Key Science Questions from the Second Conference on Early Mars: Geologic, Hydrologic, and Climatic Evolution and the Implications for Life

Abstract

In October 2004, more than 130 terrestrial and planetary scientists met in Jackson Hole, WY, to discuss early Mars. The first billion years of martian geologic history is of particular interest because it is a period during which the planet was most active, after which a less dynamic period ensued that extends to the present day. The early activity left a fascinating geological record, which we are only beginning to unravel through direct observation and modeling. In considering this time period, questions outnumber answers, and one of the purposes of the meeting was to gather some of the best experts in the field to consider the current state of knowledge, ascertain which questions remain to be addressed, and identify the most promising approaches to addressing those questions. The purpose of this report is to document that discussion. Throughout the planet's first billion years, planetary-scale processes•including differentiation, hydrodynamic escape, volcanism, large impacts, erosion, and sedimentation•rapidly modified the atmosphere and crust. How did these processes operate, and what were their rates and interdependencies? The early environment was also characterized by both abundant liquid water and plentiful sources of energy, two of the most important conditions considered necessary for the origin of life. Where and when did the most habitable environments occur? Did life actually occupy them, and if so, has life persisted on Mars to the present? Our understanding of early Mars is critical to understanding how the planet we see today came to be.

A volcanic origin for the outflow channels of Mars: Key evidence and major implications

“…Beyond this volume is the water required to maintain a cryospheric cap of global extent and~4 km thickness (e.g., Wilson et al, 2009), equivalent to a global water layer of up to~250 to 1000 m thickness if commonly cited megaregolith porosities of 10-40% are assumed and if pores are largely (~60%) filled with water in the solid or liquid phases. Consideration of the various reservoirs required for hypothesized aqueous development of the outflow channels therefore suggests a total water volume potentially far in excess of the 300-500 m commonly cited, and conceivably much larger than that of the modern near-surface reservoirs of the Earth (equivalent to a global layer of~2700 m thickness; Carr and Wänke, 1992;Beaty et al, 2005).…”

“…The possible incompatibility between the low water abundances inferred from most geochemical models and the high abundances required of aqueous channel interpretations is a long-standing issue in the study of Mars (Carr and Wänke, 1992;Wänke and Dreibus, 1994;Carr, 1996;Beaty et al, 2005). The minimum volume of water necessary for development of the Martian outflow channels, determined under assumptions of 40% sediment content, is equivalent to a global water layer of~300-500 m thickness (Carr, 1987(Carr, , 1996Baker et al, 1992a, p. 518;Baker, 2006, p. 140).…”

Lava Cave Microbial Communities Within Mats and Secondary Mineral Deposits: Implications for Life Detection on Other Planets

“…T he recognition that early Mars was quite similar to early Earth, warmer and with liquid water (Baker et al, 1991), led to the suggestion that life may have evolved on Mars at about the same time as it did on Earth (Westall et al, 2000;Beaty et al, 2005). Testing this hypothesis has focused on two rather separate paths.…”

Cave Microbiomes: A Novel Resource for Drug Discovery

“…Since similar atmospheric conditions were shared by Mars and Earth, with warmer temperatures and the presence of liquid water when life fi rst evolved, the possibility of thriving life at the same time on the Red Planet became feasible (Baker et al 1991;Beaty et al 2005). Nowadays, the surface of Mars is exposed to UV radiation and ionizing radiation and temperatures below the freezing point of water, which makes the presence of life on the surface unlikely.…”