Extrasolar Volcanoes May Soon be Detectable

Article written: 7 Sep , 2010
Updated: 24 Dec , 2015


We’ve all seen pictures of erupting terrestrial volcanoes from space, and even eruptions on Jupiter’s moon Io in the outer solar system, but would it be possible to detect an erupting volcano on an exoplanet? Astronomers say the answer is yes! (with a few caveats)

It’s going to be decades before telescopes will be able to resolve even the crudest surface features of rocky extrasolar planets, so don’t hold your breath for stunning photos of alien volcanoes outside our solar system. But astronomers have already been able to use spectroscopy to detect the composition of exoplanet atmospheres, and a group of theorists at the Harvard-Smithsonian Center for Astrophysics think a similar technique could detect the atmospheric signature of exo-eruptions.

By collecting spectra right before and right after the planet goes behind its star, astronomers can subtract out the star’s spectrum and isolate the signal from the planet’s atmosphere. Once this is done, they can look for evidence of molecules common in volcanic eruptions. Models suggest that sulfur dioxide is the best candidate for detection because volcanoes produce it in huge quantities and it lasts in a planet’s atmosphere for a long time.

Still, it won’t be easy.

“You would need something truly earthshaking, an eruption that dumped a lot of gases into the atmosphere,” said Smithsonian astronomer Lisa Kaltenegger. “Using the James Webb Space Telescope, we could spot an eruption 10 to 100 times the size of Pinatubo for the closest stars,” she added.

To be detected, exoplanet eruptions would have to be 10 to 100 times larger than the 1991 eruption of Mt. Pinatubo shown here. Image source: USGS

In 1991 Mount Pinatubo in the Philippines belched 17 million tons of sulfur dioxide into the stratosphere. Volcanic eruptions are ranked using the Volcanic Explosivity Index (VEI). Pinatubo ranked ‘colossal’ (VEI of 6) and the largest eruption in recorded history was the ‘super-colossal’ Tambora event in 1815. With a VEI of 7 it was about 10 times as large as Pinatubo. Even larger eruptions (more than 100 times larger than Pinatubo) on Earth are not unheard of: geologic evidence suggests that there have been 47 such eruptions in the past 36 million years, including the eruption of the Yellowstone caldera about 600,000 years ago.

The best candidates for detecting extrasolar volcanoes are super-earths orbiting nearby, dim stars, but the Kaltenegger and her colleagues found that volcanic gases on any earth-like planet up to 30 light years away might be detectable. Now they just have to wait until the James Webb Space Telescope is launched 2014 to test their prediction.

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9 Responses

  1. Astrofiend says


  2. Jon Hanford says

    An interesting premise and some exciting possibilities! Preprint posted here: http://arxiv.org/ftp/arxiv/papers/1009/1009.1355.pdf


    To be detected, exoplanet eruptions would have to be 10 to 100 times larger than the 1991 eruption of Mt. Pinatubo shown [above].

    Either that or a Doomsday Device. Quote from the end line in Beneath the Planet of the Apes:

    In one of the countless billions of galaxies in the Universe, lies a medium-sized star, and one of its satellites, a green and insignificant planet, is now dead.

    Maybe that’s why we have not yet detected any alien civilizations.

  4. SteveZodiac says

    I wonder if Herschel could do this already?

  5. Lawrence B. Crowell says

    Maybe by the same token we can detect whether a planet with intelligent life has a nuclear war.


  6. Jon Hanford says


    “Maybe by the same token we can detect whether a planet with intelligent life has a nuclear war.”

    In a paper earlier this year Dr Richard Carrigan of FermiLab discussed the possibility of searching for ETI by (among other things) closely examining exoplanet atmosheres. Section 5 of his paper briefly looks at current studies of exoplanet atmospheres and explores more deeply the challenges of using this technique to search for ETI( the paper mentions CFCs like Freon as possible markers) . The paper explores varied ETI search strategies, but detailed studies of exoplanet atmospheres is noted as being the closest to fruition.

    Starry Messages: Searching for Signatures of Interstellar Archaeology: http://arxiv.org/PS_cache/arxiv/pdf/1001/1001.5455v1.pdf

  7. Jon Hanford says

    last line should read “…detailed studies of exoplanet atmospheres *are* noted as being the closest to fruition.”

  8. Lawrence B. Crowell says

    I figured somehow pollution would come into that picture. It makes one think that the oldest idea for interplanetary communications is the best. In the late 19th century somebody proposed diffing huge canals in the Sarah desert in the configuration of the Pythagorean theorem diagram. These canals are then filled with something flammable and torched. If by that century’s logic about mars, then if martians happened to be looking at Earth they would see this. HG Wells painted a darker side of this idea, and Hawking in our age has curiously come out with much the same. Anyway, puting into solar orbit large masking shields could be done in a way as to send a message.


  9. Lawrence B. Crowell says

    In the above diffing was to mean digging.

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