Have Venusian volcanoes been caught in the act?

Six years of observations by ESA's Venus Express have shown large changes in the sulphur dioxide content of the planet's atmosphere, and one intriguing possible explanation is volcanic eruptions. The thick atmosphere of Venus contains over a million times as much sulphur dioxide as Earth's, where almost all of the pungent, toxic gas is generated by volcanic activity. Most of the sulphur dioxide on Venus is hidden below the planet's dense upper cloud deck, because the gas is readily destroyed by sunlight. That means any sulphur dioxide detected in Venus' upper atmosphere above the cloud deck must have been recently supplied from below. Venus is covered in hundreds of volcanoes, but whether they remain active today is much debated, providing an important scientific goal for Venus Express. The mission has already found clues pointing to volcanism on geologically recent timescales, within the last few hundreds of thousands to millions of years. A previous analysis of infrared radiation from the surface pointed to lava flows atop a volcano with a composition distinct from those of their surroundings, suggesting that the volcano had erupted in the planet's recent past.