Asteroid Ryugu’s parent body lost water due to intense heat

Sensor data from the Japanese spacecraft Hayabusa 2 explains when and how the asteroid Ryugu lost water.

In December 2020, the Japanese Hayabusa 2 mission delivered soil from the near-Earth asteroid Ryugu to Earth. While analysis of these samples is in progress, the researchers are analyzing data from other instruments on the spacecraft to reveal new details about the asteroid’s history.

A new study has suggested why Ryugu is not as rich in aquiferous minerals as some other asteroids. According to new work, the ancient parental body from which Ryugu was formed may have dried out as a result of the intense heat, even before Ryugu emerged.

One of the things we are trying to understand is the distribution of water in the early solar system and how this water could have been brought to Earth. It is believed to have been partially brought in by aquiferous asteroids, so by studying Ryugu closely, we can better understand the history of the Earth and near-Earth asteroids.

Ralph Milliken, Brown University planetary scientist and study co-author

One of the reasons why they decided to take soil samples from Ryugu is that it belongs to the class of dark asteroids and possibly contains aquiferous minerals and organic compounds. These types of asteroids are believed to be the putative parent bodies for the dark, water, and carbon-containing meteorites found on Earth also called carbonaceous chondrites.

These meteorites have been studied in detail in laboratories around the world for many decades, but it is impossible to determine with certainty which asteroid this carbonaceous-chondrite meteorite may originate from.

New evidence suggests that subsurface water is very similar to the outer surface. Therefore, Ryugu’s body was probably initially dry. However, more work is needed to confirm this discovery, the researchers said. For example, the size of particles recovered from the subsurface can affect the interpretation of spectrometer measurements.

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