Mathematics – Logic
Scientific paper
May 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agusm...p31a03k&link_type=abstract
American Geophysical Union, Spring Meeting 2001, abstract #P31A-03
Mathematics
Logic
5416 Glaciation, 6225 Mars
Scientific paper
We study the morphology of the Northern Lowlands of Mars primarily with MGS MOLA data. Most of the Northern Lowlands is covered with the Vastitas Borealis Formation (VBF), which has a distinctive kilometer-scale roughness signature. It has sharp boundaries clearly seen in the map of kilometer-scale roughness. We suggest that the VBF was formed of sediments brought by the water floods responsible for the formation of the outflow channels. These sediments were deposited in the Late Hesperian over Early-Hesperian- or Late-Noachian-age substrate interpreted as ridged volcanic plains. The VBF roughness characteristics require at least 100 m thickness of sediments. The total inferred volume of the VBF material approximately corresponds to the volume of material removed from the outflow channels. The evolution of the water loaded with sediments after it left the channels includes three phases. (1) Violent emplacement of warm water followed by a short period of intensive evaporation from the surface and near-surface layer and intensive convection. During this phase the water maintained and redistributed its large suspended sediment load. Water vapor strongly influenced the climate, at least, for a geologically short time. When the temperature of the water reached ~277K, boiling and intensive convection ceased and the water deposited the sediments. (2) Geologically fast ( ~ 104 years) freezing accompanied by weak convective water movement. Solar tides in the large ice-covered seas could have eroding potential under some specific conditions. (3) Sublimation of the ice lasted longer than freezing. The rate and latitudinal dependence of the sublimation, as well as the locations of water vapor condensation crucially depend on the planetary obliquity, climate, and sediment veneering of the ice. The ice sheet underwent bombardment with relatively small meteorites. There is evidence for sequential outflow events that occurred before the ice sheet completely sublimed. There is also evidence for emplacement of lava flows on the ice-covered surface. The modern surface of the VBF is a residue of the final sublimation of this ice sheet. The modern polar cap is probably a result of relatively recent migration of water rather than a remnant of the VBF-forming ice sheet.
Head James W.
Kreslavsky Mikhail A.
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