Red dust 'may contain building blocks of life'

Building blocks of life may have been found in a ring of red dust surrounding a distant star.

The disc appears to contain large complex organic molecules of the type believed to have given birth to life on Earth.

It is the first time evidence of life’s chemical precursors has been detected outside the Solar System.

The discovery suggests that such molecules, and possibly life itself, may be common throughout the universe.

The eight million-year-old star, known as HR 4796A, is about 220 light years from Earth and located in the constellation Centaurus, visible mainly from the southern hemisphere.

Astronomers believe the young star, which is 20 times brighter than the Sun, is in the late stages of planet formation.

The dust would have been generated by numerous collisions of small bodies, probably comets and asteroids like those in our own Solar System.

When Hubble Space Telescope scientists analysed the light scattered by the dust disc, they found that it looked very red.

The colour was typical of large organic carbon molecules called tholins, and did not match that of other red substances, such as iron oxide.

Tholins are believed to have existed on the primitive Earth billions of years ago and may have created the biomolecules that make up living organisms.

They no longer form naturally on today’s Earth, where they would be quickly destroyed by oxygen in the atmosphere.

However, they have been detected elsewhere in the Solar System, for instance in comets and on Saturn’s moon Titan, where they give the atmosphere a reddish tinge. This is the first time an indication of tholins has been found in another star system.

Many experts believe tholin-carrying comets and other small clumps of dust and gas may have sown the seeds of life on Earth more than four billion years ago. They could be doing the same for newly formed planets orbiting HR 4796A.

Dr John Debes, who led the US astronomers from the Carnegie Institution in Washington DC, said: “Astronomers are just beginning to look for planets around stars much different from the Sun. HR 4796A is twice as massive, nearly twice as hot as the Sun, and 20 times more luminous than the Sun.

“Studying this system provides new clues to understanding the different conditions under which planets form and, perhaps, life can evolve.”

The findings are reported in the latest issue of the 'Astrophysical Journal Letters'.