Saturn moon may have hidden ocean

Saturn moon may have hidden ocean

By Helen Briggs Science reporter, BBC News

Future observations by Cassini will help test the prediction

Saturn's moon Titan may have a deep, hidden ocean, according to data published in the journal Science.

Radar images from the Cassini-Huygens mission reinforce predictions that a reservoir of liquid water exists beneath the thick crust of ice.

If confirmed, it would mean that Titan has two of the key components for life - water and organic molecules.

Currently, three other Solar System objects are suspected of having deep oceans: Ganymede, Callisto and Europa.

The Cassini-Huygens mission is a cooperative project of the US space agency (Nasa), the European Space Agency (Esa) and the Italian Space Agency (Asi).

We've got to go back again with balloons and rovers and really understand this place Prof John Zarnecki

When Cassini began to observe the largest of Saturn's moons in 2004, the surface was thought to be completely covered with an ocean of hydrocarbons.

But when the spacecraft turned its radar on the moon for the first time in 2004, and the Huygens probe parachuted to the surface a year later, a different picture emerged.

Much of the surface was found to be solid, with geological features such as dunes, channels and impact craters, punctuated by vast "lakes".

Cassini's latest fly-by of Titan is providing a new glimpse of these features, which to researchers' surprise, are not in the place they should be.

Scientists would like to send an instrumented balloon to Titan

Coupled with models of how the moon spins, the data suggests that the observed seasonal variation in spin rate could only exist if a liquid ocean lay beneath the solid crust.

The researchers, led by Dr Ralph Lorenz of Johns Hopkins University Applied Physics Laboratory, US, say their predictions can be checked in the proposed extended Cassini mission or in future missions.

John Zarnecki, Professor of Space Science, at the UK's Open University, who was not part of the study, said the motivation to go back to Titan with a more sophisticated space probe was "overwhelming".

Evidence suggests that Titan has two of the key constituents for the formation of life - water and organic molecules, and possibly a third - a source of energy, he said.

Prof Zarnecki told BBC News: "We know there are organic molecules, the place is swarming in organics.

Titan: The second largest moon in the Solar System

"Titan is 50% water-ice. If it is liquid, as this paper is implying some of it is, it looks as though we've got at least two of the things to initiate the chemistry that leads to life.

"It wouldn't be too far fetched to imagine certain spots on Titan where there would be a source of energy - maybe geothermal energy, as we have on Earth at the bottom of the oceans."

Titan is the second largest moon in the Solar System; only Jupiter's Ganymede satellite is bigger.

Past observations have shown that

Titan in many ways resembles a very early Earth, particularly in the composition of its atmosphere. The major difference is the frigid temperatures out near Saturn.

Prof Zarnecki added: "We've got to go back again with balloons and rovers and really understand this place."

Methane found on distant world

Methane found on distant world

By Helen Briggs Science reporter, BBC News

The planet is a "hot Jupiter" blasted by starlight

A carbon-containing molecule has been detected for the first time on a planet outside our Solar System.

The organic compound methane was found in the atmosphere of a planet orbiting a star some 63 light years away.

Water has also been found in its atmosphere, but scientists say the planet is far too hot to support life.

The discovery, unveiled in the journal Nature, is an important step towards exploring new worlds that might be more hospitable to life, they say.

Methane, made up of carbon and hydrogen, is the simplest possible organic compound.

HD 189733b Located 63 light years from Earth, in the constellation Vulpecula, the little fox About the size of Jupiter but orbits closer to the parent star in its Solar System than Mercury does in our own Temperatures reach 900 degrees C, about the melting point of silver

Under certain circumstances, methane can play a key role in prebiotic chemistry - the chemical reactions considered necessary to form life.

Scientists detected the gas in the atmosphere of a Jupiter-sized planet known as HD 189733b.

Co-author Giovanna Tinetti from University College, London, told BBC News: "This planet is a gas giant very similar to our own Jupiter, but orbiting very close to its star.

"The methane here, although we can call it an organic constituent, is not produced by life - it is way too hot there for life."

Stepping stone

Dr Tinetti, and co-authors Mark Swain and Gautam Vasisht, from Nasa's Jet Propulsion Laboratory in Pasadena, California, found the tell-tale signature of methane in the planet's atmosphere using the Hubble Space Telescope.

The observations were made as the planet passed in front of its parent star, as viewed from Earth. As the star's light passed briefly through the planet's atmosphere, the gases imprinted their chemical signatures on the transmitted light.

My personal view is it is way too arrogant to think that we are the only ones living in the Universe Dr Giovanna Tinetti

A method known as spectroscopy, which splits light into its components, revealed the chemical "fingerprint" of methane.

The researchers also confirmed a previous discovery - made by Nasa's Spitzer Space Telescope - that the atmosphere of HD 189733b also contains water vapour.

It shows that Hubble, Spitzer and a new generation of space telescopes yet to be launched can detect organic molecules on other extrasolar planets using spectroscopy, they say.

Dr Swain said: "This is a crucial stepping stone to eventually characterising prebiotic molecules on planets where life could exist."

Dr Tinetti said the technique could eventually be applied to extrasolar planets that appear more suitable for life than HD 189733b.

She said:

"I definitely think that life is out there. My personal view is it is way too arrogant to think that we are the only ones living in the Universe."

Real worlds

The number of known planets orbiting stars other than our own now stands at about 270.

For most of them, scientists know little more than the planet's mass and orbital properties.

Adam Showman of the Department of Planetary Sciences at the University of Arizona, US, said scientists were finally starting to move beyond simply discovering extrasolar planets to truly characterising them as worlds.

Dr Showman, who was not part of the study, said:

"The discovery does not by itself have any direct implications for life except that it proves a technique which might potentially be useful for characterising the atmosphere of rocky planets when we finally start discovering them."

Excitement about finding other Earth-like planets is driven by the idea that some might contain life; or that perhaps, centuries from now, humans might be able to set up colonies on them.

The key to this search is the so-called "Goldilocks zone", an area of space in which a planet is "just the right distance" from its parent star so that its surface is not-too-hot or not-too-cold to support liquid water.