Io is the innermost of the four great moons of Jupiter and with a diameter of 3643 kilometers slightly larger than our moon. Sulfur compounds give Io a yellowish face with orange-reddish spots - this has earned the bizarre celestial body the nickname Pizza Moon. This "pizza" is annoying: Already since 1979, it has been known from recordings of the spacecraft Voyager 1 that Io is volcanically active. The moon owes its heat to its neighbors: in its ellipsoidal orbit both the gravitational pull of Jupiter and the attraction of the neighboring moon pulls Europe to Io. As a result, the moon is constantly kneaded and heats up enormously. The result is glowing rock that leaks through volcanoes.
The giant volcano Loki Patera in focus
The most active is the volcano Loki Patera named after the Nordic god Loki. Earlier observations have shown: The crater has a diameter of 200 kilometers and houses a lava lake with a kind of island of colder material in the middle. Photographs of NASA's Galileo mission showed that the intensity of the radiation of Loki Patera increases periodically every 400 to 600 days. The reason for this was already assumed that lava spreads and renews the surface of the lake. Details of the processes in the case Loki Patera were so far not detectable because of the poor visibility of the area.
But the researchers around Katherine de Kleer of the University of California at Berkeley have now got a clear view with the Large Binocular Telescope Observatory in Arizona. It was made possible by a special constellation on 8 March 2015: From the perspective of the earth, the Jupiter's moon Europe past Io. As a result, this icy moon with its special optical properties also gradually covered the region of Loki Patera. As a result, the researchers were able to accurately detect temperature differences in the lava surface and create a temperature map. It documented a characteristic temperature gradient of the surface of the lake from east to west: from about 330 Kelvin at the southeastern end to 270 Kelvin at the western one.
Two waves are emerging
Simulations of the researchers then showed that the observed temperature pattern can be explained by two lava waves, whose origin lies in the west of the glowing lake. One rises south of the island in the center, the other north, and they travel about one kilometer a day. According to the models, the southern one starts a little later than the northern one - but it spreads faster. In the East, they finally meet each other. After passing through the waves, the surface cools down. As they reach the East last, the temperature is still greatest here, the researchers explain. display
"Now it seems clear that not just one, but two waves are renewing Loki Patera. This is much more complex than we thought before, "says co-author Ashley Davies of the Jet Propulsion Laboratory in Pasadena, which has been exploring the volcanoes of Io for many years. His colleague, de Pater, is also happy: "This is a step forward in understanding volcanic activity on Io and, in particular, volcanic activity at Loki Patera".
Original work of the researchers:
- Nature, DOI: 10.1038 / nature22339