James Webb telescope to reveal alien volcanoes

Image: Wade Henning/CfA

Astronomers may be decades away from being able to determine what the surface of a distant planet looks like, but they can tell us if there are volcanoes on them.

Our own solar system already provides us with insight into volcanism on other worlds, with active volcanoes on Io and Venus and the Cryovolcanoes on Saturn’s moons Titan and Enceladus and Neptune’s ice moon Triton. But scientists at the Harvard-Smithsonian Centre for Astrophysics believe that the new James Webb Space Telescope will enable them to see volcanic eruptions on the planets outside our solar system.

The sulphur dioxide released will be the clue to volcanic activity on other planets as it is released in large amounts and takes time to “˜wash out’ of the atmosphere, leaving an atmospheric signature. Mt Pinatubo in the Philippines released approximately 17 million tonnes of sulphur dioxide into the stratosphere when it erupted in 1991. The 1815 Tambora event, the largest volcanic eruption in history, was ten times more powerful.

To measure sulphur dioxide from extra-terrestrial eruptions, scientists must wait for a secondary eclipse- when the exoplanet crosses behind its star as seen from Earth. The scientists measure the light from the star and the planet, then subtract the light measured from the star during the eclipse (when the planet is hidden). The remaining light forms the planet’s signal, which can then be examined for traces of particular chemical molecules.

Eruptions the size of Mt Pinatubo or Tambora are rare, but may be more common on younger planets. Once volcanic activity is detected, the planet can then be monitored to see how frequent the eruptions are and how volcanically active the planet is.