Decoding the Climate Signal in the Tharsis Montes Fan-Shaped Deposits: The Dynamics of Tropical Moun-

Introduction: Fan-shaped deposits (FSD) extending to the NW of the Tharsis Montes on Mars (Fig. 1) are the remnants of Amazonian-aged, cold-based, tropical mountain gla-ciations [1-5]. Geomorphological analyses of the facies within the deposits have revealed a number of ice-related features including moraines and sublimation till [1-5], as well as subglacial volcanic features [6]. Atmospheric models [e.g. 7] have shown that ice/snow will accumulate on the western flanks of the Tharsis Montes during periods of high obliquity (>45°) (Fig. 1b). These have worked in conjunction with ice-sheet models (Fig. 1c) [8-11] to reproduce possible histories for the growth and retreat of the glaciers. An understanding of both the geomorphologies within the FSDs and the atmospheric and glacial dynamics is necessary as we continue to decode the climate signal left by these glacial deposits. Here, we summarize the current progress and future steps required to extrapolate the full significance of the FSDs. In particular, we review the geology, ice-sheet models, and atmospheric models. Additionally, we stress the need for me-soscale models, which will be crucial in constraining equilibrium line altitudes (ELAs), accumulation rate distributions (ARDs) and various aspects of the evolution of the glaciers. Tropical Mountain Glacier FSDs as a Climate Signal: The Tharsis Montes FSDs have been interpreted to be glacial in origin on the basis of their facies [1-5]. The most prominent units include concentric ridges tracing the distal margin of the FSD and a knobby facies distributed over much of the FSDs. These have been interpreted as drop moraines and sublimation till, respectively. The drop moraines form at the end of the glacier, where debris is deposited and builds up during periods of glacial equilibrium. The knobs form when supraglacial material is deposited upon rapid sublima-tion/down-wasting of the glacier. Although the units have been studied in detail [1-5], more information about the past climate of Mars is cryptically held within the FSDs – information that requires a better understanding of the atmospheric and glacial dynamics in the Tharsis region. These outstanding questions include, but are not limited to: 1) What causes the differences in relative orientation of the FSDs? 2) Where are the accumulation zones of each of the glaciers and what were the maximum thicknesses of the ice sheets? 3) How frequently have these glaciers formed, and did they necessarily all form at the same time? 4) Why does the knobby facies only cover part of each …