Mercury, the closest planet to the sun, was named after the Roman messenger of the gods. It has the fastest revolution of any of the nine planets at only 87.969 Earth days. It is also a very small plant, about 40% smaller than Earth. Mercury does not have synchronous rotation, but its rotation is close enough with its revolution that a single day on Mercury lasts about 176 Earth days. Scientists speculate that millions of years ago Mercury's rotation may have been faster, perhaps closer to 8 hours per day, but the planet was slowed down by the sun. On the surface, Mercury is very similar to the moon. The planet is littered with craters, some as large as 1,300 Kilometers. The planet also has a wrinkled surface, most likely resulting from the shrinking of the planet as it cooled. One intersting feature of the planet is the Caloris Basin? This huge crater was most likely caused by the impact of an asteroid millions of years ago. The impact was so great that on the opposite side of the planet there are large outcroppings of rocks jutting from the surface.