Geology Reference
In-Depth Information
CHAPTER 11
Planetary geoscience future
11.1 Introduction
11.2 Planetary protection
Planetary geosciences are advanced primarily through
new data and are stimulated by physical and computa-
tional modeling, theoretical studies, and
field studies of
terrestrial analogs in support of planetary data analysis. As
shown in
Fig. 1.11
, missions are currently in
flight for
Mercury, Venus, the Moon, Mars, Jupiter, Saturn, and
Pluto, as well as for a host of asteroids and comets.
Particularly noteworthy is the New Horizons mission,
which will give us our
first close-up views of Pluto in
2015. Spacecraft for these missions carry sophisticated
scienti
c payloads, including imaging systems that will
provide additional coverage, higher resolution, or
rst
ever views of planetary objects of geoscience interest.
Most planetary missions are
flown by NASA, some in
partnership with the European Space Agency, which
also
flies planetary missions independently of NASA.
In addition, the space agencies of Japan, India, and
China are becoming increasingly important, especially in
lunar exploration and the eventual return of humans to the
Moon. (After a hiatus of many years, in 2012 Russia
attempted to resume planetary exploration with a mission
to one of the moons of Mars, Phobos, but that mission
failed shortly after launch.) Although NASA had planned
lunar exploration by humans early in the twenty-
rst
century, such plans have been deferred because of the
economic climate. In its place, considerations are being
given to sending humans to one or more asteroids because
of the lower costs (it is easier to return to Earth from these
low-gravity bodies), the high scienti
c potential of aste-
roids, and the need to assess asteroids as hazards to Earth.
Much of the motivation for planetary exploration is the
search for life beyond the Earth. This involves searching
for signs of past or present life and characterizing environ-
ments conducive to life as we know it. Such exploration
raises the issue of
“
planetary protection.
”
Concern over contamination of planetary objects began
with deep space exploration in the early 1960s and is
termed planetary protection. Planetary contamination
includes both forward contamination, in which terres-
trial organisms from Earth might be carried to other
objects by spacecraft, and backward contamination,in
which potential non-Earthly organisms are brought to
Earth. International protocols through the United
Nations were established for both conditions and most
space-faring nations and agencies have agreed to follow
the procedures given in the protocols. Through interna-
tional agreements for planetary protection,
five categories
of missions are de
ned.
Category I (lowest level) missions include those to the
Sun, Mercury or other objects that are not of direct
interest for prebiotic chemistry or the origin and
evolution of life.
Category II missions include those to objects such
as the Moon, Venus, Jupiter or other targets that are
of interest for prebiotic chemistry and the origin and
evolution of life but for which there is an
insigni
cant probability of contamination by
Earth life.
Category III missions are
flybys or orbiters to
objects such as Mars and Europa that could be hosts
for life and for which there is a possibility of
contamination by Earth life.
Category IV missions are landers or probes to
objects such as Mars and Europa that could be hosts
for life and for which there is a possibility of
contamination by Earth life.
Category V (highest level) missions are sample
returns to Earth from locations that have the
potential to support life.
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