ESA has released images captured by its Mars Express space probe that show the Mars area called Sirenum Fossae. The High Resolution Camera Stereo Camera (HRSC) camera allowed to take photos of an area whose appearance was determined by an ancient volcanic activity, with the result that a system of tectonic faults called graben in jargon stretched for thousands of kilometers on the red planet’s surface.
The Sirenum Fossae stretch for about 2,700 kilometers, forming a region that is only a part of a larger system around the Arsia Mons volcano in the Tharsis region, about 1,800 kilometers northeast. There are some of Mars’ largest volcanoes in that region, although the largest one, Olympus Mons, is outside the borders of Tharsis.
When the red planet was younger, those volcanoes were active and there are various possible mechanisms that can lead to the formation of the tectonic faults called graben. Traces of those ancient activities can also be seen in the nearby chain of faults called Memnonia Fossae, with curious formations such as a split crater.
On Mars, the traces indicate that the formation of graben is linked to volcanic activity with the presence of dikes. The graben of the Sirenum Fossae reach a width of 9 kilometers with depth ranging from a few hundred meters to half a kilometer. Concentrations of dikes in swarms are common in areas with volcanic fractures on Earth as well, such as in Iceland. The graben in the Sirenum Fossae on Mars could represent a giant dike swarm extending from the volcanic center.
NASA studied some geological features in the Sirenum Fossae area as well identifying gullies on some of its steep slopes close to channels and in the rims of impact craters. It’s another research front not only for that area and also linked to the search for traces of the presence of liquid water.
This is a hypothesis made in the past to explain the creation of small channels but recently other hypotheses concern the cycle connected to frozen carbon dioxide streams. Dry ice, as it’s also known, may have dug those channels during seasonal movements.
The different hypotheses for the creation of the various geological features of the Sirenum Fossae show the difficulty in reconstructing the history of an area that used to be very active in ancient times. Meteorite impacts after the volcanic activity period can help estimate the age of the graben and the channels and understand their actual origin.