July 31

781 – The oldest recorded eruption of Mount Fuji (Traditional Japanese date: Sixth day of the seventh month of the first year of the Ten'o (天応) era).
1858 – Geologist and seismologist Richard Dixon Oldham is born. He discovered evidence for the existence of the Earth's liquid core.
1923 – Chemist Stephanie Kwolek is born. She is most known for inventing "Kevlar," a polymer solution that is five times stronger than steel and had half the density of fiberglass.
1964 – NASA's probe Ranger 7 sends back the first close-up photographs of the moon.
1971 – NASA's Apollo 15 spacecraft's astronauts become the first humans to ride in a lunar rover.
1999 – NASA intentionally crashes spacecraft "Lunar Prospector" moon, ending its mission to detect frozen water on the satellite's surface.