100-C 25-C 50-C 75-C C+M 50-C+M C+Y 50-C+Y M+Y 50-M+Y 100-M 25-M 50-M 75-M 100-Y 25-Y 50-Y 75-Y 100-K 25-K 25-19-19 50-K50-40-40 75-K 75-64-64CHAPTER 17
Mars: Landing Site
Geology, Mineralogy
and Geochemistry
Matthew P. Golombek
Jet Propulsion Laboratory
Pasadena, CaliforniaHarry Y. McSween, Jr.
University of Tennessee
Knoxville, Tennessee- Introduction 5. Landing Site Mineralogy and Geochemistry
- Landing Sites on Mars 6. Implications for the Evolution of Mars
- Landing Sites in Remotely Sensed Data Bibliography
- Landing Site Geology
1. Introduction
Most of our detailed information about the materials that
make up the martian surface comes from the in situ in-
vestigations accomplished by the five successful landers
(Table 1). The focus of these landers and the era in which
they explored Mars have varied. The first successful land-
ings were the Vikinglanders in 1976, part of two or-
biter/lander pairs that launched in 1975. The overriding
impetus for theVikinglanders was to determine if life ex-
isted on Mars. Both immobile, legged landers carried so-
phisticated life detection experiments as well as imagers,
seismometers, atmospheric science packages, and magnetic
and physical properties experiments. TheVikingmission
was done in the post-Apolloera (after 1972) and involved
a massive mobilization of engineering and scientific talent
(as well as a budget befitting a major mission). The life
detection experiments found no unequivocal evidence for
life in the soil (although gases released from the soil sug-
gested a significant oxidizing component) but did image the
landing sites and determine the chemistry of soils. The suc-
cessful landings and operations of the orbiters (that lasted
years) set the stage for the systematic study of Mars and
left a legacy for landing using an aeroshell and a supersonic
parachute that have been used by all subsequent landers.
TheVikingorbiters returned imaging data of valley net-
works and eroded ancient craters and terrain that suggested
an earlier wetter and possibly warmer environment, con-
trary to the present climate whose atmosphere is generally
too cold and thin (and dry) to support liquid water (cur-
rent atmospheric pressure and temperature are so low that
water is typically stable in solid and vapor states).
TheMars Pathfindermission, launched 20 years later in
1996, was an engineering demonstration of a low-cost lan-
der and small mobile rover. The spacecraft was a small free
flyer that used aViking-derived aeroshell and parachute,
but developed and used robust airbags surrounding a tetra-
hedral lander. The lander carried a stereoscopic color
imager (IMP), which included a magnetic properties ex-
periment and wind sock, and an atmospheric structure and
meteorology experiment. The 10 kg rover (Sojourner) car-
ried engineering cameras, 10 technology experiments, and
an Alpha Proton X-ray Spectrometer (APXS) for measur-
ing the chemical composition of surface materials (Table 2).
TheMars Pathfinderlander and rover operated on the sur-
face for about 3 months (well beyond their design lifetime),
and the rover traversed about 100 m around the lander, ex-
ploring the landing site and characterizing surface materials
in a couple of hundred square meter area. Rocks measured
by the APXS appeared high in silica, similar to andesites;
tracking of the lander fixed the spin pole and polar moment
of inertia that requires a central metallic core and a dif-
ferentiated planet; and the atmosphere was observed to be
quite dynamic with water ice clouds, abruptly changing near