Bob Pappalardo’s drive to work used to take about 20 minutes, and ran along the quiet, winding North Foothills Highway from Boulder, Colorado to the small town of Lyons and the sandstone buildings of the University of Colorado. It was a fine commute, except when it snowed. Today, Pappalardo, a senior research scientist at NASA’s Jet Propulsion Laboratory, monitors the Los Angeles traffic – “quite a sport,” he says – before heading out from his home near Santa Monica for the trek up to Pasadena; there are days, Pappalardo says, when the 25-mile drive lasts an hour and fifteen minutes.
So what got Pappalardo, a planetary geologist, and his girlfriend to leave the rambling serenity of the Eastern Rockies for the bustle of L.A.? It was a no-brainer: the search for life beyond Earth.
As study scientist for NASA’s burgeoning Europa orbiter mission, Pappalardo is working with a group of Jet Propulsion Laboratory scientists and engineers to deliver a plan for return to the icy moon of Jupiter, where the Galileo spacecraft, working in the late 1990s and early 2000s, recorded evidence of a vast, subsurface, saltwater ocean. Such an ocean, many scientists believe, could support the type of single-cell organisms that emerged as the first life forms on Earth.
The proposed Europa mission would seek to further define the ocean, which lay between the moon’s icy surface and its rocky core (NASA estimates the ocean could be 31 miles deep); to look for places where water may have erupted onto the planet’s surface, leaving a frozen apron of debris; and to collect details on the moon’s magnetic field, surface geology, and tidal forces (NASA scientists believe that tidal pull from the gas giant, Jupiter, could be responsible for warming Europa’s ocean enough to keep it liquid).
But all the goals of the Europa mission – including building the most radiation-resistant spacecraft ever – pale in comparison to the search for extraterrestrial life. It’s a cause that’s kept a dedicated group of scientists after the heels of NASA and Congress for years.
“Europa arguably represents the best existing habitat for life off of Planet Earth, so I think that’s a real fundamental reason to go explore [there],” Pappalardo said in a recent telephone interview. “We want to understand how life can exist … Everywhere on Earth where there’s water, there’s life.”
The Europa Geophysical Explorer would launch in 2015, with the hopes that its discoveries would warrant a return mission to land on the moon’s surface and further explore the potential for life. First, though, Pappalardo and others working on the project must convince NASA leaders that the mission can be executed on a tight budget, and that a trip to Europa is more feasible and more worthwhile than one to Titan, a moon of Saturn where convincing evidence of surface ice was recently discovered.
You are 490 million miles from the sun, five times farther away than the Earth, standing on a moon about the size of Earth’s, orbiting a gas giant 1,000 times larger than your home planet. The surface of this frigid Jovian satellite looks something like Utah’s Monument Valley. But instead of crumbling sandstone, you take in a stark landscape of white-gray ice flecked with ochre deposits. In some places, dramatic ridges cut by deep valleys jut toward the moon’s thin atmosphere. In others, the surface is relatively smooth, broken by isolated columns of ice. It is impossibly cold: the surface temperature hovers around 230 degrees below zero (Fahrenheit). Below your feet, the ice covers a vast, salty ocean. Below that, the ocean floor is most likely rocky, and might be home to volcanic activity. Jupiter’s massive magnetic field pelts you with heavy doses of radiation.
“If you think of a snow field, I think that’s too smooth for what we think we see on Europa. There are places where the ice shelf has collapsed, places where the ice has jumbled up on a glaciers,” Pappalardo said. “There’d be mesas and cliffs, sort of like in Monument Valley, some of them many miles across with steep cliffs and aprons of debris spreading out from them.”
It’s in those aprons of debris where NASA, on a subsequent mission, would hope to start the search for material that may have originated in Europa’s ocean. For the current mission, finding a place where the ocean has cut through the icy surface will be key. Such “communication” between the ocean and surface could come in the form of an open section of ice (imagine an Eskimo fishing hole) or in the frozen remnants where water once broke through the surface. But a much more likely scenario, according to Pappalardo, would have the moon’s surface affected by warm, flowing ice. Like the wax in a lava lamp, Pappalardo explains, “Warm blobs of ice within Europa’s icy shell may be able to rise up to the surface,” causing ridges and other formations.
