Mars’ organic carbon was formed in batteries. Huge, naturally-occurring batteries — sort-of.

Image credits Aynur Zakirov.

The organic carbon found on Mars has both excited and perplexed researchers. When it was first discovered, this element reignited our hopes of finding life on the red planet. Later, it became apparent that things aren’t so straightforward. However, that still left us with a question: if not life, then what, exactly, created all this organic carbon?

New research from the Carnegie Institution for Science shows that the answer is even more surprising than you’d have assumed. Mars’ organic carbon may originate from a series of electrochemical reactions between briny liquids and volcanic minerals — in essence, natural batteries.

An electrifying find

“Revealing the processes by which organic carbon compounds form on Mars has been a matter of tremendous interest for understanding its potential for habitability,” says lead researcher Andrew Steele.

The research has roots in Steele’s previous work. Back in 2012, he led a team that found organic carbon in 10 Martian meteorites. The team also established that the carbon content wasn’t due to contamination from Earth and that it didn’t have a biological origin. All organic molecules contain carbon and hydrogen, and some include oxygen, nitrogen, sulfur, or other elements. Organic compounds are commonly associated with life, although they can be created by non-biological processes as well, which are referred to as abiotic organic chemistry.

To find out how this organic carbon was generated, the team worked with a trio of Martian meteorites that made their way to Earth — Tissint, Nakhla, and NWA 1950. Chemical analysis revealed that the hunks of rock contain organic carbon. Furthermore, its very similar chemically to the organic carbon found during the Mars Science Laboratory’s rover missions.

After establishing that the rocks did indeed contain organic carbon, and that its very likely originated on Mars, the team looked at their mineral makeup. Using advanced microscopy and spectroscopy, they determined that the organic compounds were likely created through electrochemical corrosion of minerals in Martian rocks by a surrounding salty liquid, brine.

“The discovery that natural systems can essentially form a small corrosion-powered battery that drives electrochemical reactions between minerals and surrounding liquid has major implications for the astrobiology field,” Steele explained.

Such processes aren’t new to science. We’ve seen evidence of them on Earth — particularly early in this planets’ history –, and now, we seem to have found some underway on Mars. That’s actually pretty good news — it means that they should, in theory, be able to take place anywhere igneous (volcanic) rocks are surrounded by brine. This means there’s a chance of seeing such processes unfolding in the subsurface oceans of Jupiter’s moon Europa or Saturn’s moon Enceladus. If this is the case, they could be used as a source of CO2 to jump-start potential colonies.

The paper “Organic synthesis on Mars by electrochemical reduction of CO2” has been published in the journal Science Advances.