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Enlarge/ The politics of getting to Europa are anything but straightforward.NASA

LA CAÑADA FLINTRIDGE, Calif.—At one end of the conference room, four large window panes framed a view of the San Gabriel Mountains. Outside, ribbons of greenery snaked across the hills, a vestige of spring before the dry summer season descends upon Los Angeles.

Inside, deep in discussion, a dozen men and women sat around a long, oval-shaped wooden conference table. They were debating how best to send a daring mission, known as Europa Clipper, to Jupiters mysterious, icy moon Europa. Although hundreds of scientists and engineers were already planning and designing this spacecraft, the key decisions were being made in this room on the top floor of the administrative building at NASAs Jet Propulsion Laboratory.

It will not be cheap or easy to reach Europa, which lies within the complicated gravitational tangle of Jupiter and its dozens of moons, 600 million kilometers from Earth. But the payoff, scientists feel, is potentially incalculable. Beneath Europas ice, perhaps just a few kilometers down in some areas, lies the most vast ocean known to humans. With abundant energy emanating from the moons interior into the ocean, scientists speculate life might exist—probably just microbes, but why not something krill-like, too?

In recent years, scientists have locked down a set of nine scientific instruments to fly on the Europa Clipper probe, which will look, search, and sniff for signs of life during 47 flybys that will skim to within 25 kilometers of the moon's surface. But one big question remains, and it will probably determine whether the mission costs in the range of $2 billion or $3 billion dollars: how best to get the six-ton probe from Earth to the Jupiter system?

This was a key reason for the meeting held in early April outside the San Gabriel Mountains. Barry Goldstein, who is managing the ambitious Europa Clipper mission at the Jet Propulsion Laboratory, stood at the head of the conference table. “Theres been a lot of discussion about launch vehicles,” he said. “So weve prepared a chart.”

The physics of that chart displayed the capability of commercially available, lower-cost rockets to throw the Clipper to Jupiter; it also highlighted the capability of NASAs more expensive Space Launch System. The latter rocket is more powerful than any booster flying today, but it has never launched, and when the titanic rocket will be ready for the launchpad is not certain.

Reaching Europa relies on more than physics, and invariably politics matter more when it comes to missions bound for the outer planets. This kind of exploration requires years of planning and development, as well as years of flight. In addition to costing billions of dollars, such missions must be managed across multiple presidential administrations and the comings and goings of Congress.

  • Why send the Clipper, shown here, to Europa? Because the Galileo mission to Jupiter in the 1990s and early 2000s raised a host of questions about this moon. NASA
  • This enhanced color image shows the region surrounding the young impact crater Pwyll, a 26km diameter impact crater thought to be one of the youngest features on the surface of Europa. The diameter of the central dark spot, ejecta blasted from beneath Europa's surface, is approximately 40km, and bright white rays extend for over a thousand kilometers in all directions from the impact site. These rays cross over many different terrain types, indicating that they are younger than anything they cross. NASA/JPL/University of Arizona
  • View of a small region of the thin, disrupted ice crust in the Conamara region showing the interplay of surface color with ice structures. The white and blue colors outline areas that have been blanketed by a fine dust of ice particles ejected at the time of formation of the large crater Pwyll some 1,000km to the south. NASA/JPL/University of Arizona
  • This synthetic color image shows three distinct spectral units. The bright white areas are ejecta rays from the relatively young crater Pwyll, located about 1,000km to the south. Also visible are reddish areas that can be seen along the ridges in the region of disrupted terrain in the center of the image and near the dome-like features where the surface may have been thermally altered. Thus, areas associated with internal geologic activity appear reddish. The third distinct color unit is bright blue and corresponds to the relatively old icy plains. NASA/JPL/University of Arizona
  • A close-up of Thera and Thrace, two reddish regions that disrupt the older icy ridged plains. Thera (left) is about 70km wide by 85km high and appears to lie slightly below the level of the surrounding plains. Thrace is longer, shows a hummocky texture, and appears to stand at or slightly above the older surrounding bright plains. One model for the formation of these and other chaos regions on Europa is complete melt-through of Europa's icy shell from an ocean below. NASA/JPL/University of Arizona
  • This image compares the size of Europa's ice rafts with a similarly scaled photo of the California Bay Area. NASA/JPL/University of Arizona
  • This mosaic of the Conamara Chaos region clearly indicates relatively recent resurfacing of Europa's surface. Irregularly shaped blocks of water ice were formed by the breakup and movement of the existing crust. The blocks were shifted, rotated, and even tipped and partially submerged within a mobile material that was either liquid water, warm mobile ice, or an ice-and-water slush. The presence of young fractures cutting through this region indicates that the surface froze again into solid, brittle ice. NASA/JPL/University of Arizona
  • This view of the Conamara Chaos region shows cliffs along the edges of high-standing ice plates. The washboard texture of the older terrain has been broken into plates that are separated by material with a jumbled texture. The cliffs themselves are rough and broadly scalloped, and smooth debris shed from the cliff faces is piled along the base. The height of the cliffs and size of the scalloped indentations are comparable to the famous cliff face of Mount Rushmore. NASA/JPL/University of Arizona
  • This composite image shows the distribution of ice and minerals for the structure named Tyre, the largest and likely one of the oldest on the moon. Tyre, at 140km diameter, is the size of the Island of Hawaii and thought to be the site where an asteroid or comet impacted Europa's ice crust. The blue in this image indicates areas with higher concentrations of mineral salts. These salts are similar in composition to those found in the bottom of Death Valley, California. The yellow-orange regions are areas that have a high surface abundance of water ice. NASA/JPL/University of Arizona
  • False color has been used here to enhance the visibility of certain features of the Minos Linea region. Triple bands, lineae, and mottled terrains appear in brown and reddish hues, indicating the presence of contaminants in the ice. The icy plains, shown here in bluish hues, subdivide into units with different albedos at infrared wavelengths probably because of differences in the grain size of the ice. NASA/JPL/University of Arizona
  • This is the highest-resolution image of Europa at 6m per picture element. The image was taken at a highly oblique angle, providing a vantage point similar to that of someone looking out an airplane window, albeit 500km high. The features at the bottom of the image are much closer to the viewer than those at the top of the image. NASA/JPL/University of Arizona
  • A false-color composite image of Europa. NASA/JPL/DLR

