NASA just held a press conference and has announced two interesting bits of new information from its Curiosity rover. News story from the American Chemical Society here: https://cen.acs.org/physicalChemistry/astrochemistry/Ancient-organic-molecules-found-Mars/96/i24 First, they have found organic chemicals in sedimentary rock a location that was once a liquid water lake, long long ago (3.5 billion years ago). The chemicals seem to be small fragments of what once were bigger macromolecules. But it isn't entirely clear that the macromolecules were ever associated with life. Assuming Mars and Earth formed at the same time, Mars would have been about 1 billion years old when this lake existed. Life on Earth may (speculatively) have been a few hundred million years old at that time, probably very simple prokaryotic cells like bacteria and archaea. The molecules found were (in the words of the ACS story) "thiophene, methylthiophenes, and methanethiol, which are probably fragments from larger organic macromolecules in the sediment. These organic deposits may be something like kerogen, the fossilized organic matter found in sedimentary rocks on Earth that contain a jumble of waxy hydrocarbons and polycyclic aromatic hydrocarbons." I wonder whether the "probably" and the "may" in the source of these thiols being kerogen is more than mere speculation. On Earth kerogen is an early stage in the evolution of petroleum, and it typically has a living origin. But in this Mars case we still can't be certain that these small organic molecules observed really are fragments of kerogen, or that the kerogen indeed had a living origin. https://en.wikipedia.org/wiki/Kerogen The full-text of the paper published by Science (which I haven't read yet) is here: http://science.sciencemag.org/content/360/6393/1096.full The other news concerns methane outgassing. Methane has been noted in low concentrations previously, but seemingly at random times. Now Curiosity has determined that it's always there, but the concentrations vary seasonally. Curiosity also detected occasional spikes in the concentrations. What makes this interesting is that one of the possible sources of the methane might be microbial action. (It is on Earth.) But the source on Mars might have nothing to do with life.
PAHs. Mars smells like a barbequed steak. Now I want to go there even more. https://www.precisionnutrition.com/how-to-grill-healthy-food "Polycyclic aromatic hydrocarbons (PAHs) form when meat is charred or blackened, or when fat from the meat drips onto the hot surface of the grill. This forms PAHs in the smoke, which then permeates the meat."
