The process of hydrocarbon production occurs in two steps. In the first, an iron compound in rock strips water of its oxygen, liberating hydrogen gas. In the second step, hydrogen gas and carbon dioxide (from the degassing of magma) combine to produce methane and water. The Minnesota team discovered that rocks rich in chromium minerals accelerate the second step, while also producing more complex hydrocarbons–ethane and propane. Both likely serve as food for some bacteria.
“The second step is a reaction well known to chemists,” said Seyfried, a professor of geology and geophysics. “But in several papers published in the last few years, researchers have noted great difficulty in forming hydrocarbons more complex than methane. Dionysios [Foustoukas] showed that in the presence of chromium-bearing minerals, it could happen.
“Chemists might want to tweak this process and see if they can produce hydrocarbons more efficienty. But we want to get clues about what goes on in hydrothermal vents and to understand how hydrocarbon gases are generated in the continental and oceanic crust.”
In related work, Seyfried and and his colleague Kang Ding have built chemical sensors that can be placed in hydrothermal vents to measure such items as acidity and the amounts of gases like hydrogen and hydrogen sulfide, which also serve as energy sources for microbial communities. Acidity also seems to play a role in hydrocarbon synthesis in submarine hydrothermal systems. To access the vents as deep as two miles beneath the sea surface, the researchers use the submersible ALVIN; they have now dived to a number of vent sites.
Text for this article comes from a University of Minnesota press release.
People seem to be interpreting the methane found on Mars as a sign of life. Mars’ lack of current volcanism is evidence that it’s not volcanically produced. Could this sort of superheated water process somewhere under the martian surface be a potential source though? Or is the heat too far down there?
Indeed, the methane on Mars is being interpreted as being the waste product of bacteria which may be eating a food source.
If that is the case, we are quite lucky to have gotten to Mars right now. The bacteria will die when the food is exhausted. If the food is buried organic matter from a past solar-powered surface life, there is no more food being created. With the huge growth rate of bacteria, they would consume any food source in a short time. Either their metabolic rate is excruciatingly slow or the access to the food supply is restricted.
The deep hot biosphere viewpoint is that methane is probably created by geologic/chemical processes, and is the food source for deep-living bacteria. So the methane on Mars might just be rock gas and not a sign of life. But if methane is reaching the atmosphere, there still is a supply which may be feeding bacteria.
One part of the deep biosphere theory is that the food source for bacteria has to be unavailable to the bacteria, and the food is only available at a restricted rate. Methane from depths which are too hot for bacteria would allow life to exist for as long a time as the methane continues to trickle up to cooler regions.
So the methane tells us to keep looking for life, as there is still a food source.
That’s nice. They found a chemical process which may produce methane.
Notice that they refer to the source of carbon dioxide as outgassing from magma. So they recognize that carbon is in magma, which is one possible source for carbon/methane which can create fossil fuels through geologic and microbial processes.
I thought Mars was low on oxygen – how would methane be used for food exactly?
I thought Mars was low on oxygen – how would methane be used for food exactly?
The same way it is believed to happen deep inside the Earth where there is no atmospheric oxygen. By taking oxygen from oxides in minerals.
The common example is using iron oxide as an oxygen source, and producing magnetite as a waste product. Magnetite is often found in the organic goop from oil fields.
There seems to be plenty of iron oxide on the surface of Mars, where we can see it. Magnetite has also been found in Mars-related rocks, although not the same type of magnetite which is produced by Earth life forms.