WASHINGTON — NASA has pivoted on a key design point for the Mars 2020 rover, the first of several missions required to return a martian surface sample to Earth.
Once thought of as a sample-caching mission, NASA now plans for Mars 2020 to extract several surface samples from each region it visits and leave them on the ground for a future rover to cache, Ken Farley, Mars 2020 project scientist at NASA’s Jet Propulsion Laboratory, told the Mars Exploration Program Analysis Group (MEPAG) during a Feb. 24 meeting in Pasadena, California.
When it proposed the mission as part of its 2013 budget request, NASA thought Mars 2020 would cache samples in a custom made container that would be carted around with the rover and dropped off once filled.
But if Mars 2020 carries its precious cargo with it, “there’s some point where the science starts to get penalized by the value of the cache,” Farley said.
In other words, the more samples the rover stores, the greater the value of the cache it carries to scientists on Earth. The greater the value of the cache, the less inclined NASA will be to take risks like driving to an unexplored, and possibly dangerous, areas to collect more samples, said Farley. If the rover got stuck, its expensive sample cache could be lost.
But if Mars 2020 leaves the samples it collects on the ground, it can rove and drill until it runs out of power, leaving a treasure trove that a follow-on retrieval rover could collect.
The dig-and-ditch approach also means Mars 2020 will not need a sophisticated, and massive, robotic arm to do the delicate work of putting tiny samples into a custom-made canister.
But to be sure, there are disadvantages to what NASA is calling the “adaptable caching” design for Mars 2020, Farley told MEPAG.
For one thing, the follow-on retrieval rover, which appears nowhere in NASA’s notional budget plans, would have to go hunting for samples more or less indistinguishable from the ground from which they will be cored.
The retrieval rover will also need some of the features NASA is now considering pushing off Mars 2020, such as a sample-collection container and a robotic arm to interact with it.
“We recognize that by doing this we are pushing some of the complications of this onto the next mission,” Farley acknowledged, adding that NASA might even change its mind on the Mars 2020 again.
“There are many things one might want to look at,” Farley said.