By Bill Nye
Every one of us has wondered if we’re alone in the universe. Are there living things elsewhere? Is the Earth the only place we’ll ever know that has life? That’s the question posed by this month’s cover story in National Geographic. It’s one I think we can answer, and maybe sooner than you think.
Many of us think of alien life the way it’s depicted in science fiction—creatures that look quite a bit like humans in makeup and that all speak English with a non-American accent. These made-up aliens hail from distant star systems. But there’s a place right here in our own solar system that may be teeming with life. It’s Europa, a moon of Jupiter, one of the four that you can see with an inexpensive telescope, just as Galileo Galilei did.
If you have a telescope and an evening, you can chart the position of the Galilean moons on a note card, as I used to do with my dad. They’ll appear as bright dots next to the larger disk of Jupiter. Observe them just a couple of hours later, and you’ll see how fast they’re moving in their orbits. Europa is unique among these four—it has an enormous ocean. In fact Europa’s ocean has twice the volume of seawater that we have here on Earth.
In astrobiology, the study of extraterrestrial life, it’s generally agreed that living things need a solvent to move their chemicals around. So far, no one can come up with any solvent that’s better for life than liquid water. Europa is inundated, even more than Earth is.
Out there, hundreds of millions of kilometers from the sun, you might expect the water to be entirely frozen. But Europa orbits Jupiter, and the giant planet’s enormous gravity stretches and compresses Europa like a rubber ball squeezed in your palm. That motion becomes heat. It’s like rubbing your hands together to keep warm, only on a planetary scale.
So while the outer core of Europa’s ocean is a shell of ice some 20 kilometers (12.4 miles) thick, what’s below is liquid. Shielded from radiation by solid ice and with plenty of internal heat, the sea of this alien world could well harbor life. Many investigators think it’s certainly worth investigating, because a discovery of living things on another world would utterly change this one.
Sniffing Europa’s Geysers
For the first time in history we have the chance to send a spacecraft out there to see if something is swimming around in all that water. Even better: Because of a remarkable feature of Europa, this mission would not be wildly expensive. We discovered it last year with the Hubble Space Telescope: Europa has geysers that continuously shoot Europa’s extraterrestrial seawater into outer space. They shoot hundreds of tons of the moon’s ocean to an altitude four times the height of our own Mount Everest. Can you imagine what such a thing would be like here on Earth? It would be astounding. It would be the number one wonder of our world.