Venus Express has detected the molecule hydroxyl on another planet for the first time. This detection gives scientists an important new tool to unlock the workings of Venus’s dense atmosphere.

When atoms combine to form molecules in the upper atmosphere, energy may be released in the form of photons, causing the atmosphere to weakly glow. Called “dayglow” over the dayside and “nightglow” over the nightside, such emissions of light are seen over Earth, Mars, and Venus.

One year has passed since 11 April 2006, when Venus Express, Europe's first mission to Venus and the only spacecraft now in orbit around the planet, reached its destination. Since then, this advanced probe, born to explore one of the most mysterious planetary bodies in the Solar System, has been revealing planetary details never caught before.