Six years of observations of the second planet from the Sun by ESA’s Venus Express show that changes in the planet’s atmosphere could be the result of volcanic activity.
Venus is covered in hundreds of volcanoes, but whether they remain active today is much debated. 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.
Now, an analysis of sulphur dioxide concentration in the upper atmosphere provides another clue.
“If you see a sulphur dioxide increase in the upper atmosphere, you know that something has brought it up recently, because individual molecules are destroyed there by sunlight after just a couple of days,” said Dr Emmanuel Marcq of Laboratoire Atmosphères in Milieux, France, lead author of a paper published in the journal Nature Geoscience.
“A volcanic eruption could act like a piston to blast sulphur dioxide up to these levels, but peculiarities in the circulation of the planet that we don’t yet fully understand could also mix the gas to reproduce the same result,” explained study co-author Dr Jean-Loup Bertaux.
Venus has a ‘super-rotating’ atmosphere that whips around the planet in just four Earth-days, much faster than the 243 days the planet takes to complete one rotation about its axis. Such rapid atmospheric circulation spreads the sulphur dioxide around, making it difficult to isolate any individual points of origin for the gas.
The researchers speculate that if volcanism was responsible for the initial increase, then it could come from a relatively gentle increased output of several active volcanoes rather than one dramatic eruption.
“Alternatively, and taking into account the similar trend observed by Pioneer Venus (orbited the planet from 1978 to 1992), it’s possible that we are seeing decadal-scale variability in the circulation of the atmosphere, which is turning out to be even more complex than we could ever have imagined,” Dr Bertaux said.
“By following clues left by trace gases in the atmosphere, we are uncovering the way Venus works, which could point us to the smoking gun of active volcanism,” said Dr Håkan Svedhem, ESA’s Project Scientist for Venus Express.
Bibliographic information: Emmanuel Marcq et al. Variations of sulphur dioxide at the cloud top of Venus’s dynamic atmosphere. Nature Geoscience, published online December 02, 2012; doi: 10.1038/ngeo1650