Experiment Suggests that Old Traces of Life May Still Exist on Mars.
There is a chance that microbial life once managed to survive on our neighboring red planet, just as it does here on Earth in some of the harshest and most unexpected settings.
New laboratory models simulating some of the harsh environments such life would have encountered indicate that traces of these bacteria may still exist, safely hidden beneath meters of Martian mineral soil, for future rovers, like ExoMars, to discover.
This is despite the obstacles any such ancient life would have encountered on a planet that is currently barren, icy, and practically airless — not to mention the problems we could have in identifying them.
According to pathologist Michael Daly of the Uniformed Services University, if Martian life ever existed — even if there are no living things on Mars today — its macromolecules and viruses would endure for a considerably longer period of time.
That increases the likelihood that future missions will find evidence of the existence of life on Mars.
Six microbes, including Deinococcus radiodurans, the bacteria with the highest radiation resistance currently known, and Saccharomyces cerevisiae, the yeast, were exposed to dry, chilly circumstances resembling those on Mars by Daly and colleagues.
According to chemist Brian Hoffman of Northwestern University, there is neither flowing water or much water in the Martian atmosphere, therefore cells and spores would dry out.
Additionally, it is well known that Mars’ surface is about equivalent to dry ice, indicating that the planet is truly extremely cold.
To simulate cosmic radiation, the scientists bombarded the frozen and dried bacteria and fungi with gamma rays.
The shielding from cosmic radiation that we are so lucky to have here on Earth is absent on Mars. The majority of this radiation is reflected before it reaches us on the surface by our atmosphere and planet’s magnetic field, so over the course of a year, we receive a dose comparable to two chest x-rays.
On the other hand, if we were on the surface of the red planet, we would be exposed to 40–50 times more radiation, which would be fatal within six months.
Amino acids, the fundamental units of life, can be damaged by radiation at this level, and according to earlier studies, 2 meters (6.6 feet) of ground would be necessary to shield these molecules for up to 80 million years, if we’re lucky.
Nevertheless, as Mars has been inhospitable to life as we know it for billions of years, any remnants of it would have vanished out of reach.
However, the researchers found in the latest study that the dried and frozen Deinococcus radiodurans may survive for a far longer period of time than previously thought. The group nicknamed this bacteria Conan the Bacteria because of its astounding strength.
According to their research, the team believes that Conan the Bacteria could live for 1.5 million years if it were buried just 10 centimeters into the surface of Mars, and for an incredible 280 million years if it were buried up to 10 meters beneath the planet’s surface.
Although D. radiodurans buried in the Martian subsurface couldn’t endure inactive for the estimated 2 to 2.5 billion years since flowing water vanished on Mars, such Martian ecosystems are frequently changed and destroyed by meteorite impacts, according to Daly.
We suggest that intermittent repopulation and dispersal may be possible under periodic melting.
This enhances the risk of life on Mars and Earth becoming contaminated, which would necessitate planetary protection measures, warn Horne and colleagues.
“We concluded that terrestrial contamination on Mars would be essentially permanent — over thousands of years,” Hoffman says.
“This could make scientific efforts to find Martian life more difficult. Similarly, if microbes evolved on Mars, they may have survived to the present day. As a result, returning Mars samples may contaminate Earth.”
Overall, their findings suggest that future rovers may be able to find traces of ancient microbial Mars life, albeit a very slim chance. That is, of course, assuming that such life was similar enough to what we know, if it ever existed at all.
Source: liebertpub
