American astronomer Asaph Hall discovered the moon of MarsPhobosOn this day August 17 but long ago in 1877, Hall was working at the US Naval Observatory in Washington and looking through his 26-inch reflecting telescope, then the largest in the world, when he first discovered the moon.
According to Space, six days ago, he discovered another smaller moon that he first described as a “faint star near Mars.” After further examination, he not only realized that this star was actually the Martian moon Deimos, but discovered Also, a second, larger moon is now known as Phobos.
Both discoveries were announced the next day on August 18, 1877, and Phobos is the largest moon of Mars, currently located at seven hours and 39 minutes from the Red Planet and is already approaching 0.7 inches per year.
The Moon measures 10 x 14 x 11 miles (17 x 22 x 18 km) across Mars and orbits it three times each Mars day at a distance of about 3,700 miles (6,000 km).