An international team of researchers have found evidence of a mysterious new state of matter, first predicted 40 years ago, in a real material. This state, known as a quantum spin liquid, causes electrons -- thought to be indivisible building blocks of nature -- to break into pieces.

The researchers, including physicists from the University of Cambridge, measured the first signatures of these fractional particles, known as Majorana fermions, in a two-dimensional material with a structure similar to graphene. Their experimental results successfully matched with one of the main theoretical models for a quantum spin liquid, known as a Kitaev model. The results are reported in the journal Nature Materials.

Perfectly backlit by our star. This is how Comet 67P was pictured this week by the Rosetta spacecraft.

The European Space Agency (Esa) probe was a few hundred km "downstream" of all the vapour and dust being vented from the icy dirt-ball.

Even though the duck-shaped object is heading out of the inner Solar System, it remains classically active.

Rosetta will continue to study the comet until controllers direct it to make a "landing" in September.

Mission officials will endeavour to make this touchdown a gentle one, to ensure data is returned for as long as possible. But it will bring the whole venture to an end.

Rosetta will likely be damaged by the impact and drop all contact with Earth.

The hypothetical ninth planet at the fringes of our solar system might have been captured from a star passing by long ago

Our solar system might harbour an alien interloper. The proposed Planet Nine lurking at the edge of the solar system could have been stolen from a passing star.

In January, Konstantin Batygin and Michael Brown announced evidence for an unseen planet around 10 times Earth's mass lurking in the fringes of the solar system. Other astronomers immediately came forward with suggestions for how so-called Planet Nine might have migrated from the inner solar system towards its outer edges.

But one team now suggests just the opposite: that it was captured from a nearby star.

The idea isn't all that far-fetched. The sun was born in a reasonably large stellar cluster with roughly 1000 or maybe even 10,000 stars, says Alexandar Mustill from the Lund Observatory in Sweden. In such a dense cluster, the sun would have had quite a few close encounters with other stars, potentially letting them swap planets from time to time.

"It would be pretty wild - to pick up an alien planet and bring it along for the ride," says Greg Laughlin at the Lick Observatory in California.

The International Space Station is about to get a new room - but first the crew will have to blow it up. Later this week, the ISS will take delivery of its first additional module since 2011. But unlike the rest of the station, which is built from hulking great aluminium cans, the Bigelow Expandable Activity Module (BEAM) will be carried to orbit folded neatly inside a SpaceX cargo capsule.

BEAM was developed by Bigelow Aerospace in Las Vegas, Nevada. The module is made from soft, foldable fabric that nonetheless holds up to the harshness of space - the exact material is a commercial secret. It is designed to inflate in orbit, allowing modules to launch on compact spacecraft like SpaceX's Dragon capsule, rather than requiring the heavy-lifting space shuttle that was responsible for much of the ISS's construction. BEAM is set to blast off this Friday from Cape Canaveral in Florida as part of SpaceX's latest cargo run to the ISS.

• Yesterday, more evidence for mysterious 'Planet Nine' was revealed
• Astrophysicist suggests this planet could have caused extinctions
• As Planet X orbits the sun, its tilted orbit slowly rotates and it passes through the Kuiper belt of comets every 27 million years
• This orbit causes comets to be knocked into the inner solar system

As evidence for a ninth planet in our solar system grows, a 30-year old theory about mass extinctions on Earth is resurfacing.

Evidence was discovered at the beginning of this year for the mysterious 'Planet Nine', and since then scientists have been looking for signs that could confirm its existence.But the mystery of this planet has now deepened after an astrophysicist in the US has claimed this planet could have provoked comet showers that caused mass extinctions on Earth.

Yesterday, astronomer Mike Brown of Caltech, one of the scientists behind the initial announcement of the so-called 'Planet Nine', revealed he had found further evidence to support it.This giant hidden planet is thought to sit on the edge of our solar system and is 10 times more massive than the Earth, gaseous, and similar to Uranus or Neptune.

Now, Dr Daniel Whitmire, a retired professor of astrophysics working at the University of Arkansas Department of Mathematical Sciences has suggested the planet triggers comet showers. These comet showers could be powerful enough to travel towards Earth's orbit and ultimately strike the planet and cause mass extinctions.

Scientists have grown skin with the same functions as normal tissue for the first time. The bioengineered skin has great potential to transform treatment for burns and provide an alternative to drug testing on animals.

"Up until now, artificial skin development has been hampered by the fact that the skin lacked important organs, such as hair follicles and exocrine glands, which allow the skin to play its important role in regulation. With this new technique, we have successfully grown skin that replicates the function of normal tissue," lead scientist Takashi Tsuji from the RIKEN Centre for Developmental Biology said in the press release.

After decades of theorizing and searching, scientists are reporting that they've finally found a massive reservoir of water in the Earth's mantle — a reservoir so vast that could fill the Earth's oceans three times over. This discovery suggests that Earth's surface water actually came from within, as part of a "whole-Earth water cycle," rather than the prevailing theory of icy comets striking Earth billions of years ago.

