📅 11 Augustus 1877
Hall spotted the first of Mars's two known moons; the recorded date is 11 August in US local time.
📅 11 Augustus 1877
Finding Deimos overturned the assumption that Mars had no detectable satellites.
📅 11 Augustus 1877
Accounts of the discovery describe Angelina Hall urging her husband to continue looking for Martian moons.
📅 11 Augustus 1877
Repeated observing established that the object was associated with Mars.
