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Planetary News: Mars (2004)

Methane Found on Mars Does That Mean Life? Not Yet.

By A.J.S. Rayl
2 April 2004

Is there life on Mars?

That's been the question du jour for the media this week. For many people, it just may be the biggest question of all time. In any event, the idea that there may be life on Mars hit the news again this week as reports from three different teams of researchers indicate that there is methane in the atmosphere of the Red Planet -- two from studies conducted with ground-based telescopes, one with an instrument on orbit.

It's not a lot of methane, but each of the three different studies, which utilized four different instruments, arrived at just about the same measure, something that would appear to bolster the veracity of the finding.

Where there is methane, of course, there could be life. All organics produce methane in some way -- so the finding is a significant one, and the media promptly picked up on it. Could, however, is the operative word. Contrary to some stories, none of the researchers, feet to the fire, are maintaining their work provides evidence of life on Mars (although a few do seem to be leaning toward that notion). Truth told, no one can really say for sure yet what the findings of methane point to.

Basically, each of the teams is analyzing spectra collected by instruments that measure the composition and properties of the atmosphere from the wavelengths of sunlight absorbed by the molecules there, the signatures these molecules produce by the infrared radiation they emit.

In September 2003, Michael Mumma -- chief scientist, Planetary and Astrophysical Sciences Laboratory for Extraterrestrial Physics at NASA/Goddard Space Flight Center -- and colleagues presented a poster at the annual DPS meeting that showed they had measured methane in the 10 to 30 to parts per billion (ppb) range through observations on NASA's Infrared Telescope Facility (IRTF) in Mauna Kea, Hawaii, and the Gemini South telescope in Chile, and Keck observatory Telescope in California. The abundance, they found, varies with location.

Last week Vittorio Formisano -- of the Institute of Physics and Interplanetary Space in Rome -- and his team reported that he discovered methane in readings also in the 10 to 10.5 ppb from the Planetary Fourier Spectrometer (PFS), on board the European Space Agency's Mars Express spacecraft, now orbiting the planet.

This week, Vladimir Krasnopolsky -- adjunct professor at the Catholic University of America in Washington DC -- and his team announced they too had found methane, at a level of 11 parts per billion, using the Canada-France-Hawaii telescope, in Mauna Kea, Hawaii. Krasnopolsky is scheduled to present his research later this month at the European Geosciences Union (EGU) meeting.

Methane (CH4) is a colorless, odorless gas that's all over Earth. It is the principal component of natural gas and is synthesized commercially by the distillation of bituminous coal, and by heating carbon and hydrogen. Its principal use is as a fuel.

On Earth is the primary greenhouse gas, the principal component of natural gas, a mixture containing about 75 percent CH4, 15 percent ethane (C2H6), and 5 percent other hydrocarbons, including propane (C3H8) and butane (C4H10).

While these studies beg for confirmation and need to be subjected to the rigors of peer review, the discovery of methane -- coming just weeks after both NASA's Mars Exploration Rover (MER) team and ESA's Mars Express teams produced evidence of past large bodies of water on the Red Planet -- is fueling excitement about the possibilities and giving the quest to search for life on Mars newfound credence and momentum. If Mars once featured water, the elixir of life, and now methane is being found in the atmosphere, those findings together would seem to tip the scales even more heavily toward a life source. But scientists both on the teams and observing from the outside are urging caution.

The fact is that there are three potential sources for the methane in the Martian atmosphere based on current models, and using Earth as an analogue of sorts:

  1. It could be abiotic. Volcanic or geothermal activity -- lava flowing up from an active hydrothermal environment below onto the surface or bubbling underground can produce methane that would rise to the atmosphere.

  2. Life: It could be biotic. The metabolism of biota can produce methane above the surface -- humans and other mammals produce methane as a waste byproduct, releasing it as a gas; anaerobic bacterial decomposition of animal and plant matter underwater and underground produces methane. In this case on Mars, the concept revolves around microbes, bacteria. In either scenario, it's biotic life.

  3. Since comets carry methane, an impact on the surface of Mars could create, theoretically, enough methane to be measured by current technology.

Because methane is not stable in the Martian atmosphere, it doesn't hang around forever, maybe only a few hundred years, the experts say; therefore, something has to be replenishing it. However the methane is finding its way up from the ground, the discovery is significant, if only because it means something on Mars is pumping out the gas.

Since the MER rovers are designed to search for geological, not biological, clues, they cannot follow up on this finding. Future rovers, however, could do just that. Beagle2 probably might have sniffed something out.

Look for a more detailed report on this important finding -- featuring comments from the scientists doing the work, as well as some thoughts from other scientists' weighing in from the outside -- next week.