Washington - The next robotic rover to explore Mars in 2020 should scour the surface of the red planet more closely than ever for signs of past life, a Nasa science team said on Tuesday.
The US space agency's science definition team (SDT) released a 154-page document containing its proposals for the next Mars rover, after five months of work.
The mission would use microscopic analysis for the first time, collect the first rock samples for possible return to Earth and test ways to use natural resources on site for a future human trip, it said.
The Mars 2020 mission would build on the work being done by Nasa's Curiosity rover, which has been exploring the red planet since August 2012 and has already found evidence of potentially habitable environments.
The mission would present "a major step toward seeking signs of life," said Jim Green, director of the Planetary Science Division at Nasa headquarters.
The next step is for Nasa to analyse the recommendations and issue a call for scientific instruments, which could include higher resolution imaging devices, microscopes, fine scale minerology, chemistry and organic carbon detection tools to scan for biosignatures on the surface of Mars.
"To combine this suite of instruments would be incredibly powerful," said Jack Mustard, SDT chair and professor of geological sciences at Brown University.
The rover would collect about 31 samples that might someday be returned to Earth, representing "a legacy for understanding the development of habitability on the planet", he told reporters.
The US space agency has not yet devised the technology to bring the cache back to Earth without disturbing its contents, and no plans have been set for any potential sample-return.
The next Nasa mission to Mars is a November launch of Maven, an orbiter that will study how Mars interacted with the solar wind and lost its atmosphere.
The European Space Agency will follow in 2018 with its ExoMars rover.
John Grunsfeld, NASA's associate administrator for science, said the 2020 Mars rover would get the US space agency to the next step in the "quest to answer the grand questions," before a planned human mission in the 2030s.
"Do we see any evidence of past life in those habitable environments?" he said, alluding to the aims of the future missions.