Mysteries in Nili Fossae
These new images from the high-resolution stereo camera on ESA’s Mars Express show Nili Fossae, one of the most enticing regions on Mars.
This ‘graben system’ lies northeast of the volcanic region of Syrtis Major on the northwestern edge of the large Isidis impact basin and intriguing hints of methane have been seen here.
Grabens are blocks of land that have fallen between parallel faults, sometimes forming rift valleys. The graben system in Nili Fossae contains numerous troughs oriented concentrically around the edges of an impact basin, as can be seen in the context map.
The easternmost of these troughs is partially visible at the lower left of the images. It is perhaps most obvious as a depression in the topography map from Mars Express.
The graben is most likely associated with the formation of the Isidis impact basin. Flooding of the basin with basaltic lava may have resulted in subsidence, which added stress to the planet’s crust and was then released through fracturing and trough formation.
Mars Express and other spacecraft have shown that the region displays a fascinating mineral diversity, drawing the attention of many planetary scientists. The minerals include phyllosilicates (clays), carbonates and opaline silica. These indicate a diverse history for this area resulting from the huge geological and tectonic forces that have been at play.
