JU3

JU3 is the provisional designation of the near-Earth asteroid 1999 JU3, which was later named Ryugu. It is classified as an Apollo-type, carbonaceous C-type asteroid and is noted for its dark surface and irregular, bilobed shape. With an approximate diameter around 0.9 kilometers, Ryugu is considered a primitive body that may preserve materials from the early Solar System. Observations describe a rubble-pile structure, a low bulk density, and a surface strewn with boulders and regolith. Its geometric albedo is very low, consistent with carbon-rich materials.

Discovery and naming: 1999 JU3 was discovered in 1999 by the LINEAR project at Socorro, New Mexico. It was assigned the provisional designation 1999 JU3 and was later named Ryugu, derived from the Dragon Palace in Japanese folklore; the name was approved by the International Astronomical Union.

Exploration: The asteroid was chosen as the target of JAXA's Hayabusa2 sample-return mission. Launched in 2014, the spacecraft reached Ryugu in 2018, deploying small landers and rovers and collecting surface samples in 2019. In December 2020, Hayabusa2 delivered a capsule containing the samples to Earth. Analyses of the returned material confirmed the presence of hydrated minerals and organic materials, indicating that Ryugu preserves primitive Solar System material.

Scientific significance: As a relatively accessible source of primitive carbonaceous material, Ryugu provides insights into the distribution of water and organics in the early Solar System and informs models of asteroid formation, evolution, and potential resource use.