Sometime between 1.75 billion and 3.25 billion years from now, our planet is going to be too hot to support life, according to a new study in the journal Astrobiology.
When that happens, whatever life forms are around may want to move one planet over and set up camp on Mars.
"We think that Mars will probably be our best bet once the Earth gets too hot," study leader Andrew Rushby of the University of East Anglia in Britain told the Los Angeles Times.
Rushby is interested in how long planets can remain in the habitable zone around their sun. That's the zone with just the right conditions for liquid water to exist on the planet's surface.
If a planet is too close to the sun, high temperatures would cause every drop of water to evaporate; too far away, and the planet is an icy wasteland.
For now, Earth is squarely in the habitable zone, but it will not stay that way forever. As our sun gets older, it will also get bigger, brighter and hotter.
Eventually, the 92.9 million miles between us and our host star won't be enough to keep us comfortable.
But Mars is 141.6 million miles from the sun and, according to Rushby's calculations, it will be in the sun's habitable zone long after Earth has grown uncomfortably warm.
Of course, Mars would need some major help to become truly habitable for humans.
"Mars would need some human intervention in the form of massive geoengineering and terraforming efforts to provide it with a dense enough atmosphere," he said.
This may be even more complicated than it sounds because, as Rusbhy explains, Mars' atmosphere is geologically dead.
"It's core has effectively solidified, so it has no magnetic field to protect the atmosphere from being stripped away, and no tectonic activity to replenish the atmosphere with gases from the interior," he said.
Luckily, life on Earth has between 1.75 and 3.25 billion years to figure it out.
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