Mars had an oxygen-rich atmosphere around 4 billion years ago
13
Summer on Uranus lasts for 21 years.
358
It takes a photon 170,000 years to travel from the core of the Sun to the surface, but only 8 minutes to travel the rest of the way to Earth.
6
The light hitting the earth right now is 30 thousand years old.
163
The Sun and Moon appear to be the same size because the moon is 400 times smaller than the Sun, but 400 times closer to Earth.
13
Saturn's moon, Mimas, not only looks like the Death Star, it also has a Pac Man heat signature.
15
An organisation called Mars One is planning to establish a permanent colony of humans on Mars by 2023.
9