Look at the sky on Christmas Eve and you might see this comet called ISON. "Might", because astronomers are still speculating whether the comet’s nucleus is big enough to survive its closest passage to the Sun on 28 November or whether it will disintegrate. In this respect, this Hubble Space Telescope image taken on 9 October when ISON was inside Mars’s orbit is reassuring. There is no sign of fragmentation and the coma or head surrounding the comet’s nucleus is symmetric and smooth. The comet’s coma appears cyan, due to ionized gas, while the tail is reddish from dust streaming off the icy nucleus under the pressure of sunlight. The closest approach to Earth will be on 26 December at a distance of 64 million km.