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Spread of Life through the Galaxy

Astronomers at Armagh Observatory and Cardiff University have independently discovered new mechanisms by which micro-organisms may have spread throughout the Galaxy. Scientific papers on the topic by Professor Bill Napier at Armagh, and by Dr Max Wallis and Professor Chandra Wickramasinghe at Cardiff University, will appear simultaneously in the Monthly Notices of the Royal Astronomical Society.

The discovery of these new interstellar routes for transmission of micro-organisms supports the view that life did not originate on Earth but arrived from elsewhere. It also strengthens the bacterial-organic model of interstellar dust that Professor Wickramasinghe and the late Sir Fred Hoyle had been developing since 1974.

It is known that boulders and other debris may be thrown from the Earth into interplanetary space as the result of collisions with asteroids or comets, and that micro-organisms within the boulders could survive the enormous accelerations involved. Life could easily have crossed the few astronomical units separating Mars and Earth in this way. To colonise the Galaxy, however, thousands of light years must be traversed. These enormous distances have always seemed an insurmountable barrier because of the lethal effects of cosmic radiation and the low probability that an ejected boulder would ever land on a planet in another star system.

However, Armagh astronomer Napier finds that collisions with interplanetary dust will quickly erode the ejected boulders to much smaller fragments and that these tiny, life-bearing fragments may be driven out of the solar system by the pressure of sunlight in a few years. The solar system could therefore be surrounded by an expanding 'biodisc', thirty or more light years across, of dormant microbes preserved inside rock fragments. In the course of Earth history there may have been a few dozen close encounters with star-forming nebulae, during which microbes might be injected directly into young planetary systems. A single microbe falling onto a receptive planetary surface could populate the planet within a year. If planets capable of sustaining life are sufficiently common in the Galaxy, Napier concludes that this mechanism could have infected over 10,000 million of them during the lifetime of our Galaxy. (Full Paper - PDF Format or Postscript.)

Cardiff scientists Max Wallis and Chandra Wickramasinghe have identified another delivery route. They point out that fecund ejecta would, on impact, bury themselves in the radiation- shielded surface layers of frozen comets. A belt of such comets, the Edgeworth-Kuiper belt, lies beyond the planetary system. This belt gradually leaks comets into interstellar space, some of which will eventually reach proto-planetary discs and star-forming nebulae. There they are destroyed by collisions and erosion, releasing any trapped micro-organisms and seeding the formative planetary systems.

FOR FURTHER INFORMATION CONTACT: Bill Napier at the Armagh Observatory, College Hill, Armagh, BT61 9DG. Tel.: 028-3752-2928; FAX: 028-3755-7174; wmnarm.ac.uk; Website: http://star.arm.ac.uk/ Chandra Wickramasinghe or Max Wallis at the Centre for Astrobiology, Cardiff University. Tel.: 02920-874201; FAX: 02920-876425; Wickramasinghecardiff.ac.uk; Website http://www.astrobiology.cf.ac.uk/

See also:
Report on BBC Website


(1) Independent government assessments recognise Cardiff University as one of Britain's leading research and teaching universities. In the 2001 national assessment of research quality, the University was ranked seventh of more 106 universities in the UK. Eighty seven percent of the University's academic research staff work in departments assessed as undertaking work of national and international excellence, and the University is, by invitation, a member of the Russell Group of leading research universities. Twenty-one subject areas have been assessed as "Excellent" for teaching, one of the highest totals in Britain. The University was founded by Royal Charter in 1883. Visit the University website at: www.cardiff.ac.uk

(2) Professor Bill Napier, Research Astronomer at Armagh Observatory, is also an Honorary Professor at Cardiff University's Centre for Astrobiology.

(3) Professor Chandra Wickramasinghe is Director of Cardiff University's Centre for Astrobiology, which provides the UK with a facility to contribute to space missions probing for life on solar system bodies. The Centre is a joint initiative between the University and the University of Wales College of Medicine. The Centre combines research interests in astronomy and molecular cell biology to throw light on the emergence and development of life in the cosmos and planetary bodies. The work of the Centre also provides information essential for the emergent discipline of space medicine.

Last Revised: 2003 December 15th
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