Science

Attempt no landing there? Yeah right—we’re going to Europa

Ars learns some exclusive details about a daring lander for Jupiter’s icy moon.

Eric Berger – Nov 17, 2015 9:00 am | 184

An artist’s concept shows what the surface of Jupiter’s moon Europa may look like. Credit: NASA/JPL-Caltech

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.

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.

NASA’s reluctance

In the wake of the decadal survey, NASA administrator Charles Bolden was asked about the possibility of a Europa mission during Congressional hearings. All he would say is that he couldn’t do it. The agency, he said, had enough on its plate. And it’s true, NASA does have a lot to do, and its budget has a lot of mouths to feed.

Culberson, at the time not yet the chairman but still a member of the subcommittee, kept asking about Europa. If NASA could spend more than $100 million annually on education, could it not at least begin spending a few tens of millions of dollars to study a mission to the most intriguing ocean in the Solar System? NASA was reluctant to take on a new program that would ultimately cost billions, however.

Eventually Culberson stopped asking. As a member of the House Appropriations Committee, he did what such members can do—he appropriated. For the 2013 budget, he added $43 million to NASA’s budget expressly for a Europa mission. Bolden didn’t want the money. So in 2014 Culberson gave him more, $80 million, directing NASA to work on Europa. Finally, in its fiscal year 2015 budget request, NASA acquiesced and created a Europa program. The president’s budget called for $15 million to begin preliminary studies. Culberson appropriated $100 million.

It’s not clear why NASA ultimately embraced the Europa mission. Bolden, appointed by a Democratic president, and Culberson, a staunch Republican who regularly derides Obama, don’t have a good relationship. Perhaps for NASA, Europa simply became irresistible after another key discovery in late 2013.

That’s when NASA announced that the Hubble Space Telescope’s spectrograph had observed a faint aurora near the moon’s south pole. This aurora, astronomers concluded, was very likely caused by excited oxygen and hydrogen atoms that Jupiter’s magnetic field had broken apart.

How did that water get there? The obvious explanation was plumes of water venting into space from Europa’s oceans. Intriguingly, active jets were only observed when the moon was farthest from Jupiter in its slightly eccentric, 3.5-day orbit. The researchers suspected that Jupiter’s tidal forces would wrench the vents open at the furthest point and then constrict the gaps closer in to the planet. For NASA, the presence of plumes proved a game changer.

“When we had Galileo at Jupiter we didn’t look for plumes because we didn’t know they were there,” Jim Green, a space physicist who oversees NASA’s Planetary Sciences division, said in an interview. “They were probably all over the place, and we probably missed opportunities all over the place. We were just too ignorant to recognize the opportunities.”

Plumes of water vapor on Europa? Hubble thinks so. Credit: NASA/ESA/K. Retherford/SWRI

Shortly after the Galileo probe’s demise in 2003, NASA’s next major mission to the outer planets (the Cassini spacecraft) arrived in the Saturn system. It carried a much more modern scientific payload, and soon the probe found evidence of geysers on Enceladus, which rise hundreds of kilometers into space because of the tiny moon’s slight gravity. As Cassini flew through the plumes right over the vents, it observed they were active along their entire length.

Such cracks on Europa might offer a window to the oceans below, and Green seems as eager to peer into them as Culberson does. “This mission,” he said enthusiastically, “is only getting better.”

Officially, Green says NASA hasn’t decided whether the Europa spacecraft will carry a more expensive lander or some kind of suicide flyer that will detach from the main vehicle, descend into an active crevasse, and take data all the way down before being swallowed up by the moon’s icy maw. A final decision should be made some time in 2016, Green said.

We will land

The man who could afford to pay for a more pricey lander has, unofficially, already decided. After three years of tucking money into NASA’s budget to pay for Europa studies, Culberson traveled to the hilly Southern California campus of NASA’s Jet Propulsion Laboratory (JPL) in May of this year to see how those funds were being spent.

During two days of meetings hosted by Charles Elachi, the Lebanese-born director of the laboratory, Culberson heard about the various programs being undertaken at the storied facility. Founded by rocket scientists, JPL has led or partially sponsored nearly every major robotic probe in NASA’s history from America’s first satellite, Explorer 1, through the Voyager probes, to Galileo, Cassini, and all of the Martian landers. And although he nodded attentively during briefings on a number of topics, what Culberson really wanted to hear about was progress being made on the Europa mission, called a Clipper, because it will swoop into the harsh radiation environment of Europa periodically before flying out to more benign space to preserve its lifetime.

Eventually Elachi and his engineers came to the Clipper. During a two-hour meeting, several engineers walked Culberson through the various options a Europa spacecraft could employ to better understand the nightmare glacier. The Clipper, for example, might deploy cubesats to dip down near the planet and perhaps sample any plumes emanating from its crevasses. It could drop a short-lived impactor or missile-like penetrator that would strike the icy world at about 700km/h. It might also deliver a 100 kg “rough lander” to strike the surface at about 35km/h and retain the capability to do some basic science.

