Volcanoes are in the news again! The Bardarbunga volcano in Iceland has recently started rumbling, prompting an evacuation of the local area, and fears of a repeat of the chaos caused 4 years ago by the ash cloud from another Icelandic volcano, Eyjafjallojokull.
Iceland is one of the most actively volcanic regions on Earth - but recent observations of volcanic eruptions on one of our solar system neighbours, Jupiter's moon Io, make Iceland's eruptions look like mere bonfires. Scientists recently reported observations of three massive eruptions within just 2 weeks on this violent and restless moon, at temperatures much higher than on Earth.
Colourful volcanic deposits
Io is the innermost of Jupiter's 4 large moons and can easily be seen with a small telescope like mine. It's slightly larger than our own Moon, and is the most volcanically active body known. In fact, it is the only place in the Solar System other than the Earth known to have eruptions of hot lava, and because of its low gravity, the volcanic material is thrown high above the surface. You can see from the photo above that it looks very different from our moon – the various colours are deposits of sulphur in different forms, with the orange parts indicating the areas of most recent volcanic activity.
So why is Io so active, when our own Moon is dead and barren? The answer lies in its closeness to Jupiter and its position between Jupiter and that planet's other large moons. It's about the same distance from Jupiter as the Moon is from Earth, but of course Jupiter is far, far more massive than the Earth, so it exerts a huge gravititional pull on Io. Added to this, on Io's other side are 3 other large moons, Europa, Ganymede and Callisto - their gravity also has an effect on Io, which is stretched and pulled in strongly and in many different directions as these moons orbit on their own paths around Jupiter. All this stretching and pulling keeps Io constantly hot and changing shape, hence the many lava flows and volcanoes.
Astronomers announced this month that they observed 3 massive eruptions on Io within a two-week time span. Each of these eruptions produced enough magma to cover over 130 square kilometers with a layer 10 meters thick. Eruptions of such power have never before been observed on Io, and so it's incredible that not one but three were observed in such a short period.
Although observation of such events on Io is rare, in fact astronomers have not had many opportunities to look closely at this moon so they are not sure whether or not this is normal behaviour. The Voyager (1979) Galileo (1995-2003), Cassini-Huygens (2000) and New Horizons (2007) spacecraft missions took some close-up images, but since then the only way of observing this intriguing satellite has been with telescopes on or near the Earth, and the large professional telescopes capable of imaging such a distant moon in some detail have many other demands on their time. As you can see, the level of detail in images from ground-based telescopes is much lower than that from fly-by spacecraft.
Clues about formation of the Earth?
Planetary geologists are keen to keep observing Io because the study of volcanism on Io could give important clues to the processes which shaped the Earth and other rocky planets early on. For example, the temperature of Io's largest observed eruption is estimated to be much higher than that of current volcanic eruptions on the Earth, and scientists have suggested that the composition of Io's magma today is similar to Earth's magma when our home planet was being formed.
http://www.jpl.nasa.gov/news/news.php?release=2014-260
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jup_Io
http://phys.org/news/2012-10-io-insane-volcanic-comfort-earth.html
http://www.universetoday.com/94238/first-ever-geologic-map-of-io-425-volcanoes-no-craters/
http://www.bbc.co.uk/science/space/solarsystem/moons/io_%28moon%29
1. NASA/JPL/University of Arizona
2. NASA/JPL
3. NSF/NASA/JPL-Caltech//UC Berkeley/Gemini Observatory