Observations at the Mars Pathfinder site: Do they provide “unequivocal” evidence of catastrophic flooding?

Abstract

Abstract. After Mars Pathfinder landed at the mouth of Ares Vallis, a large channel that drains into the Chryse Planitia basin, the mission reports unanimously supported the interpretation that the lander site is the locus of catastrophic flooding by noting that all aspects of the scene are consistent with this interpretation. However, alternatives cannot be ruled out by any site observations, as all aspects of the scene are equally consistent with other interpretations of origin, namely, ice and mass-flow processes subsequently modified by wind erosion. The authors discuss alternative explanations for the geologic history of the channel based on a regional view of the circum-Chryse channels from Viking images (our best broad-scale information to date) and the local view from the recent Pathfinder landing site. Mega-indicators of channel origin, the regional geomorphology, geology, and planetary climatic conditions, taken together suggest some combination of flood, mass flow, glacial, and eolian processes. The macro-indicators of channel origin (sedimentologic) are also not indicative of one process of emplacement, either as single criteria or taken cumulatively. Finally, the micro-indicators of channel origin (geochemical and mineralogic composition) do not provide very tight constraints on the deposits' possible origins other than that water was in some way involved.

Related Magma–Ice Interactions: Possible Origins of Chasmata, Chaos, and Surface Materials in Xanthe, Margaritifer, and Meridiani Terrae, Mars

“…As the onrushing floods bulk up with debris they may transition into lahars (volcanic mass flows; Van Bemmelen, 1949) that fan out on the "sandur plains" of southern Iceland and spread into the sea. In a fashion similar to jökulhlaups, catastrophic floods debouching from chasmata and chaotic terrains may have bulked up with eroded material to form mass flows (Tanaka 1997, Chapman and Kargel 1999. Mass flow deposits in Chryse Planitia are consistent with the large locally imbricated rocks observed at the Pathfinder Site below Tiu and Ares Valles and with the lobate flow fronts in Chryse basin (Fig.…”

“…Mass flow deposits in Chryse Planitia are consistent with the large locally imbricated rocks observed at the Pathfinder Site below Tiu and Ares Valles and with the lobate flow fronts in Chryse basin (Fig. 1;Nummedal and Prior 1981, Jöns 1990, Lucchitta 1998, Chapman and Kargel 1999, Nelson and Greeley 1999, Tanaka 1999. Rice (2000) noted that MOC and Pathfinder images show transverse ribs, boulders, pit craters, imbricated rocks, percussion marks, and possible conglomerate, similar to those formed by jökulhlaups on the sandur plains of Iceland.…”

“…Perhaps in the upper reaches of the channels, scour and moraine development is either buried by eolian dunes, did not occur due to flow through ice, or did not become large enough to observe in dark albedo channel/chasmata areas that are covered by mostly low-resolution Viking data. Therefore the channels may be explained by a combination of floods, glaciers, and mass-flow processes (Chapman and Kargel 1999).…”

The 1999 Marsokhod rover mission simulation at Silver Lake, California: Mission overview, data sets, and summary of results

“…There is mounting evidence that water was present at the surface of Mars early in its history and ponding took place in both topographic lows and impact craters [Grin and Cabrol, 1997;Malin et al, 1998;Smith et al, 1997;Basilevski et al, 1999;Chapman and Kargel, 1999;Jakosky, 1999;Smith et al, 1999;Golombek et al, 1999;Greeley et al, 1999;Ward et al, 1999;McEwen et al, 1999;Hartmann et al, 1999;Malin and Carr, 1999;Thomas et al, 1999;Cabrol and Grin, 1999]. Silver Lake thus presents an analog for climatic evolution (from wet to dry) on Mars.…”

Water soluble ions in the Nakhla martian meteorite

“…, 1989; Rieder et a/., 1997). The landing site of the Pathfinder mission has been interpreted to suggest "some combination of flood, mass flow, glacial and eolian processes" (Chapman and Kargel, 1999). It is possible that the detected S and C1 are due to the soluble ions sulfate and chloride (Cl-), respectively.…”