Using a new on-board experiment, NASA's Curiosity rover has discovered
traces of previously undetected organic molecules on Mars.
None of the organic molecules identified in the sand hold unequivocal signs
of life, but they do suggest the new technique, which didn't require the
rover to drill, is an effective tool when it comes to searching for evidence
of carbon-based molecules, which are important building blocks for life as
we know it.
The wet-lab experiment came about after Curiosity hit a figurative bump in
the road while looking for signs of life on the red planet at the close of
2016.
Just as the rover was preparing to sample the Martian rock at the base of Mt
Sharp, its drill suddenly stopped working.
Instead of putting a break on the mission until the issue could be fixed,
researchers at NASA simply changed gears.
Rather than pulverizing rock samples into powder, a bit of loose sand that
had already been scooped up on Ogunquit Beach was introduced into
Curiosity's 'wet chemistry lab'.
This on-board laboratory includes just nine cups of solvent, which can only
be used once each, so researchers have to be really picky about which
samples they ultimately choose.
Organic compounds within Martian rock are super challenging to detect,
because once they are heated, they break up into simpler molecules.
If these organic compounds, however, react with other chemicals first, they
are more likely to enter a gas chromatograph and mass spectrometer for
analysis without breaking down. Hence, Curiosity's nine cups of solvent.
It's a cleverly designed system that enables us to quickly analyze soil on
Mars from the comfort of our own planet. Yet in late 2016, it had never been
put to the test.
The team at NASA didn't expect the sand from Ogunquit to be organic rich,
but they weren't sure they could keep drilling on the planet going forward,
so it was worth a try.
Breaking the first seal for the Ogunquit sand, researchers found several
organic compounds including ammonia and benzoic acid. Some of the organic
compounds had never been identified on Mars before.
Now, a couple of years later, the results have been peer-reviewed and
published.
As mentioned above, the presence of these organic molecules doesn't
definitively mean there was once life on Mars, and no amino-acid derivatives
were detected in the sample.
But what's exciting is that this new technique can now be used to look for
signs of life, even without the ability to drill.
"This derivatization experiment on Mars has expanded the inventory of
molecules present in Martian samples and demonstrated a powerful tool to
further enable the search for polar organic molecules of biotic or prebiotic
relevance," wrote the NASA research team, led by astrobiologist Maëva Millan
from NASA's Goddard Space Flight Center and Georgetown University.
In the end, it took over a year before engineers on Earth were able to fix
Curiosity's drill and get it back in action, but by then, we knew the wet
chemistry cups could work.
By 2019, the second cup was ready to be used for a sample of clay-bearing
rock from further up Mt Sharp. Other analyses are soon to follow, not only
on Mars but also on Earth.
NASA plans on conducting a mission in the 2030s to collect the rest of
Curiosity's samples, so that they can be more carefully analyzed back on our
own planet.
Reference:
Millan, M., Teinturier, S., Malespin, C.A. et al. Organic molecules revealed
in Mars’s Bagnold Dunes by Curiosity’s derivatization experiment. Nat Astron
(2021).
DOI: 10.1038/s41550-021-01507-9
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