Mars: Landing Site Geology, Mineralogy and Geochemistry 333
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0 °180 ° 210 ° 240 ° 270 °^300 °^330 °^0 ° 30 ° 60 °^90 ° 120 °^150 ° 180 °180 ° 210 ° 240 ° 270 ° 300 ° 330 ° 0 ° 30 ° 60 ° 90 ° 120 ° 150 °0 °THE TOPOGRAPHY OF MARS ORBITER LASER ALTIMETER (MOLA)VL2VL1
MPFMeridiani180 °Gusev− 8 − 404128 km− 10 °
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− 40 °− 50 °− 60 °FIGURE 1 MOLA (Mars Orbiter Laser Altimeter onMars Global Surveyor) topographic map of
Mars showing the 5 successful landing sites. Elevations are reported with respect to the geoid (or
geopotential surface) derived from the average equatorial radius extrapolated to the rest of the
planet via a high order and degree gravity field. The resulting topography faithfully records
downhill as the direction that liquid water would flow. Longitudes are measured positive to the
east according to the most recent convention. The locations of the landers and their elevations are
reported in Table 1. Prior to MOLA, which provided definitive topography and an accurate
cartographic grid, elevations and locations were poorly known for landing spacecraft on Mars.
The map shows 3 fundamental aspects of Mars: the southern highlands, northern lowlands, and
Tharsis, an enormous elevated region of the planet (located southwest of VL1 on the map).
Tharsis is surrounded by a system of generally radial extensional tectonic features (including the
huge Valles Marineris canyon that extends to the east of Tharsis) and generally concentric
compressional tectonic features that both imprint the entire western hemisphere of the planet.
Located at the edges of Tharsis and the highland–lowland boundary are the catastrophic outflow
channels that funneled huge volumes of water into the northern plains (including Chryse Planitia
where the VL1 and MPF landing sites are located) intermediate in Mars history.and parachute to slow them down and sufficient atmosphere
and time were required to carry out entry and descent. This
favored landing at low elevations as shown in Fig. 1, which
shows the locations of the landing sites on a topographic
map of Mars. The map shows the southern hemisphere
is dominated by ancient heavily cratered terrain estimated
to be more than 3.7 billion years old. The northern hemi-
sphere is dominated by younger, smoother, less cratered ter-
rain that is on average 5 km lower in elevation. Astride the
hemispheric dichotomy is the enormous Tharsis volcanic
province, which rises to an elevation of 10 km above the
datum, covers one quarter of the planet, is surrounded by
tectonic features that cover the entire western hemisphere,
and is topped by five giant volcanoes and extensive vol-
canic plains. The elevated Tharsis province and the cratered
highlands have been too high to land existing spacecraft.
TheVikinglanders landed in the northern lowlands, as did
Mars Pathfinder, and the Mars Exploration Rovers landed
at relatively low elevations in the transition between the
highlands and lowlands.
Landing site selection for the five landers included in-
tense periods of data analysis of preexisting and incoming
information. TheVikinglander/orbiter pairs were captured
into Mars orbit and the orbiter cameras started a concen-
trated campaign to image prospective landing sites (at tens
to hundreds of meters per pixel) selected on the basis of pre-
viousMariner 9images. A large site selection science group
assembled mosaics (using paper cut outs pasted together
by hand) in real time and after waiving off several land-
ing sites on the basis of rough terrain and radar scattering
results (and missing the intended July 4 landing),Viking 1
landed on ridged plains in Chryse Planitia. The site is down-
stream from Maja and Kasei Valles, giant catastrophic out-
flow channels that originate north of Valles Marineris, the
huge extensional rift or canyon that radiates from Tharsis
(Fig. 1). Its low elevation and proximity to the channels