Eros
Eros was the first near-Earth asteroid to be discovered, turning up accidentally on a photograhic plate in 1898. It was also the first asteroid to be imaged by an orbiting spacecraft, having been subject to a photoshoot by the NEAR spacecraft in 1998, a century after its discovery. And to make it a trifecta of firsts, the spacecraft also landed on Eros in 2001—the first landing of a spacecraft on an asteroid. And before we could use radar to look at cosmic objects, astronomers used Eros to calculate the astronomical unit, a well-used yardstick for the Solar System.
Correction: A previous version of this slide said that a spacecraft’s landing on Eros allowed astronomers to calculate the AU; actually, that calculation occurred earlier.
