A US radar that launched into space aboard an Indian spacecraft has detected craters filled with ice on the moon's north pole, according to Nasa scientists.

The US space agency's Mini-SAR radar found more than 40 small craters ranging in size from 1.6 to 15 kilometres, each full of water ice.

"Although the total amount of ice depends on its thickness in each crater, it's estimated there could be at least 600 million metric tons of water ice," Nasa said in a statement.

The finding came weeks after President Barack Obama put on ice US ambitions to return astronauts to the moon.

The lightweight, synthetic aperture radar's findings "show the moon is an even more interesting and attractive scientific, exploration and operational destination than people had previously thought," said Paul Spudis, lead investigator of the Mini-SAR experiment at the Lunar and Planetary Institute in Houston, Texas.

The Mini-SAR has spent the last year mapping the moon's permanently-shadowed polar craters that are not visible from earth, using the polarisation properties of reflected radio waves.

"After analysing the data, our science team determined a strong indication of water ice, a finding which will give future missions a new target to further explore and exploit," said Jason Crusan of Nasa's Space Operations Mission Directorate in Washington.

The radar's findings, to be published in the journal Geophysical Research Letters, are consistent with findings of other Nasa instruments and add to the growing scientific understanding of the multiple forms of water found on the moon.

Nasa's Moon Mineralogy Mapper, which was also on board Chandrayaan-1, has discovered water molecules in the moon's polar regions, while water vapour was detected by Nasa's Lunar Crater Observation and Sensing Satellite, or LCROSS.