Today in the history of astronomy, the smaller of Mars’ two tiny moons is spotted from the U.S. Naval Observatory.
Asaph Hall won several awards after his discovery of Phobos and Deimos in 1877. Credit: Wikimedia Commons
- Asaph Hall transitioned from Harvard Observatory to the U.S. Naval Observatory in Washington, D.C., in 1862, eventually overseeing the 26-inch Clark refractor.
- During the 1877 close opposition of Mars, Hall utilized the 26-inch refractor to search for Martian moons.
- Hall initially sighted a Martian moon on August 11, 1877, but adverse weather conditions hampered observation.
- Following encouragement from his wife, Hall successfully rediscovered and confirmed the existence of Deimos, the smaller of Mars’ two moons, on August 12, 1877.
After spending the 1850s at Harvard Observatory calculating orbits, Asaph Hall became an assistant at the U.S. Naval Observatory at Washington, D.C., in 1862. He was quickly promoted, and by 1873 had not only held several scientific discussions with Abraham Lincoln during the president’s visits to the observatory, but had also been put in charge of the 26-inch Clark refractor. It was with this tool that Hall searched during an 1877 close opposition of Mars for the Red Planet’s much-speculated moons. On Aug. 11, he spotted a moon, but lost sight of it due to the poor weather that the observatory’s “Foggy Bottom” location was famous for. Frustrated, he nearly gave up the search, but his wife convinced him to keep looking. The next evening, he conclusively discovered Deimos, the smaller of Mars’ two moons.
