Prometheus Plumes on Io (Astronomy Picture of the Day (APOD))

Author: NASA APOD (Astronomy Picture of the Day)
Date Written: May 22, 2011
Title: Io: The Prometheus Plume
Subject Area: Planet Geology
Source Website: APOD
---Summary---

Images of Jupiter's moon Io show two large blue, sulfuric, volcanic plumes rising from the surface of Io. These are color composite images taken by the Galileo satellite in 1997. The volcanic plumes rise 75 km and 140 km into the air. These volcanoes occur over calderas, which are depressions in the ground that form from ground filling in the empty space left by the escaping smoke and magma. The plume in the middle of the image has been present in every image taken of Io, dating back to the 1970's, which shows that the plume has been continuously flowing for at least 18 years. Scientists have recently shown evidence that a magma ocean exists underneath Io's surface.

Here is the link to this article
http://www.universetoday.com/85615/magma-ocean-flows-beneath-ios-surface/


The orientation of Jupiter's magnetic field lines change with respect to Io (see the video on this link), as Jupiter has a rotational period of about 13 hours. As the orientation of Jupiter's magnetic field lines change, the strength of lines increases and decreases. Io's magnetic field lines remain the same, while Jupiter's magnetic field lines vary. By analyzing the change in the external magnetic field lines on Io, scientists were able to learn about Io's interior.



Here is a link to a description of Caldera's, which uses Crater Lake as an example
http://en.wikipedia.org/wiki/Caldera

---My Reaction---

That seems pretty crazy that the plume has been continuous for at least 18 years. With the presence of a magma ocean underneath Io's surface, I suppose the volcano has plenty of supply for expelling into the atmosphere. Would it be possible for Io to create it's own atmosphere from this process?




---Questions---

Why does Io's magma ocean have a high electrical conductivity? What does it mean to have high electrical conductivity?

Why do planetary bodies have magnetic fields? For the Earth, isn't it caused by the flow of magma in the interior?