Planetary scientists have long known that Mercury has been shrinking for billions of years. Despite being the closest planet to the Sun, its interior has been cooling down as internal heat leaks away. This means that the rock (and, within that, the metal) of which it is composed must have contracted slightly in volume.
It is unknown, however, to what extent the planet is still shrinking today – and, if so, for how long that is likely to continue. Now our new paper, published in Nature Geoscience, offers fresh insight.
