posted June 06, 2010 03:53 PM         

Researchers at the space agency believe they have discovered vital clues that appeared to indicate that primitive aliens could be living on the planet.

Data from Nasa's Cassini probe has analysed the complex chemistry on the surface of Titan, which experts say is the only moon around the planet to have a dense atmosphere.

They have discovered that life forms have been breathing in the planet’s atmosphere and also feeding on its surface’s fuel.

Astronomers claim the moon is generally too cold to support even liquid water on its surface.

The research has been detailed in two separate studies.

The first paper, in the journal Icarus, shows that hydrogen gas flowing throughout the planet’s atmosphere disappeared at the surface. This suggested that alien forms could in fact breathe.

The second paper, in the Journal of Geophysical Research, concluded that there was lack of the chemical on the surface.

Scientists were then led to believe it had been possibly consumed by life.

Researchers had expected sunlight interacting with chemicals in the atmosphere to produce acetylene gas. But the Cassini probe did not detect any such gas.

Chris McKay, an astrobiologist at Nasa Ames Research Centre, at Moffett Field, California who led the research, said: “We suggested hydrogen consumption because it's the obvious gas for life to consume on Titan, similar to the way we consume oxygen on Earth.

"If these signs do turn out to be a sign of life, it would be doubly exciting because it would represent a second form of life independent from water-based life on Earth.”

Professor John Zarnecki, of the Open University, added: “We believe the chemistry is there for life to form. It just needs heat and warmth to kick-start the process.

“In four billion years’ time, when the Sun swells into a red giant, it could be paradise on Titan.”

They warned, however, that there could be other explanations for the findings.

But taken together, they two indicate two important conditions necessary for methane-based life to exist.

posted June 06, 2010 03:58 PM         

The amino acid glycine was found in samples from comet Wild 2 brought back to Earth by the American Stardust probe.

The substance is one of 20 amino acids which join up in chains to create millions of different proteins, the molecules from which all the cells and structures found in living organisms are made.

Although comets are known to carry organic molecules, this is the first time one has been shown to harbour such an important element of life.

A space scientist involved in the research today described the find as “exciting and profound”.

Comets are dirty snowballs of ice and dust which date back to the birth of the Solar System.

Some scientists believe they may have planted seeds of life, as well as vast quantities of water, on the Earth.

The American space agency Nasa’s Stardust probe passed through dense gas and dust surrounding the icy heart of Wild 2 on January 2, 2004.

As it did so, a fly paper-like collection grid made from an ultralight material called aerogel captured samples.

This was stored in a capsule which was flown back to Earth and parachuted to waiting scientists on January 15, 2006.

Since then experts around the world have been busy analysing the samples in their laboratories.

Dr Jamie Elsila, from Nasa’s Goddard Space Flight Center in Greenbelt, Maryland, said: “Glycine is an amino acid used by living organisms to make proteins, and this is the first time an amino acid has been found in a comet.

“Our discovery supports the theory that some of life’s ingredients formed in space and were delivered to Earth long ago by meteorite and comet impacts.”

Dr Carl Pilcher, director of the Nasa Astrobiology Institute which helped to fund the research, said: “The discovery of glycine in a comet supports the idea that the fundamental building blocks of life are prevalent in space, and strengthens the argument that life in the universe may be common rather than rare.”

When glycine was detected in the samples collected by Stardust, scientists first had to be sure it was not put there as a result of Earthly contamination.

Sophisticated isotopic analysis eventually ruled out that possibility.

Isotopes are versions of an element with different weights. Glycine from a comet would be expected to contain heavier isotopes of carbon than glycine from Earth, and that is what the scientists found.

“We discovered that the Stardust-returned glycine has an extraterrestrial carbon isotope signature, indicating that it originated on the comet,” said Dr Elsila.

Stardust principal investigator Professor Donald Brownlee, from the University of Washington in Seattle, said: “The discovery of amino acids in the returned comet sample is very exciting and profound.

“It is also a remarkable triumph that highlights the advancing capabilities of laboratory studies of primitive extraterrestrial materials.”

The findings were presented at the annual meeting of the American Chemical Society in Washington. They are due to be published in the journal Meteoritics and Planetary Science.