Water is an extraordinary and abundant substance on Earth and throughout the universe.

It is a strange molecule that expands when frozen and boils at far too high a temperature. But if it acted any other way, life as we know it would be impossible.

For this reason, astronomers are searching for water's presence on other planets in the hope it may lead them to the discovery of extraterrestrial life.

On Earth, the existence of so much water, in the form of the oceans, means that much of our own planet still holds many mysteries. Because of its great depths, the inner space of world's oceans has been very poorly explored.

However the water is a great conductor of sound and scientists have made new discoveries about the oceans by listening to the sounds in the deep.



Programme one:
Water - The Marvellous Molecule
The structure of water

There is a very long list of the properties of water that mark the liquid out as being far from normal, not to say weird. But if it wasn't for water's profound peculiarities, life would be impossible here on Earth and most likely elsewhere too.

For instance, being made of hydrogen and oxygen - two very light elements - water should not really exist as a liquid under the conditions here on Earth. If water behaved normally, it would be a gas, which is no use as a medium for bringing together the chemical ingredients of life and hosting the biochemistry of living things.

Water also becomes lighter as it freezes rather than becoming denser like most other substances. This odd property prevents lakes and ponds freezing solid during winter. Andrew Luck-Baker explores the vital weirdness of water.

> Listen to programme one


Programme two:
Water - The Marvellous Molecule
Water in space

Setting aside the Earth, there's abundant ice in the form of comets, moons and small planets like Pluto. There's even steam in the Sun. But astronomers are particularly keen to find extraterrestrial liquid water because of its necessity to life.

Andrew Luck-Baker hears about the latest evidence for the prospects for finding it on Mars, and the location of the solar system's largest and deepest ocean – which is covers a moon in orbit around the planet Jupiter.


> Listen to programme two


Programme three:
Water - The Marvellous Molecule
Water and the oceans

This programmes explores our own planet's inner space – the oceans. The Earth is more of an aquatic world than a terrestrial one. Seventy per cent of its surface is hidden beneath deep water. As a result, the watery majority of our planet has been poorly explored. So much of it is shrouded in darkness and everything in it is difficult to access and locate.

Unless, that is, you listen to the sounds travelling through the deep ocean waters. Water is a very good propagator of sound waves, particularly low pitch ones. There's a particular layer in the oceanic water column in which sounds are focussed and travel hundreds or even thousands of kilometres. These include the noises made by undersea volcanoes, earthquakes, ice bergs and whales.
Networks of underwater microphones are constantly monitoring these sounds of the deep. As Andrew Luck-Baker reports, the recordings are revealing at least some of the deep sea's many mysteries.


> Listen to programme three


Water - The Marvellous Molecule was broadcast during April and May 2003 on the BBC World Service