New Findings Say Mars Methane Comes from Life or Water — or Both

by Nancy Atkinson on December 8, 2009

Mars from orbit. Valles Marineris and Volcanic region


A new paper that will be published Wednesday rules out the possibility that methane is delivered to Mars by meteorites, boosting the idea that the short-lived gas perhaps could be generated by either life or water, or maybe even both. Microorganisms living in the Martian soil could be producing methane gas as a by-product of their metabolic processes, or methane might be created as a result of reactions between volcanic rock and water. Either way, the prospect is exciting.

Methane on Mars was first detected in 1999, again in 2001 and 2003, which was widely reported, but not much was known about the origin or amount of the gas on Mars.

In January 2009, scientists analyzing data from telescopic observations and unmanned space missions announced that the methane on Mars is being constantly replenished by an unknown source and they are keen to uncover how the levels of methane are being topped up.
In this illustration, subsurface water, carbon dioxide and the planet's internal heat combine to release methane. Although we don’t have evidence on Mars of active volcanoes today, ancient methane trapped in ice "cages" might now be released. Credit: NASA/Susan Twardy
Methane has a short lifetime of just a few hundred years on Mars because it is constantly being depleted by a chemical reaction in the planet’s atmosphere, caused by sunlight.

Some researchers proposed meteorites might be responsible for Martian methane levels because when the rocks enter the planet’s atmosphere they are subjected to intense heat, causing a chemical reaction that releases methane and other gases into the atmosphere.

However, the new study, by researchers from Imperial College London, shows that the volumes of methane that could be released by the meteorites entering Mars’s atmosphere are too low to maintain the current atmospheric levels of methane. Previous studies have also ruled out the possibility that the methane is delivered through volcanic activity.

“Our experiments are helping to solve the mystery of methane on Mars,” said Dr. Richard Court, co-author of the study. “Meteorites vaporizing in the atmosphere are a proposed methane source but when we recreate their fiery entry in the laboratory we get only small amounts of the gas. For Mars, meteorites fail the methane test.”

The team used a technique called Quantitive Pyrolysis-Fourier Transform Infrared Spectroscopy to reproduce the same searing conditions experienced by meteorites as they enter the Martian atmosphere. The team heated the meteorite fragments to 1000 degrees Celsius and measured the gases that were released using an infrared beam.
Nili Fossae region on Mars, a methane "hotspot: Credit: NASA/JPL/U of AZ
When quantities of gas released by the laboratory experiments were combined with published calculations of meteorite in-fall rates on Mars, the scientists calculated that only 10 kilograms of meteorite methane was produced each year, far below the 100 to 300 tons required to replenish methane levels in the Martian atmosphere.

The researchers say their study will help NASA and ESA scientists who are planning a joint mission to the red planet in 2018 to search for the source of methane. The researchers say now that they have discovered that meteorites are not a source of Methane on Mars, ESA and NASA scientists can focus their attention on the two last remaining options.

“This work is a big step forward,” said co-author Mark Sephton. “As Sherlock Holmes said, eliminate all other factors and the one that remains must be the truth. The list of possible sources of methane gas is getting smaller and excitingly, extraterrestrial life still remains an option. Ultimately the final test may have to be on Mars.”

This research will be published in the Earth and Planetary Science Letters.

Source: Imperial College

About 

Nancy Atkinson is Universe Today's Senior Editor. She also works with Astronomy Cast, and is a NASA/JPL Solar System Ambassador.

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