NASA is considering a plan to get around limited budgets set in Washington by stretching out missions to bring back samples from Mars, a researcher said on Wednesday.
It may be possible to break down the complicated and expensive mission into three parts, said Steve Squyres, a Cornell University astronomer who leads the Mars Exploration Rover Mission.
"It makes the program more affordable because it strings out the cost over time," Squyres told reporters in a telephone briefing. "It brings down the cost per year of doing such a thing."
The space agency got an extra $6 billion in the latest federal budget, but President Barack Obama has said it is time to abandon the pricey Constellation program to return astronauts to the moon and focus instead on Mars and nearby asteroids and to use private contracts to support missions.
Squyres, speaking from a conference in Texas on the search for extraterrestrial life, said the new approach does not affect his team's work studying Mars using robots.
"All of us want to see humans on Mars collecting samples," he said. But the "details" of which rockets are used to launch such missions do not matter, he said.
He described a "hellish" mission in which a robot, similar to the successful Spirit and Opportunity rovers, scoops up a sample from the Martian surface. "The next mission would be a lander that would plop down beside it," Squyres said.
This vehicle could sling the sample into orbit around Mars, waiting for a third mission to retrieve it and bring it to Earth for study.
Fossils in gypsum
Other scientists at the meeting in Texas say they have better evidence that such a mission might find evidence of life, if there ever was any, on Mars.
For instance, evidence may be found in the vast fields of gypsum that cover much of the planet's surface, said Bill Schopf of the University of California at Los Angeles.
Schopf and colleagues said they found the remnants of plankton, diatoms and cyanobacteria in gypsum deposits made when the Mediterranean dried up 6 million years ago.
No one ever thought fossils could survive in gypsum, Schopf told the briefing. But if they lasted on Earth for millions of years, they could have lasted in the big fields of gypsum that strew what looks like a dried-up ocean on Mars.
"We now know that this is a good place to look for evidence of fossil life on Mars," Schopf said. "If we can find the organic matter then we have real reason to believe that there once was life there."
"These researchers are really shaping the strategy of the search for life in our solar system," said Mary Voytek, astrobiology senior scientist at NASA.
Separately on Wednesday, two teams of U.S. researchers reported they had spotted clear evidence of water on an asteroid.
Teams led by Andrew Rivkin of Johns Hopkins University in Maryland and Humberto Campins of the University of Central Florida found spectral evidence of what could be a thin layer of ice on 24 Themis, one of the largest objects in the asteroid belt between Mars and Jupiter.
Voytek said the findings add to evidence that the water now on Earth was brought by collisions with asteroids. Scientists believe water recently found on the moon was also carried there by asteroids.