The quest to return rock samples from Mars to Earth to see if they contain traces of past life is going to go through a major overhaul.
The US space agency says the current mission design could not return the materials before 2040 on the existing funds and the $11bn (£9bn) to make it happen sooner is not sustainable.
Nasa is going to canvas ideas for a cheaper, faster alternative.
It hopes to have a solution on the drawing board later in the year.
Returning rock samples from Mars is regarded as the single most important priority in planetary exploration, and has been for decades.
Just as the Moon rocks brought home by Apollo astronauts revolutionised our understanding of early Solar System history, so materials from the Red Planet are likely to recast our thinking on the possibilities for life beyond Earth.
The US space agency says the current mission design could not return the materials before 2040 on the existing funds and the $11bn (£9bn) to make it happen sooner is not sustainable.
Nasa is going to canvas ideas for a cheaper, faster alternative.
It hopes to have a solution on the drawing board later in the year.
Returning rock samples from Mars is regarded as the single most important priority in planetary exploration, and has been for decades.
Just as the Moon rocks brought home by Apollo astronauts revolutionised our understanding of early Solar System history, so materials from the Red Planet are likely to recast our thinking on the possibilities for life beyond Earth.
But Nasa now acknowledges the way it's going about achieving the samples' return is simply unrealistic in the present fiscal environment.
"The bottom line is that $11bn is too expensive, and not returning samples until 2040 is unacceptably too long," Nasa administrator Bill Nelson told reporters in a Monday teleconference.
The former US senator said he would not allow other agency science missions to be "cannibalised" by the Mars project.
He is therefore seeking fresh thinking from within Nasa and from industry.
"The bottom line is that $11bn is too expensive, and not returning samples until 2040 is unacceptably too long," Nasa administrator Bill Nelson told reporters in a Monday teleconference.
The former US senator said he would not allow other agency science missions to be "cannibalised" by the Mars project.
He is therefore seeking fresh thinking from within Nasa and from industry.
The Mars Sample Return, or MSR, programme is a joint endeavour with the European Space Agency (Esa).
The present architecture is already in play, in the sense that the rock samples to be returned home are in the process of being collected and catalogued on Mars today by Nasa's Perseverance rover.
A dedicated follow-up mission was due to be launched later this decade that would carry a rocket to the surface of the Red Planet.
The present architecture is already in play, in the sense that the rock samples to be returned home are in the process of being collected and catalogued on Mars today by Nasa's Perseverance rover.
A dedicated follow-up mission was due to be launched later this decade that would carry a rocket to the surface of the Red Planet.
Once loaded into this ascent vehicle, Perseverance's samples would then be blasted skyward to rendezvous with a European-built spacecraft that could catch them and head for Earth.
It was envisaged that roughly 300g of Martian material would land in a capsule in the western US state of Utah in 2033.
But an independent review that reported in September last year found faults with the way the mission design was being implemented. It doubted the schedule could be maintained and, even if it could, the cost was likely to balloon to somewhere between $8bn and $11bn.
It was envisaged that roughly 300g of Martian material would land in a capsule in the western US state of Utah in 2033.
But an independent review that reported in September last year found faults with the way the mission design was being implemented. It doubted the schedule could be maintained and, even if it could, the cost was likely to balloon to somewhere between $8bn and $11bn.
In its response published on Monday, Nasa doesn't disagree with the assessment - hence the desire now to re-open discussion on the best way forward.