Yet more persuasive evidence has arrived from Mars supporting the theory that the planet had a very wet past indeed. Newly analysed images from Europe's Mars Express orbiter show an area known as Candor Chasma, a small part of the great Martian rift valley Valles Marineris. The Valles Marineris is as long as the United States and in places plunges miles down, but in the Candor Chasma region, scientists have spotted some intriguing geological features. Seen in the images is a hilly landscape composed of alternating bands of light and dark coloured rock. It could have been wind or volcanic forces which forged these features, but water (and water in vast quantities) seems the most likely agent. Further supporting this contention, the striped landscape also boasts a network of cracks, known as joints. These are surrounded by prominent haloes of bleached rock. The same features have been identified here on Earth and what this seems to indicate, say a team from the University of Arizona, is "a clear indication of chemical interactions between fluids circulating within the fracture and the host rock". Most promisingly, these features are millions of years old and have been exposed slowly by the elements. Locked underground at the time the water was present in liquid form, this would have provided a very hospitable place for primitive life to take hold. The BBC has the full story.