Acquisition and history of water on Mars

摘要: The purpose of this chapter is to summarize the geologic history Mars and role water has played in evolution surface so that subsequent chapters on more specific topics can be viewed a broader context. It focuses mainly surficial processes such as erosion, sedimentation, weathering, rather than primary terrain-building impact, tectonism, volcanism, since provide information conditions under which lakes could have formed. With mean annual temperature 215 K pressure 6.1 mbar, liquid exist at only locally temporarily anomalous conditions. Yet, evidence for widespread presence compelling, particularly early Mars, claims also been made present-day activity. Martian features divided into three age groups—Noachian, Hesperian, Amazonian—on basis intersection relations numbers superimposed impact craters. A major change occurred end Noachian. rates valley formation, erosion dropped precipitously. On other hand, volcanism continued relatively high rate throughout resulting resurfacing least 30% planet. Large floods formed episodically, possibly leaving behind large bodies water. formation ice-related gullies probably varied changes obliquity affected ice-stability relations.