Recent data from the planet Mercury indicates that water ice is found near its poles. What does this mean for the Moon?
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 craters near Mercury’s poles lie in permanent shadow (“shivering” around -170° C), unaffected by the Sun’s searing heat (equivalent to more than eleven times the solar flux we get at the Earth). As on the Moon, these permanently shadowed areas get heat from only two sources – the 3 K background heat of space, created during the Big Bang some 15 billion years ago, and whatever heat is ...