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NASA Mars Exploration Program
Mars Exploration Program

Sample Returns

Collecting Rock and Soil Samples and Returning Them to Earth

Samples return to Earth
Artist's Concept
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.