We speak with Prof. Tilman Spohn of the German Aerospace Center (DLR) about the chances of finding life on other planets.
DW: What do you think: Will we ever find life on Mars?
Tilman Spohn: I certainly hope so – although I can’t be certain, unfortunately. Expecting life is one thing, but finding it is another. And it could be like searching for a needle in a haystack, the search for life on Mars.
Maybe the occurrence of life is such a rare event in our world that it happened only once, here on earth.
That is possible, although I wouldn’t consider that very likely. Although we have special conditions on this planet, if you consider the expected number of planets in the universe, we would conclude that there must be other planets that would harbor some form of life.
How many other planets are out there? Can you guess?
We’re talking about 10 to the power of 24 planets. I mean, a one with 24 zeros after it. This is a lot.
And what sort of life would you expect? Is that a highly-developed life, something like us humans, or just green slime?
Well, we couldn’t exclude higher developed life forms, although those are less likely, maybe, than life by itself. But microbes is certainly your best bet. And then there may be places out there where even life has developed, maybe not as much as on earth but further than just microbial life forms.
So you think we’re still the top of evolution? Or are there aliens, maybe, to top us?
There may be aliens that are even more evolved than we are. But that is of course entirely speculative. We don’t know. But from the likelihood, there is no reason to believe that humans on earth are the most evolved life form in the universe. There is no reason to do that.
Maybe there is just a completely different form of life. Maybe nature is a lot more fanciful than we think.
It could be. We don’t know how genius evolution could be. But you know, I think the way we are made is something that makes sense. We have two eyes because we need to judge distances. We have arms to grab things. And it’s very likely that evolution in other places would find similar tools.
They look like us, maybe. But we also say that life always depends on water. Could you imagine a different situation, without water.
Well, people talk about replacing water in other environments, where it is colder, with fluids that would be fluid at lower temperatures than on Earth. These could be hydrocarbons. For instance, on Titan which is a moon of Saturn, we could expect that.
Do we actually have a chance to recognize these different types of life?
Well, this is a good question. I think you could say “I’ll recognize it when I see it”. But there is no accepted definition in science for what life actually is. We’re still lacking that.
(Interview: Ingolf Baur)