System of gigantic valleys northwest of Tharsis, Mars: latent catastrophicflooding, northwest watershed, and implications for northern plains ocean

Mars Orbiter Laser Altimeter (MOLA) reveals a system of gigantic valleys to the northwest of the huge martian shield volcano, Arsia Mons, in the weste rn hemisphere of Mars. These newly identified northwestern slope valleys (N SVs) potentially signify previously undocumented martian catastrophic flood s and may corroborate the northern ocean hypotheses. These features, which generally correspond spatially to gravity lows, were previously obscured in Mariner and Viking Orbiter imagery by veneers of materials, including volc anic lava flows and air fall deposits. Geologic investigations of the Thars is region suggest that the NSVs were mainly carved prior to the constructio n of Arsia Mons and its associated Late Hesperian and Amazonian age lava fl ows, concurrent with the early development of the outflow channels that deb ouch into Chryse Planitia.