Out of more than 30 sites considered as possible landing targets for
NASA's Mars Science Laboratory mission, by November 2008 four of the most
intriguing places on Mars rose to the final round of the site-selection
process.
The four finalists are, alphabetically: Eberswalde, where an ancient river
deposited a delta in a possible lake; Gale, with a mountain of stacked
layers including clays and sulfates; Holden, a crater containing alluvial
fans, flood deposits, possible lake beds and clay-rich deposits; and
Mawrth, which shows exposed layers containing at least two types of clay.
The locations of these four candidates are indicated here on a background
map of color-coded topographical data from the Mars Orbiter Laser
Altimeter on NASA's Mars Global Surveyor. Red is higher elevation; blue is
lower elevation. In latitude, the map extends from 70 degrees (north) to
minus 70 degrees (south). The east-west axis is labeled at the top in
degrees of east longitude, with the zero meridian at the center.
The Mars Science Laboratory mission's capabilities for landing more
precisely and at higher elevation than ever before, for driving farther,
and for generating electricity without reliance on sunshine have enabled
consideration of a wider range of possible landing sites than for any
previous Mars mission. During the past two years, multiple observations of
dozens of candidate sites by NASA's Mars Reconnaissance Orbiter have
augmented data from earlier orbiters for evaluating sites' scientific
attractions and engineering risks.
More than 100 Mars scientists have participated in a series of open
workshops presenting and assessing data that the orbiters have provided
about the candidate sites. The four sites rated highest by researchers at
a September 2008 workshop were the same ones chosen by mission leaders
after a subsequent round of safety evaluations and analysis of terrain for
rover driving.
As a clay-bearing site where a river once flowed into a lake, Eberswalde
Crater offers a chance to use knowledge that oil industry geologists have
accumulated about locations of the most promising parts of a delta to look
for any concentrations of carbon chemistry that is crucial to life.
The mountain inside Gale Crater could provide a route for the rover to
drive up a 5-kilometer (3-mile) sequence of layers, studying a transition
from environments that produced clay deposits near the bottom to later
environments that produced sulfate deposits partway up.
Running water once carved gullies and deposited sediments as alluvial fans
and catastrophic flood deposits in Holden Crater, a site that may also
present the chance to evaluate layers deposited in a lake. Exploration of
key features within this target area would require drives to the edge of a
broad valley, and then down into the valley.
Mawrth Valley is an apparent flood channel near the edge of vast Martian
highlands. It holds different types of clays in clearly layered context,
offering an opportunity for studying the changes in wet conditions that
produced or altered the clays. The clay signatures are stronger than at
the other sites, and this is the only one of the four for which the
science target is within the landing area, not nearby.
NASA's Jet Propulsion Laboratory, operated by the California Institute of
Technology in Pasadena, manages the Mars Science Laboratory for the NASA
Science Mission Directorate, Washington.