By Devin Coldewey

That NASA intends to collect a sample from Mars and return it to Earth is well known — they’ve said so many times. But how would they go about scooping up soil from the surface of a distant planet and getting it back here? With a plan that sounds straight out of sci-fi.

Described by the project’s lead scientist in a virtual meeting reported by Nature, NASA and the European Space Agency’s proposed Mars sample retrieval program is perhaps the most ambitious interplanetary mission ever devised. (I’ve asked NASA for more details and will update this post if I hear back.)

The first part of the plan is already public: It relies on the Mars Perseverance rover, which is currently being prepared, despite the pandemic, for its launch in July. Perseverance will perform sampling using a drill and soil scoop, filling 30 small tubes with the results of its Martian delvings and storing them on board.

The next step is where things start to get wild.

A second spacecraft will travel to Mars, launching in 2026 and arriving in 2028, and land near Perseverance in Jezero crater. It will deploy a second rover, which will roll over to Perseverance, collect the sample tubes, and deposit them in the “Mars ascent vehicle” that also came with it. This small rocket will launch itself and the samples into orbit — the first time a spacecraft will have taken off from the surface of Mars.

At this point, a third spacecraft waiting nearby will synchronize its orbit with the sample retrieval craft, collect it, and return to Earth with it, where it will make its — controlled, one hopes — reentry in 2031.

“This is by no means a simple task,” said head of NASA’s Mars exploration program Jim Watzin in the meeting, uttering perhaps the greatest understatement of the 21st century so far. “But we have kept it as simple as possible.”

Indeed, it is hard to think of a simpler process given the restrictions of travel to Mars. Naturally Perseverance can’t shoot the samples back on a ballistic trajectory itself for a variety of reasons. That necessitates a second surface vehicle. And engineering that vehicle to fill the roles of outbound spacecraft, lander, rover, ascent vehicle, and return spacecraft may simply be impossible. So a third spacecraft is needed as well.