Spatial relationships between patterned ground and ground ice detected by the Neutron Spectrometer on Mars

Abstract

Patterned grounds, like polygonal features, are the signature of climatic effects in periglacial regions on Earth. Identifying similar features on Mars is important for an understanding of the past Martian climate. In this study we mapped fresh patterned landforms from the systematic analysis of Mars Orbiter Camera high-resolution images. We show that most of them are distributed at latitudes poleward of ± 55°, making a climatic control likely. This distribution correlates to the distribution of ground ice detected by the Neutron Spectrometer aboard Mars Odyssey. This correlation is likely the consequence of the Neutron Spectrometer detecting ice no deeper than about 1 m. Patterned ground formation requires ice in this range of depth because these features are triggered by the propagation of a thermal wave that is driven by seasonal or diurnal changes in insolation, which affect the temperature in the uppermost ground layers. Sublimation seems to play a role in the shaping of many of the small patterns observed at latitudes between 55° and 70°. No widespread polygonal features are correlated to the equatorial regions where hydrogen is detected by the Neutron Spectrometer. Copyright 2004 by the American Geophysical Union.