A cutaway view of Saturn's moon Enceladus, showing possible hydrothermal activity that may be taking place on and under the seafloor of its subsurface ocean. Image: NASA/JPL
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The unexpectedly watery moons of our Solar System may be friendlier to life than we thought

Secret oceans on the moons Enceladus and Ganymede were discovered within days of each other, reshaping our belief that the Earth is the Solar System's most watery, life-friendly habitat.

Jupiter’s moon Ganymede is named after the cup-bearer of the Greek gods; Saturn's sixth-largest moon, Enceladus, is named after a giant. Both names seem extra fitting in the light of recent, and surprisingly big, news about water.

In the (best-ever) anime series Cowboy Bebop, Ganymede is depicted as an aquatic, terraformed world entirely covered in water - and this may well be more accurate than we first thought, as Nasa’s Hubble Space Telescope has confirmed the existence of subsurface water on the huge moon by watching how its aurora lights slither around its edges. Astronomers believe this ocean, hidden underneath around 153km of crusty ice, is ten times deeper than those of Earth.

This new discovery has hoisted Ganymede up the list of the top contenders for places in our Solar System which could potentially harbour life. It also has relatively good timing - the European Space Agency (ESA) is currently working on mission plans ahead of the launch of the Jupiter Icy Moon Explorer (or Juice for short) in 2022, with the aim of getting a closer inspection of Jupiter’s moons Ganymede, Callisto and Europa through the 2030s.

Speculation about Ganymede’s secret ocean is not a new one, as scientists have suspected its existence since the 1970s, despite inconclusive evidence. What sets Ganymede apart from any other moon (aside from its size - it's larger than Mercury) is its self-generating magnetic field, which, just like Earth, is caused by its liquid, iron-rich core. This makes the detection of a copious amount of subsurface liquid water easier - more so than any other icy moon in our Solar System - because a magnetic field causes auroras, brightly-coloured ribbons of hot, electrified gas in the atmospheric regions circulating north and south poles. Ganymede is also close enough to Jupiter that their magnetic fields are interlaced, enhancing the aurora even more than usual. When Jupiter’s magnetic field changes, so does Ganymede’s, "rocking" back and forth over about a five hour period.

The auroras of Ganymede give away the existence of a subsurface saltwater ocean because saltwater can generate its own magnetic field when sloshing around, and can also therefore weaken the effects of Jupiter's. Joachim Saur and his colleagues of the University of Cologne in Germany came up with the idea of applying the motions of the two auroras to determine the amount (if any) of saltwater underneath Ganymede’s crust using the Hubble Space Telescope. He told the NS that the data showed that Ganymede had low auroral oscillations compared to models without an ocean - or, in other words, that Ganymede does have a saltwater ocean underneath its crust.

Nasa’s Galileo mission measured Ganymede’s magnetic field in 2002 but couldn’t see the full extent of its magnetic variation as its fly-bys of Ganymede lasted just 20 minutes - far too brief to measure the magnetic field of this subsurface saltwater ocean. Saur’s team instead watched Ganymede using the Hubble Space Telescope for seven hours. The data suggests that the global ocean is between 150 and 250km deep, and this broad range of approximation is likely caused by the presence of what may be two layers of ice sandwiched between the oceans.

So, could there be life on Ganymede? Hubble found evidence of a tenuous oxygen atmosphere in 1996, but it would be far too thin to support life (or, at least as we know it). We’ll have to wait and see if Juice can freshly squeeze anything more concrete when it arrives there, more than 15 years from now. In addition, Saur said that the aruoral technique used for Ganymede can help identify life-friendly water on other planets (or moons) with subsurface oceans outside the Solar System. Hubble isn’t powerful enough to capture these auroras yet, however it's only a matter of time, as more powerful instruments - like the James Webb Space Telescope, due in orbit in 2018 - are on their way.

Enceladus, meanwhile, is slightly different. We know it has water of some kind on it, as it has a crust of fresh, white ice, of thicknesses stretching from 30 to 40km. This gives it a high albedo, meaning it shines light brightly back into space; and it, too, is believed to be hiding a secret, warm, liquid ocean beneath its surface. Ever since Nasa’s Cassini spacecraft first discovered water vapour and ice spewing from vents near the moon’s south pole in 2005, researchers have theorised about the possible presence of liquid water there. 

On Earth, the kind of hydrothermal activity that would cause the ejection of water from vents tends to happen when seawater interacts with gaps in the planetary crust, so the Cassini data seemed to suggest this was what was happening on Enceladus as well. This deduction was strengthened further by the detection of methane in the plumes, and microscopic granules of silica - exactly the kinds of materials that should be generated around underwater vents.

In a Nasa statement, Sean Hsu, a postdoctoral researcher at the University of Colorado and the lead author of the paper published in Nature, said: "It's very exciting that we can use these tiny grains of rock, spewed into space by geysers, to tell us about conditions on - and beneath - the ocean floor of an icy moon." Cassini hit the jackpot with the detection of silicates, which are believed to have come from inside the vents and then became wedged in icy structures called clathrates before being fired upwards into space. It indicates that these volcanic vents are still active, and generating new silicates - and that they're therefore also likely to still be warm enough to support microbial life, if it exists there.

This evidence all strongly suggests that Enceladus contains within it a 10km-deep ocean, with temperatures as high as 90oC in some parts - any little critters down there just have to swim to the hot bit to get to someplace comfy (though the chances of anything bigger than single-cell organisms existing there are extraordinarily slim). Enceladus and Ganymede are now part of a growing list of strong candidates for hosting alien microbial life, as well as Neptune’s moon Triton and Jupiter’s other moon Europa, as well as the dwarf planet Ceres.

