People and most animals, plants and fungi derive their energy primarily from chemical reactions between oxygen and organic compounds such as sugars. However, microbes rely on a wider range of different reactions for energy; for example, reactions between oxygen and hydrogen help hydrogenotrophic bacteria survive deep in the Earth's interior. Previous research has also suggested that such reactions could have spurred the development of the first life on Earth.
It has long been discovered that when rocks are destroyed and crushed during earthquakes on Earth, the silicon in those rocks can react with water to generate hydrogen. Lead author Sean McMagon, a geomicrobiologist at Yale University, and his colleagues set out to find out if Marsquakes could generate enough hydrogen to support any microbes that might well live on the Red Planet.
Scientists have investigated special types of rocks that are created when rocks are crushed during earthquakes. Samples from Scotland, Canada, South Africa, the Isles of Scilly off the coast of England and the Outer Hebrides of Scotland were analyzed and showed that they retain hundreds of times more trapped hydrogen gas than surrounding rocks that were not born in this kind of milling.
“These results are very interesting and exciting because we never thought we'd find anything like this,” McMagon says.
The scientists say the hydrogen in the samples they analyzed was abundant enough to support the developing hydrogenotrophs on Earth.
“Our findings contribute to a broader picture of how geologic processes can support microbial life in extreme conditions,” McMagon says. "We thought there was not much food in the kilometers underground, but over the past few decades, scientists have discovered that the Earth has a huge amount of biomass there, maybe up to 20% of the total biomass on the planet."
As for how Marsquakes and water could have teamed up to generate hydrogen on Mars, previous studies have shown that Mars' surface was once full of liquid water. It was also confirmed that there may still be large reserves of water underground on the Red Planet, at a depth of 5 kilometers on average. Nevertheless, earthquakes on Mars are much less common than on Earth, since today there is no volcanism or plate tectonics on the Red Planet.
Nevertheless, the researchers note that conservative models of Marsquakes based on NASA Mars Global Surveyor data show that on average, the Red Planet experiences such an event of 2 magnitudes every 34 days and 7 magnitudes every 4500 years. Consequently, Marsquakes can generate on average about 11 tons of hydrogen per year throughout Mars, which will be enough to sporadically maintain foci of microbial activity.
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“This hydrogen could probably support small amounts of biomass,” McMagon says. “Nonetheless, it fits into the growing picture of the biosphere that Mars could support. If you look at bacteria and other microorganisms on Earth, you will find that some of them can stay dormant for an incredibly long time, and then wake up and reproduce, and then go back to sleep for another 10,000 years or so."
McMahon noted that even those rocks that lack water seem to be able to generate hydrogen gas during earthquakes. This suggests that grinding rocks can release hydrogen, which is usually chemically bound to the rocks. However, the exact chemical process remains to be seen.
In 2018, the InSight mission will begin measuring seismic activity on Mars. The availability of up-to-date data on Marsquakes will show how right scientists can be.
ILYA KHEL
