The first results from ESA’s Venus Express give weight to the popular theory that our planetary twin once had a similar climate to Earth’s, only for it to evolve into the hell-like place it is today. Among the results is proof that Venus has been steadily losing water as the result of a runaway greenhouse effect, and the first concrete piece of evidence that the planet is home to bursts of high-altitude lightning.

Formed at roughly the same time, orbiting closer than any two Solar System planets and possessing the same radius to within 5%, it is hardly surprising that Earth and Venus are often referred to as twins. But Venus’s barren surface coupled with temperatures reaching 450°C — higher even than Mercury — makes its present climate a far cry from cool, wet Earth.