Cardiff, Wales - Comets contained vast oceans of liquid water, supporting the theory that they may have harboured life, a study claims.
The watery environment of early comets, together with the vast quantity of organics already discovered in comets, would have provided ideal conditions for primitive bacteria to grow and multiply, according to Professor Chandra Wickramasinghe of the Cardiff Centre for Astrobiology.
The team calculated the thermal history of comets after their formation from interstellar and interplanetary dust around 4.5 billion years ago.
The formation of the solar system itself is thought to have been triggered by shock waves that emanated from the explosion of a nearby supernova. The supernova injected radioactive material such as Aluminium-26 into the primordial solar system, and some became incorporated into the comets. The Cardiff team claims that the heat from this radioactivity warmed initially frozen material in the comets to produce subsurface oceans that persist in a liquid condition for a million years.
Professor Wickramasinghe said: "These calculations, which are more exhaustive than any done before, leave little doubt that a large fraction of the 100 billion comets in our solar system did indeed have liquid interiors in the past. Comets in recent times could also liquefy just below their surfaces as they approach the inner solar system in their orbits. Evidence of recent melting has been discovered in recent pictures of comet Tempel 1 taken by the Deep Impact probe in 2005."
The existence of liquid water in comets gives added support to a possible connection between life on Earth and comets. The theory, known as cometary panspermia, was pioneered by Chandra Wickramasinghe and the late Sir Fred Hoyle, and argues that life was introduced to Earth by comets.
The paper is published in the International Journal of Astrobiology.