Earth—they have some of those already—but stuff right from the source. Cosmic radiation and extreme heat of reentry tarnish the bits of Mars that manage to reach us on their own, obscuring the subtleties of a world that, billions of years ago, resembled our own. For decades, scientists have explored the planet with rovers, orbiters, and landers, but these missions can carry only a few instruments at a time, and can’t match the equipment of the world’s best research facilities. A tiny piece of Mars in a lab, as pristine as it was on that distant rust-colored surface, is almost as good as being there.
The mission, as cutting-edge as it is, is reminiscent of an older way of doing science. In the age of Charles Darwin and Alexander von Humboldt, naturalists and other explorers traveled, welcome or not, to faraway places to gather trunkfuls of specimens for closer study. They sent their treasures back home on long sea journeys, during which hungry rats and pestilence were the most immediate dangers. Like those bygone voyages, modern efforts in space remain full of risk and unknowns. Sample missions unspool across many years and hundreds of thousands, or even millions, of miles, with potential technical tangles at every step. The Japanese mission that brought those asteroid samples to Australia a decade ago was riddled with glitches from start to finish. Transporting scientific treasures from continent to continent is no longer particularly difficult, but dispatching a robotic probe deep into space still means that years of work could come to nothing.
The first sample-return missions went to the moon. In the late 1960s and early ’70s, Apollo astronauts gathered more than 800 pounds of material from the lunar surface, guided by the wish lists of geologists back home and whatever happened to catch their eye. These were the first and last celestial samples collected by hand.
Spacecraft now do that work, but machine explorers require a bit more programming than human ones. The new Mars rover, named Perseverance, will use its robotic arms and other instruments to drill into the rock, scoop soil into test tubes, and seal them. Engineers have tested it countless times, and even included a cleaning mechanism meant to shake loose any Martian dust that gets stuck in the hardware’s crevices.
The capsules inside the Perseverance rover, 43 in total, are each about the size of a standard laboratory test tube. They are designed to protect samples from the Martian elements, and were cleaned meticulously, so that whatever comes back is “irrefutably Martian,” says Pavlina Karafillis, an engineer at NASA’s Jet Propulsion Laboratory who tested the tubes. To handle the capsules on Earth, Karafillis wore two layers of protective clothing, two pairs of gloves, and goggles. The biggest potential source of contamination is the people working on these capsules. “The contamination-control people sent out a list of approved hair products that were unscented, to make sure that, basically, the outgassing of our hair products didn’t impact the tubes at all,” Karafillis told me.