Water vapour found in Ganymede’s atmosphere & the origin of the asteroid that killed dinosaurs

ScientiFix, our weekly feature, offers you a summary of the top global science stories of the week, with links to their sources.

Jupiter's moon Ganymede as seen by NASA's Hubble Space Telescope in 1996 | NASA, ESA, John Spencer (SwRI Boulder) | nasa.gov

New Delhi: For the first time, astronomers have uncovered evidence of water vapor in the atmosphere of Ganymede, one of Jupiter’s moon.

The water vapour likely forms when ice from the moon’s surface sublimates, that is, it turns from solid to gas. The findings were made using new and archived datasets from NASA’s Hubble Space Telescope.

Previous research had offered circumstantial evidence that Ganymede, the largest moon in the solar system, contains more water than all of the Earth’s oceans put together. However, temperatures there are so cold that the water on the surface is frozen solid.

Also, Ganymede’s ocean is thought to be 100 miles below the moon’s crust. This means that the water vapor discovered by Hubble is not likely to represent the evaporation of this ocean.

Ganymede’s surface temperature varies strongly throughout the day. Around noon, near the equator, it may become warm enough for the ice surface to release small amounts of water molecules.

The European Space Agency’s upcoming mission JUpiter ICy moons Explorer (JUICE) – planned for launch in 2022 – will be able to confirm these findings. It will reach Jupiter in 2029, where it will spend at least three years, making detailed observations of Jupiter and three of its largest moons. The planet has at least 79 moons. Read more here.

310 million-year-old fossilised horseshoe crab brain found 

Scientists have for the first time discovered a fossilised brain from a 310-million-year-old horseshoe crab.

The fossilised brain belongs to an extinct species known as Euproops danae. It was discovered at Mazon Creek in Illinois, where the conditions were just right to perfectly preserve the animal’s delicate soft tissue.

Currently, there are four species of horseshoe crabs alive, all of which have hard exoskeletons, 10 legs and a U-shaped head. The species is closely related to scorpions and spiders.

While horseshoe crab fossils are relatively common, nothing was previously known about their ancient brains.

This is because the soft tissues that make up brains decay very quickly. Special geological conditions are needed for them to be preserved.

In this case, as the brain rotted away it was replaced by a clay mineral called kaolinite, which created a cast of the brain.

The researchers found that despite 300 million years of evolution, the ancient brain is similar to that of a modern horseshoe crab. Read more here.

Nauka module briefly knocks ISS out of position

Russia’s Nauka module, which was launched last week, briefly knocked the International Space Station (ISS) out of its position Friday after its rockets accidentally fired after docking.

This forced personnel aboard the ISS to fire thrusters on the Russian segment of the station to counter the effect.

The module moved the station 45 degrees out of its position. However, NASA tweeted that the recovery operations have regained attitude and the crew is in no danger.

Russia’s Roscosmos space agency attributed the issue to Nauka’s engines having to work with residual fuel in the craft.

It will now take several months and multiple spacewalks to fully integrate the module with the space station. Read more here.

Scientists create metallic water for the first time 

In another first, scientists have managed to create metallic water (water that behaves like metal – conducts electricity and is lustrous) on Earth, a feat that was so far thought to only be possible in conditions present in the core of large planets, such as the Jupiter.

While our everyday tap water, which contains salts, can conduct electricity, pure, distilled water acts as an almost perfect insulator.

To turn water into an electric conductor, like metals, water would have to be pressurised to such an extent that the orbitals of the outer electrons overlap. This pressure is only present in the core of large planets, such as the Jupiter.

Now, scientists have used a different approach to make this metallic water.

Using metals like sodium and potassium, which easily release their outer electron, researchers made a water droplet acquire properties of a metal.

They put a tiny bit of water on a drop of sodium-potassium (Na-K) alloy, which is liquid at room temperature.

The thin layer of gold-coloured metallic water was created for a few seconds, enough for researchers to image it and prove that it was in a metallic state. Read more here.

Scientists find the origin of the asteroid that wiped out dinosaurs 

Scientists have found that the asteroid that is believed to have wiped out dinosaurs and other life forms on Earth some 66 million years ago likely came from the outer half of the main asteroid belt.

This is unusual because this region was previously thought to produce few impactors.

Researchers from Southwest Research Institute have shown that the processes that deliver large asteroids to Earth from that region occur at least 10 times more frequently than previously thought and that the composition of these bodies match what we know of the dinosaur-killing impactor.

The team combined computer models of asteroid evolution with observations of known asteroids to investigate the frequency of such events.

Over 66 million years ago, a body estimated to be six miles across, hit in what is now Mexico’s Yucatan peninsula and formed the Chicxulub crater, which is over 90 miles across. This massive blast triggered a mass extinction event that ended the reign of the dinosaurs.

To probe the impact, geologists have previously examined 66-million-year-old rock samples found on land and within drill cores. The results indicate the impactor was similar to the carbonaceous chondrite class of meteorites, some of the most pristine materials in the solar system.

While carbonaceous chondrites are common among the many mile-wide bodies that approach the Earth, none today are close to the sizes needed to produce the Chicxulub impact with any kind of reasonable probability.

The team found that six-mile-wide asteroids hit the Earth once every 250 million years on average, a timescale that yields reasonable odds that the Chicxulub crater occurred 66 million years ago. Moreover, nearly half of impacts were from carbonaceous chondrites, a good match with what is known about the Chicxulub impactor. Read more here.

(Edited by Poulomi Banerjee)