“In principle, you get below the irradiated top meter or so, down to some material that is more pristine, that hasn't been disturbed by radiation or the surface environment or what they call gardening, where meteorites hit and churn up the soil,” Hubbard says.
Grunsfeld also stresses that NASA is providing its Electra radios for ESA's 2016 ExoMars orbiter, which would be able to act as a relay for the 2020 U.S. rover in case the MRO spacecraft playing that role for Curiosity goes down.
“It allowed us to reengage with the Europeans on ExoMars,” he says of the decision to launch another lander. “They're very good partners.”
Before their Mars-exploration split, NASA and ESA were working together to cache promising samples for later return to Earth, where the full array of scientific hardware and expertise can be brought to bear on finding evidence of life—past or present. After the split, NASA's Mars Program Planning Group concluded NASA could bring back samples on its own, and noted that a new rover using “build-to-print” components from Curiosity “will do exactly the science that the decadal survey was asking for” (AW&ST Oct. 1, p. 36).
Gunsfeld says continuing analysis shows NASA has the spare parts, plans and knowledge to create a new rover on the Curiosity pattern, including a spare radioisotope thermoelectric generator and an engineering model that can be converted to the backup. Jim Green, director of NASA's Planetary Science Division, says NASA's Energy Department alottment of plutonium-238 fuel is adequate for the rover's RTG.
The agency also has a supply of flight-qualified spare actuators that can be used to to move the wheels, arm joints and other elements of a new rover. The Jet Propulsion Laboratory and its Curiosity suppliers still are running inventory to see what other parts are available.
Ultimately, the configuration of the new rover will be based on recommendations generated by the science definition team being set up by Michael A. Meyer, lead scientist for NASA's Mars Exploration Program, Green says. As NASA draws on its human spaceflight and space-technology efforts for the rover project, the panel will be pulled from scientists and engineers working on human exploration and exploration-enabling technology as well as planetary science, he says.
Even the power source is on the table, with solar power a possibility if the mission requirements call for it. Some Pu-238 still would be needed for heaters to keep the rover electronics warm during the Martian nights, and a caching rover still would need in-situ science instruments like those on Curiosity to select the samples to be cached.
Curiosity is the largest payload ever landed on Mars. Its sky crane landing technique, lowering the rover to a wheels-down landing on cables played out from a platform hovering on retro rockets above the surface, was untried until its Aug. 6 success inside the equatorial Gale Crater. Grunsfeld and Green say that approach will also be used on the second rover, maintaining the skills at JPL that enabled the success with Curiosity.
But the entry, descent and landing that worked so well on Curiosity won't be duplicated. Some changes likely will be made to take advantage of lessons learned and accommodate more mission mass. Grunsfeld notes the heat shield that protected Curiosity during atmospheric entry was “very conservative, very thick,” and analysis shows there might not have been a need for so much shielding. While there might be weight savings with a thinner shield, Grunsfeld says mission planners also must decide “is that a cost-driver?”