Past orbital evolution and its effects on the surface of (162173) RyuguOPEN ACCESS 

M C Guimarães; RAN Araujo, O C Winter

Monthly Notices of the Royal Astronomical Society, stae1494
Published: 17 June 2024


“The Japanese probe Hayabusa 2 recently visited the NEA (162173) Ryugu. This mission provided valuable information about the asteroid, including in situ images and a surface sample brought back to Earth. The data suggests that Ryugu has likely been affected by space weathering, but the underlying cause of the surface modification remains unclear. This paper aims to shed light on the problem by providing new information about the possible past orbital path of Ryugu. We used a procedure to estimate how Ryugu has dynamically evolved since it entered the NEAs’ region and whether this can explain the observed data. We have conducted numerical integrations of the N-body gravitational problem. The system comprises the Sun, the solar system’s eight planets, and a group of 29, 000 test particles initially placed in the main asteroidal belt (MAB) near the ν6 secular resonance. We then tracked the particles that left the MAB and eventually arrived close to Ryugu’s current orbit. Our analysis showed that out of 307 clones of Ryugu, only 3 came very close to the Sun at a distance of less than 0.1 au. Consequently, it is unlikely that Ryugu has undergone significant surface temperature variations. We also computed that ~ 70% of the clones have spent more than 5 Myr at an equivalent distance of 1 au from the Sun. This result suggests that Ryugu has been exposed to significant amounts of solar radiation over a long period, which may have resulted in space weathering effects on its surface.”