“The sun is always just about to rise. Mercury rotates so slowly that you can walk fast enough over its rocky surface to stay ahead of the dawn. (…) Mercury’s ancient face is so battered and irregular that the planet’s terminator, the zone of the breaking dawn, is a broad chiaroscuro of black and white— charcoal hollows pricked here and there by brilliant white high points, which grow and grow until all the land is as bright as molten glass, and the long day begun. This mixed zone of sun and shadow is often as much as thirty kilometers wide, even though on a level plain the horizon is only a few kilometers off. But so little of Mercury is level. All the old bangs are still there, and some long cliffs from when the planet first cooled and shrank. In a landscape so rumpled the light can suddenly jump the eastern horizon and leap west to strike some distant prominence. Everyone walking the land has to attend to this possibility, know when and where the longest sun reaches occur—and where they can run for shade if they happen to be caught out.”
In case you don’t recognise it, this is the prologue of Kim Stanley Robinson’s 2312, which starts, as you can guess, on Mercury, in that merveille of engineering that is the Mercurian city of Terminator. In the first pages he describes people walking westward on the surface chasing the rising sun. Since reading that book I’ve kept wondering how would it be living over there and looking at sky. Terraforming apart, Mercury’s surface would not look too different from the Moon, nor would the sky. Neither of them has any atmosphere, and therefore what I have already said in the case of the Moon does apply. 2312‘s sunwalkers would have admired a Sun on average 2.5 times bigger than it appears from Earth, and 6 times as bright.
Mercury is less known compared to other planets – only two spacecrafts have visited it so far. And, while we waiting for Terminator to be built, have a look at the planet’s surface at the moment.