On the line – June 2008

Transcript

Rob: Hello. My name is Rob Edwards, and I'm with Dr Claire Bretherton, an astronomer. I'm going to be asking Claire a selection of questions that have been asked by the public after our planetarium shows.

Claire, my first question for you is: do Martians exist?

Claire: Well, not as you see in science fiction, no, but Mars is one of the most likely places in the solar system that astronomers think life could possibly exist.

Astronomers have found evidence that water once flowed on the surface of Mars, and we think that liquid water is really important for life to begin. We don't see water flowing on Mars nowadays, but we do see signs of rivers and dried-up lakes, and we think there may be water frozen in the north and south pole, and also maybe deep underneath the surface.

And it's because Mars was warm and wetter in the past that astronomers think that life could've begun there, and may even be clinging on today. Of course, it's not going to be life like you or I walking around going out for dinner, it's more likely to be the sort of microorganism that you wipe off your kitchen table with a cloth and some bleach.

Actually, the NASA Lander, Phoenix, has just touched down on the Red Planet on 25 May this year. It's taken 10 months to reach Mars, and it will now take three months doing experiments, digging under the surface to look for the building blocks of life below the Martian surface.

Rob: My next question from the general public is, 'Have astronomers discovered any Earth-like planets orbiting other stars?'

Claire: Well, astronomers have already found around 300 planets going around other stars, but most of these are much larger Jupiter-type planets.

But as our detection techniques improve, and as the research continues, we're hoping to find more and more Earth-like planets in the near future. In fact, in April, 2007, astronomers found a new planet orbiting the star Gliese 581.

This planet, called Gliese 581c is very exciting because it's thought to be a rocky planet, and it has a minimum mass of only just over five times that of the Earth. And, if this planet's mass really is close to that minimum, then it's one of the smallest and possibly the most Earth-like planets we've found orbiting another star.

We don't know very much about it because we can't see the planet itself; we only know it's there because the planet's gravity makes the star wobble as the planet moves around. But, what we do know is that Gliese 581 is at about the right distance from the star that if the planet does have water on it, then that water is likely to be liquid. And, we call this area where the water's not frozen and not evaporated the Habitable Zone, or the Goldilocks Zone, because it's not too hot, and it's not too cold.

Gliese 581 itself is a red dwarf star. It's smaller and cooler than the sun, so a planet must be closer to the star to lie within this Habitable Zone. In fact, Gliese 581c is so close to the star that it orbits once every 13 days.

Rob: My final question is, 'Do you think we'll ever find intelligent life elsewhere in the universe?'

Claire: Well, the 300 or so extra-solar planets we've found so far are probably just the tip of the iceberg. There are likely to be millions, probably billions of other planets in our galaxy alone, and some of these may be capable of harboring life. It's certainly possible, maybe probable, that there may be intelligent life on one of these planets.

But, even if intelligent life does exist elsewhere in the universe, we may never be able to contact it, let alone to actually visit other civilizations. The distances are just far too vast. Even to get a message to the nearest star, to the sun, and back again, would take nearly a decade.

But, one group of scientists called SETI, the Search for Extraterrestrial Intelligence, are looking for signs of intelligent life in the universe. They're analyzing data from radio telescopes, and what they're doing is searching for signals that we don't think could occur in nature, and these signals may, therefore, come from extraterrestrial civilizations.

But, human beings themselves have only been producing signals like this for around 70 years, so any civilization searching for us would have to be within 70 light years to have yet detected our existence. This is only a tiny fraction of the stars in our galaxy, which lie within this distance.

So the chances are that to get a signal from the nearest intelligent civilization would take thousands of years. That civilization may no longer even exist by the time we receive their message, let alone manage to reply to it.

Rob: Claire, thank you very much.