Second Conference on Early Mars (2004) 8014.pdf NOACHIAN-HESPERIAN TRANSITION AND A POSSIBLE CLIMATIC OPTIMUM: EVIDENCE FROM LANDFORMS. J. M. Moore1 and A. D. Howard2, 1NASA Ames Research Center, MS 245-3, Moffett Field, CA, 94035-100,
[email protected]., 2Department of Environmental Sciences, P.O. Box 400123, University of Virginia, Charlottesville, VA 22904-4123,
[email protected] Introduction: A climatic optimum? The often apex. Ridges are often stacked upon one another, strong contrast between the ‘pristine’ and degraded exhibiting crosscutting and superposition. One ridge Noachian channels and craters noted in [e.g. 1] might forms a well-defined loop with distinct, successive be due to a gradual climatic change superimposed scroll-bar recording the progressive growth of the upon an episode of mantling associated with early meander, and eventually its cutoff, identical to that Hesperian volcanism. On the other hand, one or more seen on terrestrial floodplains. The digitate periphery episodes of volcanism or large impacts could have in detail is scarp-like, where individual ridge flanks induced global warming [2,3] and produced a and termini exhibit alternating steep slopes and ledges relatively short-lived optimum for precipitation and forming up to on order of a dozen steps, each ~10 m runoff. The rapid cutoff of fluvial activity following high interpreted to discrete layers of indurated the development of the later ‘pristine’ fluvial features material. To date only one other feature similar to (but is consistent with this scenario. We discuss the less well presented) this delta has been found, also on changing style of erosion in the highlands during the N-H materials (Fig.