Deep fractures have been found around the giant Isidis impact basin on Mars. This area called NiliFossae is of interest to scientists because telescopes on Earth measured an increase in methane in Mars’s atmosphere over this area. This could mean life or it could be geological. Some of these incisions are up to 500 m deep and probably formed at the same time as the basin formed.
The image shows an eroded impact crater at the bottom right which measures about 12 km across and shows an ejector blanket of material thrown out during the impact. Another smaller crater can be found just to the left of the centre of the image with no ejector and it may have been eroded or simply buried. The result of a basaltic magma flow cooling and then solidifying is shown in a lava blanket at the top left of the image.
NiliFossae is what is called a “graben” type of system. Graben is the lowered terrain between two parallel faults or fractures in the rocks which collapses when tectonic forces pull the area apart.
NiliFossae was formed by an impact and this impact is thought to have caused flooding of the basin with basaltic lava. This may have caused subsidence of the basin floor which would have added to the stress in the planet’s crust eventually being released by the formation of these fractures.
This and other indications on Mars have pushed Mars to the top of NASA’s and ESA’s exploration list. As a result in 2016 ESA and NASA plan to launch the exomars trace gas orbiter which will investigate further and hopefully find life in one form or another.