ESA's Venus Express is helping planetary scientists investigate whether Venus once had oceans. If it did, it may even have begun its existence as a habitable planet similar to Earth. These days, Earth and Venus seem completely different. Earth is a lush, clement world teeming with life, while Venus is hellish, its surface roasting at temperatures higher than those of a kitchen oven. But underneath it all the two planets share a number of striking similarities. Could Venus at one time have sustained life?