Abstract
AbstractThe early climate of Mars (Noachian Period, the first ~20% of its history) is thought to differ significantly from that of its more recent history (Amazonian Period, the last ~66%) which is characterized by hyperarid, hypothermal conditions that result in mean annual air temperatures (MAAT) well below 0°C, a global cryosphere, minimal melting on the ground surface, and a horizontally stratified hydrologic system. We explore the nature of the fluvial and lacustrine environments in the Mars-like hyperarid, hypothermal McMurdo Dry Valleys (MDV), where the MAAT is well below 0°C (~ -14 to -30°C) in order to assess whether the Late Noachian geologic record can be explained by a climate characterized by “cold and icy” conditions. We find that the MDV hydrological system and cycle provide important insights into the potential configuration of a “cold and icy” early Mars climate in which MDV-like ephemeral streams and rivers, and both closed-basin and open-basin lakes could form. We review a series of MDV fluvial and lacustrine features to guide investigators in the analysis of the geomorphology of early Mars and we outline a new model for the nature and evolution of a “cold and icy” Late Noachian climate based on these observations. We conclude that a cold and icy Late Noachian Mars with MAAT below freezing, but peak seasonal and peak daily temperatures above 0°C, could plausibly account for the array of Noachian-aged fluvial and lacustrine features observed on Mars. Our assessment also provides insight into the potential effects of punctuated warming on a cold and icy early Mars, in which impact crater formation or massive volcanic eruptions cause temperatures in the melting range for decadal to centennial timescales. We outline a set of outstanding questions and tests concerning the nature and evolution of these features on Mars.
Highlights
Deciphering climate history has been one of the major goals of the scientific exploration of Mars
In order to provide perspective on this debate, we review the nature of groundwater, fluvial and lacustrine processes in the hyperarid, hypothermal environment of the Antarctic McMurdo Dry Valleys (MDV), and describe the hydrological system and cycle currently characterizing this Mars-like region (Marchant & Head 2007)
On the basis of the synthesis of MDV climate settings, microenvironments and groundwater, fluvial and lacustrine processes, we highlight the following summary points that are relevant to analysis and further understanding of a possible cold and icy Noachian climate on Mars
Summary
Deciphering climate history has been one of the major goals of the scientific exploration of Mars. Recognizable geomorphic features (Fig. 5) range from local dark fringes around melting snow patches, to dark slope streaks on slopes below larger accumulations of melting snow and ice (Fig. 6b & c), to surface channelization (streams) where additional snowmelt and glacial meltwater flows (Fig. 7) and soaks into the regions adjacent to the streams (Fig. 7b & c) (hyporheic zones; Fig. 8a & b) This meltwater can move in the shallow subsurface above the ice table (Fig. 4b & d), often wicking to the surface in low-lying areas to produce small ponds and their wetted perimeters (Gooseff et al 2010) (Fig. 8b). The MDV amplifier lakes are excellent laboratories for the study of lakes in extreme geological and biological environments, and unique systems like Don Juan Pond offer the opportunity to study end-member enrichment processes
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