Finally—but this would be expensive, the scientists warned, perhaps adding as much as $1 billion to the mission’s cost—they discussed a “soft lander” that would touch down at less than 5km/h. This lander could bring a much more sophisticated scientific payload to the moon’s surface, and it would offer the best chance of finding life.

For Culberson, it was an easy decision. Do the soft lander, he said. Why traverse half of the Solar System if you’re not going to look for life? He would find the money. He told the engineers to get to work on adding a soft lander to the Clipper.

A couple of weeks later, at the end of May, NASA announced that it had selected nine scientific instruments for its Europa mission. According to the space agency’s news release, the solar-powered spacecraft would launch in the 2020s and, after reaching the Jupiter system, fall into a long, looping orbit around the gas giant. During a three-year period, it would perform 45 flybys at altitudes ranging from 25 kilometers to 2,700 kilometers. The release made no mention of a lander, but it did note the president’s budget for fiscal year 2016 had requested $30 million to continue developing the mission.

Meanwhile Culberson, energized after his discussions with JPL engineers, went back to work in Washington DC. Elachi and the other lander experts had told Culberson they would need more than $100 million during the coming year to rapidly develop the lander concept in time to make the Europa mission. Eventually, the House passed a budget for the 2016 fiscal year that included $140 million specifically for Europa.

Although the budget process stalled in the summer and fall months, Congress and the White House recently struck a deal for the next two budget years that allows for modest increases in discretionary spending, including NASA’s budget. When that appropriation finally gets approved later this year, will the $140 million for the Europa program be there?

“I’m very optimistic,” Culberson said. “Let me put it this way, they have to have my signature on the bill.”

Mr. Chairman

During the first weekend in November, instead of returning to his home in west Houston or attending a fundraiser, Culberson went back to JPL. He’d given the engineers six months, and he was curious to learn about their progress, however clandestine, with development of a lander.

Whenever he visits JPL, Culberson feels almost at home, even though many of the scientists and engineers at the lab do not share his politics, which veer toward the hard right wing of the political spectrum. Both the Heritage Foundation and American Conservative Union rank him comfortably above most Republicans in the House on their conservative scorecards. But Culberson is as much defined by his politics as a curiosity about the natural world. With science, he finds common cause with the JPL engineers.

At JPL in November, Culberson, center, holds a 550 million-year-old Treptichnus pedum trace fossil of some of the earliest multi-cellular life on Earth. NASA’s associate administrator for the Science Mission Directorate, John Grunsfeld, to the left of Culberson, and Charles Elachi, JPL’s director, is to the right. Credit: John Culberson

Culberson grew up in Houston, just down the road from Rice Stadium where John F. Kennedy gave his famous “We choose to go to the Moon” speech in 1962. He was six years old at the time. Later he and his brother would shoot off model rockets from Rice Stadium and pretend to be astronauts in their backyard. The family vacationed in Florida twice to see Apollo launches.

Politics ultimately called, and he ended up taking a Congressional seat that covers much of the affluent western suburbs of Houston. His district doesn’t include Johnson Space Center, but as a member of the House Appropriations Committee, its leaders there look to him for support. Yet they sometimes grumble that the Houston House member seems more interested in JPL than his hometown space center.

During the November 2014 midterm elections, Culberson won his eighth term in Congress, and, finally, seniority brought him to a cherished chairmanship—not of the entire Appropriations Committee, but the Commerce, Justice and Science Subcommittee that oversees NASA’s budget. This gave him immense power to set priorities for the space agency. Instead of trying to deliver pork for Johnson Space Center, he’s continued to show more interest in planetary science.

These interests have brought him allies, including the decidedly left-leaning Bill Nye, chief executive of The Planetary Society, a nonprofit organization that promotes the exploration of space. The organization has no qualms about working with Culberson, said Casey Dreier, the Society’s director of advocacy. In fact, the society is thrilled to have found an able champion in Congress for planetary exploration.

“That’s the beautiful thing I think about space exploration, it brings together a wide and diverse group of people for the love of exploring the Solar System and the Universe,” Dreier said. “We’re not going to agree on everything. But we can agree on the value of exploration, and that gives you a bedrock of common ground.”

The same holds true for the scientists and engineers at JPL. They not only share Culberson’s passion for Europa, they recognize he’s the one person who can commit us to acting upon it. So when John Culberson visits JPL, he’s not referred to as John, or Mr. Culberson. He is “Mr. Chairman.” And in November, Mr. Chairman learned a bit more about the lander JPL had been working on. NASA would not allow him to make the briefing materials publicly available, but he recounted them later to Ars.

The lander

First, the bad news. Adding a lander to the Clipper will require additional technical work and necessitate a launch delay until late 2023. At that time, the massive Space Launch System rocket NASA is developing could deliver it to Jupiter in 4.6 years. Once there, the lander would separate from the Clipper, parking in a low-radiation orbit.

The Clipper would then proceed to reconnoiter Europa, diving into the harsh radiation environment to observe the moon and then zipping back out into cleaner space to relay its data back to Earth. Over a three-year period, the Clipper would image 95 percent of the world at about 50 meters per pixel and three percent at a very high resolution of 0.5 meters per pixel. With this data, scientists could find a suitable landing site.

