Magma Flow at Mid-Ocean Ridges
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چکیده
Liquid water is not stable under current martian surface conditions, but the presence of small gullies on the polewardfacing slopes of midto highlatitude martian surfaces suggests that erosion by liquid water might have occurred. Costard et al. (p. 110) developed a global climate model for Mars when it had a higher obliquity (about 300,000 years ago). Their model shows that more melting of the polar ice caps would have occurred and an increase in the surface pressure and temperature at midto high-latitudes in the summer would have allowed liquid water to flow. Similarly shaped gullies have been observed in periglacial debris flows from eastern Greenland. These observations, taken together with the modeling, suggest that the martian gullies formed by a freeze-thaw cycle of water on the surface, rather than through flow of an aquifer system.
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