When asked why the mission is so important, Europa advocates are quick to answer: it’s about the search for life beyond our own planet. “It’s why we do space exploration,” said Louis Friedman, executive director of the Planetary Society, a science outreach and lobbying group he co-founded with Carl Sagan. “It’s the dominant reason we explore – to understand ourselves. And everything else [in space exploration] is almost secondary because it’s about life and our relationship to the life in the universe.” Astrobiology is about “trying to understand life and the meaning of life, and now we have a chance to do it with real space craft.”
The case for life is strong with Europa. James Cutts, Chief Technologist for JPL’s Solar System Exploration Programs Directorate, said in a recent interview that Europa’s ocean floor is “almost certainly” rocky and might harbor volcanic activity, which could serve as an active energy source on the satellite, providing the minimal amount of energy required to support single-cell organisms, which have extremely low metabolic rates.
“If there’s life there, then it’s probably much more likely to be single cell organisms than it is to be whales,” Pappalardo said.
Like Europa, Titan has its supporters. Jonathan Lunine, professor of planetary science and physics at the University of Arizona’s Lunar and Planetary Lab, explained in a recent email that exploration of Titan can teach us about Earth’s past and future. “It’s the Earth of the past, in terms of active abiotic [non-living] organic chemistry, and mimics (with methane instead of water) the climate of the Earth’s future, when we lose our ocean,” Lunine wrote.
The proposed Titan mission would include an orbiter, a low flying balloon, and a surface probe, all designed to further document the moon’s Earth-like geological features and – as with the Europa mission – look for signs of life.
Before Pappalardo and others can start piecing together a space craft designed to endure the intense radiation bands of Jupiter, the project must first pass muster with leaders at NASA and the European Space Agency. The two agencies are expected to decide by November whether to go to Europa or Titan.
Cutts, who got his start working on camera systems for the Mariner missions to Mars in the 1970s, is overseeing the competing studies at JPL. Such a competitive study process is “quite unusual” for a mission of this magnitude, Cutts said, noting, “I think it’s a result of the fact that the science community has been split on what mission is the most important mission to do next.”
But Friedman, whose Planetary Society has been pushing Congress and NASA to aim for Europa, points out that the National Research Council, a branch of the National Academy of Sciences, placed a high priority on a mission to Europa in 2006.
“We have a mission to Titan,” Friedman said in a recent interview. “We actually have a spacecraft working there.” NASA’s Cassini continues to work in orbit around Saturn, and sent back new information regarding surface ice on the moon that bolstered a report in Science in March. NASA this month (April) announced an extension of the Cassini mission, originally set to expire in July. Instead, the orbiter will stay online for two more years, circling Saturn 60 more times, and passing by Titan 26 more times.
Lunine, of the University of Arizona countered that Cassini deployed a probe to just one location on Titan, and pointed out that the orbiter’s imaging resolution is limited compared to the cameras that would be used on the proposed mission. A report this month (April) in Aviation Week claims that recent radar data from Cassini which “continues to return data on Titan showing lake, river, stream and mountain features similar to those found on Earth, especially the southwestern Africa region,” gives the Titan mission a “competitive edge” in the NASA study.
Meanwhile, Europa waits. A plan to return there that surfaced in the early 2000s came at a time of shoestring budgets at NASA, then under the direction of Bush appointee Sean O’Keefe. “There was a great pressure then to do things very inexpensively,” Cutts said. “He [O’Keefe] wanted it done for $1 billion.” The mission was widely panned for being to thin on science, and never got off the ground. A later iteration of the Europa mission swung too far the other way – it would have used a craft powered by nuclear fission, an expensive and unpopular idea that was shot down resolutely by current NASA administrator Michael Griffin. Griffin told Congress on numerous occasions in 2005 that “Project Prometheus” was simply too expensive.
