Mars Express Yields Provocative Observations
Arabia Terra is one of the three equatorial regions where Europe¡¦s Mars Express PFS instrument detected both water vapor and methane concentration. The other two areas are Elysium Planum and Arcadia Memnonia.
Credit: NASA/JPL/Malin Space Science Systems

Europe's Mars Express is gathering data regarding the geological and atmospheric processes on the red planet -- information that might shore up the case that present-day life is percolating subsurface.  

Recent analyses of data gleaned by the Planetary Fourier Spectrometer (PFS) carried by the spacecraft reveal that concentrations of water vapor and methane in the atmosphere of Mars significantly overlap.

New in-depth looks at the PFS data also bears out that methane is not uniform in the atmosphere, but thick in some areas. The PFS team observed that the areas of highest concentration of methane 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. 

One exciting prospect bolstered by the data: 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? Indeed, the PFS data could be hinting at the presence of extant life on Mars in terms of the presence of 'biomarker' gases.

Concentrated in regions

The Mars Express data and what they could mean were reported today by Vittorio Formisano, PFS principal investigator, at the International Mars Conference being held this week in Ischia, Italy, and organized by the Italian Space Agency.

The PFS is an Italian Space Agency instrument, developed by the Istituto di Fisica dello Spazio Interplanetario (IFSI) of the Istituto Nazionale di Astrofisica (INAF).

ESA released today an overview of the PFS data, noting that at 6-9 miles (10-15 kilometers) above the surface, water vapor is well mixed and uniform in the atmosphere. However, the instrument found that, close to the surface, water vapor is more concentrated in three broad equatorial regions: Arabia Terra, Elysium Planum and Arcadia-Memnonia.

In those locales on Mars, the concentration is two to three times higher than in other regions observed. These particular areas of water vapor concentration also match up with places that NASA's Mars Odyssey spacecraft found a water ice layer just below the Martian surface, Formisano reported.

Ice table

The ESA press statement also explained that an underground ice layer - dubbed an "ice table" - could be the product of geothermal heat from below the surface that pushes water and other material towards the surface. It would then freeze before getting there, due to the very low surface temperature on Mars.

While further investigations are needed to fully understand the correlation between the ice table and the presence and distribution of water vapor and methane in the atmosphere, the ESA statement today poses several questions:

         Can the geothermal processes which 'feed' the ice table also push 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?

Provocative observations

"This is great news," said James Garvin, Chief Scientist for Mars and the Moon and Deputy Exploration Chief Scientist within the Science Mission Directorate at NASA Headquarters, Washington, D.C.

"All of us are encouraged by this first 'retrieval' from Mars orbit of such noteworthy species [gases], clearly relevant to the photochemical evolution of Mars and potentially linked to provocative possibilities, including active volcanism among others." 

Garvin added that "the real test" will come when the broadest possible participation by the international community gains an opportunity to analyze these new data, given the potentially controversial nature. "That's the way science breakthroughs gain standing in the science community."

While "encouraged, excited, and delighted" that the Mars Express PFS investigators have reported such provocative observations, Garvin said the findings must undergo open peer
review by external experts, including those who have made similar detections from Earth-based systems.

Corroboration needed

Garvin explained that NASA's Mars Odyssey detected a higher concentration of hydrogen, not necessarily water ice. Mars Odyssey cannot observe "water ice layers", Garvin said, only the presence of hydrogen.

Furthermore, that hydrogen, he added, could be due to hydrated minerals, such as those found on the surface by the Mars Exploration Rovers and also detected from orbit by the Mars Express OMEGA imaging spectrometer.

In Garvin's view, the real test will come when future spectrometers -- such as those destined to fly aboard the NASA Phoenix lander to be launched in 2007, and potentially carried on the Mars Science Laboratory in 2009 -- corroborate the Mars Express measurements.

"The message here is that exciting initial observations such as those reported by the Mars Express PFS are what catalyze new questions, observations, and ultimately testable hypotheses," Garvin concluded.