As always, the more we understand about how the Earth formed, and how its multitude of interior layers continue to function, the more accurately we can predict the future. Weather, sea levels, climate change — these are all closely linked to the tectonic activity that endlessly churns away beneath our feet.

This new study, authored by a range of geophysicists and scientists from across the US, leverages data from the USArray — an array of hundreds of seismographs located throughout the US that are constantly listening to movements in the Earth's mantle and core. After listening for a few years, and carrying out lots of complex calculations, the researchers believe that they've found a huge reserve of water that's located in the transition zone between the upper and lower mantle — a region that occupies between 400 and 660 kilometers (250-410 miles) below our feet.

As you can imagine, things are a little complex that far down. We're not talking about some kind of water reserve that can be reached in the same way as an oil well. The deepest a human borehole has ever gone is just 12km — about half way through the Earth's crust — and we had to stop because geothermal energy was melting the drill bit. 660 kilometers is a long, long way down, and weird stuff happens down there.

Basically, the new theory is that the Earth's mantle is full of a mineral called ringwoodite. We know from experiments here on the surface that, under extreme pressure, ringwoodite can trap water. Measurements made by the USArray indicate that as convection pushes ringwoodite deeper into the mantle, the increase in pressure forces the trapped water out (a process known as dehydration melting). That seems to be the extent of the study's findings. Now they need to try and link together deep-Earth geology with what actually happens on the surface. The Earth is an immensely complex machine that generally moves at a very, very slow pace. It takes years of measurements to get anything even approaching useful data.

An asteroid doesn't need to be massive to cause serious damage. The Chicxulub asteroid that wiped out the dinosaurs is estimated to have been about 6 miles in diameter. That may sound like a pretty big space rock, but relative to Earth it's pretty tiny.

But what's the likelihood of an asteroid of that size coming into contact with Earth again? The following is from NASA's website:

Every day, Earth is bombarded with more than 100 tons of dust and sand-sized particles.

About once a year, an automobile-sized asteroid hits Earth's atmosphere, creates an impressive fireball, and burns up before reaching the surface.

Every 2,000 years or so, a meteoroid the size of a football field hits Earth and causes significant damage to the area.

Only once every few million years, an object large enough to threaten Earth's civilization comes along. Impact craters on Earth, the moon and other planetary bodies are evidence of these occurrences.

Some mental illnesses may stem, in part, from the brain's inability to correctly assign emotional associations to events. For example, people who are depressed often do not feel happy even when experiencing something that they normally enjoy.

A new study from MIT reveals how two populations of neurons in the brain contribute to this process. The researchers found that these neurons, located in an almond-sized region known as the amygdala, form parallel channels that carry information about pleasant or unpleasant events.

Learning more about how this information is routed and misrouted could shed light on mental illnesses including depression, addiction, anxiety, and posttraumatic stress disorder, says Kay Tye, the Whitehead Career Development Assistant Professor of Brain and Cognitive Sciences and a member of MIT's Picower Institute for Learning and Memory.

"I think this project really cuts across specific categorizations of diseases and could be applicable to almost any mental illness," says Tye, the senior author of the study, which appears in the March 31 online issue of Neuron.

A white dwarf discovered in the constellation of Draco is unique in having an atmosphere dominated by oxygen rather than hydrogen and helium, astronomers reported. The scientists are not sure how this could have happened.

"We only found one, so it is a rare event," Kepler de Souza Oliveira Filho, an astronomer at the Federal University of Rio Grande do Sul in Porto Alegre, Brazil, told Science.com. Kepler and other authors of a paper about the unusual star, which was published on April 1 in the magazine Science, combed through data collected by the Sloan Digital Sky Survey (SDSS).

A white dwarf is what is left behind by almost any star but the heaviest ones, when it sheds off its outer layers and leaves only the exposed core. Heavier elements like oxygen or carbon sink to the core's center while the remaining lighter hydrogen and helium floats on the surface. This is for some reason not what happened to the star described in the study.

Located about 1,200 light-years away, its surface is 99.9 percent pure oxygen - a record for oxygen richness - with neon and magnesium coming as distant second and third. The composition of elements is what would be expected to be inside the core of a star with a mass between six and 10 times that of the sun.

But, such a star would leave behind a white dwarf about as heavy as the sun, while the newly-discovered dwarf is about 60 percent as heavy. And a star corresponding to the size of the freak dwarf would not have been big enough to fuse its fuel into oxygen. "You have to wonder where this oxygen even came from," said Kepler.

The scientists consider several theories of how the misfit, which they dubbed Dox, could come into existence. One is that it's part of a binary system and that its companion had siphoned lighter elements off. Another is that the interaction went the other direction and Dox siphoned matter from its companion and it triggered a thermonuclear explosion, which expelled the outer layers of the dwarf.