From: Goddard Space Flight Center
Posted: Thursday, February 21, 2002
Proceedings of the National Acacdemy of Sciences: PNAS 2002 99: 1780-1783.
Oded Aharonson, Maria T. Zuber, Daniel H. Rothman, Norbert Schorghofer, and Kelin X. Whipple
Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 Communicated by Sean C. Solomon, Carnegie Institution of Washington, Washington, DC, December 27, 2001 (received for review November 15, 2001)
Measurements acquired by the Mars Orbiter Laser Altimeter on board the Mars Global Surveyor indicate that large drainage systems on Mars have geomorphic characteristics inconsistent with prolonged erosion by surface runoff. We find the topography has not evolved to an expected equilibrium terrain form, even in areas where runoff incision has been previously interpreted. By analogy with terrestrial examples, groundwater sapping may have played an important role in the incision. Longitudinally flat floor segments may provide a direct indication of lithologic layers in the bedrock, altering subsurface hydrology. However, it is unlikely that floor levels are entirely due to inherited structures due to their planar cross-cutting relations. These conclusions are based on previously unavailable observations, including extensive piece-wise linear longitudinal profiles, frequent knickpoints, hanging valleys, and small basin concavity exponents.
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