In 1996, amidst a huge fanfare which included a statement by then US President Bill Clinton, a team of researchers announced they had discovered evidence of past Martian microbial life within a meteorite called ALH84001, discovered in the Allen Hills of Antarctica in 1984.
The claim lead to a high degree controversy, with many scientists disputing the findings of the original team. While that discovery has never been conclusively disproved, it has never been verified, either. However, it has – alongside the controversial results from two of the Viking Lander experiments in the 1970s – encouraged teams researching the potential for microbial life on Mars to be cautious in their work.
So it was with a sense of excitement that on Thursday, June 7th, 2018, NASA announced that the Mars Science Laboratory (MSL) Curiosity rover has once again found potential evidence of both organic molecules and methane on Mars. The news came via two papers Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars and Background levels of methane in Mars’ atmosphere show strong seasonal variations.
In the first paper, the authors indicate how Curiosity’s Sample Analysis at Mars (SAM) suite detected traces of methane in drill samples it took from Martian rocks in 2016. Once these rocks were heated, they released an array of organics and volatiles similar to how organic-rich sedimentary rocks do on Earth – where similar deposits are indications of fossilised organic life.
What is particularly exciting is the first paper indicates that the material discovered on Mars is similar to terrestrial kerogen, a solid organic matter found in sedimentary rocks. Comprising an estimated 1016 tons of carbon, Kerogen on Earth exceeds the organic content of all living matter on Earth by a factor of 10,000.
Essentially, want happens on Earth is that organic material gets laid down within the sedimentary layers, then over the aeons, fluid flowing thought the rock initiates chemical reactions to break down the organic deposits until only the insoluble kerogen is left. It has already been established that Gale Crater was once the home of several liquid water lakes, and also that perchlorate salt – particularly good at breaking down organics – is present on Mars. Hence why the discovery of the kerogen-like material on Mars is a cause for excitement – it could be a similar process to that seen on Earth is present.
While the team responsible for the styudy point out the material SAM has found is similar to an insoluble material discovered in tiny meteorites known to fall on Mars, that it might have formed naturally on the planet is somewhat strengthened by the fact Curiosity has previously confirmed Gale Crater contains the chemical building blocks and energy sources that are necessary for life. However, the legacy of ALH84001 urge caution when dealing with these findings from the rover, as one of the authors of the first paper explained.
Curiosity has not determined the source of the organic molecules. Whether it holds a record of ancient life, was food for life, or has existed in the absence of life, organic matter in materials holds chemical clues to planetary conditions and processes… The Martian surface is exposed to radiation from space. Both radiation and harsh chemicals break down organic matter. Finding ancient organic molecules in the top five centimetres of rock that was deposited when Mars may have been habitable, bodes well for us to learn the story of organic molecules on Mars with future missions that will drill deeper.
Jennifer Eigenbrode, co-author, Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars
In the second paper, scientists describe the discovery of seasonal variations in methane in the Martian atmosphere over the course of nearly three Mars years, which is almost six Earth years. This variation was also detected by Curiosity’s SAM instrument suite over the 3-year period.
Water-rock chemistry might have generated the methane, but scientists cannot rule out the possibility of biological origins. Methane previously had been detected in Mars’ atmosphere in large, unpredictable plumes. This new result shows that low levels of methane within Gale Crater repeatedly peak in warm, summer months and drop in the winter every year.
This is the first time we’ve seen something repeatable in the methane story, so it offers us a handle in understanding it. This is all possible because of Curiosity’s longevity. The long duration has allowed us to see the patterns in this seasonal ‘breathing.’
Chris Webster, co-author, Background levels of methane in Mars’ atmosphere show strong seasonal variations
In 2013, SAM detected organic molecules in rocks at the deepest point in the crater. These more recently findings, gathered further up the slopes of “Mount Sharp” add to the inventory of molecules detected in the ancient lake sediments. Thus, finding methane in the atmosphere and ancient carbon preserved on the surface gives scientists confidence that NASA’s Mars 2020 rover and ESA’s ExoMars rover will find even more organics, both on the surface and in the shallow subsurface.
NASA Successfully Transfers Sample
Following my last two Space Sunday updates concerning attempts to resume the collection of rock samples using Curiosity’s drilling mechanism, the US space agency has indicated a successful transfer of material gathered within the rover’s hollow drill bit into the rover’s on-board science suite (which includes the SAM instrument referred to above).
The new drilling capability is referred to as Feed Extended Drilling (FED), designed to bypass a formerly critical, but at risk of failure, piece of the rover’s drill system called the drill feed mechanism. This mechanism also used to form a part of the means by which samples used to be transferred from Curiosity’s arm-mounted turret to the on-board science suite. As it can no longer be used, engineers instead determined the sample could potentially be transferred to the science suite by positioning the drill bit directly over the sample intake ports and then running the drill in reverse, causing the gathered sample to (hopefully) trickle backwards and into one of the hoppers.
Referred to as Feed Extended Sample Transfer, the approach was tested on May 31st, 2018, and successfully saw the transfer of part of a sample obtained on May 19th into the hopper serving the rover’s Chemistry and Mineralogy (CheMin) unit.
The approach had already been successfully tested on Earth, but there were concerns the thin, dry atmosphere of Mars might not produce the same results. There’s also a matter of balance. Previously, any sample gathered by the drill would pass through the rover’s CHIMRA sieving system, which helps ensure the right amount is transferred to the on-board instruments. Without this, transfers become a matter of judgement, as engineer John Moorokian explained following the transfer:
On Mars we have to try to estimate visually whether this is working, just by looking at images of how much powder falls out. We’re talking about as little as half a baby aspirin worth of sample.
John Moorokian, lead developer of the FEST delivery method
The problem here is, were too little materials transferred, and CheMin and SAM would not be able to provide accurate analyses, but transfer too much of the unsorted material, and it could either clog instruments or remaining unused, potentially contaminating measurement of future samples. So far, it appears the first attempt has succeeded, although it will still be a while before the outcome of any analysis is known.
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