Is there really life in outer space?

We put this question to Dominic Ford from Naked Astronomy.

Dominic - Well, it's of course very hard to know what life there is out there. People have looked for radio radiation from other civilisations using the Arecibo telescope in America and there are future telescopes that we'd hope to pick up radiation from aircraft radar and television transmitters on other planets. So far, they haven't picked up anything in the closest thousand, tens of thousands of stars around the earth. So we probably think there's not much life immediately close to the Earth but it's very hard to know what is out there.

Chris - A few years ago, in fact it was five years ago, I was in Washington DC at the AAAS conference and there was number of people at the conference talking about things like the SETI program looking for life. Some of the world's leading space scientists were right there and so we had them on a radio program, and I went along the table and said, "I'd like you all to guess or give any estimates as to the likelihood of us finding alien life within the next 50 years." Just out of interest, where would you put that number?

Dominic - I think there were a number of very interesting space missions coming up in the next 10 or 15 years which have the potential to see earth-like planets surround other stars. If we see those planets and we manage to see the light from those planets, we can take a spectrum of them and we can see what molecules are in their atmospheres. And if we start to see organic molecules in those atmospheres, we will know there is almost certainly life on those planets. It may not intelligent. It's very hard to tell whether it's intelligent, but I think there is a lot of potential to see microbial life in the next 10, 15 years. Chris - Whether or not you'd call life on earth necessarily intelligent is also open to debate. It depends where you look, I think. Dominic, thank you very much.