30 May

1975: On 30 May 1975, the text of the ESA Convention was approved by the Conference of Plenipotentiaries in Paris.

The European Space Agency began operations on the following day, 31 May 1975. However, the ESA Convention only officially entered into force on 30 October 1980, when France deposited its instrument of ratification.

1971: On 30 May 1971, American scientists launched the mission Mariner 9 to Mars. In November 1971, Mariner 9 arrived in orbit around the Red Planet and returned 6900 images by using its ultraviolet and infrared spectrometers and infrared radiometer.