A paper soon to appear (as of September 2016)describes a dramatic event captured by the Rosetta instruments earlier in the year. As a shadowed region of the coment rotated into sunlight, it is thought that thermal stresses led to a landslide and subsequent rapid evaporation of fresh ‘ice’. Rosetta saw large increases in brightness, gas temperature and density and the number of dust particles. A few days later, astronomers on Earth noticed that the density of the comet’s coma had increased.
Click for high-resolution version of the image. Copyright image: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; all data from Grün et al (2016)