Enlarge / The surface of Ryugu. Image credit: JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University, Aizu University, AIST (credit: JAXA)

An asteroid that has been wandering through space for billions of years is going to have been bombarded by everything from rocks to radiation. Billions of years traveling through interplanetary space increase the odds of colliding with something in the vast emptiness, and at least one of those impacts had enough force to leave the asteroid Ryugu forever changed.

When the Japanese Space Agency’s Hayabusa2 spacecraft touched down on Ryugu, it collected samples from the surface that revealed that particles of magnetite (which is usually magnetic) in the asteroid’s regolith are devoid of magnetism. A team of researchers from Hokkaido University and several other institutions in Japan are now offering an explanation for how this material lost most of its magnetic properties. Their analysis showed that it was caused by at least one high-velocity micrometeoroid collision that broke the magnetite’s chemical structure down so that it was no longer magnetic.

“We surmised that pseudo-magnetite was created [as] the result of space weathering by micrometeoroid impact,” the researchers, led by Hokkaido University professor Yuki Kimura, said in a study recently published in Nature Communications.

Enlarge / All galaxies have large amounts of gas that influence their star-formation rates. (credit: NASA, ESA, CSA, and J. Lee (NOIRLab))

Galaxies pass gas—in the case of galaxy NGC 4383, so much so that its gas outflow is 20,000 light-years across and more massive than 50 million Suns.

Yet even an outflow of this immensity was difficult to detect until now. Observing what these outflows are made of and how they are structured demands high-resolution instruments that can only see gas from galaxies that are relatively close, so information on them has been limited. Which is unfortunate, since gaseous outflows ejected from galaxies can tell us more about their star formation cycles.

The MAUVE (MUSE and ALMA Unveiling the Virgo Environment) program is now changing things. MAUVE’s mission is to understand how the outflows of galaxies in the Virgo cluster affect star formation. NGC 4383 stood out to astronomer Adam Watts, of the University of Australia and the International Centre for Radio Astronomy Research (ICRAR), and his team because its outflow is so enormous.

Enlarge (credit: NASA Goddard/ASU)

Our Moon may appear to shine peacefully in the night sky, but billions of years ago, it was given a facial by volcanic turmoil.

One question that has gone unanswered for decades is why there are more titanium-rich volcanic rocks, such as ilmenite, on the near side as opposed to the far side. Now a team of researchers at Arizona Lunar and Planetary Laboratory are proposing a possible explanation for that.

The lunar surface was once flooded by a bubbling magma ocean, and after the magma ocean had hardened, there was an enormous impact on the far side. Heat from this impact spread to the near side and made the crust unstable, causing sheets of heavier and denser minerals on the surface to gradually sink deep into the mantle. These melted again and were belched out by volcanoes. Lava from these eruptions (more of which happened on the near side) ended up in what are now titanium-rich flows of volcanic rock. In other words, the Moon’s old face vanished, only to resurface.