This artist's conception shows an extremely volcanic moon orbiting a gas giant planet in another star system.
Credit: Wade Henning
SYDNEY: Astronomers may soon be able to detect volcanic activity on planets outside our Solar System, providing further insight into ‘Earth-like’ alien worlds, according to a recent paper.
When large, explosive volcanic eruptions occur, they emit high quantities of sulphur dioxide into the stratosphere. Without an eruption, however, sulphur dioxide only occurs in an Earth-like stratosphere in very small amounts.
Now scientists have developed a model for eruptions on an Earth-like exoplanet, finding that the presence of volcanic sulphur dioxide could be used to remotely detect a volcanic eruption, despite the fact that technology for imaging the surface of an exoplanet remains decades away.
Catching that first glimpse
“Measuring volcanic activity can be just one new tool in our near-term toolbox, along with atmospheric spectra, to get an early ‘first glimpse’ into a planet's behaviour, long before we can see anything like the pattern of oceans, mountain ranges, islands, or continents,” said co-author, Lisa Kaltenegger, from the Harvard-Smithsonian Centre for Astrophysics in Boston, Massachusetts.
To look for volcanic sulphur dioxide, astronomers would rely on a technique known as the secondary eclipse, which requires the exoplanet to cross behind its star, as seen from Earth.
By collecting light from the star and planet, then subtracting it from the star (while the planet is hidden), astronomers are left with the signal from the planet alone. They can then search that signal for signs of particular chemical molecules.
Finding planets like our own
“If we can find volcanoes on other planets, we can figure out if they are similar to our own planet when it was young,” said Kaltenegger.
“Or, if [the exoplanet] is as old as the Earth, but still has huge volcanoes, the question would be, why is that so? What makes that ‘Earth’ different from ours?”
Scientists think that the Earth was much more volcanic when it was ‘young’, and that this helped bring the temperature into a habitable range.
NASA to test theory
Brad Carter from the University of Southern Queensland said the paper presents a useful method for studying or detecting terrestrial planets orbiting “even nearby” stars.
“Given the important role of volcanism in the development of Earth's atmosphere and climate, this paper suggests a practical new way to compare rocky extrasolar planets with our own world,” said Carter.
“The line of research taken in this paper suggests an extension of the method of 'comparative planetology' that has already been successful in understanding the worlds of our Solar System using comparisons of different planets," he said.
Kaltenegger hopes to test the theory, and several others, when NASA launches the James Webb Space Telescope (JWST) in 2014.
