Mars 2020 Rover - Depot Caching Strategy
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In this illustration of depot caching, the red X represents the landing site. During its primary mission, the rover travels routes noted by the solid white lines to collect samples at "regions of interest," indicated by the blue dots. One region of interest serves as a "depot" to hold the sample cache (the blue dot covered by sample core cylinders). In the event of an extension of the mission, the rover would supplement the original sample cache by traveling to and from additional regions of interest by routes indicated by the dashed lines. Credit: NASA/JPL-Caltech
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What is Surface Operations?

The surface operations phase is the time when the Perseverance rover conducts its scientific studies on Mars. After landing safely (Feb. 18, 2021), the rover has a primary mission span of at least one Martian year (687 Earth days).

The Perseverance rover uses a depot caching strategy for its exploration of Mars.

What does Perseverance do during surface operations?

While exploring Mars during surface operations, Perseverance:

  • finds rocks that formed in, or were altered by, environments that could have supported microbial life in Mars’ ancient past (Objective A)
  • finds rocks capable of preserving chemical traces of ancient life (biosignatures), if any existed (Objective B)
  • drills core samples from about 30 promising rock and “soil” (regolith) targets and caches them on the Martian surface (Objective C)
  • tests the ability to produce oxygen from the carbon-dioxide Martian atmosphere, in support of future human missions (Objective D)

How does Perseverance explore during surface operations?

Step 1: Find Compelling Rocks

As the Perseverance rover explores Mars, scientists identify promising rock targets.  They especially look for rocks that formed in, or were altered by, water.  Water is key to life as we know it.  Such rocks are even more interesting if they have organic molecules, the carbon-based chemical building blocks of life.  Some special types of rocks can preserve chemical traces of life over billions of years. Finding rocks that formed in water, have the chemical building blocks of life, and can preserve signs of organics and life is key.  Together, they improve the chances of finding ancient traces of microbial life on Mars, if any ever existed.  In addition to these special rocks, Perseverance also collects volcanic and other rocks to help establish a record of geologic and environmental changes over time.

Step 2: Collect Rock Samples

Once scientists identify a rock target of interest, Perseverance drills a core sample from it.  With a pre-cleaned tube for the sample, the rover’s rotary percussive coring drill penetrates about 2 inches (5 centimeters) into the target material.

Step 3: Seal the Rock Samples

Perseverance breaks off the core sample from the rock, and caps and hermetically seals the sample in its tube. Each sample weighs about a half of an ounce (15 grams).

Step 4:  Carry the Samples

The Perseverance rover places each sealed tube in a storage rack on board and transports it until the mission team chooses to deposit it on the Martian surface.  The team uses a strategy called depot caching to determine when and where to leave tubes.  In the baseline plan, Perseverance places one or more large groups of samples in strategic locations. 

Step 5: Cache the Samples

The Perseverance rover puts the Martian samples, the witness blanks, and procedural blanks in the same place on the Martian surface so that a future mission could potentially retrieve and return them all together. The rover may cache over 30 selected rock and “soil” (regolith) samples.

 

Follow-on Steps potentially completed by a later Mars mission

The sample cache(s) will remain on the Martian surface, awaiting potential pick-up by a future mission.  Images taken by orbiters can identify locations of the samples with a precision of about 3 feet (~one meter).  Images taken by the rover’s own cameras will increase that precision to less than half of an inch (~one centimeter).