Marrakesh, Mar. 22 (Maroc-Actu) –
Ryugu, along with other similar debris-piled asteroids, may actually be the remains of extinct comets, suggests a new study by a group of EU researchers. a new theory supported by a relatively simple physical model.
The Japanese space probe Hayabusa 2 visited this asteroid – discovered in 1999 – reaching its orbit in July 2018, and brought back a capsule with samples of its surface on December 5, 2020..
Comets are small bodies that form in the colder outer regions of the solar system. They are composed primarily of water ice, with some rocky components (debris) mixed in. If a comet enters the inner solar system, the space bounded by the asteroid belt “before” Jupiter, the heat of solar radiation causes the ice to sublimate and escape, leaving behind rocky debris which compacts under the effect of gravity and forms an asteroid in a pile of debris.
This process matches all of the observed features of Ryugu, explains Associate Professor Hitoshi Miura of Nagoya University, Japan: “The sublimation of the ice causes the comet nucleus to lose mass and shrink, which increases its rotational speed. Thanks to this rotation, the nucleus of the comet can acquire the rotation speed necessary for the formation of a top shape. Additionally, the icy components of comets are thought to contain organic matter generated in the interstellar medium. These organic materials would be deposited in the rocky debris left by the sublimation of the ice.« .
To test their hypothesis, the research team ran numerical simulations using a simple physical model to calculate the time it would take for the ice to sublimate and the asteroid’s rotational speed to increase. which would result.
The results of their analysis suggest that Ryugu probably spent a few tens of thousands of years as an active comet before moving through the inner asteroid belt, where high temperatures vaporized its ice and turned it into a debris asteroid. These results are published in The Astrophysical Journal Letters.
Taken together, this study indicates that high organic content spinning top-shaped debris cluster type objects, such as Ryugu and Bennu (the target of the OSIRIS-Rex mission) are Comet-Asteroid Transition Objects (CAT ). “CATs are small objects that were once active comets, but are now extinct and seemingly indistinguishable from asteroids,” says Miura. “Due to their similarities to comets and asteroids, CATs could provide new information about our solar system.”
Hopefully, detailed analyzes of the composition of the Ryugu and Bennu samples will shed some light on these questions.