Europe South Asia Asia Pacific Americas Middle East Africa BBC Homepage World Service Education



Front Page

World

UK

UK Politics

Business

Sci/Tech

Health

Education

Sport

Entertainment

Talking Point

In Depth

On Air

Archive
Feedback
Low Graphics
Help

Thursday, June 3, 1999 Published at 19:15 GMT 20:15 UK


Sci/Tech

Radar finds Moon's cold spots

The Moon's pitted north pole revealed by radar

By BBC News Online Science Editor Dr David Whitehouse

The first three-dimensional images of the Moon's poles have taken using radar.

The observations were made with Nasa's Goldstone Deep Space Network radio telescopes and reveal deep craters in permanent shadow that could potentially contain water ice. The south pole appears particularly suitable.


[ image: The cold traps appear white at the Moon's south pole]
The cold traps appear white at the Moon's south pole
The new data will be vital in selecting and hitting a target for the crash landing of the orbiting Lunar Prospector spacecraft on 31 July. This was also announced on Wednesday and hopes to blast water vapour high enough out of a crater for observatories to confirm its presence.

"In order to impact the spacecraft at the desired location, very accurate knowledge of the topography is needed," says Donald Campbell, professor of astronomy at Cornell University, one of the team who created the maps.

Hydrogen clue

In 1996, researchers working with radar data from the orbiting lunar spacecraft Clementine reported indications of ice at the south pole of the Moon.

Last year, the neutron spectrometer aboard the Lunar Prospector orbiter, launched in January 1998, detected significant deposits of hydrogen at the Moon's north and south poles.


[ image: Cold traps at the north pole are less common]
Cold traps at the north pole are less common
This was interpreted as indicating the presence of water ice, since hydrogen in water molecules is thought to be the most likely source of the element at the poles.

Cold Traps

The new, detailed topographic maps of the poles have made it possible to identify the potential ice-containing regions, called "cold traps". These are areas where the sun never shines and the temperature hovers around 100 Kelvin (-173 degrees Celsius).

The sun's limb rises less than two degrees above the horizon at the south pole, meaning the floors of impact craters and other low areas can be in permanent shadow.

In contrast, the radar beam from Goldstone reaches up to seven degrees above the horizon, allowing many polar features hidden from the sun to be imaged by radar.

The floors of five large craters in the south polar region are hidden from the sun, the researchers say. These five crater floors constitute the largest potential deposits of water ice at the south pole and would be expected to display an excess of hydrogen if they contained ice.

Radar record

The scientists making the maps used the Goldstone 70 metre (230 feet) antenna to transmit the radar signals. Two 34 m (110 ft) antennas at the Goldstone site received the echoes.

Scientists derived a three-dimensional digital elevation model of the lunar poles by comparing the images from the two antennas, which are 20 kilometres (12 miles) apart.

Their three dimensional maps have measurements every 150 m (500 ft) over the imaged area and a height accuracy of 50 m (165 ft).

The maps are published in the journal Science.



Advanced options | Search tips




Back to top | BBC News Home | BBC Homepage | ©


Sci/Tech Contents


Relevant Stories

03 Jun 99 | Sci/Tech
Spaceprobe to smash into Moon

22 Apr 99 | Sci/Tech
Prehistoric Moon map unearthed

17 Mar 99 | Sci/Tech
Earth smash spawned Moon

16 Mar 99 | Sci/Tech
Best site for Moonbase revealed





Internet Links


Lunar Prospector

Moonlink

Deep Space Network

Science


The BBC is not responsible for the content of external internet sites.




In this section

World's smallest transistor

Scientists join forces to study Arctic ozone

Mathematicians crack big puzzle

From Business
The growing threat of internet fraud

Who watches the pilots?

From Health
Cold 'cure' comes one step closer