This document is part of the Martian Time Boneyard. It was originally located at http://helio.estec.esa.nl/intermarsnet/redreport/node20.html.
Author: Jeffrey E. Moersch

Geologic History



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Geologic History

By mapping the age and distribution of the features seen on Mars, it is possible to derive a general history. The earliest history on Mars, termed the Noachian Period, is recorded in the heavily cratered terrain and ancient impact basins, such as Hellas. These reflect the final stages of crustal solidification and the end of the period of heavy bombardment seen throughout the inner Solar System. The development of the crustal dichotomy to form the northern lowlands occurred in this period, accompanied by extensive erosion by wind and water. Sediments and volcanic materials (lavas and possibly ash deposits) blanketed parts of Mars, but were then eroded in many places, leaving the valley networks seen today.

The Hesperian Period marks Mars' middle age. Extensive flood lavas were erupted from long fissures, creating many of the plateau regions, such as Hesperia Planum. Some of the eruptions then evolved to a different type, in which magma reached the surface through local vents, in contrast to the earlier fissure eruptions. Earliest representations of this style of volcanism are the highland patera, seen around the Hellas Basin, and the Elysium volcanoes. The older volcanoes of the Tharsis area also began to grow during the Hesperian Period. This growth was accompanied by extensive crustal deformation along the equator, which opened up Valles Marineris. The enormous outflow channels were carved in this period and released tremendous floods of water that washed across many areas of Mars.

The Amazonian Period is the youngest subdivision of time on Mars. It is represented by late-stage lava flows in the Tharsis region, including those that make up most of the volcano Olympus Mons, and the younger lavas of the Elysium region. Wind and water sediments of this age fill parts of the Hellas, Argyre, and Isidis impact basins, as well as parts of the northern lowlands, and show that extensive erosion and deposition were taking place.

Currently, the surface of Mars is shaped primarily by wind and landslides, punctuated by the occasional formation of impact craters. Whether Mars experiences active volcanism or marsquakes is unknown at present but will be an important question to be addressed by future missions. We are just beginning to understand the complexity of the history of Mars. New measurements of the atmosphere, surface, and interior will be required before we can advance our understanding of the Red Planet.



next up previous contents
Next: GEOCHEMISTRY AND MINERALOGY Up: GEOLOGY Previous: Aeolian Features



Jeffrey E. Moersch
Thu Apr 4 17:57:31 EST 1996