Searching for Life Where the Sun Donít Shine (part 6) Explorations to the Seafloors of Earth and Europa
Rock star communicator of astrophysics and space exploration, Neil deGrasse Tyson, agrees. “I want to go ice-fishing on Europa, cut a hole, put a submersible, look around, see if anything swims up to the camera lens and looks at the camera,” says Tyson.
One future mission to the Galilean moon that isn’t a part of NASA’s current plans yet could do just that. This concept is the cryobot: a robotic probe that could land on the surface of the ice, drill down through to the ocean by melting the ice using heat from its nuclear power source and then release a hydrobot (fancy term for robotic submarine) into the potential ocean below. The hydrobot would then begin collecting chemical measurements and start hunting for sea creatures.
Problem is, without detailed radar data of its surface, no one knows exactly how thick the ice layer is. Just as pizza aficionados debate the merits of New York thin versus Chicago-style deep-dish crust, so do planetary geologists argue over the thickness of Europa’s ice. According to Vance, there’s at least a mile and a half of ice at some points in Europa’s shell.
“Some of the craters have raised central peaks,” says Vance, a bit like if you imagine watching a commercial where a drop of milk falls in slow motion into a bowl, making a momentous splash, and you pause it right at the height of the upward splash. “In the case of these craters, the mechanics lead to the central peak freezing in place. And the central peak needs a certain amount of material underneath to support it.”
But that doesn’t necessarily mean you’d have to drill through all that ice to reach the ocean. Richard Greenberg, professor of planetary sciences at the University of Arizona, is an outspoken advocate for the New York-style thin crust ice layer. He thinks evidence from Voyager and Galileo show that Europa’s geology cycles water up through the ice repeatedly, potentially bringing fresh seawater up to the surface and eliminating the need to drill through miles of ice to figure out if there’s life in Europa’s oceans.
Ultimately, whether life can be found at the surface, below the surface, or not at all could depend on whether Europa’s geology supports similar types of volcanic gases mixing with transition metals and cold salt water, like the ROV Jason witnessed up close at the MCR hydrothermal vents. And even though we can get real-time photos and samples of vents on Earth, we still can’t observe anything about the mantle below the seafloor crust on our own planet, let alone a moon 500 million miles away.
“It’s an interesting parallel with the things that we don’t know very well on Earth,” says Vance. “Mantle convection on Earth is a big, difficult topic because we have to infer things indirectly from seismic data. We have to infer the structure and composition of the mantle from seismic observations.”
Planetary scientists apply similar inference techniques in determining the structure and composition of other planets and moons. To reconstruct the composition of Europa, Vance says “you apply the same physics that you’d apply to mantle geology to ice geology.” Observations to date have been able to give scientists a good idea of the rough magnitude of tidal energy that should be on Europa. But no one knows whether that energy gets dissipated in the ice shelf, the ocean or the rocky interior of the moon. “So there’s a partitioning problem which then relates to whether you can have underwater volcanoes,” says Vance. “It’s not as obvious.”
Tyson may have to wait awhile before packing up his ice fishing pole. Unfortunately for Vance and his colleagues at JPL, the agency’s planetary science budget just got hosed, to put it lightly, to the tune of a cool $300 million. These cuts to NASA’s 2013 budget (which has still not been approved at the time of this writing in January 2013) have forced the agency to renege on an agreement for joint U.S.-European robotic missions to Mars in 2016 and 2018, forcing the European Space Agency to scramble to find another partner—Russia. It’s also forced NASA to scale back ambitious missions to other planets and moons.
A shrinking budget is one reason Vance is part of the NASA team tasked with slimming down a previous proposed mission to Europa that would have placed an orbiter around the moon in 2026. With a planned launch in 2020, the very originally named Jupiter Europa Orbiter (JEO) would have spent 30 months touring the Jupiter system. The mission would have included four flybys of Io, nine of Callisto, six of Ganymede, and another six of Europa before entering a circular orbit around Europa for nine months, then ultimately meeting a fiery death in a controlled crash landing into the icy moon. The team had just finished its proposal when the planetary science Decadal Survey—a roadmap for figuring out priorities among thousands of planetary science mission proposals—came out. The survey brought mixed news. The good: Europa was deemed the second highest priority (behind Mars) for finding life in the solar system. The bad: the JEO mission was far too expensive at $4.7 billion to fund as it was originally designed.
Today, it seems that NASA’s next mission will be another flyby, but no one knows when or if Congress will approve the budget for such a mission. Meanwhile, other space agencies are already moving forward on their plans—the European Space Agency recently announced its next large space science mission will be the Jupiter Icy Moons Explorer — JUICE — to be launched in 2022. JUICE will arrive at the Jupiter system in 2030 and will focus on Europa’s neighbor Ganymede but will also include two flybys of Europa.
As for future missions, Vance is torn between the flyby and the lander concepts. Both have tradeoffs. He says Europa’s extremely high radiation levels are actually an advantage in the lander case. “It turns out you’d save a lot of money on operations for a lander mission,” said Vance. “The lander doesn’t live that long on the surface, because of the radiation environment. So it’s short and sweet. A lot of money that you spend on a mission is to keep a standing team of 100 people working on it for a long period of time. So a lander has [brevity] going for it.” That saves money.
In addition, a flyby mission could yield a priceless result that could serve the whole scientific community for a long time: data.
“If you’re going to do this thing once every fifteen years, you want to get a whole, huge chunk of data that will keep you busy after your mission is over. And I can picture having detailed global mapping for geological and compositional interpretations as being that big chunk of data that you would want,” says Vance. These data could then be used to figure out an ideal landing spot for a future lander or cryobot mission.
Only getting one shot every fifteen years means the pressure’s on for Steve and his colleagues at JPL. He’s been studying Europa for about seven years. He’s 34 now. If a Europa mission — whatever it is — is launched during the proposed window for JEO, he’ll be 41. By the time that spacecraft makes it to the moon, he’ll be 47.
Last year before the Decadal Survey came out, he used to joke to friends and colleagues that if he was to father a child now, that child would have been born, taken a first step, learned to read, passed through adolescence, scared Steve to death at being behind the wheel for the first time, and well on his or her way to preparing for college all before the potential spacecraft made it to the Galilean moons.
No wonder planetary scientists often think of their spacecraft as children: alive, young, naïve, full of potential, in need of protection, nourishment, guidance, and ultimately, deliverance.
To Wächtershäuser, there is elegance in this predictability. “One day we will know how life starts and we will know that there is a chemical law for life’s beginning. It’s a chemical law. And we will know that as well as we know (that) the summation formula for water is H2O.”
As for Lake Vostok, the Russian team hasn’t been able to retrieve samples of the lake yet because their drill can only bring back ice samples, not liquid. They plan to return to the drill site early this year when the lake has frozen again over the Antarctic winter.
Meanwhile, Chris German is already busy planning his next two expeditions—he’s returning to the Mid-Cayman Rise this summer then taking what he’s learned there to the similarly ultra-slow-spreading, but also ice-covered, Gakkel Ridge in the Arctic Ocean (another great Earth-bound Europa analog) in the summer of 2014.
And Steve Vance is preparing the instruments that will be used, hopefully, to tell humanity whether or not we’re really alone in our own solar system.
And maybe, somewhere, a tubeworm will grow a little bit longer.