Steve is a "remarkably common" gas ribbon in the upper atmosphere.
Kuki Gallmann, author of I Dreamed of Africa, is flown to hospital after an ambush.
The Cassini satellite puts itself on a trajectory that will take it to destruction in September.
Answering critics of a radical redesign for airports
Satellites to monitor every land volcano on Earth
Antarctic scientists stumble across an ancient stench
Stunning footage shows feeding and social habits
Scottish fossils shed light on four-limbed land animals
Other zoo animals get on with it while we wait for April the giraffe
Programmes, video and downloads: Solutions to air pollution from across the world
Will and Kate on their new mental health campaign