A small piece of rock that came from Mars will be going back to the Red Planet when NASA's Perseverance rover mission finally launches on Thursday.
The piece of martian meteorite, which had resided in the collection of London's Natural History Museum (NHM) for years, will go back home to act as a calibration target.
It will allow the Perseverance team to make sure that one of the rover's key instruments is working correctly during the mission as it tries to find signs of life on Mars.
Going back home
"This little rock's got quite a life story," Prof Caroline Smith, head of Earth sciences collections at the NHM, and a member of the Perseverance science team explained to the BBC.
"It formed about 450 million years ago, got blasted off Mars by an asteroid or comet roughly 600,000-700,000 years ago, and then landed on Earth; we don't know precisely when but perhaps 1,000 years ago. And now it's going back to Mars," she continued.
Essentially, the piece of Mars meteorite will be attached to the front of the Mars Perseverance rover, along with other materials, so that the machine's SHERLOC device can scan it to make sure the rover's instruments are working correctly.
By doing this, the team behind Perseverance will avoid having a "eureka moment," only to then discover that it was caused by a systematic error in SHERLOC's observations.
Collecting samples for future Mars colonizers
The fact is that analyzing rocks and minerals so far from home in search of traces of life — one of Perseverance's main objectives — is impossible to do with 100 percent accuracy.
"I don't think we'll ever be necessarily 100% sure because that's a hard measurement to make, which is why the sample-return aspect of Perseverance is so important," Dr Luther Beegle, SHERLOC's principal investigator from NASA's Jet Propulsion Laboratory, told the BBC.
The rover will collect its most interesting rock samples in small tubes, which will hopefully return to Earth in the 2030s after humans will have reached Mars for the first time.
NASA's Perseverance rover is scheduled to lift off on a United Launch Alliance (ULA) Atlas rocket from Cape Canaveral, Florida. A two-hour launch window is scheduled for Thursday, July 28, which will begin at 07:50 EDT local time.