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.

Europa's geysers present us Earthlings with a remarkable, tantalizing opportunity. We could design and build a robotic spacecraft that would fly through these plumes and sniff around. It would cost each U.S. taxpayer about the equivalent of one reasonably priced burrito, albeit without extra guacamole. All we have to do is decide to go. The proposed name for the mission is the Europa Clipper. Some work has been done on the design, but funding for the project has been unsteady. At the Planetary Society we work to put the funding for missions like this into law so that NASA can get going.

Imagine it. The Clipper would make dozens of orbits, mapping the Europan surface with cameras and radar, flying through Europa's seawater plumes and analyzing them, looking for the chemistry of life, and perhaps finding some otherworldly microbes. That would be astonishing.

The Bottom Line

At NASA's Jet Propulsion Lab, engineers, scientists, and skilled technicians design interplanetary spacecraft and schemes to get them to their extraordinary destinations. Europa mission plans have always come in pretty expensive, because everybody figured that we'd have to land there and drill through many kilometers of solid ice, potentially contaminating any ecosystem that might already be there. That's a strange but real science-fiction-style concern. But if we can analyze samples flung out into space, there's virtually no chance of contamination, and there's no need to build landing gear, drills, or complex anchor and tether systems. It would be much cheaper than anyone had calculated.

People everywhere know and respect NASA. It's the best brand the United States has. But like everything else, the agency's budget has been reduced over the years; it hasn't kept up with inflation.

Within NASA's budget is a line for planetary science. It's the part of NASA that does the most amazing things. Other space agencies put spacecraft in orbit around the Earth; a few even go to Mars. But no other space agency on Earth can land anything on Mars, let alone lower a small car there from a rocket-powered crane. (Read "Mars Gets Its Close-Up" in National Geographic magazine.) And no other agency can mount a mission like the Europa Clipper. The expertise is here in the United States. It allows people here to solve interplanetary problems that have never been solved before. It leads to innovation that, at last reckoning, produces $3.60 for every dollar that goes in.

The decision rests with the White House, which can ask permission from Congress to build the spacecraft, and with Congress, which can agree to set aside the money. That's where we at the Planetary Society come in. It's the reason my old professor Carl Sagan was one of the society's founders. We advance space science and exploration. With the support of our 45,000 members, people like you, we work with Congress and the administration, reminding them of the enormous value of planetary exploration and the great bargain that it is.

Just think what it would mean if we were to find a living thing in a geyser of seawater on another world. Every one of us here on Earth would stop and ponder what it means to be a living thing. I hope it would fill each of us with reverence for the cosmos and for our place within it. A mission to Europa would bring humankind together—and perhaps change the world.

Bill Nye is the CEO of the Planetary Society. Follow him on Twitter.