Geology Reference
In-Depth Information
To avoid forward contamination, spacecraft and space-
craft components, including the scienti
c instruments,
must be sterilized to certain levels. Sterilization can be
achieved by methods that include heating to speci
ed
temperatures for minimum times or exposure to radiation.
After sterilization, the surfaces are swabbed, the swabs are
placed in media to encourage growth of potential cultures,
and each swab is analyzed. It is nearly impossible to reach
100% sterilization and thus maximum allowable levels are
de
ned by mission category in the protocol before the
spacecraft and components are certi
ed for
flight. If
there is a failure to achieve the acceptable levels, the
process is repeated until the acceptable levels are reached.
As you might imagine, the process for sterilization and
certi
cation for
flight is expensive and adds signi
cantly
to the cost of a mission.
Another consequence of sterilization is the impact on
sensitive components, such as scienti
c instruments,
many of which cannot survive heating or exposure to
radiation. In these cases, components must be housed in
“
and were found to contain bacteria that presumably had
been carried to the Moon by forward contamination. This
meant that the organisms had survived in the harsh lunar
environment for some 31 months, although some investi-
gators suggested that the bacteria were from Earthly con-
tamination after return from the Moon.
In more recent times, extraterrestrial samples have been
returned to Earth from deep space, including those of the
Stardust and Hayabusa missions. These have all been
placed in laboratories under controlled conditions and
analyzed. Currently, plans are being formulated by
NASA and the ESA for a facility to receive the anticipated
samples to be returned from Mars.
11.3 Missions in
flight and anticipated
for launch
The previous chapters on planetary systems outline the
current missions that are in
flight. For example, missions
at the Moon (
Chapter 4
) include the Lunar Reconnaissance
Orbiter (LRO). This mission was designed primarily to
collect data to support future robotic and human exploration
activities. After completion of these goals in 2010, the LRO
continued operations to meet a host of scienti
c objectives,
many of which are directly contributing to lunar geology.
Similarly, the ARTEMIS mission was originally launched to
collect data on lunar solar interactions. In 2011, the space-
craft was reposititioned to collect geophysical information
for the Moon to complement the Discovery-class GRAIL
mission, led by MIT PI Maria Zuber, which was launched in
2011. GRAIL consists of two orbiters collecting detailed
information on the nature of the lunar interior. These mis-
sions were followed by LADEE (Lunar Atmosphere and
Dust Environment Explorer)in2012,whichwasdesigned
to collect data on the mysterious
that would contain any Earthly organisms, even
in the event of a catastrophic failure such as an explosion.
Again, such an approach increases the cost and the com-
plexity of planetary missions.
One could ask, why go through this at all? From a
scienti
c perspective, recall that one of the primary moti-
vations for planetary exploration is the search for life
beyond Earth. If forward contamination were to occur,
the problem would be that we might
“
“find ourselves
”
on
some future mission, thus calling into question forever the
existence of extraterrestrial life on the contaminated
planet. Moreover, should life already be present on the
planet, there is the possibility that forward contamination
could cause irreparable harm through introduced diseases,
mutations, or even extinction.
Backward contamination is the stuff of countless science
fiction stories but is also of great concern in planetary
exploration. For example, in the early Apollo program, the
astronauts and the lunar samples returned from the Moon
were placed in quarantine to determine whether any lunar
organisms had caught a ride back to Earth. Cultures were
grown and other tests were carried out, all with negative
results, and follow-on Apollo missions abandoned the pro-
cedure. Subsequent studies have shown that the quarantine
procedures during Apollo were rather
awed and had a
great many
vaults
”
that has been seen
for decades near the lunar surface and is possibly caused by
light scattering from a nebulous atmosphere and dust raised
by electrostatic processes. China
'
slaunchofChang
'
e2in
2010 enabled acquisition of high-resolution images of the
Moon in support of future missions. China
“
glow
”
s plans call for
the launch of a lunar rover, possibly in 2012, to be followed
by a second rover with the return of lunar samples to Earth
in about 2017.
MESSENGER was placed into orbit around Mercury in
2010 and will complete its prime mission in 2012. Data
from this Discovery-class mission are revolutionizing
our understanding of this innermost planet of the Solar
System, as discussed in
Chapter 5
. If all goes well,
'
paths that could have led to problems
if any lunar organisms had been brought to Earth.
Interestingly, pieces of the unmanned Surveyor 3 spacecraft
(
Fig. 4.6
) were returned to Earth by the Apollo 12 astronauts
“
leaky
”
