@andreab

Major water-related episodes on the lowlands of Mars

, , and . EGS - AGU - EUG Joint Assembly, Abstracts from the meeting held in Nice, France, 6 - 11 April 2003, abstract \#3282, (April 2003)

Abstract

Throughout the recorded history of Mars, liquid water has distinctly shaped its landscape, including the prominent circum-Chryse and the northwestern slope valleys outflow channel systems (Dohm et al., 2001), and the extremely flat northern plains topography at the distal reaches of these outflow channel systems. Paleotopographic reconstructions of the Tharsis magmatic complex reveal the existence of an Europe-sized Noachian drainage basin and subsequent aquifer system in eastern Tharsis. This basin is proposed to source the magmatic-triggered outburst floods that sculpted the circum-Chryse and NSVs outflow channel systems (Dohm, et al., 2001), entrained boulders, rock, and sediment during passage, and ponded to form sequentially through time various hypothesized oceans, seas, and lakes in the northern plains (Parker et al., 1993; Baker et al., 1991; Scott et al., 1995; Head et al., 1999) and glaciers and rock glaciers and lacustrine environments such as in the southern hemisphere (Baker, 2001). The floodwaters decreased in volume with time due to inadequate groundwater recharge of the Tharsis aquifer system. Basing on the ideas of episodic greenhouse atmosphere and water stability on the lowlands of Mars (Baker et al., 1991), a conceptual scheme for water evolution and associated geomorphologic features on the northern plains can be proposed. This model highlights Tharsis-triggered flood inundations and their direct impact on shaping the northern plains, as well as making possible the existence of fossil and/or extant life. Martian topography, as observed from the Mars Orbiter Laser Altimeter, corresponds well to these ancient flood inundations, including the approximated shorelines that have been proposed for the northern plains (Parker et al., 1993). Stratigraphy, geomorphology, and topography record at least one great Noachian/early Hesperian northern plains ocean (Fairén and De Pablo, 2002), best portrayed by the martian dichotomy boundary or Contact 1, but in Arabia Terra, where the initial shoreline might have been as far south as Sinus Meridani (Edgett and Parker, 1997), forming an almost equipotential line (total elevation differences are ∼2 km) that we name Contact 0, which is also consistent with the location of the boundary in crustal thickness dichotomy, as deduced from topography and gravity data (Zuber et al., 2000), and with the locus of debouch of almost every valley network in Arabia (Edgett and Parker, 1997; Carr, 2002); a Late Hesperian sea, which would have extended over the deeper areas in the lowlands inset within the boundary of the first great ocean, and so portrayed by Contact 2; and a number of widely distributed minor lakes that may represent a reduced Late Hesperian sea, or ponded waters in the deepest reaches of the northern plains related to minor Tharsis (e.g., Anderson et al., 2001) and Elysium (Skinner and Tanaka, 2001) induced Amazonian flooding. Possible biologic evolution throughout the resulting different climatic and hydrologic conditions would account for very distinct metabolic pathways for hypothesized organisms capable of surviving and perhaps evolving in each aqueous environment, those that existed in the dry and cold periods between the flood inundations, and those organisms that could survive both extremes. Terrestrial microbiota, chemolithotrophic and heterotrophic bacteria, provide exciting analogues for such potential extremophile existence in Mars, especially where long-lived, magmatic-driven hydrothermal activity is indicated (Farmer and Des Marais, 1999). Such Martian environments and related materials and life forms may have been excavated to the surface by catastrophic outflows making targets readily available for sampling and in-deep analyses. References Anderson, R. C. et al.: Primary centers and secondary concentrations of tectonic activity through time in western hemisphere of Mars. J. Geophys. Res. 106, 20 563--20 585, 2001. Baker, V.R., et al.: Ancient oceans, ice sheets and the hydrological cycle on Mars. Nature, 352, 589--594, 1991. Baker, V. R.: Water and the martian landscape. Nature, 412, 228--236, 2001. Carr, M. H.: Elevations of water-worn features on Mars: Implications for circulation of groundwater, J. Geophys. Res., 107, 5131, doi:10.1029/2002JE001845, 2002. Dohm, J.M., et al.: Ancient drainage basin of the Tharsis region, Mars: Potential source for outflow channel systems and putative oceans or paleolakes. J. Geophys. Res., 106, 32 943--32 958, 2001. Edgett, K.S. and Parker, T.J.: Water on early Mars: Possible subaqueous sedimentary deposits covering ancient cratered terrain in western Arabia and Sinus Meridani. Geophys. Res. Lett., 24, 2897--2900, 1997. Farmer, J.D. and Des Marais, D.J.: Exploring for a record of ancient martian life.

Links and resources

Tags