25143 Itokawa

Itokawa was discovered on 26 September 1998 by astronomers with the Lincoln Near-Earth Asteroid Research (LINEAR) program at Lincoln Laboratory's Experimental Test Site near Socorro, New Mexico, in the United States. It was given the provisional designation . The body's observation arc begins with its first observation by the Sloan Digital Sky Survey just one week prior to its official discovery observation. The minor planet was named in memory of Japanese rocket scientist Hideo Itokawa (1912–1999), who is regarded as the father of Japanese rocketry. The official was published by the Minor Planet Center on 6 August 2003 (). == Orbit and classification ==

Itokawa belongs to the Apollo asteroids. They are Earth-crossing asteroids and the largest dynamical group of near-Earth objects with nearly 10,000 known members. Itokawa orbits the Sun at a distance of 0.95–1.70 AU once every 18 months (557 days; semi-major axis of 1.32 AU). Its orbit has an eccentricity of 0.28 and an inclination of 2° with respect to the ecliptic. It has a low Earth minimum orbital intersection distance of , which corresponds to 5.1 lunar distances. == Exploration ==

In 2000, it was selected as the target of Japan's Hayabusa mission. The probe arrived in the vicinity of Itokawa on 12 September 2005 and initially "parked" in an asteroid–Sun line at , and later , from the asteroid (Itokawa gravity was too weak to provide an orbit, so the spacecraft adjusted its orbit around the Sun until it matched the asteroid's). Hayabusa landed on 20 November for thirty minutes, but it failed to operate a device designed to collect soil samples. On 25 November, a second landing and sampling sequence was attempted. The sample capsule was returned to Earth and landed at Woomera, South Australia on 13 June 2010, around 13:51 UTC (23:21 local). On 16 November 2010, the Japan Aerospace Exploration Agency reported that dust collected during Hayabusa's voyage was indeed from the asteroid. Surface features Names of major surface features were proposed by Hayabusa scientists and accepted by the Working Group for Planetary System Nomenclature of the International Astronomical Union. The following tables list the names of geological features on the asteroid. No naming conventions have been disclosed for surface features on Itokawa. Craters Ten impact craters on the surface of Itokawa were named on 18 February 2009. Regiones Regiones (singular: regio) are large area marked by reflectivity or color distinctions from adjacent areas in planetary geology. The following regiones have been named on Itokawa. == Physical characteristics ==

suggest that these were stand-alone bodies that came into contact later on, making the rubble pile also a likely contact binary. and Arecibo Furthermore, the density of the asteroid is too low for it to be made from solid rock. This would mean that Itokawa is not a monolith but rather a rubble pile formed from fragments that have cohered over time. Based on Yarkovsky–O'Keefe–Radzievskii–Paddack effect measurements, a small section of Itokawa is estimated to have a density of , whereas a larger section is estimated to have a density of 1.8 g/cm3. Scientists' analysis suggested that Itokawa was probably made up from interior fragments of a larger asteroid that broke apart. Another team of scientists determined that the dark iron color on the surface of Itokawa was the result of abrasion by micrometeoroids and high-speed particles from the Sun which had converted the normally whitish iron oxide coloring. The water concentrations of the Itokawa grains would indicate an estimated BSI (Bulk Silicate Itokawa) water content in line with Earth's bulk water, and that Itokawa had been a "water-rich asteroid". 2020 Hayabusa results At the 2020 Lunar and Planetary Science Conference, a third group reported water and organics, via a third Hayabusa particle- RA-QD02-0612, or "Amazon." Olivine, pyroxene, and albite contain water. Isotopic compositions indicate a clear extraterrestrial origin. 2021 Hayabusa results A further report by Daly's group was published which supported the theory that a large source of Earth's water has come from hydrogen atoms carried on particles in the solar wind which combine with oxygen on asteroids and then arrive on Earth in space dust. Using atom probe tomography the study found hydroxide and water molecules on the surface of a single grain from particles retrieved from the asteroid Itokawa by the Japanese space probe Hayabusa. Dust ponds are identified in the asteroid. They are a phenomenon where pockets of dust are seen in Celestial bodies without a significant atmosphere. Smooth deposits of dust accumulate in depressions on the surface of the body (like craters), contrasting from the Rocky terrain around them. In the Sagamihara and Muses-Sea regions of the asteroid dust ponds were identified. Dust particles had a size varying from millimeters to less than a centimeter. == See also ==