摘要
Space missions targeting asteroids,loosely bound clumps of rock,ice,and metals,some of which are thought to pre-date the sun,are on a roll.In December 2020,the Japan Aerospace Exploration Agency(JAXA)completed a mission to scoop up a small amount of material from the asteroid Ryugu and deliver it back to Earth[1].Earlier,in October 2020,the US National Aeronautics and Space Administration(NASA)acquired a sample,which will begin its return to Earth in March 2021,from the asteroid Bennu[2].Meanwhile,the China National Space Administration(CNSA)has proposed a similar mission to retrieve a sample from the near-Earth asteroid Kamo‘oalewa[3],and a joint NASA–European Space Agency(ESA)effort is preparing a mission to demonstrate the feasibility of nudging an asteroid away from a collision course with Earth[4].
