A robotic submarine designed to explore the oceans thought to lie beneath the icy crust on Jupiter鈥檚 moon Europa will prove its mettle in an Antarctic lake in 2008. A previous version of the vessel has already mapped the balmier waters of a Mexican sinkhole.
The submarine, named Endurance, is set to survey Antarctica鈥檚 West Lake Bonney in October 2008 and again in 2009, scientists reported on Thursday at a meeting of the American Geophysical Union in San Francisco, California, US. The 4-kilometre-wide lake is 40 metres deep and is capped by a perennial layer of ice about 4 metres thick. The crust has kept the lake鈥檚 waters pristine and virtually unexplored.
Hot water drills will bore a hole for Endurance to enter the water. Once beneath the ice, the sub will gather data for a 3D map of the lake and the submerged face of its adjacent glacier. At the same time, it will sample the frigid waters for signs of life.
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West Lake Bonney should prove a rigorous test of the submersible鈥檚 ability to function on Europa. Once released, Endurance will navigate on its own for up to eight hours at a time 鈥� a crucial requirement, since sending radio commands to the distant, icy moon from Earth would take about half an hour.
鈥淓uropa鈥檚 far enough away where you鈥檙e not going to be able to drive it like a video game,鈥� says lead investigator Peter Doran of the University of Illinois in Chicago, US. 鈥淭he robot would need a fair amount of its own intelligence to make its own decisions. With Endurance, we鈥檙e at that point.鈥�
At the lake, Endurance will follow a pre-programmed path just beneath the ice. 鈥淭his is so we don鈥檛 disturb the environment we鈥檙e studying with the robot鈥檚 propellers,鈥� Doran says.
Instead, the sub will stop and lower a package of scientific instruments into the water column. These will measure water temperature, salinity, turbidity, dissolved organic carbon, and scan for chlorophyll. Together, these measurements should be enough to detect the presence of life.
Docking station
And life may not be so unlikely on Europa. Data from NASA鈥檚 Galileo spacecraft has revealed hints of carbon 鈥� a building block of life 鈥� in the moon鈥檚 purported seas. Both carbon dioxide and sulphur dioxide, a potential signal of volcanism, are leaking from discrete areas on the moon鈥檚 surface.
Operating a spacecraft at Europa may also be easier than originally thought because radiation on the moon is low enough to operate a probe there for a year or more, says William McKinnon of Washington University in St Louis, Missouri, US.
Still, many hurdles remain before an underwater vehicle will get to tackle otherworldly seas. At present, Endurance is too massive to send on interplanetary travel. 杏吧原创s must also devise a means to drill through Europa鈥檚 icy crust and lower the sub safely through the ice.
And because radio waves travel poorly through water, a docking station anchored in or around the ice will need to relay data from the submersible to Earth. No one has even begun working on such a transmitter, not least because they need a better understanding of Europa鈥檚 ice crust first.
According to McKinnon, an orbiter mission to Europa would need to pave the way before any submersible left the launch pad. Using radar, such a spacecraft could measure ice depth, look for convection cells, and perhaps even detect plumes of volcanic activity in addition to demonstrating the presence of liquid water.
NASA has committed to launching a mission to one of the icy moons of Jupiter or Saturn sometime between 2015 and 2020. The target of that mission, however, is still being decided. According to Curt Niebur of NASA, the space agency has just completed studies of missions to Jupiter鈥檚 moons Europa and Ganymede and Saturn鈥檚 moons Titan and Enceladus. NASA plans to announce which missions have been selected for further study in mid-January 2008.
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