A rock with the unassuming name SaU008 has the most remarkable biography in our entire solar system. It formed and spent billion of years on Mars before a giant impact flung it into space, where it spent more than a million years. In 1999, it hit Earth, specifically the country of Oman. And two years from now, NASA is going to take it home.

The agency announced Tuesday that a piece of the meteorite will travel to the red planet with the Mars 2020 rover, set to launch in July of that year. Sweet as reuniting the rock with its home planet might sound — at least to those who are into anthropomorphizing space rocks — the rover is actually set to blast the rock apart once it gets there to help calibrate its laser instrument, known as SHERLOC.

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Martian meteorites are incredibly rare, with fewer than 200 confirmed specimens on our entire planet. So why take even a piece of one of these irreplaceable objects and send it back to Mars, especially when it’s not like it’s going to be reunited with its rock family?

The sacrifice is all in a good cause, as ensuring the laser is precisely aligned will let NASA scientists study other rocks — those that never left home — with precision as fine as the width of a human hair.

Previous rovers have used terrestrial objects like metal or glass for calibration. Indeed, SHERLOC will also test itself using materials that will likely go into the creation of eventual spacesuits for human Mars missions.

NASA/JPL-Caltech

But using an actual Martian rock gives Mars 2020 the perfect training for actually studying the planet’s surface. It’s the ideal reference point.

“We’re studying things on such a fine scale that slight misalignments, caused by changes in temperature or even the rover settling into sand, can require us to correct our aim,” Luther Beegle, NASA’s principal investigator for SHERLOC, said in a statement. “By studying how the instrument sees a fixed target, we can understand how it will see a piece of the Martian surface.”

The laser uses ultraviolet light to detect carbon-based chemicals, which are the fundamental building block for organic life. SaU008 shares that same composition, and NASA scientists determined it was hardy enough to survive blastoff and landing and still be in usable shape.

NASA notes that this will be the first rock to make it all the way home to its world of origin, though it’s not the first to make the journey between planets. The now inactive NASA satellite Mars Global Surveyor also has a bit of Mars rock on board, floating in orbit above the planet.

When SHERLOC does blast that rock sample apart nearly three years from now, it will mark the end of a homecoming story more than a million years in the making. But at least that piece of SaU008 will be destroyed under the same skies it formed all those eons ago.