Shock testing

The impetus behind these tests is that for many decades scientists have speculated about the possibility of ice at the lunar poles having accumulated there over geologically long periods of time.

Into the plywood

The ice would be from impacting comets. If some of the ice from the comets found its way into dark lunar polar craters where the Sun never reaches, it could be trapped for billions of years.

The lunar polar ice hypothesis was finally confirmed by observations made by the Lunar Prospector spacecraft in 1998.

Technically, the Lunar Prospector data is compelling evidence for the presence of hydrogen. However, most scientists are convinced a small amount of water ice is present at the lunar poles, though other hypotheses exist.

Because of the scientific attraction of lunar polar exploration the University of Hawaii, with engineers and scientists from the US Naval Research Laboratory, Utah State University, the Jet Propulsion Laboratory, Los Alamos National Laboratory, and Sandia National Laboratory are proposing an adventurous mission called Polar Night.

"Polar Night would conduct a highly detailed remote sensing survey of the poles to refine our understanding of the temperatures and distribution of hydrogen, then directly sample the polar ice with three hard-landing probes," Professor Paul Lucey of the University of Hawaii told BBC News Online.

"The probes are based on bunker-buster penetrators, but instead of explosives, would carry sophisticated scientific instruments hardened against the shock of striking the lunar surface."

"The instruments were recently shock tested in the New Mexico desert by firing them at high speed into 2 metres (6 feet) of plywood, where they experienced 1200 G's of shock and worked perfectly afterwards."

New questions

According to Professor Lucey the existence of lunar polar ice raises a new set of questions.

• What is the nature of the deposit?
• What is the source of the water?
• Are other ices besides water ice present?
• Is the hydrogen actually in the form of water ice, or is it hydrogen from the solar wind?

He told BBC News Online, "The lunar poles are a potential science bonanza, possibly having recorded the volatile history of the solar system for 2 billion years."

"That potential has an analogy with the poles of the Earth, where meteorites are routinely preserved by the Antarctic icecap and collected by scientists. There is a nice symmetry here: on the Earth, the ice of the poles collects rocks from space, while on the Moon, the rocks of the poles collect ices from space."

Easily collectable ice at the lunar poles could also transform the economics of space exploration.

Professor Paul Lucey

"For resources for future space travel the chemical form and concentration are clearly relevant to the economic value of these deposits, regardless of our current ignorance of the economics of the future," says Professor Lucey.

The scientists hope the mission will be funded by Nasa's Discovery program of moderate cost planetary science missions.

Lunar Prospector was a mission in this series, and the current missions in flight are Genesis, returning a sample of the solar wind, and Stardust to return cometary and interstellar dust.

The proposals for the next round of the Discovery Missions Program are due later this year with the selection of the 3-5 finalists taking place a few months later.

If Polar Night survives the proposal process, the first impacts would occur in 2007.