Maloof Home

Adam Maloof
Assistant Professor of Geosciences (Geology)

Department of Geosciences
213 Guyot Hall
Princeton University
Princeton, NJ 08544

Phone: (609) 258-2844
E-Mail: maloof@princeton.edu

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 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 and I have begun an intensive, field-based study of the the only impact crater on Earth preserved in a thick pile of ~65 million year old Deccan Trap basalt flows (our best terrestrial analog for the Martian surface). Lonar Crater is 1.8 km in diameter, ~240-m deep, surrounded by a rampart-like distribution of ejecta, and 15,000 and 67,000 years old. We are in the process of generating a detailed geologic map, coupled to a 3 meter resolution GPS-derived digital elevation model of the crater. In addition to basic mapping, we are focussing on two aspects of the crater that may be excellent analogues for Mars: The first involves a paleomagnetic and rock magnetic survey of the crater wall rock and ejecta to understand shock effects on the magnetization of basalt. The second involves understanding the conditions necessary for the development of ground hugging flows and distal overthickening within the ejecta blanket.

Since our first field season, we have begun new collaborations to further characterize Lonar Crater. Pascale Poussart (WHOI) currently is 14C dating pre-impact soils that were penetrated by fall-out ejecta in order to obtain a precise maximum age of the crater. Robert Ackert (Harvard) is preparing to determine a series of cosmogenic exposure ages for the crater wall. Brad Samuels of Situ Studio has built 1:5000 scale 3D models of the crater based on our digital elevation model and geologic map for presentation at the Mars Volatiles workshop in July 2005, and the American Geophysical Union Fall 2005 Meeting.

Adam Soule (WHOI) accompanied us during our second field season in January 2006 to study, in detail, the structure, morphology, petrology and chemistry of basalt flows in Lonar Crater and within nearby undeformed Deccan Trap flood basalts. Ian Garrick-Bethell also joined the field team in January 2006 and found hundreds of tektites around the crater rim, including aerodynamic dumbell, donut and spherical forms. Garrick-Bethell and Weiss currently are using traditional microscopy and SQUID Microscopy to compare Lonar and lunar spherules, with the eventual goal of constructing a 4 billion year history of magnetic field intensity on the moon.