Rovers and other space vehicles do a great job studying Mars.
However, the most exhaustive studies of rock, soil, and atmospheric
particles can only be conducted in laboratories here on Earth. After all,
nothing beats the hands-on expertise of scientists. However, bringing
samples back is challenging since it requires rockets that can ascend
from the surface of Mars to orbit and may require vehicles that can
rendezvous and capture the sample for delivery to Earth.
Sample Selection
With all of the rock and soil samples that are available on Mars, we
need the ability to determine which samples are the most scientifically
interesting. Scientists and engineers 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 (several feet), 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 also
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.
