The Moon: water ice crops up once again

The saga of the precious liquid on our natural satellite continues! This time an American team is talking about water ice several meters thick...

 

An artistic impression of the Indian Chandrayaan-1 probe which carried instruments that were not only designed in India, but also in Europe and the United states. Credit: ISRO

With Chandrayaan-1, India became a member of the select club of nations that explore the solar system. Not only did this small probe orbit (the mission came to an end in August 2009) the nearest celestial body to us, the Moon, but it was also an undeniable success. Chandrayaan-1 was carrying instruments that were designed in India, together with others that were created in Europe and the United States. It is NASA’s Mini-SAR radar which is at the centre of this new announcement concerning lunar water.

600 million tonnes of ice
We would reiterate first of all that the data gathered by Chandrayaan-1 was used to prove that water was to be found on the actual surface of our natural satellite, although it was in a molecular form and in extremely small amounts (see this Enjoy Space article). This was followed by the double voluntary crash of NASA’s LCROSS mission in October 2009 which made it possible to conclude that this liquid, so common on the Earth, existed in one form or another on the Moon (see this article). The water ice was therefore thought to be mixed with lunar subsoil.
But the conclusions of the scientific team for the American Mini-SAR from the Indian Chandrayaan-1 probe go much further. The instrument is a radar and the polarisation of the wavelengths returned by the surface reveal the presence of ice in 40 small craters around the Moon’s north pole.

The Moon’s north pole and the craters (red and green circles) examined by the American Mini-SAR radar aboard the Indian Chandrayaan-1 probe. Credit: NASA

To quote NASA’s words in order to explain the data from the Mini-SAR, “the ice must be relatively pure and at least a couple of meters thick”! If confirmed, this result goes in the direction of theories that claim that the areas which are permanently in the shadow of certain craters at the poles of our natural satellite act like gigantic “cold rooms”, thus maintaining water in ice form (in the Sun, water ice would instantly sublime into gas). Scientists estimate that there could be 600 million tonnes of water ice. By way of comparison, the Hoover Dam in the United States (fifty or so kilometres from Las Vegas and which is used as a backdrop in numerous Hollywood productions) alone holds about 35 billion tonnes of water, which is 58 times more.

Published on 2 March 2010