Now, Europa mission supporters hope, the pendulum has come to rest. The mission under study would use a few trips around Earth and Venus to slingshot itself into deeper orbit, eliminating the need for a heavy, fuel-laden launch vehicle, Cutts said. And, significant technologies have been developed in the interim. The proposed mission would employ the same type of surface-penetrating radar that has worked well on the Mars Express mission, which sent back new three-dimensional images of the red planet’s surface this month. Plus, scientists and engineers are closer to building the hearty components a Europa orbiter would need to survive flight through Jupiter’s powerful radiation belts (a manifestation of the planet’s unruly magnetic field), which are at least 20 to 30 times more intense than Earth’s.
“The radiation is much more severe for a longer amount of time than any past mission,” Pappalardo said. Everything on the Europa orbiter will have to be radiation-hardened, or rad-hard, including traditionally soft materials like computer memory.
“The scientific community might have some instrument concept where they can’t use the parts that they’re used to using, so they might have to switch to different ways of doing things,” Pappalardo said. “A big part of the challenge is simply informing the planetary science community that they’ll have to redesign [their instruments].”
While the competition between the Titan and Europa missions may be somewhat unusual for NASA, there have been no reports of bloodshed at JPL. Whichever mission goes forward, after all, will be headquartered there. Several JPL scientists and engineers, in fact, work on both mission proposals. “I’m officially a member of the Titan group. We work together all the time, we discuss it,” Pappalardo said. “It’s a competition, but we’re all trying to ensure that the best mission happens.”
NASA officials involved in both missions say both are scientifically strong. So, it’s budgeting and engineering that will decide which one goes launches. Titan is farther away, easier to land on, and boasts a less compelling case for life. Europa is smack in the middle of Jupiter’s’ intense, concentrated radiation belts, is difficult to land on because of a thin atmosphere, and demonstrates a more believable case for life.
“It think both objects are interesting, but Europa has the edge.” said Cutts, the NASA engineer overseeing both studies.
Either project would launch for about $2.1 billion, with ESA (with potential help from Japan) pitching in an additional $1 billion. That funding level, which has members of both teams attempting to streamline their missions, “sounds like a lot, but when you’re trying to go into orbit around a satellite, its not,” Pappalardo said.
When he discovered them in the early seventeenth century, Galileo named his four moons of Jupiter after Europa and a few of the Greek/Roman god’s other prizes. Europa, like many another mythological young lady of the Greek tradition, was minding her own business one day when Zeus – disguised as a bull and, with his wife out of the house, feeling saucy – appeared to her, and carried her on his broad back to his private island of Crete. There, young Europa bore the Cloud-gatherer two sons, Minos and Rhadmanthus, and they became the judges of the dead.
The others include Io, Europa’s sister (who also got the bull treatment); Ganymede, a beautiful boy-prince snatched up by Zeus’s eagle; and Callisto, another unlucky girl who found herself the target of the god’s affections – after a fight between Zeus and his wife, Hera, Callisto was turned into a bear and stuck up in the sky. She’s been known as the Big Dipper ever since.
After astronomer Gerard Kuiper showed in the mid-twentieth century that Europa’s surface was composed of water-based ice, Arthur C. Clarke wrote the moon into his “Space Odyssey” series, imagining Europa as a home to a race of aquatic creatures. In the climax of “2010: Odyssey Two,” the rebellious supercomputer, HAL, issues the ominous warning: “All these worlds are yours except Europa. Attempt no landings there.”
Back on Earth, Bob Pappalardo fights the smog and congestion of L.A. traffic everyday in hopes of discovering a new story line for the icy moon and its salty ocean. This time around, he’s hoping we simply find a reason to return, to try and land on the surface. “If that is a habitable environment then that’s going to really effect the way we think about where there can possibly be life throughout the universe,” Pappalardo said. Maybe then, aquatic Europans will capture our imagination, even if they are just single-cell microorganisms – not whales – swimming beneath the ice in an alien world.