It is a nightmare glacier, tormented by the giant of our Solar System ever looming on its horizon.

Jupiter showers its moon Europa with enough radiation to kill a human in just a few days. Europa must also contend with the massive planet’s powerful tidal forces. The moon literally creaks as Jupiter’s bulk rends its frozen surface in deep crevasses, pushing and pulling the ice upward and downward by tens of meters every few days. And with only a very tenuous atmosphere, it is so very cold: -210 degrees Celsius.

Yet as forbidding as Europa’s surface may be, just a few kilometers below lies the largest ocean in the known Universe. It dwarfs any on Earth, encircling the entire moon and plunging as far as 100 kilometers deep. The tidal forces that wrench Europa's icy surface also tug on the core of this ocean, dissipating heat and providing ample energy to warm the ocean.

Outside of Earth, many astrobiologists say Europa’s vast, dark ocean probably offers the best hope for finding life elsewhere in the Solar System. For these scientists, Europa beckons like the sirens of a Homeric epic.

Landing on a nightmare

NASA is very publicly planning a mission to Europa in the 2020s, one that will soar over the intriguing moon dozens of times. Yet the reality is more thrilling. Quietly, the same engineers who masterminded the daring Curiosity landing on Mars in 2012 have been plotting how best to drop a lander onto the nightmare glacier. In early November, they presented their preliminary findings for a 230-kg lander to the one person in the world who can, and who dearly wants to, make that happen.

“I told them to do whatever it takes,” said Representative John Culberson after meeting with the NASA scientists. “All of humanity is going to want to know what’s under the ice.”

A God-fearing, cowboy-boot wearing conservative Texas Republican, Culberson is far from a household name. But as chairman of the House Appropriations Subcommittee with oversight of NASA’s budget, he has the final say on the agency’s budget in the House. As much as anything else he has ever wanted in his life, Culberson yearns for NASA to land on Europa. And with the federal purse in hand, he’s doing everything possible to make it happen.

Culberson isn’t the first to fall under the moon’s spell. In Greek mythology, Zeus, the Greek counterpart to the Roman god Jupiter, abducted the Phoenician princess Europa and made her the queen of Crete. The moon is named after her. In the seminal science fiction series Space Odyssey, novelist Arthur C. Clarke recognized Europa’s special place in the Solar System. At the end of the series’ second novel, 2010: Odyssey Two, a ship sent to Jupiter appears to receive a message from aliens: “All these worlds are yours except Europa. Attempt no landing there.”

Sorry HAL, we’re going. It’s difficult to imagine a more compelling mission for NASA in the next 10 to 15 years than the exploration of Europa. NASA touts its human “Journey to Mars,” but in reality the most astronauts will accomplish by the mid-2020s is a repeat of the Apollo 8 flight around the Moon, which already happened in 1968. Likewise, while Curiosity awed the world, it was the eighth probe NASA has successfully landed on Mars. Cold, dry, and probably lifeless today, Mars no longer seems all that exotic.

Europa, by contrast, is undiscovered country. NASA last visited the Jupiter system in the 1990s and early 2000s with the Galileo spacecraft. Galileo snapped images of Europa during 11 flybys, but everything about those photos ended up limited. The best of those pictures had a resolution of only about 10 meters per pixel. The spacecraft stored those images on a tape recorder with a capacity of 114 megabytes, but a flawed rewind mode hampered even that modest device. Additionally, Galileo’s closest approach to Europa brought the probe only to within about 200 km of the moon’s surface.

NASA/JPL/DLR

NASA/JPL/University of Arizona

NASA/JPL/University of Arizona

NASA/JPL/University of Arizona

NASA/JPL/University of Arizona

NASA/JPL/University of Arizona

NASA/JPL/University of Arizona

NASA/JPL/University of Arizona

NASA/JPL/University of Arizona

NASA/JPL/University of Arizona

NASA/JPL/University of Arizona

Despite all of this, Europa dazzled, and Galileo confirmed that a large ocean must exist beneath the moon’s icy shell. The spacecraft’s tantalizing findings left scientists grasping for more. During the most recent “decadal survey” published in 2011, a document in which the scientific community sets priorities for planetary explanation, a mission to return a sample Martian soil and a Europa orbiter were rated as the two highest priorities.