Geology Reference
In-Depth Information
landers and rovers is the ability to obtain data directly
from planetary surfaces and near-surface materials, as
from drill cores, which was
first done robotically by the
Soviets on the Moon. The disadvantage is the relatively
limited number of sites that can be visited; can you imag-
ine characterizing the complex geology of the Earth from
only a handful of stations on the surface?
Samples returned from planetary objects represent the
next stage in exploration. These enable sophisticated lab-
oratory analyses of compositions, measurements of phys-
ical properties, and searches for signs of past or present
life. Although signi
cant advances in instruments that can
be applied on robotic missions have been made in recent
years, none can approach the accuracy and precision
afforded by full laboratory facilities on Earth.
Particularly critical for geology are the ages of rocks
determined on returned samples using techniques based
on the decay of radioactive materials (see
Section 2.4
).
While some measurements can be made from robotic
spacecraft, the complexities of obtaining and properly
handling samples in order to make the measurements
have not been solved satisfactorily for determining ages.
The ultimate in planetary science is human exploration.
Humans have the ability to analyze and synthesize data
quickly, make decisions on the spot, and respond to the
results. No machine can match these attributes. But, of
course, sending humans into space is both risky and
costly. Currently, it is far more cost-effective to send
robotic spacecraft throughout the Solar System.
However, the time will come when humans will be
required for the ultimate step in exploration.
Figure 1.11
shows the
“
score-board
”
for the different
stages of Solar System exploration. Nearby objects, such
as our Moon, have been explored extensively, while
most of the outer Solar System has been viewed only
by
flyby missions. Despite this uneven coverage, we are
now well poised to address many of the fundamental
aspects of the origin and evolution of the major planetary
objects.
Figure 1.8. What are the signs of life that might be sought in the
search for present or past life beyond Earth? From our
“
Earth
bias,
we might think that we know what fossils look like. But
even on Earth, some cases are not so clear: (a) living
cyanobacteria (courtesy of Jennifer Glass, Arizona State
University), (b) synthetic non-biological
”
1.4 Flight projects
filaments containing
silica and the mineral witherite (from Garcia-Ruiz, J. M., Hyde,
S. T., Carnerup, A. M. et al.(
2003
), Self-assembled silica
Getting a NASA spacecraft
“
off the ground
”
is a long
process that involves many constituencies, including
NASA, Congress (which appropriates the money), the
aerospace industry (which builds much of the hardware),
-
carbonate structures and detection of ancient microfossils,
Science, 302, 1,194
1,197. Reprinted with permission from the
AAAS), and (c) an image of martian meteorite ALH84001
(courtesy of NASA Astrobiology Institute).
-
