We have yet to find alien life on Mars...
But one day, in about 2 billion years, human beings may call the red planet home.
Earth will no longer be able to support life...
Dr Chris McKay, NASA Ames Research Center – "I think thinking about the planets, and the Sun and the Solar System as a family of objects and wondering what's their long-term future, I think is a sobering process, because we tend to think of the Earth as forever, the eternal sea we call it – but yet when we start looking at the planets in the Solar System we realise that they are not eternal, that the Earth is in some sense halfway through its lifetime."
The Earth is middle aged, because the Sun is middle aged.
The Sun will die in another 5 billion years...
Long before then, we will have to find a new home – because the Sun will get hotter as it ages.
Around 10% every 1 billion years.
The Sun will die in 5 billion years
It gets 10% hotter every 1 billion years
Earth too hot for life in 2 billion years
The extra heat will gradually change Earth's landscape.
Dr Chris McKay, NASA Ames Research Center – "If we were to come back in our Solar System in a billion years, it's still a place where you can find liquid water and go for a swim. Maybe 2 billion years or 3 billion years, it's now starting to become a hot house here."
A thick, insulating atmosphere caused by evaporating oceans, will cause a runaway greenhouse effect.
Earth will be more like Venus is today... a hostile inferno.
Meanwhile, 100 million kilometres further away, the freezing, dry planet of Mars will begin to warm up.
Once average temperatures exceed melting point, frozen oceans on Mars will melt, releasing vast amounts of liquid water and carbon dioxide.
Rivers, lakes and oceans will transform Mars' landscape.
Greenhouse gases like carbon dioxide will rebuild the atmosphere, and trap the increasing heat on the planet.
Mars will be more like Earth is today, than Earth will be itself.
Around 100 million kilometres further from the Sun, Mars will be a much more viable place to live... but for how long?
Dr Chris McKay, NASA Ames Research Center – "Mars is probably not a long-term place for home, but if you think about it there's no place that's going to be suitable for life forever – it's just a question of how long. How long do we want to have the rent on this planet or that planet? Earth, we've been lucky we've had several billion years. Mars we may have half a billion years. But still, a place to live for half a billion years is a good place."
As we leave Earth behind, Mars could be the next stop.
But eventually, our home will have to be on a different planet, orbiting another star.