Earth Planet. Sci. Lett. doi:10.1016/j.epsl.2009.04.037 (2009)

Baked by the Sun and blasted by impacts, Mercury is thought to have lost much of its volatile content — such as water vapour and carbon dioxide — early in its history. But its interior may have been bubblier than thought, according to Laura Kerber of Brown University in Providence, Rhode Island, and her colleagues. Using observations from the MESSENGER spacecraft, the researchers spotted the remnants of a volcano that they say was driven by explosive magma with high volatile concentrations.

Credit: ELSEVIER

The large size of the volcanic dome (marked by box) suggests a volatile content comparable to that seen in eruptions on Earth. The discovery favours the idea that Mercury formed from volatile-rich planetesimals from the outer Solar System that migrated inwards.