[Dave882 (David)]

Like many others I was taking advantage of the good conditions on 1st Sept and doing some imaging of Jupiter during the transit of Io. For the first time I was actually able to discern what looked like some surface detail on Io just as it finishing transiting.

Got me thinking about what this was that I was seeing, so did some research the last couple of days trying to make sense of it all… Here goes!

Io is a hellish land of volcanic activity, with hundreds of active volcanos that spew out sulphur and silica compounds . This is thought to be caused by tidal heating - the gravitational interactions that Io has with Jupiter, Europa and Ganymede. It is literally squeezed, pulled and deformed every few days, enough to generate friction to melt rock.

Volcanic plumes of sulfur and sulfur dioxide climb as high as 500 km, and lava flows create huge patches of yellow, red, white, black, and green – different compounds of sulfur. The dark lava flows (mostly silicates) are said to be relatively young (still warm), as when the lava has cooled the sulphur in the atmosphere freezes and deposits onto these features, causing bright yellow sulphuric frosts. This accounts for the majority of visible surface details, as seen by a true colour image by the Galileo spacecraft.

Infrared imaging shows huge areas of activity, including the largest of its volcanos called Loki Patera, measuring some 202km diameter. Attached is a composite image created by shots from Juno spacecraft’s Jovian Infrared Auroral Mapper instrument, put together by Roman Tkachenko to show the extent of the volcanic activity.

Which brings me to the question that still remains unanswered: why does there seem to be a darker band through the middle of my images of Io? I have noticed this in a couple of my shots from the same night, and some from other people as well – but it doesn’t seem to be backed up by much in the scientific record.

Image/processing artefact, or something real? I'd really love to find out! Any ideas??