Mars had an oxygen-rich atmosphere around 4 billion years ago
13
All of the Earth's continents are wider at the north than in the south - and nobody knows why.
194
Only 55% of Americans know that the sun is a star.
986
A 100-pound person on Earth would weigh 38 pounds on Mars.
102
There are two golf balls sitting on the moon.
721
Astronauts get taller when they are in space.
224
More than 20 million meteoroids enter Earth's atmosphere every day.
139