An American astronomer who in August 1877 discovered two moons around Mars. He called them Deimos and Phobos, 'fear' and 'terror', the two horses that pulled the chariot of Ares (Mars) in Greek mythology.

He was deliberately searching Mars for such a thing. He first saw one on the 11th of August at about 2.30 a.m. (so what I presume we non-astronomers would call the morning of the 12th). Poor weather delayed him until the 16th, when he confirmed the observation. Now that he could predict its location, he watched for it on the 17th, and in so doing detected another one on an orbit further in.

Hall was born in Goshen, CT, on 15 October 1829, and was apprenticed as a carpenter. He joined the Harvard Observatory in 1856 and in 1862 went to the U.S. Naval Observatory, where he became professor of mathematics in 1864. Their 26-inch "Great Equatorial" refracting telescope was the largest of its kind in the world.

His discovery made him (and the Naval Observatory) famous. It was one of the great astronomical discoveries of the age. In 1879 he was awarded the Gold Medal of the Royal Astronomical Society, and in 1896 the Légion d'Honneur. (His descendants presented the medals to his observatory in 1997 and 1998.) He retired in 1893 and died in 1907. His son, Asaph Hall Jr, also worked for the observatory between 1882 and 1929.

In fiction, he was beaten by a good century and a half. In Gulliver's Travels the inhabitants of the Floating Island of Laputa are described as having observed two satellites of Mars. The orbits Swift describes for them are not dissimilar to the real ones.

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