Volcanoes can be an indication of a planet that can support life. There are studies that show that lightning together with the chemicals volcanoes produce may have provided the spark that produced life on early Earth. This experiment called the Miller-Urey experiment has been shown to students for years from 1953 to mimic the chemical reactions that could have occurred on early Earth in vapour rich volcanic eruptions. The experiment uses methane, ammonia, water vapour and hydrogen in a closed experiment simulating the early Earth’s atmosphere and then using a lightning like spark to stimulate organic compounds.
Volcanoes are already known to exist on other bodies in the solar system i.e. Io. Io is a moon around Jupiter and is very active, much more active than the Earth. It looks like a pizza mainly because of the many volcanic eruptions. So, if volcanoes can exist in the solar system then it would seem logical that they could exist on exoplanets around stars in this galaxy and others. That doesn’t necessarily mean that they exist of course so we have to detect them.
To see a volcano on a distant exoplanet it would have to be a massive eruption that produced a lot of gases that would eventually find their way into the atmosphere . The James Webb telescope would be the most likely telescope to be used for dictation and could spark an eruption which would be hundreds of times the size of the Pinatubo eruption and would only be seen on the star’s closest to the Earth.
Atmospheres of exoplanets have been analysed but information on the surface of exoplanets won’t be available for another 10 years or so. So, at the moment we would be able to detect volcanoes by looking at the atmosphere and not by observing the surface. The main chemical looked for would be sulphur dioxide because a large explosive eruption would produce vast amounts which could be measurable.
A volcanic eruption as large as Pinatubo would be infrequent and therefore a lot of Earth sized planets would have to be monitored over many years to record one of these eruptions. These type of eruptions may be more or less frequent than a similar type of eruption on the Earth.
To detect sulphur dioxide and therefore a volcano, astronomers would rely on a technique known as a secondary eclipse. This requires the exoplanet to cross behind this star as seen from the Earth. The light from the star and planet is collected and then the light from the star is subtracted from the total of the star’s light and the planets light and therefore a signal from the planet alone is found. This signal is then searched for signs of chemicals.
The best scenario would be for an Earth or super Earth to orbit alpha centauri so that a large signal could be observed. It is estimated that any earthlike planet which is less than 30 light years away could show signs of volcanism when studied by the James Webb telescope.
Discoveries are happening quicker than ever in the exoplanets field and therefore volcano spotting may not be too far in the future.