In the cold of space, a tiny moon is keeping warm with a fluffy heart. Enceladus, the pipsqueak of a world renowned for shooting huge watery plumes into space as it orbits Saturn, has a secret 鈥� a core that contradicts everything we thought we knew about the structure of planetary bodies.

Planets and moons usually follow the classic 鈥渙nion鈥� model: an outer crust or atmosphere over a large mantle, with a sphere of dense material at the core. But new research presented at the Geological Society of America meeting in Vancouver on 19 October suggests Enceladus isn鈥檛 following the rules.

The moon鈥檚 density suggests it contains some rock. And since its surface is icy and it has a penchant for spewing water and ammonia into space, researchers have concluded it probably has a crust of ice, a watery mantle and a core of solid rock.

As Enceladus orbits Saturn, changes in the planet鈥檚 gravitational pull flex the moon, heating it up. But when James Roberts at Johns Hopkins University developed computer models to test just how this works, something didn鈥檛 add up.

A stiff rocky core would not flex enough to generate the heat necessary to melt the ice or explain the jets. When Roberts made the core more like a snow cone than a stone, it flexed and created enough heat to fuel its famous water jets.

Cold but not dead

鈥淓nceladus has been surprising us all along,鈥� Roberts says. 鈥淵ou鈥檇 think something the size of the North Sea would be cold and dead, but the has been observing activity since it arrived.鈥�

Roberts says several other bodies in the solar system 鈥� including Saturn鈥檚 moon Mimas, and the dwarf planet Ceres 鈥� could have similarly 鈥渇luffy鈥� cores.

The finding has intriguing implications for finding life on these small worlds, says at the Southwest Research Institute in San Antonio, Texas, who has studied Enceladus鈥檚 plume eruptions. 鈥淵ou have the ability for water to interact with rock over a vast region,鈥� he says. 鈥淵ou can create hydrothermal systems like those on early Earth where life may have formed.鈥�

However, because of Enceladus鈥檚 diminutive size, the chemistry necessary for life may have petered out by now. 鈥淚t鈥檚 been around a long time, and there鈥檚 not that much rock,鈥� Waite says. 鈥淪o after a point you have pretty much taken the free chemical energy out of the rock.鈥�

The only way to find out if the moon is still habitable is to go back on a future mission, he says. 鈥淎re we living in the perfect time to observe this? That鈥檚 a kind of the wild card here.鈥�

Fracking wasn鈥檛 invented by humans. The method of using pressurised fluids to break apart rocks was around at least 700聽million years ago, and explains one of the world鈥檚 strangest rock formations.

The Tava sandstone has baffled scientists for over a century. Found along a large fault in the Front Range of the Rockies in Colorado, it appears to have defied the rules of geology. The rock formed by sandstone being injected as a liquid into surrounding layers of granite. Igneous rocks start life as a liquid, but sandstone forms by sedimentation, and will usually bend or break under stress rather than liquify.

at Colorado College in Colorado Springs and her colleagues suggest that between 660聽and 800聽million years ago, a nearby fault cracked the region with a series of massive earthquakes. When earthquakes strike loose, wet sediments, the material begins to behave like a liquid, Siddoway says.

As for the pressure that would have been needed for this natural fracking event, she says it could have come from the collapse of huge slabs of rock shearing off from a cliff-like section of the fault. As these fell onto the sediments below, they could have hit them with enough force to drive them into solid granite.

The Tava sandstone has been claimed by creationists as evidence of the biblical flood that carried Noah鈥檚 Ark.

According to them, the rock was deposited as a sandy muck just a few thousand years ago. By analysing isotopes of lead and uranium, Siddoway found that the minerals from the Tava came from rocks dating to more than a billion years ago. These were, she believes, eroded over time and washed into an ancient basin as sediments.

鈥淭hese are really extraordinary rocks,鈥� says Siddoway.

Journal reference:

A death penalty execution in Oklahoma has gone horribly wrong. And it has happened despite warnings that as states tinker with the drugs used in lethal injections, they are in uncharted territory and risk violating the US Constitution鈥檚 provision against 鈥渃ruel and unusual punishment鈥�.

Yesterday, two inmates, Clayton Lockett and Charles Warner, were scheduled to be killed using an untested drug cocktail. This included the sedative midazolam, which was first used in an execution in January, where an inmate reportedly gasped for air for more than 10 minutes after it was administered. Shortly after the state gave Lockett the drug, in what should have been a lethal dose, it was clear something was not right.

several minutes after he should have been unconscious, according to a local news report. After the other drugs, vecuronium bromide and potassium chloride, were administered, a prison official reported that his vein had ruptured and they were not properly delivered. The execution was stopped, and Lockett died of a heart attack a few minutes later.

