Having long broken its record of firsts on Mars, the Perseverance rover, still pootling around sciencing the sh*t out of the Red Planet, has just locked and loaded its third sample to send home to Earth. Peering inside a rock, Percy scraped a small patch to get a look at something no one has ever seen before: what lies under the surface layer. In this case, it appears rock that carries a curious "greenish mineral" known as olivine.  

"Another little piece of Mars to carry with me," the rover's representatives on Earth revealed on social media. "My latest sample is from a rock loaded with the greenish mineral olivine, and there are several ideas among my science team about how it got there. Hypotheses are flying! Science rules."

In the rover's enthusiasm to show that geology indeed rocks, it revealed a few days earlier that it had "zeroed in on its next target" with some images of the scraped-away surface to reveal the rock's insides, which appear to show some concentrated minerals and sediments. 

Olivine is magnesium iron silicate that makes up most of Earth's mantle. It is greenish in color, famously on Earth the cause of Hawaii's green sand Papak?lea Beach. Minerals like olivine are commonly found in solidified pieces of volcanic rock. 

Jezero Crater, where Percy first landed, was in fact chosen because it was once an ancient lakebed, part of a vast river delta where minerals such as olivines and carbonates, and organic molecules gathered. NASA is exploring the correlation between olivine and carbonates, which typically form when carbon dioxide mixes with liquid water. Because Mars has no plate tectonics, geological formations that formed billions of years ago haven't changed much today, offering us a fascinating insight into the planet's history and the potential habitability of Mars.  

As Percy's team pointed out, hypotheses about how the olivine may have got there are flying. More proof the crater is a dried up lakebed or an explosive ash deposit from an ancient volcano? Oh, to be a fly on the walls of NASA's Jet Propulsion Laboratory as they get stuck into studying these rock samples in *checks calendar* 2031. Stay tuned!