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Planetary News: Mars (2004)

Mars Express Instrument Finds Possible New Evidence in Search for Life Water and Methane Maps Overlap

By A.J.S. Rayl
22 September 2004

When Vittorio Formisano, the principal investigator for the Planetary Fourier Spectrometer (PFS) aboard the European Space Agency's Mars Express, announced Monday that his team found that concentrations of water vapor and methane significantly overlap in the atmosphere of the Red Planet, the notion that some kind of microbes may be alive and present on Mars today found a life of its own in the global headlines. Scientists, however, are cautioning that it's going to take more analysis and independent confirmation of the data before any leap to life can be made.

Formisano told the gathering of scientists at the International Mars Conference, being held this week in Ischia, Italy, that data obtained by the PFS showed that water vapor is well mixed and uniform in the atmosphere at 6 to 9 miles [10-15 kilometers] above the surface, but close to the surface, it is two to three times more concentrated in three broad equatorial regions. These regions -- Arabia Terra, Elysium Planum and Arcadia-Memnonia -- correspond to the areas where NASA's Mars Odyssey spacecraft has observed hydrogen below the surface. Moreover, recent in-depth analysis of PFS data confirms, he reported, they found that methane is not uniform in the atmosphere, but concentrated in some areas that overlap with the areas where water vapor and underground water ice are also concentrated.

"This spatial correlation between water vapor and methane seems to point to a common underground source," noted the official ESA press release. Since water and methane are key markers of life on Earth, that "common underground source" could be a clue that will lead to life -- or not. The PFS -- an instrument developed at the Istituto Fisica Spazio Interplanetario, in Rome, Italy, for the Italian Space Agency -- determines the composition of the Martian atmosphere from the wavelengths of sunlight (in the range 1.2-45 microns) absorbed by molecules in the atmosphere and from the infrared radiation the molecules emit. Specifically, it measures the vertical pressure and temperature profile of carbon dioxide which makes up 95% of the Martian atmosphere, and looks for minor constituents, including water, carbon monoxide, methane, and formaldehyde.

Formisano's announcement comes nearly six months after he reported the PFS had detected the presence of methane in the Martian atmosphere. That finding was previously and subsequently corroborated independently by two other teams that also detected the presence of methane using ground-based telescopes: one led by Michael Mumma, of NASA's Goddard Space Flight Center, and the other led by Vladimir Krasnopolsky, of Catholic University. The fact that each of these three teams -- utilizing four different instruments -- measured about the same amount of methane in the atmosphere -- around 10 parts per billion -- appears to bolster the veracity that methane does exist in the atmosphere. Even so, because the spectral lines recorded in each of these studies are, to one degree or another subject to interpretation and because some features, such as water, could 'masquerade' as something else, the methane findings and the implications are being hotly debated within the scientific community studying the Red Planet.

Based on current models, there are a number of potential sources for the methane in the Martian atmosphere, including:

  1. Volcanic or geothermal activity that involves the oxidation of iron in basaltic rocks, mainly by water and in the presence of carbon dioxide, would generate methane.

  2. Biological life, such as microbes (like methanogens on Earth) below the surface, producing methane that moves above the surface. If such microbial life does exist on Mars, the general consensus is that it would exist below the permafrost layer, which could also generate methane;

  3. A frozen clathrate hydrate that is being vaporized and in the process is releasing the two gases together;

  4. Hydrated minerals, such as those found on the surface by the Mars Exploration Rovers, Spirit and Opportunity, and also detected by Mars Express' OMEGA imaging spectrometer.

"The [Formisano/ESA] statement that water vapor and methane are commingled or enhanced in certain regions together doesn't really tell you whether it's biology or geothermal processing," says Mumma, chief scientist, Planetary and Astrophysical Sciences Laboratory for Extraterrestrial Physics at Goddard.

One hypothesis under consideration by the ESA group suggests that an underground ice layer subjected to geothermal heat from far below the surface makes water and other material move towards the surface. But the very low surface temperature (many tens of degrees Celsius below zero) cause the water to freeze before getting to the surface. Further investigations are needed to determine, however, if an 'ice table' actually exists. Although some news reports have stated that Odyssey has detected a water ice layer, the spacecraft actually can only measure hydrogen, and the ice table has been inferred or theorized from that.

If there is an ice table, additional research will be needed does to fully understand the correlation between it and the presence and distribution of water vapor and methane in the atmosphere. Are there geothermal processes that 'feed' the ice table and also bring water vapor and other gases, like methane, to the surface? Can there be liquid water below the ice table? Can forms of bacterial life exist in the water below the ice table, producing methane and other gases and releasing them to the surface and then to the atmosphere?

"The PFS instrument has also detected traces of other gases in the Martian atmosphere. A report on these is currently under peer review," according to the ESA press release. What those other gases are it did not say.

As interesting and insightful as these new findings may turn out to be, for now, most Mars scientists agree that it is probably going to take in situ observations by future lander missions to the Red Planet -- such as Phoenix and Mars Science Laboratory and possibly ESA's Aurora -- to really resolve whether or not microbial life is there.