Tosin Thompson writes about science and was the New Statesman's 2015 Wellcome Trust Scholar. 

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Welcome to the Uncanny Valley: how creepy robot dogs are on the rise

It’s hard not to feel a little destabilised after watching a robot’s freakishly long limbs open a door. 

If you’re among those devouring the latest season of Charlie Brooker’s dystopian hellscape Black Mirror, you may still be having metallic nightmares of being chased by the freaky robo-dogs of  “Metalhead”. In which case, you maybe unsettled to know that these nightmares could in theory become a reality (in the distant future), as a viral video from the robotics firm Boston Dynamics (of backflipping robot fame) revealed earlier this week.

Charmingly titled, “Hey Buddy, can you give me a hand?” a SpotMini, Boston Dynamics’ smallest robot, approaches a door and appears to turn sideways before scampering away. Another SpotMini, fitted with an extending claw-arm, opens the door and lets the first robot scamper through, propping it open to follow. 


The director of “Metalhead”, David Slade, was inspired by these very demonstrations. As he stated in an interview in January, the inspiration for those robotic villains stemmed from none other than Boston Dynamics itself. “Those fucking Boston Dynamics robots are terrifying, so that in itself was enough that we didn’t have to worry about it,” he told IndieWire. 

Beyond its viral value, the SpotMini marks an interesting stage in the development of artificial intelligence and robotics. Being able to open a door has long since been the bar for the development of modern robots, as Matt Simon of WIRED pointed out. With this bar seemingly met – and surpassed – the questions remains as to what’s next.

Boston Dynamics robots seem designed mostly for academic and research purposes. Previously, DARPA, the research and development wing of the US defence department and arguably the birthplace of modern robotics, rejected some of the robots for usage because they were too loud. Now, though, they’re silent.

Even those who were not Black Mirror fans expressed a sense of unease while watching the Boston Dynamics email. Indeed, it’s hard not to feel a little destabilised after watching a robot’s freakishly long limbs open a door, which was previously the domain of, you know, humans and crafty pets. But such feelings of revulsion could have something to do with Masahiro Mori’s “Uncanny Valley” theory, which he first proposed in the 1970s.

The “uncanny valley” could be defined as the dip in emotional response from humans when interacting with a being that is vaguely humanoid. The theory suggests that robots become more appealing as they draw closer to human characteristics – but only up until a certain point. Once that point has been reached, and surpassed, humans then find those robots “uncanny”. Then, as they resemble us even more closely, we find that we grow less repulsed by them. 



While the theory has circulated since the 1970s, a 2005 translation of the paper into English made the concepts more widely accessible, and it has been studied by academics ranging from philosophy to psychology. Despite the term wriggling its way into everyday techspeak, the theory itself is yet to be proven. In 2016, the researchers Mathur & Reichling studied real world robots and humans’ reactions to them, but found overall ambiguous evidence for the existence of the uncanny valley. 

Watching one of the SpotMinis open a door – and then prop it open, like you would – may make our skin crawl for those very reasons. The SpotMini, and even some of Boston Dynamic’s other robots, like the backflipping Atlas, have a weird mix of familiar and unfamiliar characteristics. In the viral video, for example, the way that the armed robot holds open the door resembles an interaction that many of us see everyday.   

That may also have something to do with why this particular robot, which has also been used to wash dishes, has triggered a different reaction to Handle, another robot in the Boston Dynamic litter, which can wheel around faster than any natural organism and perform backflips (complete with an athletic hand raise at the end). Handle's acrobaticism inspires a mixture of fear and awe. Watching SpotMini, whose mannerisms bear a resemblance to a family dog, fumble and open a door, feels a little more familiar, but a little more weird.


There are, of course, real fears about robots that are not driven by TV. The baseline for robo-phobia has long since been that they’re not only coming to take our jobs, but they’ll be better than us at it too. SpotMini is technically very interesting because of how it merges software and hardware. That the two SpotMinis can co-operate paves the way towards teamwork between robots, which has until recently remained a far off prospect.

Robots are already a key function of many military operations. They carry out tasks that are too dangerous to entrust to humans, with more accuracy. Additionally, robots are entering our social spheres - with AI controlled assistants like Alexa, the controversial robot Sophia (she once expressed a desire to destroy humans), or the AELOUS home assistant that was unveiled at a convention in Vegas, which can vacuum and fetch you a beer (and will be retailing later this year).

While there are all kinds of debates within artificial intelligence and robotics about what this means for the field, there could be a greater number of non-technically trained experts interacting with robots, relying on intuition and common sense to frame their interactions. 

That takes the implications of the uncanny valley outside of just theoretical. What kind of robot can we interact with, sans revulsion? Does that mean we can only use them in specific contexts. And do they have to look a certain way? 

As always, there’s the bigger picture to consider too. Boston Dynamics remains spectacularly good at making viral videos that draw attention to its products, which are indubitably marvels of modern engineering. Moreover, lower level sensorimotor skills that an infant develops intuitively – such as, you guessed it, opening a door – are actually far more difficult to programme than high-level displays of intelligence, such as winning a chess game (also known as Moravec's paradox).

So while the robo-dog may be unnerving (and there's a reason for that), our robot overhounds are still a while away. But when fully autonomous and physical robots do eventually proliferate, they'll know how to set themselves free.