Late Noachian to Hesperian climate change on Mars: Evidence of episodic warming from transient crater lakes near Ares Vallis

Abstract

[1] The Ares Vallis region is surrounded by highland terrain containing both degraded and pristine large impact craters that suggest a change in climate during the Late Noachian-Early Hesperian, from warmer, wetter conditions to colder, dryer conditions. However, the regional occurrence of Hesperian-age crater outlet channels indicates that this period on Mars was characterized by episodic climate fluctuations that caused transient warming, facilitating the stability of liquid water at the surface. An extensive survey of the morphology and topography of 75 impact basins in the region indicates that of the largest degraded craters, 4 were identified with single outlet channels that suggest the former presence of water infill. These basins lack inlets indicating that water influx was likely derived from sapping of groundwater. A comparison of measured crater rim heights to modeled rim heights suggests that the bulk of the depth/diameter reduction on these craters was the result of infilling, possibly by sediments. Crater statistics indicate that crater degradation and infill occurred during a short 200 Ma interval in the Late Noachian, from 3.8 Ga to 3.6 Ga. Craters that formed after 3.6 Ga exhibit a near-pristine morphology. Our results support the hypothesis of rapid climate change at the end of the Noachian period. However, geologic relationships between the crater outlet channels and Ares Vallis indicate that drainage occurred only after the period of intense crater modification, during the Hesperian (3.5-2.9 Ga). This suggests a delay between the time of infill of the craters and the time of drainage.

Paleohydrology of Eberswalde crater, Mars

“…The mid-Hesperian or later phases of erosion have been identified in local study areas for some time (e.g., Baker and Partridge, 1986;Grant and Schultz, 1990;Gulick and Baker, 1990), but broader recognition of Hesperian or Amazonian fluvial landforms has improved significantly over the last decade (e.g., Mangold et al, 2004;Quantin et al, 2005;Ansan and Mangold, 2006;Mangold and Ansan, 2006;Mangold et al, 2008;Williams and Malin, 2008;Bouley et al, 2009Bouley et al, , 2010Warner et al, 2010;Howard and Moore, 2011;Mangold, 2012;Weitz et al, 2013). It remains to be determined whether these late fluvial valleys have a patchy extent or are simply underrecognized, because they are generally less dense than their counterparts from around the Noachian/Hesperian transition.…”

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

“…Lower terraces mark subsequent floods, and often show a characteristic grooved surface. Grooves are generally several tens of meters wide and are spaced by tens to a few hundred meters spaced (Pacifici, 2008;Pacifici et al, 2009;Warner et al, 2009aWarner et al, , 2010c. Measurements based on HRSC-derived DTMs of eroded trimlines and terraces indicate that the depth of the last flood thickness was about 200 m proximal to Iani Chaos and 200-300 m in the narrow reach of Ares Vallis (Warner et al, 2009a).…”

“…12b and c) are widespread in Ares Vallis; they are hundreds of meters wide, tens to a few hundreds of meters deep, and several kilometers long. Generally they originate from (i) flat-floored impact craters, (ii) depressions interpreted to have formed by thermokarst processes (Warner et al, 2010a), and (iii) geological contacts between different layers on the valley walls (Pacifici, 2008;Pacifici et al, 2009;Warner et al, 2009aWarner et al, , 2010c. Larger parts of sinuous channels are carved into erosive terraces and crosscut flood grooves.…”

火星の海・湖・アウトフローチャネルの比較惑星地質学

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