Huge potentially inhabited water lake found on Jupiter moon
Europa ice-cap now best known prospect for alien life
In major extra-terrestrial news, scientists have announced the first discovery of at least one huge body of liquid water beyond planet Earth, offering confirmation at last of a potential offworld habitat for alien life.
The water in question - roughly enough to fill one of the North American Great Lakes - has been spotted beneath the ice cap covering Europa, one of the moons of Jupiter. Better still, it's thought that the ice floating atop the hidden lake is collapsing and mixing with the water below, offering evidence that the Europan ice cap mixes with the oceans of water beneath it - which makes it much more probable that life could exist in the deeps below.
"One opinion in the scientific community has been, 'If the ice shell is thick, that's bad for biology — that it might mean the surface isn't communicating with the underlying ocean,'" says Britney Schmidt, lead author on the new study documenting discovery of the Jovian moon-lake. "Now we see evidence that even though the ice shell is thick, it can mix vigorously. That could make Europa and its ocean more habitable."
Schmidt and her colleagues discovered the lake by examining imagery of the Europan ice cap from the Galileo probe, which surveyed Jupiter and its moons from 1995 to 2003. The scientists focused on circular, bumpy regions of ice known in boffinry circles as "chaos terrains". Their theory at last resolves several conflicting indications, suggesting that liquid water lies several kilometres beneath the ice: but that the ice does nonetheless churn and mix with the water.
"I read the paper and immediately thought, yes, that's it, that makes sense," comments Robert Pappalardo, senior NASA Planetary Science brainbox, who didn't work on the study himself. "It's the only convincing model that fits the full range of observations. To me, that says yes, that's the right answer."
Don Blankenship, who did work with Schmidt on unravelling the Europan ice cap's secrets, is an expert on studying earthly ice sheets using radar.
"This new understanding of processes on Europa would not have been possible without the foundation of the last 20 years of observations over Earth's ice sheets and floating ice shelves," he says.
There has been much speculation on the likelihood of watery oceans beneath Europa's ice ever since the time of Galileo. This new research will surely be seen as providing justification for a mission to establish more details: but nonetheless such a mission may not occur.
Following Galileo's discoveries NASA formed bold plans to send a Jupiter Icy Moons Orbiter (Jimo) robot ship to find out more. Jimo would have had a capable ion drive powered by a nuclear reactor, allowing it to carry out extensive operations in the Jovian system, far from the Sun.
In the end, however, following protest over the idea of spacegoing reactors (and also for cost reasons) Jimo was cancelled. A much less ambitious Jupiter probe, Juno, was launched in August and is expected to reach its destination in five years' time. However it has only solar cells for power, which will struggle to provide much juice so far from the Sun.
The need to save electricity means that Juno will power up its instruments for only a few hours in each 11-day-long orbit round the giant gas planet, and any manoeuvring or use of powerful radars to probe the Europan ice is not an option. However NASA is considering radar for a possible future Jovian moon mission.
Blankenship, Schmidt and their collaborators' paper Active formation of 'chaos terrain' over shallow subsurface water on Europa is published today in hefty boffinry mag Nature. ®
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