Skip over navigation

Adam Maloof - Research

Lonar Crater, India

One of the most unexpected results from the Mars Global Surveyor mission was the discovery of strong, spatially variable remanent magnetization in the crust. The peak intensities of the crustal magnetizations on Mars are an order of magnitude greater than typical for Earth rocks at spacecraft altitude. However, the crust within the younger impact basins does not preserve any magnetization above the detection limits and may suggest that shock waves generated during impact events demagnetized large sections of the Martian crust. The timing and generation of the dynamo on Mars places fundamental constraints on the thermal evolution of the planet. Therefore, the magnetic signatures in the crust and in meteorites place important constraints on the evolution of Mars. However, interpreting the complex patterns in the Martian crust (below) requires a better understanding of the effect of shocks on magnetization.

Another peculiar property of craters on Mars is that nearly all fresh craters with diameters greater than several km are surrounded by ejecta blankets with fluidized morphologies (i.e., preferential thickening along the outer edge of ejecta blanket). The occurrence of so-called rampart ejecta craters has been linked to the presence of ground water or ice, and/or interactions with the Martian atmosphere. Hence, impact craters on Mars could be a powerful probe into the physical properties of the surface and the history of climate change. However, the physical processes which govern the fluidization of Martian ejecta remain unknown.

Sarah Stewart, Ben Weiss, Karin Louzada, Adam Soule, Nick Swanson-Hysell, Ian Garrick-Bethell and I conducted a two year field study of the the only impact crater on Earth preserved in basalt, our best terrestrial analog for the Martian surface (in this case, a thick pile of ~65 million year old Deccan Trap basalt flows). Lonar Crater is 1.8 km in diameter, ~240-m deep, surrounded by a rampart-like distribution of ejecta, and 15,000 and 40,000 years old. We published our rock magnetic results in 2007 in EPSL and demonstrated a near complete of shock remagnetization of the target basalts.  Our GPS-derived digital elevation model and geological map of the crater and its ejecta blanket were published in GSA Bulletin in 2010.