At Mercury's poles there are large reservoirs of water ices that are never exposed to direct sunlight, which has an estimated mass of about 0.025–0.25% the Antarctic ice sheet. Having almost no atmosphere to retain heat, Mercury has surface temperatures that change wildly during the day, ranging from 100 K (−173 ☌ −280 ☏) at night to 700 K (427 ☌ 800 ☏) during sunlight across the equator regions. Mercury has a dynamic magnetic field with a strength about 1% of that of Earth's and has no natural satellites.Īccording to current models, Mercury may have a solid silicate crust and mantle overlying a solid outer core, a deeper liquid core layer, and a solid inner core. Despite being the smallest planet in the Solar System with a mean diameter of 4,880 km (3,030 mi), 38% of that of Earth, Mercury is dense enough to have roughly the same surface gravity as Mars. These features are well preserved since the planet has no geological activity and an extremely tenuous atmosphere called an exosphere. It is a terrestrial planet with a heavily cratered surface due to overlapping impact events. Mercury is the first planet from the Sun and the smallest in the Solar System.

Spinning earth animation