Rovers and other space vehicles do a great
job studying Martian rocks and soil. However, the most exhaustive studies
of a sample's geology and biology can only be conducted here on Earth,
where we can most effectively use the enormous international capabilities
in scientific instrumentation. To conduct these in-depth studies, we would
like to bring samples of Martian rocks, soil and atmosphere back to Earth
early in the next decade. After all, nothing beats the hands-on expertise
of scientists. While it is highly unlikely that a living organism would be
found in any sample, we are taking the utmost care to protect our
environment here on Earth. To this end, we are developing procedures
to analyze all samples in containment to determine if they are hazardous.
Only after we are sure they are non-hazardous will they be studied for
their scientific information.
A sample return mission will require
the use of lander technologies to safely reach
the surface and rover technologies to reach
areas with suitable samples. Orbiters may play
a key role in capturing the sample in Mars orbit. We are also putting
together a program to develop some additional technology capabilities
that are unique to sample return.
With all of the rocks and soil samples
that are available on Mars, we need the ability to determine which samples
are the most scientifically interesting. We are currently developing many
tools and instruments to make the right choices. The initial identification
of interesting rocks will probably be done in the same way that a field
geologist studies rocks on Earth, by using visual information such as
color and texture. For this job, electronic imaging systems are essential.
We need some systems to take high-quality images of rocks from a
distance of several meters, while we need others to look at rock features
on microscopic scales of millimeters or less. These abilities along with
spectroscopy, a technology using ultraviolet, visible or infrared light to
analyze a rock's chemical composition, are being developed. This
chemical information will give clues to a rock's origin and history
Drilling for a Rock Sample
After a scientifically interesting rock has
been selected based on its chemical composition and other factors, we
must obtain a sample of it that is small enough to be brought back to
Earth, yet large enough to preserve important texture and structure.
Instruments have already been designed to drill into rocks and retrieve
cores from the inside. These interior rock samples should be better
preserved than the outside of the rock, which will have been exposed
to and chemically altered by the Martian atmosphere.
Protecting the Sample
Since searching for evidence of present
or past life is a key objective, the sampling system carried on the rover
must not contaminate the sample with any organisms brought from
Earth. The coring apparatus must be thoroughly cleaned before launch
so the samples won't interact with dust or biological material from
Earth. After all, we wouldn't want to bring a sample all the way from
Mars and study its features, only to discover that we're studying Earth
materials along with it. We want "pure" Martian samples,
straight from the source!
Launch into Space
Once the rover has its samples, they
will be placed in a small spherical container weighing a few kilograms. To
increase our ability to bring back samples untainted with Earth materials,
samples must be sealed in a capsule for launch. This capsule must be
able to seal completely in order to prevent contamination of the sample
by the Earth's atmosphere or biosphere upon landing on Earth.
Technologies for remotely welding metal to make clean airtight seals
are needed to protect the returned samples. The sealing process must
also assure that material of Martian origin remains on the outside of the
container to avoid inadvertent release of the material on Earth. Once
sealed, a small rocket called a Mars Ascent Vehicle will launch the
capsule from the surface of Mars.
From this point, there are several
possible approaches to bringing the sample to Earth. The most practical
of these appears to be using an orbiter to capture the sample
container while it is in Mars orbit. Methods are being studied for finding
a small canister in Mars orbit, navigating the orbiter to rendezvous with
the canister and capturing the canister, all with commands initiated
100 million kilometers away. Although traveling at the speed of light,
the commands will take almost half an hour to reach the spacecraft.
Return to Earth
The journey back to Earth involves
special precautions to ensure safe containment of the sample. The
samples may be delivered directly to Earth, but could be returned via
the space shuttle. Although it is highly unlikely that living organisms
will be found on the samples, NASA will implement a wide range of
precautions to preclude inadvertent release. This protocol will analyze
the samples in containment to determine if they are hazardous. The
samples will be released for scientific analysis only when it is determined
that they are non-hazardous.