What Happened When on Mars?: Some Insights into the Timing of Major Events from Mars Global Surveyor Data.

Details What Happened When on Mars?: Some Insights into the Timing of Major Events from Mars Global Surveyor Data. What Happened When on Mars?: Some Insights into the Timing of Major Events from Mars Global Surveyor Data.

May 2001

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agusm...p31a06s&link_type=abstract

American Geophysical Union, Spring Meeting 2001, abstract #P31A-06 INVITED

Physics

5430 Interiors (8147), 5440 Magnetic Fields And Magnetism, 5475 Tectonics (8149), 5480 Volcanism (8450)

Scientific paper

Global data sets acquired by experiments on the Mars Global Surveyor (MGS) spacecraft, together with data from prior missions and Martian meteorites, permit a new synthesis of the relative timing of major events in the early history of Mars. Core-mantle differentiation occurred within the first tens of millions of years of planet formation, on the basis of isotope systematics in Martian meteorites. A magnetic dynamo was active in the early Noachian but apparently ceased before the end of heavy bombardment. Crustal formation in the southern crustal province predated the end of the core dynamo, although the general south-to-north thinning of the crust may have been established subsequent to crustal emplacement (e.g., by lower crustal flow). Crustal formation in the northern crustal province, marked by nearly uniform crustal thickness, may have occurred later than in the south, on the basis of the absence of prominent magnetic anomalies detected by MGS, but the crust was in place well before the end of heavy bombardment. The onset of the Tharsis province as a site of voluminous magmatism and concentrated deformation likely postdated the establishment of the crustal thickness dichotomy, but much of the magmatism occurred prior to or during the middle Noachian. Late Noachian valley networks formed after much of Tharsis magmatism had occurred. Extensive resurfacing of the northern hemisphere occurred in the Noachian, on the basis of the detection of large impact structures superposed on older filled basins. Extensive evidence for water-surface interactions during this period supports the view that much of the Noachian resurfacing occurred by the transport and deposition of sediments. Impact stripping of the atmosphere was substantial during the Noachian, and solar wind sputtering would have contributed to further atmospheric loss after cessation of the core dynamo. The northern hemisphere was resurfaced by early Hesperian volcanic plains, which were subjected to an episode of contractional deformation of widespread extent. Even this abbreviated summary raises many questions, including the mechanism and duration of crustal formation, the links between the crustal thickness dichotomy and Tharsis, the cause of the dynamo shut-down, the Noachian-Hesperian volcanic flux history, and its links to volatile outgassing and climate change.

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