The Earth has an expiration date, and it's coming up in about five billion years - that's when the Sun is going to start running out of fuel, getting bigger and brighter, eventually turning into a huge hot giant.
And while that may spell the end of life on Earth, it might also mark the beginning of a real estate boom for life in the outer Solar System. (Yeah, it's free real estate).
As the Sun increases its energy output, its habitable zone the cozy, not too hot, not too cold region where water can stay. Liquid will begin moving further out into the Solar System, and where there's water, there's the potential for life.
It's difficult to predict what kind of life might take advantage of this new chapter in the Solar System's history. But what we know for sure is that the habitable zone will eventually move, so here's what we think will happen when it does.
In about seven billion years, the habitable zone will catch up to Jupiter, and that's when things will start to get interesting.
Jupiter itself is so huge and inhospitable that making it a little warmer won't change much. Instead, the real excitement is going to happen among its neighbors, like one of its moons, Europa. It’s already considered one of the prime contenders for hosting life because of the huge ocean beneath its solid icy crust, though we aren't sure whether that ocean is more like liquid water or slush. Either way, when the Sun's supercharged habitable zone finally reaches Europa, it's going to bring with it enough energy to melt the entire ocean, ice and all.
The inside of Europa is already heated by tidal interactions with Jupiter. All that moving around generates a lot of friction, which heats up the moon's inside. So when Europa begins to thaw, it'll then have two potential energy sources for life to feed off of: the internal heat escaping from thermal vents at the bottom of the ocean floor, and sunlight warming the surface of the ocean. These changes will be gradual, so if there are local life forms, then they will have millions (if not billions) of years to slowly adjust to the warming temperatures.
However, Europa is not the only moon becoming a hot spot.
Ganymede and Callisto are two other moons of Jupiter, which may both have subsurface oceans as well, and a place for microbes to potentially call home.
Eventually, the habitable zone will reach all the way out to Saturn, where Titan, its largest moon, already has a huge abundance of organic compounds that can provide basic building blocks for microscopic life-forms. And unlike the moons of Jupiter, Titan has a pretty good chance to develop an Earth-like surface with the mixture of liquid oceans and solid ground.
Right now, the average temperature on Titan is about -275 degrees Fahrenheit (-170 degrees Celsius). It only needs to increase a small amount to create the perfect temperature for liquid methane, and Titan could stay around that useful temperature for a long time - hundreds, millions, or maybe even a couple billion years. And for any methane-dependent life forms, that's a pretty long party.
Saturn is nearly twice as far from the Sun as Jupiter, so it'll take a while for it to warm up enough to melt water ice. But eventually, even Titan will reach a point where the ice starts to melt and give water-based life a chance to grow.
The sad news is that when compared to the entire lifetime of the Sun, these new habitable worlds won't last very long, either. They might reach a few tens to a couple hundred million years for Jupiter's moons, and maybe up to two billion years if you include the cooler temperatures needed for liquid methane oceans on Titan.
But let’s try to remember that life on Earth only moved out of the oceans and onto land about 400 million years ago, and look at all the progress we've made since then.
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Sources: This story was originally published on SciShow Space. I am republishing a lightly edited version on SkyFeed in light of interest in the subject. Hofmeister, Caitlin. "The Future Of Life In The Solar System." SciShow Space, YouTube. 5 May 2015. Web video.
Citation: Rovira, Lia N. "As Earth Dies, Other Planets in the Solar System May Inherit Life." SkyFeed. 27 June 2018. Web article.