August 17

1877 – Astronomer Asaph Hall discovered Mars' second moon, which he named "Phobos." (He had discovered "Deimos" five days earlier).
1958 – The world's first attempt at lunar orbit, a probe named "Pioneer 0", is launched by the United States, but unfortunately fails.
1970 – Spacecraft "Venera 7" is launched, becoming the first of its kind to successfully transmit data from the surface of another planet - Venus.