Neil: And I'm Neil. Sophie, did you see the beautiful sky last night?

Sophie: No, I went to bed early. Why?

Neil: I was wondering if there was life out there.

Sophie: You mean life on other planets? That's just science fiction, Neil.

Neil: It isn't! People are fascinated by life on other planets for a good reason.

Sophie: You believe in little green men?

Neil: Not necessarily... but possibly.

Sophie: Well, Mars is our closest neighbour in the solar system

and the subject of today's show.

And that brings me on to our usual quiz question. How long is a day on Mars?

Is it about... a) 5 hours? b) 25 hours?

Or c) 45 hours?

Neil: And I think it must be c) 45 hours. Things are weird on other planets.

And Mars is further from the sun than us... Mars may be our closest neighbour, but it's

hardly in our backyard, is it?

Sophie: It is in astronomical terms, Neil

it's visible to the naked eye

meaning without using instruments

and it's reachable by spacecraft.

Well, we'll find out later on in the show whether you got the answer right or not.

Now can you tell me Neil why people like you get excited about the possibility of life on Mars?

Neil: Well, Mars is similar to the Earth in some important ways

which means if life developed on our planet, why not Mars?

Sophie: That's true. Its temperature is in the right zone

not too hot and not too cold.

But actually we could find Mars pretty cold

an average temperature would be around minus 63 degrees Celsius compared to Earth's 14 degrees Celsius.

It's also very arid – or dry.

Neil: And it needs to be wet for life to develop, doesn't it?

Sophie: That's right. Many scientists think that liquid water is essential for life!

But there may have been water on the surface of Mars in the past.

And recent research suggests that there may be water underground.

Let's hear some more about this from Professor John Zarnecki,

who teaches Space Science at The Open University.

John Zarnecki: We are now seeing that in fact Mars probably does have water – not liquid water

that there is ice just below the surface

and there's even just recently tantalizing evidence that perhaps water does flow periodically...

Now, and also coupled with the fact that here on Earth we're finding that life in very primitive form

exists in the most extreme environments, these are the so called 'extremophiles'

that exist at the bottom of the oceans...

So life is much, much tougher.

Neil: What does tantalizing mean, Sophie?

Sophie: It means something you want that's almost, but not quite, within reach.

So, scientists would love to think water flows on Mars

but the evidence isn't strong enough for this to be certain.

The other interesting point the professor makes

is that life may exist in the very harsh Martian environment

because primitive life exists in extreme places on Earth.

Neil: Extremophiles are organisms – or small creatures

that live in very extreme environments

and can survive conditions that would kill most other organisms.

But on Mars they would be living underground

because the radiation – or light and heat

from the Sun would kill any organisms living on the surface of the planet.

So why doesn't the Sun's radiation kill us then, Sophie?

Sophie: The Earth has a strong magnetic field created by its hot molten core or centre ...

and this protects us from the Sun's harmful solar winds.

Neil: And what about Mars - why doesn't it have a magnetic field?

Sophie: It used to ... 4 billion years ago.

It's possible that a massive collision with an asteroid

might have heated up Mars's core, disrupting the magnetic fields.

Neil: And if you disrupt a process you stop it from continuing normally.

Now, to return to the subject of collisions, Sophie, I have something very interesting to tell you.

Sophie: Yes?

Neil: A meteorite – or a piece of rock from outer space – might've crashed into the Earth millions of years ago.

That meteorite might have contained Martian life forms.

So we might be descended from Martians!

Sophie: That's actually an interesting idea, Neil.

But let's listen to Professor John Zarnecki talking about interplanetary life.

John Zarnecki: If we do find traces of life on Mars we don't know, do we

whether it evolved independently or was it perhaps seeded from Earth.

It is possible that life forms from Earth travelled to Mars and perhaps existed there

or the other way round.

Neil: So life on Mars may have evolved – or developed – on its own.

Or it might have arrived from Earth in a lump of rock... Or the other way round!

So Martians might be humans or we might be Martians!

One big interplanetary happy family, Sophie!

Sophie: Well Neil, let's hope you stay happy after you hear the answer to today's quiz question.

I asked: How long is a day on Mars? Is it ... a) 5 hours? b) 25 hours? Or c) 45 hours?

Neil: And I said c) 45 hours – they must have a long day over there.

Sophie: And you were ... wrong!

The correct answer is b) because a day on Mars is slightly longer than here on Earth

it's 25 hours.

Anyway, can we at least hear the words we learned today?

Neil: They are:

the naked eye

arid

tantalizing

extremophiles

organisms

radiation

core

disrupt

meteorite

evolved

Sophie: Well, that's the end of today's 6 Minute English.

Join us again soon!

Both: Bye.