Known for now as Mars 2020, the machine will be a skeletal duplicate of the Curiosity rover that landed on Mars in August 2012. It will use the same chassis and "sky crane" landing system as Curiosity, and will even use some of the existing robot's spare parts, saving time and money on design. The team estimate that the 2020 rover will cost about $1.5 billion - a billion less than Curiosity.
Having so much already in place freed up NASA to start thinking about what the 2020 rover should do. In a press conference today, the mission's science definition team unveiled a report detailing the new rover's goals, which includes searching for compounds such as organics that would indicate ancient life and collecting and storing rock samples for a future mission to bring back to Earth.
The team says these goals are a natural extension of Curiosity's objectives. Curiosity is not directly searching for life, past or present - its charge is to find evidence that Mars could once have supported life.
In March, Curiosity showed that the rover's landing site, Gale crater, most likely had both running water and the chemicals necessary to make a cosy home for past microbes. It is now on its way to a 5-kilometre-high mountain called Mount Sharp, where layered sediments may reveal even more about the planet's past habitability.
Now that we are confident at least some parts of the planet were once habitable, Mars 2020 can check if anything actually lived there, says Jack Mustard of Brown University in Providence, Rhode Island.
"We are not looking for the life that must have been there, because we don't know the answer to that," Mustard said in the press briefing. "But had life been there and left a mark in the geologic record, we want to be able to seek those signs."
The 2020 rover will bring high-resolution mineralogy instruments to identify potential biosignatures in the rocks and soil. It will also bring a drill capable of taking core samples from rocks, rather than pulverising them as Curiosity does. Taking cores preserves the geological record in the sample, allowing scientists to place any signs of life in historical context.
Those cores will be stored in a cache to be picked up at a later date, the first part of a long-awaited sample-return mission. In 2011, an expert panel rated sample-return a top priority in the once-per-decade review of potential missions. Many scientists argue that bringing a chunk of Mars back to Earth is the only way we will know for sure if it holds signs of life.
"If you have samples on Earth you can do sequential analysis, repeat analysis, analyses using technology that is not currently flight-qualified," Mustard said.
One challenge will be designing a system that will keep the cache pristine, John Grunsfeld, NASA's associate administrator for science, said during the press briefing. Curiosity was supposed to have a cache for collected samples, but the plan was scrapped over concerns that the hockey-puck-shaped box used to store them would be open to the Martian elements and so the samples would degrade.
For now the proposed plans are light on details about how exactly the cache will get back to Earth. The agency is only committing to sending this rover and collecting and storing a cache - not figuring out how to bring it home, said Grunsfeld.
"A lot of considerations go in there, including planetary protection: how do we protect Earth from anything that might be on Mars?" he said. "All of that is future work."
The 2020 mission also stops short of seeking creatures currently living on Mars. "The feeling is that, from many points of view, the planet's surface is currently quite inhospitable to life. To do an extant-life exploration drives you to parts of the planet that are difficult to access," Mustard said in justifying the decision. "The best prospect to look for signs of life would be in the ancient geologic record."
Lindy Elkins-Tanton of the Carnegie Institution in Washington DC, says that in focusing on past life, the Mars 2020 rover will actually have a better chance of reaching its aims. "If we were only looking for microbes on the surface right now, that's a tiny snapshot of the history of life." By using rock samples to look further back in time, she says, "we're basically integrating over time and maximising our chances of getting results".
Syndicated content: Lisa Grossman, New Scientist