Thermal isostasy and deformation of possible paleoshorelines on Mars

Abstract

Variations in martian surface heat flow, similar to those observed in terrestrial continental tectonothermally stable areas, could result in elevation differences of kilometric scale through differential thermal isostasy. This effect is enhanced with the increase of heat sources located within the crust. Local differences in the thermal history of the Mars' lithosphere could have appreciably distorted the original long-wavelength topography of putative martian paleoshorelines. So, this work shows that a paleoequipotential surface does not necessarily have to fit well a present-day equipotential surface when evaluating paleoshorelines through assessment of high-resolution topography. r

The present-day thermal state of Mars

“…5 and 10 of Carr and Head (2003) ). Deviations of equipotentiality along martian paleoshorelines could be caused by modification of the original topography due to thermal isostasy related to different thermal histories between the regions transected by these paleoshorelines (Ruiz, 2003;Ruiz et al, 2004 ).…”

GRS evidence and the possibility of paleooceans on Mars

“…Several processes could significantly deform the originallong-wavelength topography of Martian paleoocean boundaries following the disappearance of the possible oceans. Different thermal histories among Martian regions could produce elevation differences of kilometer scale through thermal isostasy, even for initial variations in surface heat flow of relative amplitude similar to those in tectonothermally stable terrestrial continental areas (Ruiz et al, 2004 ). Lithospheric rebound due to water unloading associated with the disappearance of an ocean with irregularly shaped margins could result in deviations of equipotentiality of up to several hundreds of meters (Leverington and Ghent, 2004 ).…”

Marine‐target craters on Mars? An assessment study

“…The hypothesis, which suggests short-lived hydrological cycles, contrasts with the general belief that Mars was warm and wet and later transitioned into persistent cold and dry desert conditions. Controversy exists concerning whether contacts 1 and 2 (Parker et al 1989(Parker et al , 1993 are actual shorelines of paleooceans (e.g., Head et al 1998Head et al , 1999Ruiz et al 2003) and whether standing bodies of water have existed for more than a few hundred years (e.g., Segura et al 2002;Banfield et al 2003;Hoefen et al 2003). Several arguments have been advanced to assess whether water masses ever accumulated on the martian surface, including: insufficient Mars Orbital Camera (MOC)-based evidence to support the existence of coastlines (Malin and Edgett 1999); CO 2 as the primary erosional agent to explain the geomorphic characteristics of the martian surface (Hoffman 2001); the rough coincidence between the peak in the valley network formation and the period of heavy bombardment in the Noachian (Segura et al 2002); the hydrodynamic escape of atmospheric volatiles, including CO 2 (e.g., Anders and Owen 1977); and the lack of Smith et al [1999]).…”