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Discovery of Phobos

Name: Discovery of Phobos
Start: 1877-08-18
Location: Washington, D.C.

When: 18 August 1877
Where: Washington, D.C.
Part of: Asaph Hall discovers Phobos, the inner moon of Mars

Asaph Hall discovered Phobos, the inner moon of Mars, on 18 August 1877 at the United States Naval Observatory in Washington, D.C.

After an unsuccessful examination in the early part of the night, Hall found the faint object some hours later, on the following side and a little north of the planet. The discovery occurred at approximately 09:14 GMT on 18 August, corresponding to 04:06 in the modern convention; contemporary sources using the pre-1925 convention recorded it as 17 August at 16:06 Washington Mean Time.

Sources

Asaph Hall Wikipedia, revision of 2026-08-31
Phobos (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.