ESA’s Mars Express has returned some remarkable new imagery of Tractus Catena area, revealing a series of pit-chains on the flanks of Alba Mons, one of the largest volcanoes in the Solar system.
Researchers say these features might be tempting targets in the search for microbial life on the planet.
The images cover Tractus Catena in the Arcadia quadrangle, part of the vast Tharsis region on the Red Planet. This region boasts a number of huge volcanoes, including the three collectively known as Tharsis Montes. To their north sits Alba Mons, also known as Alba Patera, one of the largest volcanoes in the Solar system by area and volume.
Tractus Catena sits on the southeastern flank of Alba Mons and the pit-chains in that region are a series of circular depressions that formed along fracture points in the martian crust.
There are some explanations of the origin of these pit-chains. They can have a volcanic origin: lava streaming from a volcano solidifies on the surface, leaving a molten tube of lava running below.
Pit-chains can also be caused by strains in the Martian crust, which translates into a series of parallel elongated depressions known as grabens, in which pits can also form.
The most dramatic explanation involves groundwater: on Earth, there are clear examples of similar structures in ‘Karst’ regions – after the German name for a region extending from Slovenia to Italy, where this phenomenon was first studied.
Some of Earth’s most famous examples are the network of ‘cenotes’ on the Yucatan peninsula of Mexico. These deep natural pits form when the surface limestone rocks collapse, exposing the groundwater underneath.
This origin is the most interesting in the context of the search for microbial life on Mars. If there are any cave-like structures associated with the pits, microorganisms could have survived, protected from the harsh surface environment.