Vast pockets of water ice numbering in the millions of tons have been discovered at the north pole of the Moon, opening up another region of the lunar surface for potential exploration by astronauts and unmanned probes, NASA announced March 1.

A NASA radar instrument on India’s Chandrayaan-1 Moon probe found evidence of at least 600 million metric tons of water ice spread out on the bottom of craters at the lunar north pole. It is yet another supply of lunar water ice, a vital resource that could be mined to produce oxygen or rocket fuel to support a future Moon base, NASA officials said.

More than 40 craters ranging from 12 kilometers to 15 kilometers wide were found harboring the water ice, which was detected using NASA’s Mini-Synthetic Aperture Radar instrument on Chandrayaan-1. The instrument is also known as Mini-RF in NASA parlance.

“After analyzing 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, program executive for the Mini-RF Program for NASA’s Space Operations Mission Directorate, in a statement.

The ice was discovered in permanently shadowed craters at the Moon’s north pole. Similar conditions of perpetual night exist at the Moon’s south pole, where water ice was also confirmed to be present last year. Because these regions never see sunlight, water can stay in its frozen form indefinitely.

Last September, NASA and other scientists confirmed the existence of water ice at the Moon’s south pole, as well as signals of water molecules across large areas of the lunar surface. Several spacecraft, including India’s Chandrayaan-1 probe, found hard evidence of water on the Moon.

In October, NASA crashed two impactor probes into the lunar south pole in an attempt to kick up clouds of water ice and measure it from an orbiting spacecraft and other space and ground-based observatories. The subsequent analysis turned up significant amounts of water and water vapor in the debris cloud, NASA scientists said.

“The emerging picture from the multiple measurements and resulting data of the instruments on lunar missions indicates that water creation, migration, deposition and retention are occurring on the moon,” said Paul Spudis, principal investigator of the Mini-SAR experiment at the Lunar and Planetary Institute in Houston, in a statement. “The new discoveries show the moon is an even more interesting and attractive scientific, exploration and operational destination than people had previously thought.”

Water ice is a tantalizing find anywhere on the Moon because it can serve as a natural resource for astronauts on future lunar landing missions. The ice could be melted into drinking water or be separated into its component oxygen and hydrogen to provide breathing air and rocket fuel, NASA officials have said.

NASA had planned to send astronauts on new lunar landing missions by 2020 as part of its Constellation program that President Barack Obama has proposed canceling in order to focus on using commercial spacecraft to launch U.S. astronauts to the international space station instead.

NASA Administrator Charles Bolden told members of Congress Feb. 24 that Mars is expected to be the ultimate destination for astronauts. But the Moon, he said, is still a good interim target to serve as a stepping stone for more distant space exploration goals.

Chandrayaan-1’s Mini-SAR radar was one of two instruments involving NASA on India’s Chandrayan-1 spacecraft. The probe also carried the Moon Mineralogy Mapper for NASA. A version of Mini-SAR, called Mini-RF, is riding on NASA’s Lunar Reconnaissance Orbiter, which launched in June 2009.

The Chandrayaan-1 probe launched in October 2008 carrying 11 instruments to observe the Moon from lunar orbit. It was India’s first Moon probe and carried an impactor probe that it released in November 2008. The spacecraft went offline in late August 2009 after a heat-related malfunction cut off communications with Earth.

India is planning a successor to Chandrayaan-1, dubbed Chandrayaan-2, in 2012.