Nasa has announced it can’t afford to land humans on Mars.

NASA has announced that it doesn't have the budget for a manned mission to Mars.

NASA's chief of human spaceflight, William H. Gerstenmaier revealed during a meeting of the American Institute for Aeronautics and Astronautics on Wednesday that the space agency is failing in its Mars mission goal because of low budget.

'I can't put a date on humans on Mars, and the reason really is that at the budget levels we described, this roughly 2 percent increase, we don't have the surface systems available for Mars,' said NASA's William H. Gerstenmaier, responding to a question about when NASA will send humans to the surface of Mars.

'The entry, descent and landing is a huge challenge for us for Mars,' he said.

'We think an unfuelled mars asset vehicle would weigh around 20 tons, that's a 20 fold increase on a rover.'

The NASA chief hinted at returning back to its moon missions instead.

'If we find out there's water on the Moon, and we want to do more extensive operations on the Moon to go explore that, we have the ability with Deep Space Gateway to support an extensive Moon surface program,' he said

'If we want to stay focused more toward Mars we can keep that.'