The episode, which prompted Oklahoma governor Mary Fallin to order an investigation and postpone Warner鈥檚 execution, is the latest in a series of fresh concerns over how death sentences are meted out in the US.

As we reported yesterday, a recent study published in Proceedings of the National Academy of Sciences estimates that more than 300 inmates now on death row may be innocent. And in a study due to be published in the Georgetown Law Journal next month, Deborah Denno of Fordham University in New York shows that over the last six years, states have modified their drug protocols for lethal injection more than 300 times. That is in response to long-running shortages caused by European manufacturers refusing to sell lethal injection drugs to prisons.

In her study, Denno concluded that these changes are often implemented haphazardly, and without sufficient oversight. 鈥淟ethal injection is worse than it ever has been,鈥� she told New 女生小视频.

Read more:
鈥淯S death penalty practices raise disturbing questions鈥�
鈥淥ptions running out for the US death penalty鈥�

Read more: 鈥�2014 preview: 10 ideas that will matter next year鈥�

Continuing revelations of the US National Security Agency鈥檚 massive spying apparatus redefined the term 鈥渟urveillance state鈥� in 2013. But researchers are developing new technologies to preserve online freedoms, including private, secure wireless networks and ways of disguising web traffic.

The year has been about more than just spooks, of course: robots are taking architecture to superhuman heights, computers are learning to diagnose and help treat depression, and kids are learning to program computers even before they can read. Virtual reality is getting in on the act, too, with some of the most exciting developments in decades hinting at a future where computer worlds become mesmerisingly immersive.

We also launched ButtonMasher, our new column about video games and gaming culture. But while technology is undeniably making our lives better, easier, and more entertaining, 2013 will be remembered as the year we learned that it brings a risk we hadn鈥檛 fully realised.

Submarine internet cables are a gift for spooks
Shortly after the first news of the NSA鈥檚 spying dragnet became public, we learned that the agency siphons information directly from the backbone of the internet

Meshnet activists rebuilding the internet from scratch
Worried about the NSA snooping on your email? Maybe you need to start creating your own personal internet

Throw off the spooks by disguising your web traffic
The NSA鈥檚 massive dragnet could be ripped apart by tools that make it impossible to know what you are doing on your computer

ButtonMasher: DIY video game tools put you in control
In the first edition of our column about video games and gaming culture, New 女生小视频 finds an exploding community of amateur gamers who are creating new games from the ground up

Digital shrinks find depressed faces and body language
Automatic systems that analyse gestures and facial expressions may soon be helping psychologists pick up the easily missed symptoms of depression

Beyond 3D printing: The all-in-one factory
3D printing not enough for you? Meet the device that鈥檚 a self-contained manufacturing plant

Virtual reality: Get your head in the game
VR is making a comeback, fuelled by the Oculus Rift, a 3D headset that promises a mind-blowingly immersive experience

Multi-shot video can identify civil rights abusers
A video shot during a protest may look like hard evidence, but software that stitches together multiple perspectives helps ensure the full story comes to light

Making your own phone is easier than you might think
Tired of all phones looking the same? New 女生小视频 learned that the best way to be unique is to build your own

Robot builders deliver architects鈥� dreams
Unlike humans, robots have no problem building tremendously intricate designs that push the boundaries of modern architecture

Citizen cartographers fill the gaps in maps
People in the developing world are charting everything from slums to rural footpaths, providing online maps that can be crucial for urban planning or in times of disaster

Kindergarten coders can program before they can read
New 女生小视频 sat in on a classroom where kids as young as 4 years old are learning programming as part of an effort to bolster computer science in schools

Google Glass has its electronic eye on health
Early adopters of the headset computer are using it to transform our view of medicine

Hacked Google Glass recognises finger gestures
Google鈥檚 experimental Glass headset has been hacked to respond to a wearer鈥檚 hand movements

Frugal science gets DIY diagnostics to world鈥檚 poorest
From bicycle pumps to pressure cookers, researchers are turning common objects into ways of delivering healthcare to people in the developing world

(Image: UCL/NASA)

WE THOUGHT we knew the solar system. Apart from Earth, all the worlds out there were dead lumps freezing in the blackness of space. But when Voyager I started beaming back images as it flew by Jupiter鈥檚 moon Io in 1979, something wasn鈥檛 right.

