Billions of years ago, Venus may have harbored life-giving habitats similar to those on the early Earth. Today, Earth's twin is a planet knocked upside down and turned inside out. Its burned-out surface is a global fossil of volcanic destruction, shrouded in a dense, toxic atmosphere. Scientists are now unveiling daring new strategies to search for clues from a time when the planet was alive.

Four billion years ago, Venus held the promise of supporting life. Then it entered a death-spiral of ever-increasing heat. But, 50 km above its desolate surface, the cool cloud tops of Venus offer a potential refuge. Solar-powered ships and habitats could effortlessly float there, sailing the winds that circle the globe. That has inspired scientists to take the first steps toward settling Venus.

For more than 100 years astronomers have seen dark patches swirling in the clouds of Venus, visible only in ultraviolet light. Could there be life-forms thriving in the balmy zone 50km above the hellish surface? On Earth, researchers find life everywhere they look, including acid-loving bacteria that could easily live in Venus' air. How will the experts investigate this fascinating possibility?

At Venus' surface, the temperature is twice as high as in a pizza oven. The atmospheric pressure would make you feel like being 1 kilometer deep in Earth's oceans. Yet visionary engineers are pushing the boundaries of materials science to build probes that can deliver data from the depths of this crushing inferno. Experts describe their battle strategies and technologies.

Venus is virtually a twin of Earth in size, mass and composition; much more like our planet than is Mars. Yet it has gone down a completely different - and deadly - evolutionary path. Experts share valuable lessons from Venus on the origins of life, acid rain, ozone loss, global warming and other questions. They make the passionate case for further exploring Earth's "evil twin sister."