A digest of popular science news for the week that we haven't written about

Chinese Team Finds First Traces of Water on Moon

Chinese scientists for the first time discovered water molecules in lunar soil – a discovery that could be fundamental to understanding how the Moon evolved and how to use its resources.

Samples brought back by American Apollo astronauts decades ago showed no signs of water, leading scientists to conclude that lunar soil must be completely dry, Nasa reports.

Now, after studying lunar soil samples returned by China's Chang'e-5 mission in 2020, Chinese scientists have discovered a hydrated mineral “enriched” with molecular water, the Chinese Academy of Sciences (CAS) said on Tuesday.

The study, conducted jointly by scientists from the Beijing National Laboratory of Condensed Matter Physics and the CAS Institute of Physics, as well as other domestic scientific institutions, was published on July 16 in the peer-reviewed journal Nature Astronomy.

Using a sample provided by the China National Space Administration, the team isolated more than 1,000 mineral “clumps.” Among them, the researchers said, was a plate-like transparent crystal dubbed “unknown lunar mineral” (ULM-1) that contained water molecules.

Fast-Spinning Dead Stars Could Reveal Secrets of Dark Matter

Scientists plan to use 'timers' from the remains of stars to illuminate the most mysterious thing in the universe: dark energy.

These timekeepers are actually pulsars, rapidly spinning neutron stars that are created by the deaths of stars at least eight times more massive than the Sun. The extreme conditions of neutron stars make them ideal laboratories for studying physics under conditions found nowhere else in the universe.

So-called “millisecond pulsars” can spin hundreds of times per second and emit beams of electromagnetic radiation from their poles, like cosmic lighthouses that streak across space. They got their name because when they were first discovered, these neutron stars were found to pulse, increasing in brightness when their beams were aimed directly at Earth.

The ultra-precise timing of millisecond pulsars' brightness changes means they could be used as cosmic timekeepers in “pulsar arrays.” These arrays are so precise that they can measure gravitational perturbations in the fabric of space and time, combined into a four-dimensional entity called spacetime, which could be an ideal way to search for dark matter.

“Science has developed very precise methods of measuring time,” he said in his statement pulsar researcher John LoSecco of the University of Notre Dame. “On Earth we have atomic clocks, and in space we have pulsars.”

Even though dark matter doesn't interact with light, it does exert a gravitational influence, and its presence can be inferred from how that influence affects light and ordinary matter. It's the effect of that gravitational influence on light that Losecco and his colleagues wanted to study with pulsars.

Webb Directly Images Giant Exoplanet That's Not Where It Should Be

What do you need to directly image a planet orbiting a star light years away? First of all, a piece of equipment called a coronagraph attached to a telescope. It is responsible for blocking the light from the star the planet is orbiting; without it, that light would drown out all other sources in the exosolar system. Even with a good coronagraph, the planet needs to be orbiting a significant distance from the star to be separated from the signal blocked by the coronagraph.

Then you need the planet to emit enough light. While a planet with the right surface composition can be highly reflective, that's not ideal given the distances at which a planet would have to orbit to be visible at all. Instead, the planets we've spotted so far have been young, still heating up from the processes that brought material together to form the planet in the first place. It doesn't hurt that they're very big, either.

Put all this together, and we would expect to find a very young and very distant planet, massive enough to fall into the super-Jupiter category.

But the launch of the Webb Space Telescope has given us new infrared capabilities, and a large international team of researchers has pointed it at the star Epsilon Indi A. It’s just under a dozen light-years away (very close in astronomical terms), and the star is similar in size and age to the Sun, making it an interesting target. Crucially, previous data had suggested that a large exoplanet would be found, since the star appeared to shift as the exoplanet gravitated toward it in its orbit.

And indeed, the signs of a planet were there. Only it didn't look much like the planet we expected. “It's about twice as massive, a little further from its star, and has a different orbit than we expected,” speaks Elizabeth Matthews, one of the study participants.

There is currently no explanation for this discrepancy. The likelihood that it is an unrelated background object is extremely low. And reanalysis of Epsilon Indi A's motion data suggests that it is likely the only large planet in the system – there may be others, but they will be much smaller. So the researchers named the planet Epsilon Indi Ab, even though the same name has been given to a planet that does not seem to match this one's properties.

Deep in Mercury there is a diamond layer 15 km thick

The solar system's tiniest planet may be hiding a big secret. Using data from NASA's MESSENGER spacecraft, scientists have found that Mercury, the planet closest to the Sun, may have a 15-km-thick diamond mantle beneath its crust.

Mercury has long puzzled scientists because it has many properties that are not found in other planets in the solar system. These include a very dark surface, a surprisingly dense core, and the premature end of Mercury's volcanic era.

Also among these mysteries are patches of graphite, a form (or “allotrope”) of carbon, on the surface of the innermost planet in the solar system. These patches have led scientists to speculate that a carbon-rich magma ocean existed on the tiny planet early in Mercury’s history. This ocean bubbled to the surface, creating the graphite patches and the dark hue of Mercury’s surface.

The same process would have led to the formation of a carbon-rich mantle beneath the surface. The team behind these findings believes that this mantle is not made of graphene, as previously assumed, but of another, much more valuable allotrope of carbon: diamond.

“We calculated that, given the new estimate of the pressure at the mantle-core boundary, and knowing that Mercury is a carbon-rich planet, the carbon-containing mineral that forms at the mantle-core boundary is diamond, not graphite,” told team member Olivier Namur, associate professor at KU Leuven. “Our study uses geophysical data collected by NASA's MESSENGER spacecraft.”

MESSENGER (Mercury Surface, Space Environment, Geochemistry, and Ranging) was launched in August 2004 and became the first spacecraft to orbit Mercury. The mission, which ended in 2015, explored the tiny world, discovered abundant water ice in the polar shadows, and collected vital data on Mercury’s geology and magnetic field.

Uranus' moon Ariel may also have an ocean

Recent observations by the James Webb Space Telescope suggest that Uranus' moon Ariel is also a strong candidate for a subsurface ocean. How did they come to this conclusion? JWST found carbon dioxide ice on the surface at the trailing edge of objects that deviate from their orbital direction. Possible reason – the presence of an underground ocean!

Uranus is the seventh planet in the solar system and has five moons. Ariel is one of them, notable for its icy surface and amazing variety of geological features. It was discovered in 1851 by William Lassell, who financed his love of astronomy from his brewing business! Ariel's surface is a veritable mix of canyons, ridges, faults and valleys, mostly caused by tectonic activity. Cryovolcanism is a prominent process on the surface, causing constant resurfacing, giving Ariel the brightest surface of all Uranus' moons.

Upon closer inspection, Ariel's surface appears to be covered in significant amounts of carbon dioxide ice. Ariel's trailing hemisphere appears to be particularly icy, which surprised the community. At Uranus's average distance from the Sun of 2.9 billion kilometers, carbon dioxide typically turns to gas and disappears into space rather than freezing.

Until recently, the most popular theory for delivering carbon dioxide to Ariel’s surface was interactions between its surface and charged particles in Uranus’s magnetosphere. The process, known as radiolysis, breaks down molecules through ionization. A new study just published in the Astrophysical Journal Letters offers an intriguing alternative: carbon dioxide molecules are being ejected from Ariel, perhaps from a subsurface liquid ocean.

A team of astronomers used JWST to analyze the spectra of Ariel and compared the results with laboratory data. The results showed that Ariel contains some of the richest carbon dioxide deposits in the solar system. These are not just deposits, but traces about 10 millimeters thick across the entire trailing hemisphere. In addition, the results showed signals from carbon monoxide, which should not be there given the average temperatures.