For one thing, its surface was too young 鈥� nothing like the antique landscapes of our moon or Mars, whose craters date back billions of years to the early days of the solar system. There were strange pock marks interspersed among smooth plains and mountains that jutted higher than Everest, but they looked more like open sores on a world that could not heal.

There was no Photoshop back then, so scientists assembled the jigsaw of images by hand as they arrived from the distant probe (which recently left the solar system鈥� honest!). Though primitive by the standards of the full-colour visuals brought to us by later probes, they allowed scientists to watch volcanic eruptions as they happened. It was smoking-gun evidence: after billions of years out in the cold, Io was more than still warm 鈥� it was seething with volcanic activity.

The reason for this is Io鈥檚 unique position in the Jovian system. It sits closer to Jupiter than any of the other large moons. Here, tugged and flexed by the planet鈥檚 huge gravitational pull, as well as that of the more distant moons Europa and Ganymede, friction keeps Io piping hot.

This article appeared in print under the headline 鈥淎 world on fire鈥�

THINK you鈥檝e got game? Try this on for size: a sensor-laden sleeve promises to improve basketball players鈥� shooting skills by tracking their arm movements and calculating the arc of their shots.

The sleeve is equipped with accelerometers that sit over the player鈥檚 biceps, forearm and back of the hand. As they practise, the sleeve keeps track of every arm movement and compares it with an ideal model of arm motion for a basketball shot.

聯The sleeve keeps track of every arm movement and compares it with an ideal model of arm motion聰

It can either provide feedback through a series of light and sound cues from the sleeve鈥檚 sensors, or run in silent mode so the player can focus on practising. Afterwards, they can check their performance on a laptop.

鈥淲e asked coaches, 鈥楬ow do you teach a shot? What do you consider good form?'鈥� says Cynthia Kuo, co-founder of Vibrado in Sunnyvale, California, which developed the sleeve. 鈥淭hey look at things like keeping your elbow in, following through with your wrist, and keeping your arm up, but not too far up. So we created a model of the textbook shot.鈥�

The software can also calculate the arc of the ball as it leaves the hand. This could be useful as previous studies have shown that there is an ideal release angle depending on where the player is on the court. Releasing the ball at an angle of around 52 degrees gives the best chance of success for free throws, which are always taken from around 4.5 metres from the basket, for example.

鈥淐oaches can give players specific skills to work on 鈥� they can say, 鈥業 want you to go home and take 100 free throws鈥� or something 鈥� and the sleeve will help them work on their form,鈥� Kuo says.

The sleeve has been in testing over the last few months at the in San Jose, California, which trains promising teenage players hoping to play at college level. An app is being developed so that players can check their performance on a smartphone.

鈥淭his would be very good for teaching consistency,鈥� says Larry Silverberg at North Carolina State University in Raleigh, who studies the mechanics behind basketball shots. But he says the device鈥檚 usefulness is limited as it can鈥檛 help players with footwork, which can be crucial. A shot 鈥渟tarts with the feet and goes up from there鈥�, he says.

This article appeared in print under the headline 鈥淏asketball sleeve helps you make the perfect shot鈥�

LORNA is 4, going on 5. I鈥檝e never met her before, but her eyes light up when she sees me. She rushes over, blonde curls bouncing. 鈥淚鈥檓 going to sit on you!鈥� she declares. I demur, so she climbs into the chair next to me. 鈥淚 weigh forty pounds!鈥� she exclaims.

I hand her the iPad I鈥檓 carrying and the silliness melts away in an instant. A teacher helps her load up an app, gives her a quick tutorial and she鈥檚 off, pulling at icons, stringing instructions together, building animations. Lorna is on her third day of learning to program a computer.

Lorna and her classmates, who range in age from 4 to 7, are taking part in a pilot study here at Tufts University in Medford, Massachusetts, to see how young children respond to , a spin-off of the . Scratch was invented to teach students as young as 8 how to program using graphical blocks instead of text. Now even children who haven鈥檛 yet learned to read or write are getting in on the act.

Tools like Scratch aim to address what their developers see as a lack of computer programming instruction in schools today. The general thinking is that children are growing up surrounded by powerful machines they do not understand and teaching needs to be overhauled to prepare today鈥檚 youth for a future living and working closely with computers.

Unlike typical programming languages, which require users to type in complicated text commands, Scratch uses coloured blocks that are strung together to create lines of code. ScratchJr is similar, only the commands are even simpler. After assembling a rudimentary program, the child clicks a green flag at the beginning of the list of commands to run it.

