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Moons

3.2.5 Is Europa habitable?

In this video several scientists explain why this moon is now the subject of so much interest. The video illustrates the surface features on Europa and discusses how they have led scientists to see Europa as a potentially habitable world. In this context, ‘habitable’ refers to suitability for simple, microbial, life to survive there. It does not imply that humans could live there without protection.

Bear in mind the following issues as you watch.

  • What is the evidence for a young surface?
  • Could you sketch the ball-of-string, raft and matrix textures?
  • What features might Europa have that makes it potentially suitable for life? Give examples of where such features are found on Earth.
  • What adaptations might life need to make in order to survive on Europa?
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Transcript

NARRATOR
Ever since Man first looked into the heavens, the most intriguing question has always been 'are we alone?' A small icy world circling Jupiter could answer that age-old question.
MICHELE DOUGHERTY
Moons in our Solar System are very important because if we can understand how they formed, what their interiors are made of, we'll better understand how our planets form - and so we we'll understand where we came from.
LEWIS DARTNELL
We now think that beneath the frozen shell of Europa, there lies an ocean with more liquid water in it than all of the seas, and lakes, and rivers, and oceans, of the whole of the Earth put together. And on Earth, where there's water, there's life.
NARRATOR
Europa first attracted attention back in the 1970s when the Voyager spacecraft flew past Jupiter, and took the first close-up images of its moons.
DAVID ROTHERY
The Voyager fly by showed that Europa had a young surface - and we already knew that it was icy, and we already knew that the ice couldn't be more than about a hundred kilometres thick. The question was, is the ice all the way to the rock, or is the ice sitting on top of some water? Now because it looks like the surface has moved around a little bit, a lot of people- including Arthur C. Clarke, the famous science fiction author- were suggesting there's water down there below the ice.
ANNOUNCER
The spacecraft is stable. Galileo is on its way to another world.
MICHELE DOUGHERTY
People have been interested in Europa for many years. But really, their interest in it was focused following the Galileo spacecraft, which orbited around the Jupiter system 20 years ago now.
LEWIS DARTNELL
As we've been exploring Europa, we see great signs of activity on its surface. Great big ridges and cracks from the tectonic pulling and stretching of this world. And also regions where the ocean from beneath has risen up and melted through the ice.
DAVID ROTHERY
What the high resolution view from Galileo showed us is this kind of terrain- which is called ball-of-string terrain - with multiple generations of double ridged grooves, crisscrossing the surface. But also shows places where the ball of string terrain has been broken apart, in what we now call chaos.
I can show you this here, there's a global view with this area magnified here at higher resolution. There's ball-and-string terrain all over it except in this chaos region here, where the ball of string terrain has broken apart. And at even higher resolution, you can see rafts of terrain with ball-of-string texture separated from one another by just a jumbled mess. And many of these rafts could be fitted back together like pieces of a jigsaw- round here or round here.
And what's happened is the ice has become thinner from below. There's been some melting of the base of the ice sheet. And eventually, the edges of the ice have drifted into the temporarily exposed ocean, which has now refrozen, and they're just locked in place.
When you look at the chaos terrain, it's very much like you see at the edge of the ice pack round Antarctica or in the Arctic Ocean, where rafts of ice drifted apart, and then perhaps refrozen again. So once you've got an ocean sitting on rock below ice, there's all kinds of ways that can be inhabited by various kinds of life.
LEWIS DARTNELL
I think the issue of whether there is life beyond our planet is one of the most current and important questions in modern science today. My research is all about the most hardy and tolerant life forms on our planet. The so-called extremophiles.
And one of the most exciting places on Earth for finding extreme living life is Lake Vostok. Now Lake Vostok is in Antarctica, and is buried beneath miles and miles of solid ice. And the kind of biology that we might find in Lake Vostok would be potentially very similar to what might be able to survive in the sealed ocean of Europa.
MICHELE DOUGHERTY
When people talk about life at Europa, they think about us? I don't think that's what we'll find. We'll find bacteria of some kind.
LEWIS DARTNELL
Life on Europa is going to have to have developed without powering itself by sunlight. You have to live by fuelling yourself and powering yourself from inorganic energy, like ecosystems we find around hydrothermal vents.
NARRATOR
But it may be some time before we find out just what lies beneath Europa's ice
MICHELE DOUGHERTY
What we really want to do is try and get an understanding about where the life is. How it might have formed. And what we'll do is we'll actually go into orbit around Europa because people are talking about trying to get below the surface. And for us to be able to do that, what we need to have an understanding of is where the ice layer is at its narrowest.
DAVID ROTHERY
The next mission to Europa is probably going to always be 20 years into the future, the way things are going. There was meant to be a joint NASA-European Space Agency mission to Europa. That's on hold at the moment- some people say it's on ice- waiting for budgets to be unfrozen. So I don't know when it's going to happen. I'm not holding my breath.
MICHELE DOUGHERTY
This orbiting mission at Europa, that's just a precursor really for us to be able to go back in the future, to be able to tunnel through the ice, and make measurements in the water itself. Because for us to be certain that there's life, we really need to be able to go and almost taste it.
DAVID ROTHERY
If life began on Europa and began on the Earth, that's twice in one Solar System. Then it's very likely that life began on many places elsewhere in the galaxy.
MICHELE DOUGHERTY
Discovering bacteria or life on another body in our Solar System would probably be the most important discovery that scientists have ever made. Because it will mean that the Earth isn't the only place where the conditions were just right for life to form. I can't believe that in our entire universe, we're the only place where the conditions were perfect. There has to be somewhere else.
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