BY DR EMILY BALDWIN
Posted: 27 March, 2009
According to scientists presenting their research at the Lunar and Planetary Science Conference (LPSC) this week, mud volcanism on Mars could provide a unique window into the astrobiological exploration of the red planet.
On Earth, mud volcanoes appear as domes ranging in size from around one metre to one kilometre, and form when gases and liquids several kilometres deep burst to the surface, typically carrying slurries of muddied fluid. They are also associated with significant quantities of methane emission.
This mud volcano is around a metre wide and is located in the region surrounding Mt Etna in Sicily. Image: copyright Emily Baldwin.
Scientists from NASA’s Johnson Space Center and Brown University used data from the Mars Reconnaissance Orbiter’s CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) instrument and the HiRISE (High Resolution Imaging Science Experiment) camera to study dome-like structures on Mars. They found that the domes stand out as bright protrusions against the dark basaltic rock of the surrounding plains, and that many exhibit central depressions. There is also evidence for multiple episodes of eruptions and that the domes appear to be constructed mostly of sediments, just like mud volcanoes on Earth.
Furthermore, although there is no large scale evidence for the extrusion of water as is seen at these features on Earth, the dome material is more oxidised than the surrounding plains, suggesting that the domes’ ingredients likely interacted with water at depth at some point in their history. And since mud volcanoes are not associated with the extreme heat or high pressures that “normal” volcanism or impact events induce, materials transported from depth are likely to be relatively unaltered. That means that as well as providing useful information on the planet’s subsurface water inventory, mud volcanoes could potentially host organic material that has remained preserved in the mud several kilometres below the surface.
Some scientists think these domed features on Mars are mud volcanoes, and could provide windows into Mars' astrobiological past. Image: NASA/JPL/University of Arizona.
On Earth, many terrestrial mud volcanoes are located in regions where hydrocarbons are common. For example, those located in Azerbaijan and around the Caspian Sea are associated with oil and gas fields, and are known to erupt large amounts of methane. Since methane has been detected in the Martian atmosphere where its short lifetime suggests currently active sources, scientists are exploring the possibility of mud volcanoes as a potential source. However, there is currently no direct evidence that the domes are still active.
To date, no Martian lander has explored an area containing these possible mud volcanoes, but they may offer targets for future missions aimed at sampling potentially habitable areas of the red planet.
The abstracts presented at LPSC discussing these results were prepared by Carlton Allen, Dorothy Oehler (NASA JSC) and David Baker (Brown University).