Insist on creating a sample cache for later return to Earth

WASHINGTON — NASA and the European Space Agency have selected a site on Mars to store samples collected by the Perseverance rover, one step in the overall process of returning those samples to Earth.

NASA announced Oct. 28 that the agencies agreed to deposit some of the 14 samples Perseverance has collected so far at a site called “Three Forks” in Jezero Crater, near the remains of an ancient river delta that once flowed through the crater. These samples, encased in metal tubes, will be taken back to Earth by later missions.

“NASA and ESA reviewed the proposed site and the Martian samples that will be developed for this cache as soon as next month. When this first tube is placed on the surface, it will be a historic moment in space exploration,” Thomas Zurbuchen, NASA’s associate science officer, said in a statement.

The sample cache is part of a revised strategy for the overall Mars Sample Return campaign announced in July. This strategy eliminates a European “fetching” rover that was to retrieve cached samples from Perseverance. Instead, it will rely on Persistence as the primary means of returning samples to a future lander, which will then launch them into orbit to be picked up by an ESA orbiter for return to Earth.

This cache serves as a backup if Perseverance is unable to return to the lander. This lander will have two small helicopters, based on the Ingenuity helicopter accompanying Perseverance, that will fly into the crypt, collect sample tubes and return them to the lander.

“The depot is the risk mitigation if the rover doesn’t make the long journey” to the lander, said Francois Spoto, head of the Mars Exploration Group at ESA, during a presentation on Mars Sample Return at the International Astronautical Congress (IAC) in Paris in September. 20.

Perseverance took duplicate samples from each location so that one set could be kept in Perseverance and the other cached. “Once we do that, we’ll stop double-sampling and continue to build the cache that will be maintained on Perseverance,” Jeff Gramling, director of the Mars Sample Return program at NASA, said at the IAC presentation.

In announcing the sample storage plans, NASA also said that on Oct. 1 the Mars Sample Return program entered Phase B, which covers preliminary design work and completion of key technologies required for the future lander mission.

Both NASA and ESA officials remained reticent to discuss the cost of the revised Mars Sample Return architecture, including any cost savings from deleting the fetch rover and a second lander that would have delivered it. NASA generally does not provide official cost and schedule estimates for a mission until it is ready to enter Phase C, where design is completed and component manufacturing begins.

Asked about the cost of the Mars Sample Return during their IAC presentation, neither Gramling nor Spoto gave a specific cost or cost range. However, they estimated that ESA’s share would be 15-20% of the total cost.

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