It may sound very simple, says at Tufts, who co-created ScratchJr, 鈥渂ut it teaches sequencing 鈥� the idea that order matters鈥�.

Concepts become more complex as the child progresses. On just their third day with ScratchJr, the youngsters are being introduced to the idea of programming tasks in parallel 鈥� in this case, making a snake wriggle across a grassy meadow while a bird glides down from the air. This involves two separate strings of commands, one governing the bird and the other the snake, and they must be made to work simultaneously.

Once the students have completed their task, they get the opportunity to experiment with what they鈥檝e learned. William, aged 6, adds a loop to his program, so the snake slithers through the grass over and over again. Then he adds a command so the bird only glides down after the snake has reached most of the way across the screen. In computer science terms, William is showing that he understands control flow 鈥� a concept every programmer must master.

Being able to think like this can help children with more than just computing, Bers says. Maths, science, even learning to write, all require children to be able to organise their thoughts into the best order.

Early exposure to programming seems to have helped some of the world鈥檚 top coders. Earlier this year, Google engineer in Mountain View, California, polled over 100 of his co-workers about when they first picked up coding, and then compared that with their performance on a simple test of skills. He found that those who wrote their first code between the ages of roughly 8 and 11 were most likely to develop advanced coding skills.

聯People writing their first code at an early age are more likely to develop advanced coding skills聰

鈥淲e didn鈥檛 see an effect before 3rd grade, but certainly earlier is good,鈥� Fraser says.

In the UK, the Department for Education is now looking to address the lack of programming taught in schools. Under draft guidelines for the National Curriculum, due to take effect in 2014, children are to begin learning the rudiments of programming at the age of 5. Coding is already proving popular with the nation鈥檚 children. Last year Clare Sutcliffe and Linda Sandvik co-founded , where children aged 9 to 11 learn how to build basic programs on Scratch at first and then move on to more complicated languages such as HTML. There are now 948 Code Clubs in the UK.

The picture in the US is much less rosy. Just over 10 per cent of secondary schools there offer computer science classes. The federal government does not consider computer science a core subject and allocates it little funding. 鈥淚n the US, most computer science classes won鈥檛 start until grade 10 [ages 15 to 16], if you鈥檙e lucky,鈥� says Fraser.

A bill introduced to the House of Representatives in June could change that, but the task of changing teaching practices has fallen mostly to advocacy groups like and the Teachers Association.

Back in the classroom, William takes me through one of his creations 鈥� a program in which a bird flies out of a tree and greets a friendly cat. But the bird doesn鈥檛 fly on cue. 鈥淲hat?!鈥� he exclaims, frowning. 鈥淟et me check the bird鈥檚 program.鈥� He tweaks a few icons and runs it again. All fixed. I ask him whether he might like to be a programmer some day. 鈥淧robably,鈥� he says. 鈥淚t鈥檚 edging out 鈥榮cientist鈥� right now.鈥�

Correction: We lowered our figure for the proportion of secondary schools in the US offering computer science classes since this article was first published on 26 July.

This article appeared in print under the headline 鈥淭he kindergarten coders鈥�

Editorial: 鈥�It鈥檚 too early to herald a US nuclear renaissance鈥�

YOU could be forgiven for thinking a new era of nuclear energy is under way in the US. On 11 March, crews at the Virgil C Summer power plant in South Carolina completed a 51-hour marathon of pouring concrete. Three days later, in Burke County, Georgia, another concrete base was completed.

The two reactors that will sit on these bases will be Westinghouse AP1000s. Like older models, they will use uranium fission to heat water and drive a turbine, but these reactors will be smaller, simpler to build, and each will add more than 1100 megawatts of capacity to the region鈥檚 power grid when they come online in 2016 or 2017 鈥� without emitting carbon dioxide.

They will be the first new reactors on US soil in over three decades. Besides the two reactors in progress, two more are planned 鈥� one at each plant. And work has resumed on a half-built reactor, Watts Bar 2 in Tennessee. It could be connected to the grid by 2015.

鈥淭here鈥檚 no question it鈥檚 a big deal,鈥� says of the Electric Power Research Institute in Palo Alto, California. 鈥淭here were no new plants being constructed for decades, and now there is a new wave of building going on.鈥�

聯There鈥檚 no question it鈥檚 a big deal. There were no new plants being constructed for decades聰

What seems like a sudden rush back to nuclear was actually put in motion years ago, when US utility companies began to pre-empt the possibility of government-mandated cuts in carbon emissions. But to get construction under way, the firms needed a big helping hand from the government. As part of President Barack Obama鈥檚 goal of promoting clean sources of energy, he guaranteed $8.3 billion in federal loans for the reactors, which helps spread the massive cost of the projects.

