THARSIS SUPERPLUME (3): IMPLICATIONS ON THE ROLE OF WATER, ENVIRONMENTAL CHANGE, AND LIFE

We propose a superplume origin for the Tharsis magmatic complex (also see Maruyama et al. and Dohm et al., this volume) in tandem with the MEGAOUTFLO hypothesis that explains many otherwise enigmatic aspects of Mars geology and atmospheric history. The cyclic character of the triggering heat flow events, cataclysmic outburst flooding, ocean formation, transient greenhouse atmosphere, and subsequent sequestering of water and CO2 in the subsurface all combine into a single coherent conceptual model, MEGAOUTFLO, binding together the numerous diverse components of paleoenviromental history for Mars [see Nature, v. 252, p. 589-594, 1999; Lunar. Planet. Sci., v. 31, abstract no. 1863, 2000]. Similar to Earth’s superplumes, internal planetary heat from a stable, long-lived, water-enriched, and pulsating Tharsis superplume would provide the trigger for the massive outburst flooding that transformed Martian climate during the geologically short epochs of ocean formation. Superimposed on the long-term monotonic decline in mantle heat flux for Mars, we envision short-duration episodes of higher heat flux to the surface, perhaps of a type modeled by Herrick and Parmentier for terrestrial planetary histories. These episodes of higher heat flow are consistent with the magmatic and tectonic history of Mars [Planet. & Space Sci., v. 47, p. 411-431, 1999; Anderson et al., JGR Planets in press]. The hypothesized superplume-related higher heat flow is directly evidenced in the warm-based glacial processes responsible for the character of the glacial landforms and the periglacial environments that reflect recent environmental change similar to those of superplume-related change on Earth, unlike the conditions prevailing today [Nature, v. 412, p. 228-236, 2001]. The superplume and MEGAOUTFLO hypotheses serve as working hypotheses that form the basis for further productive inquiry into the role of water, environmental change, and life on Mars.