NASA managers hope to begin procuring science instruments this fall for a $1.5 billion copy of the Curiosity rover now exploring Gale Crater on Mars, with an eye to finding definitive evidence whether the planet ever supported life, and whether its resources could support human life today.

Collecting rock cores for eventual return to Earth is also on the list of goals set by the science definition team that NASA established to begin planning the rover it hopes to send to Mars in 2020. The idea is to build on Curiosity's engineering and discoveries to answer the priority question for planetary scientists—“Are we alone?”—while scouting for an eventual human mission to Mars.

“This rover will get us that next step—from 'Was there a habitable environment?', transitioning from planetary science to astrobiology, to ask, 'Do we see any evidence of past life in those habitable environments?'” says John Grunsfeld, associate administrator for science.

Headed by Jack Mustard, professor of geological sciences at Brown University, the science definition team was charged with reusing as much from Curiosity as possible to advance the decadal priorities set out by the National Research Council. At the top of that list was returning samples from Mars to Earth, where the full panoply of laboratory gear can be applied to finding evidence of past life. Mustard's team of experts in astrobiology, geophysics and geology, instrument development, science operations and mission design recommended an instrument suite designed to conduct “context” mineralogy and imaging, and move from that down to “fine scale” elemental and organic chemistry, mineralogy and imaging.

Because the surface of Mars today is apparently toxic to life, the science definition team recommends collecting subsurface core samples that leave the chemistry in context instead of grinding it to powder, as Curiosity does. Those cores would be retrieved and returned to Earth at an unspecified date.

Regardless of when and how the cache is returned, the instrument suite on the 2020 rover would be able to spot the most promising candidates for analysis on Earth. Jim Green, director of NASA's planetary science division, says he and his colleagues will issue an announcement of opportunity as early as “late fall” seeking proposals for the instrument suite, which will cost $80-100 million.

The rover itself is estimated to cost $1.5 billion plus launch, with recycled Curiosity elements allowing a reduction in that mission's $2.5 billion price tag. While the two rovers will have many components in common, including the chassis and a radioisotope thermoelectric generator for power, the science definition team called for improvements in its landing precision, in part to develop the accuracy needed later on to retrieve the samples.

Recommended “high-priority” technologies for achieving that precision are a range trigger that deploys the parachute based on range to the target; terrain-relative navigation that uses a stored surface map instead of inertial propagation for guidance; and an upgrade of the Mars Entry, Descent and Landing Instrumentation that directly measures such terminal-guidance factors as parachute drag.

Target selection would require another competition among promising sites, like those that determined where earlier landers set down. “That process has worked exceptionally well,” says Mustard.

NASA also asked the science definition team to recommend payloads for its human-exploration and space-technology organizations. For that, the team's top priority would be a device to extract oxygen from the planet's carbon dioxide atmosphere, and characterize atmospheric dust so the in-situ resource utilization (ISRU) system could function without clogging.

“It would be an architecture enabling technology for human missions to Mars, which likely will depend on ISRU for producing the propellants needed for the return trip to Earth; ISRU can greatly reduce mass transported to the Martian surface,” the team's report states.