The question of whether life once existed on Mars may be answered by a new laser instrument from the University of Bern. The device can be carried by a rover to zap samples of the Red Planet to see if they contain traces of microfossils.
As we learn more about Mars after half a century of exploration by an armada of robotic spacecraft, the odds of our finding any life there today becomes increasingly unlikely. Even if some form of life does improbably exist in some subterranean oasis, it is unlikely to be more than some very simple kind of bacteria.
There are a number of reasons for this, but the facts on the ground are that Mars has been so dry for over two billion years that it makes the driest spot on Earth look like a rain forest. The surface of the Red Planet is constantly exposed to cosmic rays, and the Martian soil is so reactive that it's hostile to any organic compounds.
However, in the distant past Mars was a very different place with a thicker atmosphere and so much liquid water that much of the surface was covered by a shallow ocean with rivers running into it. Though it's by no means certain, this was a wetter environment that could have supported some sort of microbial life.
If that's the case, then it's possible that some geological formations could contain fossils of these ancient Martians.
One analog of this on Earth can be found in Algeria, where five-million-year-old Messinian gypsum deposits serve as a proxy for Martian hydrated sulfate that could hold fossil microbes because these require water to form.
The Bern team in collaboration with the University of Science and Technology Houari Boumediene in Algeria used a miniaturized Laser Ablation Ionization Mass Spectrometry (LIMS) instrument. This high-resolution mass spectrometer uses a 258-nm double-pulse femtosecond laser to zap samples 40 times per second and cause some of the material to ablate and ionize.
These ions are then fed into a mass spectrometer, accelerated, and analyzed to form a 3D, real-time chemical map of the sample area with a minimum of damage. This allows the LIMS to seek and map traces of carbon, hydrogen, oxygen, potassium, sulfur, magnesium, calcium, phosphorus, chlorine, iron, cobalt, manganese, vanadium, and chromium.
According to the researchers, the LIMS can not only detect traces of organic compounds, it can also differentiate between minerals formed by living organisms and ones created by non-living processes. In tests of the Algerian gypsum, the team using the LIMS found evidence of fossil filaments of sulfur-oxidizing bacteria, sinilar to modern Beggiatoa and Thioploca. This was confirmed using optical and electron microscopes.
The hope is that by installing a LIMS on a rover, it will be possible for a future Mars mission to seek out possible Martian fossils within Martian gypsum.
"Our study shows that gypsum can preserve fossil microorganisms and is able to preserve microbial life over long geological time periods," said Youcef Sellam from the Division of Space Research and Planetology at the Physics Institute of the University of Bern. "Deposits similar to those in Algeria that exist on Mars in the former Martian seas are, in our view, promising targets for astrobiological research and for the detection of life on Mars."
The research was published in Frontiers in Astronomy and Space Science.
Source: University of Bern
