All the while the stars would be moving three times faster across the sky. Observers at other points on Mercury's surface would see different but equally bizarre motions. The temperature on Venus is slightly hotter but very stable. Mercury is the second densest major body in the solar system, after Earth. This indicates that Mercury's dense iron core is relatively larger than Earth's, probably comprising the majority of the planet.
Mercury therefore has only a relatively thin silicate mantle and crust.
Mercury's interior is dominated by a large iron core whose radius is 1800 to 1900 km. At least some of the core is probably molten. Mercury actually has a very thin atmosphere consisting of atoms blasted off its surface by the solar wind. Because Mercury is so hot, these atoms quickly escape into space. Thus in contrast to the Earth and Venus whose atmospheres are stable, Mercury's atmosphere is constantly being replenished.