September 15

1910 – A paper on cosmic radiation is published, suggesting that Earth is under constant radiation bombardment from outer space, and from sources other than the sun.
1968 – The Soviet Zond 5 spaceship is launched, becoming the first spacecraft to fly around the Moon and re-enter the Earth's atmosphere.
1998 – Jupiter's planetary rings are declared to be made of dust from the impacts of cosmic bodies that crashed into the planet's moons.