Famous asteroid Ryugu may have been bombarded by a swarm of tiny space rocks 1,000 years ago

In 2020, Japan's Hayabusa2 spacecraft brought samples of an asteroid named Ryugu to Earth — and now, scientists examining those samples found that the object bears the scars of a recent encounter with tiny space rocks. The reason the research team believes Ryugu was bombarded by micrometeorites is due to a fine layer of sodium, just 10 nanometers thick, on the surface of the asteroid 's fragments. This kind of build-up is unusual because volatile elements like sodium, which can get exposed after an object is blasted with micrometeorites, are usually later depleted by solar winds blowing from the sun and the general influence of space. Based on the volume of sodium observed by the researchers, they estimate that Ryugu's passage through a dense cloud of micrometeorites must have occurred around 1,000 years ago. That's an extremely recent event considering the asteroid formed 4.6 billion years ago, while planets like Earth were still taking shape around our infant sun. "Over the past thousand years, the asteroid has passed through a particularly intense swarm that has profoundly altered the chemical properties of its surface. We were able to detect these changes by analyzing two millimeter-thin fragments of Ryugu, using techniques capable of studying the morphology and chemistry of layers just a few billionths of a meter thick," lead researcher Ernesto Palomba of the Italian National Institute for Astrophysics (INAF) said in a statement translated from Italian. …