Abstract
Geological mapping and establishment of stratigraphic relationships
provides an overview of geological processes operating on Mars and
how they have varied in time and space. Impact craters and basins
shaped the crust in earliest history and as their importance declined,
evidence of extensive regional volcanism emerged during the Late
Noachian. Regional volcanism characterized the Early Hesperian and
subsequent to that time, volcanism was largely centered at Tharsis
and Elysium, continuing until the recent geological past. The Tharsis
region appears to have been largely constructed by the Late Noachian,
and represents a series of tectonic and volcanic centers. Globally
distributed structural features representing contraction characterize
the middle Hesperian. Water-related processes involve the formation
of valley networks in the Late Noachian and into the Hesperian, an
ice sheet at the south pole in the middle Hesperian, and outflow
channels and possible standing bodies of water in the northern lowlands
in the Late Hesperian and into the Amazonian. A significant part
of the present water budget occurs in the present geologically young
polar layered terrains. In order to establish more firmly rates of
processes, we stress the need to improve the calibration of the absolute
timescale, which today is based on crater count systems with substantial
uncertainties, along with a sampling of rocks of unknown provenance.
Sample return from carefully chosen stratigraphic units could calibrate
the existing timescale and vastly improve our knowledge of Martian
evolution.
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