Composite image of the north pole of Mercury. Red are the areas of permanent shadow; yellow delineates radar bright deposits mapped from Earth. Data are plotted on a photomosaic of MESSENGER images. NASA Mercury – the planet, not the element – was in the news this past week. For some time, we had suspected that the poles of Mercury might harbor deposits of water ice. This – on a planet so close to the Sun that the surface temperature at the equator is hot enough to melt lead! Yet like the Moon, Mercury’s spin axis is perpendicular to the plane in which it orbits the Sun. This means that large [...]
