Credit: © NASA/JPL/UNIVERSITY OF ARIZONA

J. Geophys. Res. http://dx.doi.org/10.1029/2011JE003816 (in the press)

Mars is thought to be less geologically active than Earth, but recent faulting and young volcanism near Cerberus Fossae suggest this particular region could still be active. Spacecraft imagery of boulder populations along this fracture system suggests recent seismic activity.

Gerald Roberts of Birkbeck College, University of London, and colleagues measured boulder size and distribution around faults in Cerberus Fossae as observed in HiRISE imagery. The images show that boulder sizes decrease with increasing distance from the fault centre, in contrast to the random distribution that would be expected from processes associated with ground ice. Instead, the distribution closely compares to that of earthquake-triggered boulder avalanches on Earth. The researchers thus conclude that past marsquakes best explain their observations.

Not only are there boulders associated with faulting that occurred less than 2.5 million years ago, the trails produced by some rolling boulders have not been erased by aeolian activity. This suggests that local seismicity — and volcanism — may be ongoing.