The JPL engineers have concluded the best way to deliver the lander to Europa’s jagged surface is by way of a sky crane mechanism, like the one successfully used in the last stage of Curiosity’s descent to the surface of Mars. With four steerable engines and an autonomous system to avoid hazards, the lander would be lowered to the moon’s surface by an umbilical cord.

Although the SLS rocket has been designed to lift as much as 70 tons into low-Earth orbit, it can only propel a small fraction of that across the 800 million kilometers of space to Jupiter, and fuel and the Clipper will consume most of that mass. The engineers have calculated they can spare a total of about 510 kg for the sky crane and lander, and of the 230 kg lander, about 20 to 30 kg can be given over to scientific instruments. That may seem slight, but it’s equivalent to what the Spirit and Opportunity rovers had to work with on Mars.

That payload would contain a mass spectrometer to identify any complex biological molecules. The engineers are also trying to add a second type of spectrometer, based on Raman scattering, to provide independent confirmation of any significant findings. “Honestly,” Culberson said, “if you’re going to go all that way to determine if there’s life on another world, why wouldn’t you double-check it?”

To gather samples for the spectrometers, the lander will have a scooper and sampling arm with at least one set of counter-rotating saw blades that could penetrate to a depth of about 10 cm. At Europa’s low surface temperatures, its ice is harder than steel.

This artist’s concept shows the sky crane maneuver during the descent of NASA’s Curiosity rover to the Martian surface. Credit: NASA/JPL

Scientists will attempt to find this hardware a landing site near an active crevasse. If the Hubble telescope data is correct, this would offer a potential opening to the ocean far below. Ideally, if the lander can be placed near a vent, it might sample spouts from the ocean below. The engineers are also working through the feasibility of more exotic options, such as bots that might detach from the lander and examine the crevasses.

On Europa’s harsh surface, the battery-powered lander would have about a 10-day lifespan, although solar cells might extend that further. But with dim sunlight and continual radiation, the lander’s functional time would necessarily be short.

Finally, the JPL engineers are working on a “plume probe,” not as part of the lander but which would detach from the Clipper and fly close to the moon’s surface, perhaps 2 km or lower, to obtain samples and relay that data back to the Clipper.

If all this sounds fantastical, well, consider the source. The engineers and planetary scientists at JPL have a motto, Dare Mighty Things. The very idea of landing on a creaking ice world nearly 1 billion kilometers from Earth seems absurd. But there is a place in America where such missions are considered and discussed with all due gravity. It’s in a conference room at JPL known as “Left Field,” precisely because that’s where crazy ideas come out of.

As to what the lander might ultimately discover, it is impossible to say. That is the joy of science, delving into the unknown. The New Horizons probe recently found unexpected wonders such as active geology and ice volcanoes on Pluto, at the cold edge of the Solar System. Imagine why lies in wait at Europa, a far more dynamic world capable of supporting life.

NASA buys in

One of the scientists in attendance at the November briefings with Culberson was the physicist and five-time astronaut John Grunsfeld. He was enthusiastic, Culberson recalled. “Grunsfeld said several times during the briefing that if this mission is like others we’ve flown to other mysterious worlds, Europa will prove far more interesting than we can ever imagine.”

Grunsfeld is NASA’s associate administrator for the Science Mission Directorate, which means he oversees all of the agency’s scientific activities, including planetary science. His presence at those meetings and enthusiasm for the mission signifies the space agency has finally bought fully into Europa. And why wouldn’t it, Culberson mused. “I cannot think of anything that would energize the public more than the discovery of life on another world,” he said. “It would inspire the public to support NASA even further.”

There are very few guarantees when it comes to spaceflight, and especially so with NASA’s budget. The agency is bedeviled by a year-to-year budgetary subsistence that makes long-term planning a continuous waltz of uncertainty. But consider this: the US House is solidly in Republican hands, and Culberson probably has more than five years left in his post as subcommittee chairman. That gets the Europa mission through 2020, to within three years of launch, by which point NASA and the scientific community will be heavily invested in the spacecraft.

Over in the Senate, he has allies, too. Key Republican and Democratic senators support development of the Space Launch System, which is so expensive to build and fly that NASA’s human exploration program can’t afford to build payloads for crewed missions. The big rocket needs meaningful launches, and getting the Clipper to Jupiter fast would fit snugly into its launch manifest. Even if the SLS rocket never flies, private companies such as SpaceX and United Launch Alliance are building smaller, but still capable, heavy-lift rockets that could get a lander to Europa, albeit over a longer period of time.

Now that NASA has the will, a way can be found. And so humans will wake the nightmare glacier, knowing not what secrets sleep within.

Listing image: NASA/JPL-Caltech

Eric Berger Senior Space Editor

Eric Berger is the senior space editor at Ars Technica, covering everything from astronomy to private space to NASA policy, and author of two books: Liftoff, about the rise of SpaceX; and Reentry, on the development of the Falcon 9 rocket and Dragon. A certified meteorologist, Eric lives in Houston.

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