NASA’s Perseverance rover, currently rolling around a dried out lakebed on the surface of Mars, has completed the first, critical step in a decade-long mission to return pieces of Mars to Earth. On the 190th day of its mission «Percy,» as the rover is affectionately known, overcame earlier sampling problems and snatched a core of rock, slightly thicker than a pencil, from Mars’ surface.

On Sept. 1, the space agency announced data had arrived from the Mars rover indicating it had successfully obtained a core from a briefcase-sized rock known as «Rochette.» But the team wanted to be «extra certain» that was the case. To be sure, the rover would need to take a few photographs of the drill device with one of its cameras.

The first images beamed back to Earth appeared to show rock had been successfully snatched. However, after an operation to vibrate the drill bit, a second round of images were taken. The sun, however, was not playing nicely with Percy. The lighting conditions were too poor to confirm exactly what was in the tube — and the team wanted to be doubly sure.

On Saturday, they got their wish.

Adam Steltzner, NASA chief engineer on the mission, tweeted his congratulations on Sep. 4. «We got it,» he wrote.

«For all of NASA science, this is truly a historic moment,» said Thomas Zurbuchen, NASA’s associate administrator for science.

The early images show a rust-red sediment that could be iron-rich minerals, according to Steven Ruff, a planetary geologist at Arizona State University and creator of YouTube channel Mars Guy. Percy’s landing site in Jezero Crater was once home to a great body of water and its two sampling attempts are already revealing some of the geologic history of Mars. «Both of those rock targets that they’ve interrogated look different than really anything that we’ve seen anywhere else on Mars,» Ruff says.

The successful collection is part 1 of the most elaborate and complex mail run of all time.

Getting the Martian rock core in the sampling tube is like placing a letter in an envelope. The next step is for Perseverance to process, seal and stamp that envelope and get it ready to send. Perseverance has 43 of these envelopes and can collect dozens of diverse rock samples. On Monday, NASA announced the rover had stored the sample in its interior, locked away in an airtight titanium tube. (I’m sure this will become a trivia question in the future so, for reference, the very first sample was stored in tube number 266)

Percy intends to leave these titanium tube-letters scattered across the surface of Mars for a mail carrier to collect at a later date. The key issue here is: The mail carrier hasn’t even been built yet.

NASA and the European Space Agency plan to send a Martian lander and sample collection rover to the surface of Mars in 2026. The rover (our mail carrier in this extended metaphor) will roll out, gather up Percy’s tubes and place them in its mailvan — a rocket bound for Earth. Sometime in early 2030, Percy’s mail will finally reach its intended recipient, provided everything goes according to plan.

Should the mail make it home, it would be the first time humans have returned materials from another planet.