Lori Fenton

It has long been unclear whether the many sand dune fields on Mars are actively evolving in the present climatic era. Recent evidence of sand avalanching and active sustained saltation has been identified in high resolution images. In particular, we report the first clear indications of ripple migration over dark dune slopes observed from orbit. We propose a comprehensive study that will specifically address this knowledge gap, via the careful analysis of high-resolution spacecraft imagery over the majority of the planet (between 60° N and 60° S). In fact, even the preliminary investigation of a small sampling of such imagery has already yielded evidence of recent sand avalanching on dark dune slip faces and the first clear indications of ripple migration (superposed on the dark dunes) observed from orbit. Such morphological indications provide unprecedented details of sustained saltation on Mars. This newly found activity refutes the commonly held belief that dunes on Mars are inactive in the present-day wind regime. Such a provocative topic deserves immediate, detailed study to determine how current dune activity provides unique ground truth for today's weather patterns on Mars.