All four new plants will be AP1000s. These reactors are descendants of the ones that have been in service since the middle of the 20th century. However, they have major safety upgrades, new pump designs and more straightforward circulation systems. More exotic designs remain on the horizon, such as reactors powered by thorium fuel, but the AP1000 and other more conventional designs are important for one simple reason: they are being built. That means adding reliable, low-carbon energy to the US grid on a scale that other technologies can鈥檛 yet match.

Whether the construction signals the start of a US nuclear energy boom remains to be seen. Reactors are expensive and fossil fuels are cheap enough that utility companies are nervous about undertaking such long, costly projects. 鈥淚t鈥檚 a bet-the-company proposition,鈥� says Wilmshurst.

That鈥檚 not the case in China, where massive government backing has allowed construction there to race ahead of the US. Across China, 28 reactors are being built, many of them AP1000s, including one nearing completion at the Sanmen Nuclear Power Station in Zhejiang Province. It will become the first operative AP1000 if it comes online later this year as planned.

Mitchell Singer of the Nuclear Energy Institute, an industry advocacy group in Washington DC, says the comparatively slow take up of the AP1000 could be down to its unproven nature. 鈥淪omeone鈥檚 got to take the first step and blaze the trail into the wilderness,鈥� he says. 鈥淚n the next decade, once plants come online successfully, that will give confidence to others to follow with their own projects.鈥�

This article appeared in print under the headline 鈥淎 nuclear dawn for the US鈥�

SITTING down with the Inquire system is, at first, a lot like trying to cosy up to an intimidatingly dense biology textbook. Sure, its presentation on the iPad is slick, but that can鈥檛 hide the fact that you are in for a tough old read.

That is until you highlight the first bit of particularly impenetrable text. Suddenly a list of questions pops up in the right-hand margin. Touch one and you are whisked away to a Wikipedia-like page full of information specific to the concept you are stuck on. Terms like 鈥渃hloroplast鈥� and 鈥減lasma membrane鈥� are succinctly defined, and the page explains how each concept fits into the wider field of biology.

Want to know more? Type in your own question and artificially intelligent software will construct a new page to answer your query.

The aim of is to provide students with the world鈥檚 first intelligent textbook, says its creator David Gunning of Seattle-based . At first glance, the system just looks like an electronic version of , the tome that forms the bedrock of biology classes for first-year university and advanced high school students in the US. But behind the scenes is a machine-readable concept map of the 5000 or so ideas covered in the book, along with information on how they are all related.

When a student asks a question 鈥� 鈥渨hat does a protein do?鈥�, for instance 鈥� the system first converts it into a more structured query, such as 鈥渨hat is the function of a protein?鈥�, and then uses this to search and find results from the concept map.

Earlier this year, the team recruited 72 first-year students from in Cupertino, California, to put the system to the test. Students were given either the full Inquire system, the Inquire system with the query function switched off, or a paper copy of Campbell Biology. They were then asked to spend 60 minutes reading a section of the book, 90 minutes on homework problems, and to take a 20-minute-long quiz.

Students who used the full Inquire system scored a grade better on the quiz, on average, than the other groups. 鈥淲hen we did our assessment, we didn鈥檛 see any Ds or Fs, which we did see in the control groups,鈥� says Debbie Frazier, a high school biology teacher who works on the project. 鈥淥ur students could use Inquire as a tool and ask it questions that they might be embarrassed to ask a teacher in person because it makes them feel stupid.鈥�

聯Students who used the Inquire system scored a grade better on a quiz than those who didn鈥檛聰

A video on the work was presented at the in Toronto, Canada, last week.

While such results are promising, perhaps it鈥檚 a little soon to crown Inquire the future of textbooks. For starters, after two years of work the system is still only half-finished. The team plan to encode the rest of the 1400-page Campbell Biology by the end of 2013, but they expect a team of 18 biologists will be needed to do so. This raises concerns about whether the project could be expanded to cover other areas of science, let alone other subjects.

Still, adhering to the textbook format makes sense because it means students won鈥檛 have to wade through reams of irrelevant information, as they do when searching the web, says of the University of Sussex in Brighton, UK.

Such habits are common, says Inquire team member , of SRI International in Menlo Park, California. 鈥淚鈥檓 not going to name names, but all of the students go to Wikipedia to study,鈥� he says. 鈥淚t鈥檚 open while they are reading their books.鈥