The Perseverance rover may have just found evidence of organic compounds in the rocks of Jezero Crater.
Previous studies have found evidence of organic compounds on Mars before. The Curiosity Rover and the Mars-Express the orbiter has provided proof of this, as have the data from Perseverance. None of this necessarily involves any kind of biology – a variety of geological phenomena can facilitate carbon-based chemistry, after all.
But studying these compounds in more detail could tell more about Mars’ water history, and whether or not the Red Planet could have at least once hosted some sort of living process.
Obtained from two different sites in the crater, the minerals contain evidence of aquatic processes that dig the perfect little pits for preparing organic chemistry. Depending on one type of analysis, they may even contain traces of carbon-based compounds.
Jezero Crater was, many aeons ago, a much wetter place than it is today. There are still traces of the old river delta that once stretched across the crater floor. Interactions between water and rock can result in the formation of organic compounds of the type already found in the ancient delta.
However, the question of whether there are also organic compounds elsewhere on the crater floor remained open. Scientists expected the rock there to be largely sedimentary, deposited by water long ago – but, when Perseverance arrived, we learned that much of the crater floor was volcanic and not sedimentary.
Using Perseverance’s SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals) instrument, an international team led by planetary scientist Eva Scheller of Caltech and MIT conducted a survey of igneous rocks in the bottom from the crater.
They used deep ultraviolet Raman spectroscopy and fluorescence spectroscopy on three rocks from two crater sites and found signs that significant water contact had weathered the rocks.
There was evidence for two types of weathering, which suggested two distinctly different aqueous environments, at different times in the distant past.
First, reactions with liquid water resulted in the formation of carbonates in olivine-rich igneous rock about 3.8 to 2.7 billion years ago.
Later, around 2.6 to 2.3 billion years ago, salt-rich brackish water could have induced the formation of sulphate-perchlorate (salt) mixtures in the rocks.
Carbonates and perchlorates need water to penetrate rocks, dissolving and depositing minerals in hollows created by water erosion. It is unlikely that water has touched the rocks since the perchlorates were deposited, as the perchlorates dissolve easily.
In all three rocks, the team found fluorescence signatures consistent with aromatic organic compounds similar to benzene. These appear to be conserved in minerals related to both aqueous environments, the researchers say, but we can’t yet tell what they are.
“Collectively, the data show that drill samples collected by Perseverance from the floor of Jezero Crater are likely to contain evidence of carbonation and the formation of sulfates and perchlorates,” they write in their paper.
“Fluorescence signatures consistent with organics present in these materials indicate an interaction between igneous rocks, aqueous weathering, and organic matter on Mars.”
Perseverance has long since moved away from the sites where these data collections were conducted. Fortunately, he also collected samples of the rocks themselves, in case they could be brought back to Earth later on a mission that has yet to be launched.
“I hope that one day these samples can be returned to Earth so that we can examine evidence for water and possible organic matter, and explore whether conditions were suitable for life early in Earth’s history. March”, says geochemist Mark Sephton from Imperial College London in the UK.
So it will take some time before we get the confirmation we need. But bringing these rocks to an Earth lab, with equipment capable of studying the compounds in detail, could tell us more about Mars’ past habitability or uninhabitability.
In the meantime, Perseverance, continuing its slow exploration of the crater of Jezero, could pick up more solid clues.
We just have to wait and see.
The research has been published in Science.
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