Astronomy: One of your research goals is to understand the origins of life. How does this intersect with exoplanet science?
Queloz: I feel that we cannot solve the mystery of life on Earth without trying to address it on other planets. We cannot go back to our beginning. But if we find different beginnings, different possibilities, maybe we can understand.
For example: Venus. A billion years ago, it was like the Earth – a beautiful blue planet. Perhaps it was living. And then the atmosphere completely changed. Now the belief is that there is no life on Venus. This might be wrong, but this is believed.
Astronomy: What do you think of the phosphine detection on Venus?
Queloz: Well, they saw phosphine twice, with two different telescopes, at two different times. So, I think it can’t be an artefact. But the way it was reduced because of Venus’s brightness is tricky. And they really need another line, because what if it is just a similar molecule?
It is very difficult when you are on the edge of science; I know this well. Your arguments are weak at first, because you do not yet have robust evidence. So, you have to play with assumptions. But sooner or later, the scientific truth prevails, because, whatever you do, anyone else should be able to do it again. The intrinsic facts build up and help you to sort it out.
As for phosphine, I think it shows we do not know all we should about Venus. We should go there soon, perhaps with a balloon. As for life, to be honest, I think we will find it on Mars.
Astronomy: There's been some criticism of the phosphine paper in terms of the way it was presented. Some say that life should always be the explanation of last resort in science. What do you think of that?
Queloz: I think it's stupid. Why discard life? It reminds me of my paper [on 51 Pegasi b] 25 years ago. First, we ventured all the possible explanations for the observation. And then we said, “The only way we know to explain this bizarre object is that it is a planet.” Nobody believed what we said at that time.
I think the phosphine team has done well. They say: “It might be this, or this, but none of our calculations are a good fit.” So, it is unknown – perhaps geochemical, but possibly life. What is the matter with suggesting this? Life is nothing special. It is mysterious, not mythical. I think these critics have lost a sense of perspective.
Astronomy: You have been quoted as saying that humans will find alien life in 30 years’ time. How can you be so sure?
Queloz: My view is very simplistic on this: I think life is just chemistry. And chemistry is everywhere. If you have the right ingredients at the right time, you will have life. But how likely is it? That's a very interesting question. Could it exist on a planet that just looks Earth-ish, [but] a bit bigger, a bit smaller? I don't know.
There are things we think are needed to sustain life, like plate tectonics, a magnetic field to shield from high-energy ultraviolet radiation, and liquid water. Planetology will advance in the next 50 years, alongside instruments, and we should be able to measure all these parameters within a hundred light-year bubble around the Sun. And we’ll learn whether the likelihood of the conditions we have here on Earth is slim or tiny.
Even so, the galaxy is full of stars, and most of them have planets, so there must be plenty with life according to these criteria. Even if it's one out of a million.