For Europa, one Congressman matters more than all the rest. Since 2004, John Culberson has been on a quest to make a Europa mission happen. In the just-completed budget for fiscal year 2018, the Texas Republican pushed funding for planetary science missions to its highest-ever level, more than $2 billion. And of that, he had funneled $495 million to this NASA facility for Europa exploration.

So before the discussion of launch vehicles began, Goldstein had something he wanted to tell the politician who had flown in from Houston. “On behalf of the entire project, let me start with this,” Goldstein said. “Thank you, thank you, thank you, thank you, thank you. And I could go on for what, 60 minutes? We are in really good shape.”

Is Block 1 ready?

In a white dress shirt, sans tie, Culberson shook off the compliment. First elected to Congress in 2001, he started agitating for a Europa mission only a few years later during the presidency of George W. Bush. The White House wasnt having it. At the time, an already cash-strapped NASA was shoveling every spare dollar into the Constellation Program for human exploration, which would ultimately go nowhere.

By the time Barack Obama won his second term in the White House, Culbersons seniority and membership on the House Committee on Appropriations allowed him to begin providing limited funding for a Europa mission. (Scientists have long had Europa atop their wish-list, but NASA leadership had been hesitant to take on such an ambitious, costly program). At the end of Obamas presidency, Culberson had risen to chair of the Appropriations subcommittee that sets NASAs budget, and the Europa Clipper had become an official NASA program.

Culberson loves space. He views planetary exploration and the potential for finding life elsewhere in the Solar System as the most enduring legacy he can leave behind for humanity. Since last summer, however, Culberson has focused on securing funding for victims of Hurricane Harvey, which dropped four feet of rain on Houston and ranks with Hurricane Katrina as the costliest storm to ever hit the United States. Some of his own family members had only just moved out of a trailer back into renovated housing. But on this Friday, he had come to California to see how the Clipper mission was doing, as well as a follow-on mission to land on Europa.

The missions are coming along nicely, but soon critical decisions about how to get Clipper to Jupiter must be made. The JPL scientists and engineers want to send the Clipper, which is so big that its solar panels have a wingspan as long as a basketball court from end to end, directly to Jupiter. They prefer this because a quicker trip to Jupiter will require less thermal protection, and, more importantly, they want the Clipper to reach Jupiter before the follow-on mission designed to land on and sample the moons icy surface. Ideally, the Clipper will scout Europa for several years and identify the most interesting, safest landing location.

A direct shot of a six-ton satellite to Jupiter requires a rocket with a lot of muscle. During the briefing, Culberson was told no commercial rocket can do this, even SpaceXs Falcon Heavy rocket, which flew for the first time in February. (It is not clear whether NASA specifically asked SpaceX about the Falcon Heavy and Europa, as Goldstein said figures for all the commercial rockets were provided by a competitor to SpaceX, United Launch Alliance.) In the charts shown in the JPL conference room, engineers had modeled a Falcon Heavy with a small “kick stage,” but they had not considered alternatives, such as a Falcon Heavy with a more powerful Centaur upper stage for a direct-to-Jupiter mission.

Because the existing commercial rockets were not powerful enough, Goldstein said only NASAs Space Launch System could get Clipper directly to Jupiter. The first version of this rocket, Block 1, can put 70 tons into low Earth orbit, and its Interim Cryogenic Propulsion upper stage has enough oomph to reach Jupiter in about three years. This is half the time of the commercial rockets, which will require more time to slingshot around inner Solar System planets to attain a Jupiter trajectory.

What Culberson really wanted to know is whether the big NASA rocket will be ready for a second launch in June 2022. This is a good question. Congress has patiently funded the SLS rockets development since 2011 and now spends more than $2 billion annually to fund work to design and build it. Even so, the SLS remains at least two years away from the launchpad for its maiden test flight. A few lawmakers have begun to ask questions about why it is taking so long.

Meanwhile, the engineers in California have told the Texas congressman that the Europa spacecraft can be ready for launch in just four years, thanks to his generous funding. Especially important, money has been front-loaded to arrive earlier in the project when development costs are highest.

If the spacecraft will be ready by mid-2022, Culberson wanted to make sure the booster was ready, too. “Block 1 is on time and on target?” he asked. “I want to make sure the SLS Block 1 is the rocket you need, and its on time.”

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