Searching for Life Where the Sun Don’t Shine (part 6) Explorations to the Seafloors of Earth and Europa
This is the final part of a series that tells the story of humankind’s efforts to understand the origins of life by looking for it in extreme environments where life thrives, without relying on the Sun as an energy source. This series follows an oceanographic expedition to the Mid-Cayman Rise led by Chris German of the Woods Hole Oceanographic Institution, and NASA’s efforts to plan a future mission to Jupiter’s moon, Europa. By understanding how life can live without the Sun we may discover how life began on our planet, and whether or not Earth is the only place in the universe capable of supporting a biosphere.
Steve Vance is still in the middle of planning discussions at JPL for a potential Europa mission that could launch as early as 2020. In early 2012, the team he’s on finished developing three different mission designs with three different vehicles—an orbiter, a flyby (like Voyager and Galileo) or a lander mission—that they’d pitched in a report to NASA agency brass the previous May. At the time, the lander mission was determined to be too expensive and risky. Today, the agency is currently considering another flyby mission as the leading candidate to be Earth’s next ambassador to Europa.
Collecting samples on Europa and sending them back to Earth for laboratory analysis — like German’s team does on Atlantis — is probably many decades away from becoming a reality. Vance says a lander could collect samples, but it would be confined to collecting and analyzing only what it could reach at its landing spot. An orbiter or flyby mission, on the other hand, might be able to bounce radar waves off the icy surface to send back data about the moon’s mysterious ocean.
“If we had a mission with radar on it, you can construct a radar observation that could possibly see through more than ten kilometers of ice. Depending on how pure the ice is, radar propagates pretty well through ice,” says Vance. “There’s a possibility if (Europa has) a thin ice shell, you could see all the way to the ocean. At least to the extent that you could say, ‘here’s an ocean layer.’ You couldn’t see a whale…” Vance paused for a second, then clarified. “Not that we’re expecting to see a whale, per se.”
The mere thought that alien fishes, sharks and squids could be chasing each other around in the pitch black waters of Jupiter’s moon right now has astrobiologists like Vance itching to get a look below the ice. If there’s life on Europa, it’s much more likely to be microscopic bacteria — somewhat akin to what early Earth life was like for the vast majority of our planet’s biological history, some four billion years — but that doesn’t mean we can’t speculate.
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.
“Everything on Europa’s surface came up from the ocean not long ago. If we were to land at a random place, we could hardly go wrong,” writes Greenberg in his book, Unmasking Europa. “If there is life on Europa, it may be hard to miss it.”
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.
Such is the stark reality of planetary science in the 21st century in a country still recovering from a serious economic recession.
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.
Despite savings in operational cost, higher initial up-front costs mean the lander mission will most likely have to wait for future funding opportunities. According to a May 2012 report from the Outer Planets Assessment Group (a NASA-sponsored forum for scientists and engineers to discuss plans for exploration of the outer solar system), the planetary science community favors either the flyby or orbiter mission options, given NASA’s current budget outlook. In particular, the group says that the flyby concept, with more than 30 close-range flybys of the moon, “offers the greatest science return per dollar, greatest public engagement, and greatest flow through to future Europa exploration.”
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.
This is on the chance such a mission gets funded, launches successfully (on-time and on-budget), travels several billion miles through space using the gravity well of Venus as a slingshot, then lands (if they pick the lander) on the icy terrain of a radiation-soaked world that flexes by a hundred feet every 85 hours.
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.
Eight days after German and his crew reached the sunny Florida Keys, a team of Russian scientists finally reached the surface of Lake Vostok — a sub-glacial lake in Antarctica buried under 12,362 feet of ice. It took the team more than 15 years of stop and go drilling to reach the surface of the lake in the same spot that happens to hold the record for coldest temperature ever recorded on Earth: minus 89 degrees Celsius (minus 128 F).
The lake is roughly 14 million years old and has been completely untouched by humans for all of our history. It’s average temperature is calculated to be about minus 3 degrees Celsius and the only reason it remains in liquid form is because of the extremely high pressure caused by the weight of the ice above it. It has oxygen levels fifty times higher than most other freshwater lakes on Earth. It’s one of the largest lakes on the planet. It’s also completely cut off from the Sun.
But what could be most intriguing about this isolated lake is that it represents a bridge: a terrestrial environment that’s perhaps as close as we can get to studying an extraterrestrial one without leaving Earth. In other words, Lake Vostok is a bit like a mini-Europa ocean right here in our own backyard.
That the lake has been isolated for millions of years draws interesting questions about life, its origins and evolution. Is there life in the lake? If so, did it venture off on a completely different evolutionary branch than every other place on Earth? Could there be a heat source sustaining a chemosynthetic ecosystem like we find near hydrothermal vents in the oceans?
Just what’s down there?
By studying extraordinary environments like Lake Vostok, we’re building answers to these and other questions that help define life’s place in the universe. And that place is hardly defined yet. When confronted with the intricacies of life’s processes and the string of events that were required to create it, some speculate the origin of life is so improbable even on the scale of the entire universe that the only way it could have possibly arisen is if there exists an infinite number of universes, or a multiverse — ensuring the one we’re in had to have developed, eventually.
Others, like Günter Wächtershäuser, argue that life’s not only likely to arise given the right starting conditions, but probably inevitable to emerge throughout the universe. “If this theory is in principle correct,” he says, “then life starts the same way everywhere—on Earth, or anywhere else in the universe. It starts with the same elements, with the same chemical properties of these elements and they will do the same reactions, with the same feedback and so forth.”
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.