Scientists blew up a piece of Mars, you’ll be amazed what they found out!

Or: Indigenous Organic-Oxidized Fluid Interactions in the Tissint Mars Meteorite, Jaramillo EA, Royle, SH, Claire MW, Kounaves SP and Sephton MA. (2019). GRL

Apologies for the clickbait title, it seems as though this is now compulsory with all space-related scientific writing. I did blow up a piece of Mars though and I did find stuff out, you can read all about it in a paper I co-authored which is now published in GRL. Alternatively, here is a summary, it is massively biased towards the organic geochemistry side of things as that is the bit I did (and the only bit I really understand).

On the 18^th July 2011 a meteorite was observed exploding over the desert in Morocco. Over the following few months fragments were collected near the village of Tissint, which the meteorite has been named after. Very few meteorites have actually been found so soon after impact, usually they have sat around on Earth for many years. In this time they become contaminated, they sit in dirt, water flows through them and (Earth) microbes make them their home. Previous studies have shown that the Tissint meteorite is actually a piece of Mars; Martian igneous rocks that were formed around 600 million years ago were blasted off into space by a large meteorite impact on the surface of that planet around 1 million years ago. This means that the Tissint meteorite gives us a unique opportunity to explore the geochemical processes happening in the Martian crust, with the freshest samples we’re going to get until (if) Mars Sample Return happens.

the fragment of Tissint used in the study

Elizabeth, the lead author, had collected samples from the fall site and analysed them, along with fragments of the meteorite to compare their salt contents as part of her PhD. This had raised a few questions that needed answering, so I was drafted in to pyrolyze (i.e. flash heat/blow up) the same samples to see what organic molecules were present and what they could add to the story.

Tiny bits of Mars ready for me to grind up and pyrolyze

As I have mentioned before in my posts, organic does not equal biological. We were not looking for aliens here, organic molecules are just those molecules that contain carbon and hydrogen. While they are the ‘building blocks’ of life, they also form from non-biological process, including in space and in hot fluid (hydrothermal) systems deep underground. As such they are common in meteorites and comets and we expect to find them on Mars.

Looking at the organic content had 2 purposes: 

1. We wanted to know if the meteorite showed signs of becoming contaminated in the short period of time before it was found (biologically sourced contaminants from Earth-bugs finding their way into the samples would be pretty easy to spot);

2. If no signs of contamination then we hoped to identify actual Martian organic molecules and see what they could tell us about ancient Mars.

Neither the inorganic salt content nor the organic molecular compositions of Tissint suggested that the meteorite was contaminated (Yay!). While I detected evidence of microbial life in the soil samples, these hadn’t got into the meteorite. What I did detect in the meteorite were simple aromatic (ring-shaped) organic molecules, some of which contained sulphur. This was quite exciting as these were the same kinds of compounds that have been found in other Martian meteorites AND on the surface of Mars by the Curiosity Rover. Suggesting that we had detected actual Marian organic matter!

Organic molecules found on Mars (by Eigenbrode et al. (2018)), we also found various thiophenes, alkylbenzene, chlorobenzene and napthalene in Tissint, along with other sulphur-bearing compounds 

The mixture of salts and organic molecules within Tissint suggest that less than 600 million years ago, recent in Mars-terms, an oxygen-rich, salty water-brine flowed through the near-surface crustal rocks of Mars. Electrochemical reactions likely formed both the organic molecules and the salts in this fluid as reactions occurred on the surfaces of variously charged minerals.

As the composition of this fluid was similar to seawater and, there was a readily available source of organic carbon as a food source, this could have produced a temporarily habitable environment near the surface of Mars during the late Amazonian period. This is much later than the surface of Mars was potentially habitable and although we don't go as far as saying anything actually lived in it, it could have done....