📅 11 August 1877
Hall spotted the first of Mars's two known moons; the recorded date is 11 August in US local time.
📅 11 August 1877
Finding Deimos overturned the assumption that Mars had no detectable satellites.
📅 11 August 1877
Accounts of the discovery describe Angelina Hall urging her husband to continue looking for Martian moons.
📅 11 August 1877
Repeated observing established that the object was associated with Mars.
📅 17 August 1877
Hall found the inner Martian moon days after identifying Deimos.
📅 17 August 1877
Phobos's appearance completed the discovery of the planet's two familiar moons.
📅 17 August 1877
The newly discovered moon orbits nearer to Mars than Deimos.
📅 17 August 1877
With both moons identified, astronomers could study their motions around Mars.
