Rheological evidences of water-rich stratification in Mars
Abstract
Early Mars would have enough water to cover its entire surface, perhaps paleo-ocean reaching depth greater than several hundred meters (e.g., Carr, 1966). However, such liquid water has been disappeared and the preset atmosphere on Mars becomes highly dry. Water might have been escaped to space due to a relatively small gravitational energy on Mars, as indicated by an enrichment of deuterium in the present-day martian atmosphere. However, these estimates do not fully account for the water concentration inferred from surface geology such as fluvial and glacial features on Mars. This means another water reservoir possibly existed in Mars, probably in its interior, because the water-rock interactions can result in the incorporation of large amounts of water and such processes are common in Earth. We focus on elastic thickness of martian lithosphere estimated from gravity and topography data obtained by the Mars Global Surveyor and other orbiters, in which early formed terrains (ca. >3.7 Ga) are characterized by a thin elastic layer, whereas during the later periods the elastic layer was relatively thick (McGovern et al. 2002). Since rock rheology is largely influenced by water, we investigate how water influence the elastic thickness based on recent rheological data, and test whether water-rich lithosphere can account for the variation of the elastic thickness observed in Mars. Our preliminary results indicate that, given sensitivity of elastic thickness to water, the temporal change in elastic thickness can be explained by a transition from a wet to a dry rheology in the martian lithosphere. This suggests the presence of ancient water reservoir in Mars, possibly related to operation of plate tectonic and downward transport of water during the early evolution of Mars.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMMR23B0079K
- Keywords:
-
- 1038 Mantle processes;
- GEOCHEMISTRYDE: 3924 High-pressure behavior;
- MINERAL PHYSICSDE: 3630 Experimental mineralogy and petrology;
- MINERALOGY AND PETROLOGYDE: 5199 General or miscellaneous;
- PHYSICAL PROPERTIES OF ROCKS