Space Smells Like Seared Steak: Astronauts have reported that space smells like hot metal or seared steak when they return to the confines of their spacecraft after a spacewalk.
Venus Spins Backwards: Unlike most planets in the solar system, Venus rotates in the opposite direction to its orbit around the Sun, meaning the Sun rises in the west and sets in the east.
Neutron Stars Can Spin at 600 Times per Second: Neutron stars, the remnants of supernova explosions, can rotate incredibly rapidly, sometimes making hundreds of revolutions per second.
There Are More Stars in the Universe Than Grains of Sand on Earth: Estimates suggest there are about 10^22 to 10^24 stars in the observable universe, vastly outnumbering the grains of sand on all the Earth's beaches.
Space Is Completely Silent: Because space is a vacuum with no medium for sound waves to travel through, it is utterly silent, unlike any environment on Earth.
A Day on Mercury Lasts Longer Than Its Year: Mercury has a very slow rotation relative to its orbit around the Sun, so one day (sunrise to sunrise) on Mercury is about 176 Earth days, while its year is only about 88 Earth days.
There Is a Planet Made of Diamonds: 55 Cancri e, a super-Earth exoplanet, is believed to have a carbon-rich composition that could include large quantities of diamond.
A Spoonful of a Neutron Star Would Weigh About a Billion Tons: Neutron stars are incredibly dense, so much so that a small amount of neutron star material, roughly the size of a sugar cube, would weigh billions of tons on Earth.
The Largest Volcano in the Solar System is on Mars: Olympus Mons on Mars is the tallest volcano and mountain in the solar system, standing about 13.6 miles (22 kilometers) high, nearly three times the height of Mount Everest.