Geology Reference
In-Depth Information
re
ectedbeamspickedupbytheEarth-basedradar
observatory in Puerto Rico. Although the results were
not de
nitive, the radar signature gave hints that ice
could be present.
The Lunar Prospector mission was the
first of the
scientist Principal Investigator-led projects in NASA
s
Discovery Program. Carrying a payload that included a
gamma-ray spectrometer, a neutron spectrometer, and a
magnetotmeter and launched in 1998, this mission had the
primary objectives of searching for traces of water, map-
ping surface compositions, and characterizing the signa-
tures of magnetic
fields preserved in the rocks. Initial
results from the neutron spectrometer revealed hydrogen
in some areas, which was interpreted to be due to water-
ice contained within the regolith. At the end of the mis-
sion, it was decided to crash the spacecraft into the south
polar highlands and observe the impact from Earth in
the hope of detecting released water vapor. Although the
results were negative, it is generally thought that the
impact energy was insuf
cient to release signi
cant vola-
tiles and that the Earth-based telescopic resolution was too
low for their detection.
In the fall of 2003, the European Space Agency
launched the SMART-1 (Small Missions for Advanced
Research in Technology) spacecraft to the Moon.
Although, as the name implies, this was primarily an
engineering mission to test solar-electric propulsion and
a set of small instruments, part of the payload included an
imaging system and spectrometers to collect scienti
c
information for the lunar surface. The mission was an
engineering success and returned new data, including
excellent images, such as those of the poorly understood
Reiner Gamma Formation (
Fig. 4.16
) on the western near
side of the Moon. This bright swirling pattern has been a
matter of controversy for decades, with ideas including
the possibility that transient magnetic
fields generated by
impacts caused sorting and redistribution of
fine lunar
dust. The feature had been imaged previously and planet-
ologist Peter Schultz suggested that a low-density comet
impacted the area at a low angle, with the debris mixing
with local lunar surface materials.
The SMART-1 mission ended with its planned crash on
the near side in September 2006. The light
ash generated
by the impact was recorded at various Earth-based observ-
atories with the hope of detecting water vapor but, again,
the results were inconclusive.
The early part of the twenty-
rst century saw renewed
interest in the Moon, with many nations entering the
“
deep
space club.
”
Following the successes of previous missions,
'
Figure 4.16. The swirling bright pattern seen in the lower half of this
SMART-1 image is part of the Reiner Gamma Formation in Oceanus
Procellarum. This pattern could represent the impact of a comet, with
the debris altering the lunar surface soils, as suggested by Pete
Schultz, Patrick Pinet, and others. The area shown is about 30 km by
60 km (ESA SMART-1 image SEMWQCVNFGLE).
Japan, China, India, and other nations began plans for
robotic exploration of the Moon. Launched in 2007 by the
Japan Aerospace Exploration Agency (JAXA), the Kaguya
(also referred to as SELENE in earlier years) spacecraft
carried 14 instruments into orbit, including an imaging
system (
Fig. 4.17
), and began returning data in October of
that year. The mission also included two sub-satellites to
enable communication from the lunar far side; careful
tracking of the three craft enabled the generation of precise
gravity maps. A radar sounder system provided subsurface
profiling to detect the boundary between mare lava flows
and the underlying regolith. The Kaguya mission came to
an end in June 2009 with the intended crash on the
Moon. The year 2007 also saw the launch of the Chinese
Chang
e1orbiter, which began returning images from its
200 km orbit in late 2007 (
Fig. 4.18
). This mission was
primarily for engineering purposes and for collecting
images for subsequent landed missions to the Moon. It,
too, ended with a planned crash on the Moon in March
2009.
India
'
s entry to lunar exploration was marked with the
launch of Chandayaan-1 in October 2008. This mission
had both engineering and scienti
c objectives, and carried
'
