Life in the Universe

  Professor N C Wickramasinghe

Recently, in the news, it has been reported that Spanish bluebells are threatening our own native species. Conservationists are concerned to such an extent that they plan to carry out a survey to determine how the Spanish hybrids are ousting our own beloved blue woodland carpets; as the Spanish variety are able to grow in a greater variety of habitats and also hybridise with our own species. The spread of Spanish bluebells is an example of an artificially introduced species but the colonisation of suitable habitat by the various kingdoms of life is a natural process on our planet.

Our speaker, Professor Chandra Wickramasinghe Director of Cardiff University's Centre for Astrobiology, thinks that this may also be true for our own galaxy and even beyond. Recent spacecraft missions by NASA such as Deep Impact and Stardust have found a mixture of organic and clay particles inside comets. The clay particles, it is proposed, can act as a catalyst to convert simple organic molecules into more complex structures which are potential building blocks of life. There may even be liquid water present deep inside some comets as the natural decay of radioactive elements within the comet produces heat which will melt any water ice.

That comets, interstellar dust and giant molecular clouds in deep space contain surprisingly complex molecules is an undisputed fact. The more contentious issue is whether these basic ingredients could come together to form a primitive form of life such as a bacterium which could survive the hostile space environment.

The theory of "panspermia" (literally "all seed") that Prof Wickramasinghe is researching is the proposal that life exists throughout the Universe and that its various 'seeds' are propagated by hitching a ride on comets and the like. It is not a new theory as the Greek philosopher Anaxagoras wrote about it in the 5th Century. The fact that bacteria and other simple lifeforms are extremely hardy does add some support to the theory. Scientists have found types of bacteria known as 'extremophiles' in some of the harshest environments on Earth. There are bacteria that can survive freezing desert conditions in the dry valleys of Antarctica and others that can live in the extreme temperatures of hot springs or deep below our planet's surface at tremendous pressures.

To see how microbes cope with the rigours of space travel different types of organism have been deliberately (or even accidentally) exposed to the vacuum of space. A future experiment is planned for 2011 whereby some microbes will hitch a ride aboard the International Space Station. Some will be encased in clay to protect them and others will have no shielding and be exposed to the space environment for up to five years. One of microbes will be Deinococcus radiodurans otherwise known as "Conan the Bacterium". This little bug is listed as "the world's toughest bacterium" in the Guiness Book of World Records.