Sample Handling

STEP 1: Collecting Samples

A big job for the rover is collecting carefully selected samples of Mars rock and soil. These samples will be sealed in tubes and left in a well-identified place, or more than one spot, on the surface of Mars. Detailed maps will be provided for any future mission that might go to Mars and pick up these samples for study by scientists.

Sampling Equipment in the Rover Belly

The belly of the rover houses all the equipment and supplies needed to collect samples. It contains a rotating drill carousel, which is a wheel that contains different kinds of drill bits. Next to that are the 43 sample tubes waiting to be filled.

While the rover’s big arm reaches out and drills rock, the rover belly is home to a small robotic arm that works as a "lab assistant" to the big arm. The small arm picks up and moves new sample tubes to the drill, and transfers filled sample containers into a space where they are sealed and stored.

Witness Tubes

Perseverance must meet extraordinary cleanliness requirements. These measures are in place to avoid contaminating Martian samples with terrestrial contaminants that may inadvertently be brought from Earth. Strict rules limit the amount of inorganic, organic and biological materials from Earth in the rover and its sample handling system.

Perseverance carries five "witness tubes" along with sample collection tubes. The witness tubes are similar to the sample tubes except they are pre-loaded with a variety of witness materials that can capture molecular and particulate contaminants, such as:

• gases that may be released, or "outgassed," from different materials on the rover;
• chemical remnants from the firing of the landing propulsion system;
• any other Earthly organic or inorganic material that may have arrived on Mars with the rover.

One at a time, the witness tubes will be opened on the Martian surface to "witness" the ambient environment near sample collection sites. They are exposed to the local environment where samples are collected and they go through the motions of drilling and other movements that the sample containers experience. The witness tubes do not, however, collect soil or rock samples. The witness tubes will also be sealed and cached like the actual Mars samples.

In the future, if the Perseverance samples are returned to Earth for analysis, the witness tubes will show whether Earth contaminants were present during sample collection. This will help scientists tell which materials in the Martian materials may actually be of Earth origin.

STEP 2: Storing Onboard

After a sample is collected, the sample tube is transferred back to the rover's belly. There, it is handed off to the small interior robotic arm and moved to inspection and sealing stations. Once the tube is hermetically sealed, nothing can enter or leave it. The tubes are stored in the rover belly until the team decides on the time and place to drop the samples off on the surface.

STEP 3: Depositing Samples on the Surface

At a time and place of the team's choosing, the samples are deposited on the surface of Mars at a spot that the team designates as a "sample cache depot." The depot location or locations must be well-documented by both local landmarks and precise coordinates from orbital measurements. The cache of Mars samples remains at the depot, available for pickup and potential return to Earth.