> At least within the precision limits of the Perseverance’s instruments, the material roughly matches terrestrial kerogen. Using the word “kerogen,” though, was a no-go, the researchers decided. On Earth, kerogen is made almost exclusively of biological matter, mainly fossilized microbes that were buried millions of years ago. “The term kerogen implies biogenic source,” Murphy explained. “Macromolecular carbon implies we don’t know whether its origin is biotic or abiotic.”

I'm pretty convinced the catchphrase "There's no Planet B" is imprecise. In fact there is a Planet B, Earth. Mars was Planet A[1], our ancestors came here billions of years ago, perhaps in a rock fragment full of organics like this "completely not shale".

[1] https://badspacecomics.com/apostles-of-mercy

Bad news is that if we screw the Planet B where our lineage took refuge after Mars dried out, there is no habitable Planet C left in the solar system.

They talk about bringing these samples back to earth but don't mention how. Have they already planned how to get perseverance and its samples back?

The surface layer of a planet maybe sterile, but the deep crust biom may linger on..

"not clear why", by which I guess the implied ask is how it got there, which is likely because the universe has a bunch of carbon in it, and a whole other bunch of ways of distributing it, while also making and remaking it via a couple of other processes that the universe has running,

but the real ask, is the martain carbon concentrations derived from life, like the very random rock my left shoulder is leaning on, with whit patches, speckled with black dots, not counting the lichens, clearly also making the rock there home. and that answer will probable come from someone going to mars and doing a few simple tests. Mars ho!