The survival characteristics that we see with bacteria under extreme conditions both here on Earth and on the moon would seem to suggest that it is feasible for bacteria to travel across the galaxy. The vast vast majority of instellar bacteria would probably be destroyed. But all it would require is for minute amounts of bacteria to survive the journey and arrive on a planet like Earth, seed the planet and then go forth and multiply. And we now know that the potential lifetime of bacteria is extremely long, up to 250 million years. Bacteria that were last 'alive' 50 million years before the first dinosaur appeared on Earth have been discovered in a core sample. They were contained within crystals in a type of suspended animation until 'revived' in a laboratory. Maybe bacteria are natural space travellers!

For the theory of Panspermia to have credence, we must show that life could exist in the harsh condition of space. It was once thought that outer space is just too harsh an environment for life to exist, these environments were outside the limits (we defined) of life. They were too hot, or they were too cold, or they didn't have liquid water. But scientist have began to discover microbes that live in some of the most inhospitable environments imaginable here on our own planet. These 'miracle' microbes seem equally at home in the scalding hydrothermal vents deep in the Pacific ocean as much as buried beneath the frozen wastes of the Antartic. Some examples of these microbes, so called extremophiles, which live, reproduce and indeed thrive in harsh environments on Earth are;

• Alkaliphiles thrive in high pH environments such as in Mono lake, California. Here, Richard Hover, a NASA scientist and extremophile 'hunter' has identified microbes thriving in this extreme condition of high alkalinity with a pH of 10. In fact when they are exposed to Oxygen they can't survive!
• Psychrophiles thrive in cold temperature. They are found in Antartica, as well as the harsh Siberian, Alpine and Artic environments.
• Hyperthermophiles thrive in very high temperatures, and are found in hot springs and deep-sea thermal vents.

Microbes have even been discovered in a highly alkaline water in the presence of nuclear fuel rods. They are able to live and thrive in this incredibly high radiation and high alkaline environment and feed on the iron from the stainless steel of the reactor.

In fact man has participated unknownly (at the time) in panspermia. Surveyor 3 landed on the moon in April 1967. In November 1969 the Apollo 12 astronauts recovered the camera attached to Surveyor 3. And when the camera was analysed back on Earth, microbes were detected inside it. These were a common Earth microbe and were shown (how?) to have been been in the camera at launch. But how could microbes survive for 30 months, in a vacuum, with no water, in extreme cold and heat and completely unprotected from the high levels of radiation from the sun? Well apparently they are made of sterner stuff than you or I! So evidently microbes can be transferred from one planet to another (the moon) and could survive in the harsh environment of the moon. This is possibly the most important discovery of any mission to the moon! After all, isn't this the essence of panspermia?

One lesson learned from this incident is how vital it is not to contaminate the places we travel to in space. And how could we distinguish if discovered microbes were alien or some contaminant brought along with the space ship? And more importantly, we need to ensure that any samples returned to Earth in the future do not pose a biological risk to terrestrial life. Planetery Protection Officer, John D Rummel, is at the helm for NASA to do just this.

Meteors too have a part to play

Hundreds of tonnes of meteorites make their way to the Earth's surface each year. Of these, the Carbonaceous Chondrite meteorites would appear to be the most suitable taxi ride for alien bacteria, as they have been discovered to contain water and organic compounds. But do they show any evidence of life?

The Murchison meteorite, which fell in Australia in 1969 has been extensively studied. When examined under an electron micorscope, complex structures were identified, There shape along with some precise details such as reproductive structures, suggested evidence of life in that it appeared to contain the remains of living organisms. But this claim is contentious.

The Murchison meteorite contained over 100 amino acids (the protein builders), both common to Earth and alien to Earth. The chirality or handedness of the amino acids was equally left and right handed, suggesting that they were not as a result of Earth contamination as amino acids on Earth are left-handed. But the jury is still out, with many scientists convinced that you cannot just easily dismiss these discoveries as recent contamination.

Life on Europa?

Will we find life on Europa, one of Jupiters moons? There are plans to send a robot to find alien life on Europa in the near future. Europa is of great interest, because we are almost certain it has water.

Europa