The fluvial history of Mars

Abstract

River channels and valleys have been observed on several planetary bodies in addition to the Earth. Long sinuous valleys on Venus, our Moon and Jupiter's moon Io are clearly formed by lava, and branching valleys on Saturn's moon Titan may be forming today by rivers of methane. But by far the most dissected body in our Solar System apart from the Earth is Mars. Branching valleys that in plan resemble terrestrial river valleys are common throughout the most ancient landscapes preserved on the planet. Accompanying the valleys are the remains of other indicators of erosion and deposition, such as deltas, alluvial fans and lake beds. There is little reason to doubt that water was the erosive agent and that early in Mars' history, climatic conditions were very different from the present cold conditions and such that, at least episodically, water could flow across the surface. In addition to the branching valley networks, there are large flood features, termed outflow channels. These are similar to, but dwarf, the largest terrestrial flood channels. The consensus is that these channels were also cut by water although there are other possibilities. The outflow channels mostly postdate the valley networks, although most are still very ancient. They appear to have formed at a time when surface conditions were similar to those that prevail today. There is evidence that glacial activity has modified some of the water-worn valleys, particularly in the 30-50 • latitude belts, and ice may also be implicated in the formation of geologically recent, seemingly water-worn gullies on steep slopes. Mars also has had a long volcanic history, and long, sinuous lava channels similar to those on the Moon and Venus are common on and around the large volcanoes. These will not, however, be discussed further; the emphasis here is on the effects of running water on the evolution of the surface.

Identification and Characterization of Early Mission Phase Microorganisms Residing on the Mars Science Laboratory and Assessment of Their Potential to Survive Mars-like Conditions

“…The focus to search for life on Mars is supported by recent findings that ancient environments on Mars could have supported microbial life (Grotzinger et al, 2014). Despite the fact that present-day Mars is quite cold and dry, these conditions are thought to be analogous to conditions on early Earth when single-celled life was gaining a foothold (Rasmussen et al, 2009;Carr, 2012). Current explorations of Mars confirm that all the basic necessities for microbial life are present, but it remains unclear whether microorganisms that are metabolically capable of living on Mars can actually survive in the martian environment.…”

“…Thus, it is expected that there was an even greater diversity of microorganisms on MSL when the total bacterial, archaeal, and fungal community is taken into account (La . Previous studies in which culture-independent techniques were used on samples collected from clean rooms of various NASA facilities have shown a wide variety of microorganisms present, but their activity has not been evaluated, so it is not clear whether all the microbes represented are viable (La Duc et al, 2004, 2012Moissl et al, 2008;Vaishampayan et al, 2010). At present, international policy is primarily concerned with the number of spore-forming microorganisms/bacteria on board the spacecraft, since spores have a higher probability of surviving the trip to Mars.…”

“…Previous studies testing survival of Earth microorganisms in simulated martian conditions have focused on spore-forming microorganisms, particularly bacteria of the Bacillus genus, since spores are hardy forms of terrestrial life that can survive Mars-like conditions (Horneck, 1993;Nicholson et al, 2000;Riesenman and Nicholson, 2000;Schuerger et al, 2003;Link et al, 2004;Newcombe et al, 2005;Tauscher et al, 2006;Zenoff et al, 2006;Fajardo-Cavazos et al, 2010). Several studies have reported on the survival of spore-forming Bacillus species isolated from clean room facilities after exposure of microbes to specific Mars-like environmental conditions (Setlow, 2001(Setlow, , 2006Nicholson et al, 2002), but recent culture-independent analyses have shown that spore-formers are not the only types of microorganisms present in assembly and clean room facilities (Venkateswaran, 2001;La Duc et al, 2007a, 2012Moissl et al, 2007Moissl et al, , 2008Vaishampayan et al, 2010Vaishampayan et al, , 2013. Some studies have focused on testing survival of extremophilic microbes that have the metabolic capabilities to inhabit Mars (La Duc et al, 2007a;Morozova et al, 2007;Gómez et al, 2010;Bauermeister et al, 2014), while a lesser number of studies have addressed survival of non-extremophilic, non-spore-forming microbes exposed to Mars-like environmental conditions (La Duc et al, 2007b;Osman et al, 2008;Berry et al, 2010).…”

Quantifying geological processes on Mars—Results of the high resolution stereo camera (HRSC) on Mars express

“…At the boundary between the Late Noachian and Early Hesperian, environmental and climate conditions changed significantly and resulted in a transition towards a colder and drier climate. The intensity of aqueous activity decreased throughout the Hesperian, including a transition from long-term and repeated precipitation-induced fluvial activity towards reduced, short-term, spatially isolated and groundwater-dominated fluvial erosion (e.g., Harrison and Grimm, 2005;Solomon et al, 2005;Erkeling et al, 2010;Jaumann et al, 2010b;Carr, 2012). By the end of the Hesperian, fluvial erosion had mostly ceased and volcanic, aeolian and glacial processes are interpreted to be dominant on Mars.…”

River history

“…The channels on Mars have invited comparison with terrestrial networks because Schiaparelli's canali were mistranslated as canals, and there is growing acceptance that they were fashioned at least partly by running water. Carr [30] has assessed the evidence and compared its chronology with that of the Earth. The discussion can be broadened to consider whether river-like features on other terrestrial planets and their moons were created by water or another fluid and what the answer tells us about past millennia (figure 1).…”