It is not (it has a 88d year, and a 58.65d.. day[0]) , we just had a post about it - if you travel at 4kph you can chase the sun.. A Mercury Rover Could Explore the Planet by Sticking to the Terminator (18 points, 1 week ago, 6 comments) https://news.ycombinator.com/item?id=47720941

[0]: https://en.wikipedia.org/wiki/Mercury_(planet)