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Discovery of Deimos

Name: Discovery of Deimos
Start: 1877-08-12
Location: Washington, D.C.

When: 1877-08-12
Where: Washington, D.C.
Part of: Asaph Hall discovers Deimos, the outer moon of Mars

Asaph Hall discovered Deimos on August 12, 1877, at the United States Naval Observatory in Washington, D.C., using the 26-inch telescope.

Hall found a faint object on the following side and a little north of the planet during his search for Martian moons. The discovery occurred at about 07:48 UTC, though contemporary sources using the pre-1925 convention give the time as 11 August 14:40 Washington mean time.

Sources

Asaph Hall Wikipedia, revision of 2026-08-31
Deimos (moon) Wikipedia, revision of 2026-10-07

Machine-drafted from the cited Wikipedia passages and checked by a reviewing model, not by a human editor. Every passage cites the revision it was written from; dates and places follow those passages.