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Water found on the Moon. -

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Robyn Williams: Which takes us to Moon, which is wet, and Jonathan Nally.

Jonathan Nally: Despite 40-plus years of on and off exploration, it's taken until now for
scientists to spot one of the things they have most wanted to find; water on the Moon. In the last
couple of weeks they've released data collected by three space missions that show unequivocal
evidence for water across the entire lunar landscape and particularly near the poles. Data from a
NASA instrument aboard India's Chandrayaan-1 spacecraft (now sadly defunct), plus data collected
earlier this year by a mission called EPOXI on its way to a comet, and still more data gathered way
back in 1999 by the Cassini Saturn probe all reveal the spectral signature of water.

That's not to say there are lakes or rivers on the Moon, but mixed in with the lunar soil are
traces of the water and hydroxyl molecules, the latter being water with one hydrogen atom missing.
But there's not much of it. One tonne of lunar soil might hold, at most, about one litre of water.
Still, even that amount could come in handy for future Moon bases. Water can be used for drinking,
for growing food, and for splitting into oxygen and hydrogen for breathing and rocket fuel.

But how did it get there in the first place? Analysis of the Moon rocks brought back by the Apollo
astronauts suggests that the Moon was actually bone dry, at least inside. But it has long been
speculated that pockets of ice might exist deep into the permanently shadowed craters near the
lunar poles. Impacts by comets, which are made largely of ice, could have deposited water into
these craters. It's also been suggested that protons or hydrogen nuclei streaming out from the Sun
in the solar wind could spray the lunar surface and react with oxygen in the soil to form water
molecules.

The ice in the polar craters idea is going to be tested this coming Friday night by LCROSS, the
Lunar Crater Observation and Sensing Satellite. At about 9.30 Eastern Standard Time, NASA will send
LCROSS into a death dive into a crater called Cabeus A nears the Moon's south pole. In fact it will
be a double whammy. First the spacecraft's empty booster rocket, which weighs just under 2.5
tonnes, will crash into the crater at 9,000 kilometres an hour and cause an explosion that should
hurl about 350 tonnes of lunar soil high above the surface. Only minutes later LCROSS will fly
through the debris plume and 'smell' and 'taste' it using it delicate instruments, looking for
signs of water. Then LCROSS itself, which only weighs less than a tonne, will also hit the ground
causing its own debris plume. Telescopes back here on Earth will monitor both plumes to see what
they can find too.

It might seem crazy to spend all that money on a space craft only to have it deliberately crash,
but the alternative, sending one that could safely land in a permanently dark crater and then dig
up and test samples of frozen rock, would have been far tricker and much more expensive. No, it's
much better to get a big bang for your buck.

Robyn Williams: Thanks Jonathan Nally. The crash onto the Moon is coming up next Friday.

Guests

Jonathan Nally

Editor Spaceinfo.com.au

http://spaceinfo.com.au/

Presenter

Robyn Williams

Producer

David Fisher

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