Several lines of evidence suggest that water – an essential requirement for known life – was once abundant at the surface of Mars. Yet despite the substantial evidence for the existence of water at the surface, early Mars may have been too cold for liquid water to have been continuously stable, and cold conditions appear to have dominated since the Hesperian. Several workers have attempted to reconcile this discrepancy by invoking episodic warming of either the atmosphere or the ice, which could explain the ancient valley networks and water-altered minerals. The episodic presence of water across much of the surface also implies that Mars may have also have experienced episodic habitability.
Alternatively, episodically or continuously habitable environments on Mars may have existed for much of its history resulting from the interplay of long-lived magmatism and obliquity-driven ice deposition . Climate modeling of Mars suggests that ice deposition at low latitudes likely occurred at periods of high obliquity (≥ 45˚), leading to the preferential deposition of ice at a rate of up to several millimeters per year within the calderas and along the flanks of volcanic summits, such as those of Olympic Mons. Given the obliquity period of ~120 kyr and the timescale for construction of the volcanic edifices, the co-occurrence of glaciation and magmatism is highly probable.
Furthermore, if the stresses imposed on the magma chamber by the overlying ice are on the order of the magma chamber overpressure required to erupt basaltic lavas (~1 MPa), glacial loading above magma chambers may have affected or modulated later eruptive activity, as has been suggested for Earth. In such a scenario, observations of periodic bedding in volcanic materials that correlate with the modulation of the ~120-kyr obliquity period may be evidence of previous cycles of glacial loading of a magma reservoir.
Through the use of finite-element modeling, we model the obliquity-driven coupling Of magmatism and ice deposition to understand the effects on habitability and volcanism.
Collaborators: Jeffrey C. Andrews-Hanna.
Affiliation: This work was started while A. J. Evans was affiliated with the Lunar and Planetary Laboratory at the University of Arizona.