Mercury's surface looks similar to our Moon's. Each is heavily cratered and made of rock. Mercury's diameter is about 4800 km, while the Moon's is slightly less at about 3500 km (compared with about 12,700 km for the Earth). But Mercury is unique in many ways. Mercury is the closest planet to the Sun, orbiting at about 1/3 the radius of the Earth's orbit. As Mercury slowly rotates, its surface temperature varies from an unbearably cold -180 degrees Celsius to an unbearably hot 400 degrees Celsius. The place nearest the Sun in Mercury's orbit changes slightly each orbit - a fact used by Albert Einstein to help verify the correctness of his then newly discovered theory of gravity: General Relativity. The above picture was taken by the only sp ...

This Bonsai tree was planted in 1626, and survived the atomic bomb at Hiroshima on August 6th, 1945, 68 years ago today. It was given to the people of the United States as a Bicentennial Gift in 1976.

"The ISS is the largest man made object in space. Here's how it compares to other notable objects, both real and fictional, all drawn to scale."

The ISS isn't just the largest space craft ever built, it's also the world's most expensive object. According the Government Accountability Office, it cost upwards of 100 billion dollars to complete.