GEOLOGICAL FRAMEWORK OF THE NORTHERN LOWLANDS OF MARS AND EVIDENCE FOR EXTENSIVE AMAZONIAN CLIMATE CHANGE PROCESSES

Following formation of the dichotomy boundary, the history of the northern plains includes impact-crater modification of a Noachian basement, volcanic emplacement and deformation of Hesperian ridged plains, emplacement of Late Hesperian-Amazonian outflow channel effluent and formation of the Vastitas Borealis Formation, formation of Lyot crater, Amazonian-aged modification of the dichotomy boundary and adjacent surface of the northern lowlands by spin-axis/orbital variation induced climate change processes, culminating in the Late Amazonian polar layered terrain and latitude-dependent mantling deposits. We outline this basic framework for the history of the northern lowlands, and describe evidence for Amazonian: 1) systematic latitude-dependent, climate-related preferential modification of impact crater interior slopes, 2) modification of impact crater interiors by cold-based glaciation, 3) modification of the dichotomy boundary and the northern lowlands interior margins by cold-based ice sheets and valley glacial systems, 4) formation of circumpolar ice-filled craters, 5) formation of the polar layered terrain, and 6) emplacement of latitudinal dependent ice-rich mantles representing geologically recent ice-ages. We use terrestrial analogs to assess the nature of these processes at the macro (orbital) to micro (lander/rover) scales. At the meso to micro scales, orbital remote sensing data and geological evidence from terrestrial analogs indicates the presence of abundant ground ice, and strongly suggests that local latitude-dependent melting has occurred in geological micro-environments. Finally, we outline the implications of the Amazonian history of the northern lowlands for the nature of the surface and near-surface materials being assessed by orbital remote sensing data and future landers.