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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An antibiotic-resistant superbug is silently spreading through UK hospitals

There have already been outbreaks in Manchester, London, Edinburgh, and Birmingham, but deaths are not centrally recorded. 

Lying in a hospital bed, four months pregnant, Emily Morris felt only terror. She had caught a urinary tract infection and it was resistant to common antibiotics. Doctors needed to treat it as it could harm the baby, but the only drugs that could work hadn’t been tested on pregnant women before; the risks were unknown. Overwhelmed, Emily and her husband were asked to make a decision. A few hours later, gripping each other’s arms, they decided she should be given the drugs.

In Emily’s case, the medicine worked and her son Emerson (pictured below with Emily) was born healthy. But rising antibiotic resistance means people are now suffering infections for which there is no cure. Doctors have long warned that decades of reliance on these drugs will lead to a "post-antibiotic era"– a return to time where a scratch could kill and common operations are too risky.

It sounds like hyperbole – but this is already a reality in the UK. In the last four years 25 patients have suffered infections immune to all the antibiotics Public Health England tests for in its central lab, the Bureau of Investigative Journalism has discovered.

While these cases are rare, reports of a highly resistant superbug are rising, and infection control doctors are worried. Carbapenem resistant enterobacteriaceae (CRE) are not only difficult to pronounce, but deadly. These are bugs that live in the human gut but can cause an infection if they get into the wrong place, like the urinary tract or a wound. They have evolved to become immune to most classes of antibiotics – so if someone does become infected, there are only a few drugs that will still work. If CRE bacteria get into the bloodstream, studies show between 40 per cent and 50 per cent of people die.

These bugs are causing huge problems in India, certain parts of Asia, the Middle East and some countries in southern Europe. Until recently, most infections were seen in people who had travelled abroad, had family members who had, or had been in a foreign hospital. The boom in cheap cosmetic surgery in India was blamed for a spate of infections in Britain.

Now, doctors are finding people who have never boarded a plane are carrying the bug. There have already been outbreaks in Manchester, London, Liverpool, Leeds, Edinburgh, Birmingham, Nottingham, Belfast, Dublin and Limerick among other areas. Patients found with CRE have to be treated in side rooms in hospital so the bacteria does not spread and harm other vulnerable patients. But in many of Britain’s Victorian-built hospitals, single rooms are in sparse supply. Deaths from CRE aren’t centrally recorded by the government - but it is thought hundreds have already died. 

Across the country, doctors are being forced to reach for older, more toxic drugs to treat these infections. The amount of colistin – called the "last hope" antibiotic as it is one of few options still effective against CRE infections - rose dramatically in English hospitals between 2014 and 2015, the Bureau has revealed. Colistin was taken off the shelves soon after it was introduced, as it can harm the kidneys and nervous system in high doses, but was reintroduced when infections became immune to standard treatment. The more we use colistin the more bacteria develop resistance to it. It’s only a matter of time before it stops working too, leaving doctors’ arsenal near-empty when it comes to the most dangerous superbug infections.

Due to a kidney problem, Emily Morris suffers repeat urinary tract infections and has to be hospitalised most months. Her son Emerson comes to visit her, understanding his mummy is ill. If she catches a superbug infection, she can still be given intravenous antibiotics to stem it. But she worries about her son. By the time he is an adult, if he gets ill, there may be no drugs left that work.

Madlen Davies is a health and science reporter for the Bureau of Investigative Journalism