NOACHIAN MARTIAN HIGHLANDS; THE HABITAT OF ANCIENT LIFE?

摘要

About 40% of the total Martian crust consists of heavily cratered Noachian crust (older than 3.7 Ga), also called the Martian highlands. To date, only one of the found Martian meteorites is derived from these Noarchian highlands, the so-called ALH84001. The antiquity of the ALH84001 meteorite indicates that it originated from the Martian Highland area, and that these highlands may have been the habitat of ancient Martian life. The part of the Martian highlands centered on 180° exhibits large magnetic anomalies. However the origin of the magnetic anomalies remains enigmatic and it is not clear yet what the relation is between magnetite in the meteorite and the magnetic anomalies. In 2004, one of the MER landers, called Spirit, will study the Gusev crater which straddles the boundary between the Martian highlands and the northern lowlands. To characterize the highland areas neighboring the landing site craters we study the available visual and IR image data (THEMIS, MOC), TES spectroscopy data and MOLA altimetry data. This provides a geological framework in anticipation of lander geochemical analysis of rock samples.