NASA’s Perseverance rover has been on Mars for fifteen months now and is about to begin its trek into the fossil delta of Jezero Crater. It’s a big deal for the mission, because the delta is where water once flowed long enough and strongly enough to smooth, round and move large rocks.
Since proof of the long-ago presence of water means the area was potentially habitable — especially a delta that spreads out into what were once calm rivulets — this is where the astrobiology goals of the mission come to the fore.
Or so the Perseverance team thought it would play out.
But the big surprise of the mission so far has been that the rover landed on igneous rock, formed in the Martian interior, spewed out and crystalized and solidified on the surface.
That Perseverance would land on igneous rock was always seen as a possibility, but a more likely outcome was landing on sedimentary rock as in Gale Crater, where the Curiosity rover continues its decade-long explore. Sedimentary rock is laid down in layers in the presence of water.
As explained last week at the Ab-Sci-Con 2022 conference in Atlanta, the deputy program scientist for the mission — Katie Stack Morgan of NASA’s Jet Propulsion Lab — from the mission’s perspective the presence of both igneous and nearby sedimentary rock offers the best of both worlds.
While sedimentary rock is traditionally where scientists look for signs of ancient life, igneous rock can date the site more exactly and it can potentially better preserve any signs of early microbial life.
And in the context of Perseverance, the presence of accessible and compelling igneous formations provides for the diversity of rock samples called for in the Mars Sample Return effort — another central part of the rover’s mission.
“We did a lot of work with our different instruments to come to the conclusion that we landed on igneous rock,” Stack Morgan later said in an interview. … Read more