Professor Lewis Dartnell, Professor in Science Communication, was interviewed on The Guardian’s Science Weekly podcast about life on distant planets.
Discussing what observations scientists can make about life on distant planets that orbit stars other than the sun, Professor Dartnell said “If we’re talking about an Earth-like extrasolar planet, the principle technique is spectroscopy.
“We take the light from this other planet orbiting another star in the galaxy and we effectively make a rainbow out of that light. You split it into a spectrum and then we look for particular absorption features in that spectrum.”
He also spoke about biosignatures, substances that provide scientific evidence of life. When asked how we are able to look at this evidence in atmospheres beyond our solar system, he said these measurements are very tricky.
He added: “We’re right down on the detection limits, at the threshold of some of the best telescopes we have around the Earth. These are very difficult measurements, you’re looking for a very subtle signal.”
Professor Dartnell also discussed whether evidence can prove there is life on other planets, and said that if a mix of methane and oxygen was found, this would be a very exciting discovery.
He said: “But there is a caveat here, because there is a non-living abiogenic process putting lots of oxygen in the atmosphere as well and this is what happened to Venus.
“Let’s say in twenty years, we’ve got ten nearby Earth-like planets that have oxygen in their atmosphere. We know the majority are probably due to life, but we couldn’t say with absolute certainty that any one of them has life on its surface.”