162173 Ryugu (provisional designation 1999 JU3) is a near-Earth object and also a potentially hazardous asteroid of the Apollo group.

[18] The parent body of Ryugu probably experienced dehydration due to internal heating[17] and must have formed in an environment without a strong magnetic field.

[19] After this catastrophic disruption, part of the surface was reshaped again by the high speed rotation of the asteroid forming the equatorial ridge (Ryujin Dorsum), through internal failure and/or mass wasting.

[2] Early analysis in 2012 by Thomas G. Müller et al. used data from a number of observatories, and suggested that the asteroid was "almost spherical", a fact that hinders precise conclusions, with retrograde rotation, an effective diameter of 0.85–0.88 km (0.528 miles) and a geometric albedo of 0.044 to 0.050.

[25] After a few months of exploration, JAXA scientists concluded that Ryugu is actually a rubble pile with about 50% of its volume being empty space.

The ridge was shaped by strong centrifugal forces during a phase of high-speed rotation, through landslides and/or internal failure.

Observations from Hayabusa2 showed that the surface of Ryugu is very young and has an age of 8.9 ± 2.5 million years based on the data collected from the artificial crater that was created with an explosive by Hayabusa2.

The measurements with the radiometer on board of MASCOT, which is called MARA, showed a low thermal conductivity of the boulders.

This result showed that most meteorites originating from C-type asteroids are too fragile to survive the entry into Earth's atmosphere.

[29][30] The images from the camera of MASCOT, which is called MASCam, showed that surface of Ryugu contains two different almost black types of rock with little internal cohesion, but no dust was detected.

[31][32] An unanticipated side effect from the Hayabusa2 thrusters revealed a coating of dark, fine-grained red material.

[34] The surface has one artificial crater, which was intentionally formed by the Small Carry-on Impactor (SCI), which was deployed by Hayabusa2.

The high number of boulders is explained with a catastrophic disruption of Ryugu's larger parent body.

[37] In September 2022 the Hayabusa 2 initial Analysis Stone Team announced the results of their study, which includes:[38] The deuterium-rich and nitrogen-15-rich isotopic compositions of fine-grained minerals and organics suggests that the parent body of Ryugu formed in the outer Solar System.

[39] Titanium, chromium and molybdenum isotopic anomalies provide more evidence that ties Ryugu's origin to the outer Solar System.

[40] Based on preserved magnetism in the samples researchers concluded that the parent body of Ryugu was probably formed in the darkness of nebular gas.

[38] The Hayabusa2 sample capsule was significantly upgraded from Hayabusa, to preserve water, light organics, gases, and other volatiles.

[48] The lower-than-expected water signature seen by Hayabusa2 instruments was the result of space weathering, producing a dehydrated rind.

[38] An international team found particles in the samples that contained small amounts of material unaltered by water.

Unlike previous instances when nucleobases and vitamins were found in certain carbon-rich meteorites, the samples were collected directly from the asteroid and delivered to Earth in sealed capsules, which meant Earthside contamination was not possible.

[60][61] NanoSIMS-based analysis at the Carnegie Institution found that the Ryugu samples contained grains older than the solar system.

[62] Researchers using the particle accelerator in J-PARC, used Muon beams to analyse the chemical composition of the samples.

The researchers found a similar composition when compared to CI chondrites, but a 25% lower oxygen abundance relative to silicon for the Ryugu samples.

The Japan Aerospace Exploration Agency (JAXA) spacecraft Hayabusa2 was launched in December 2014 and successfully arrived at the asteroid on 27 June 2018.

[70] On 3 October 2018, the German-French Mobile Asteroid Surface Scout (MASCOT) lander successfully arrived on Ryugu, ten days after the MINERVA rovers landed.

[72] The second sampling was from the subsurface, and it involved firing a large copper projectile from an altitude of 500 metres to expose pristine material.

[13] On 6 December 2020 (Australian time), a capsule containing the samples landed in Australia and after a brief search was retrieved.