Lava in space!

Every five years, two of Jupiter’s largest moons align so that Europa crosses in front of Io. Because Europa is slightly smaller than Io, it’s able to block out large amounts of light which makes it easier for scientists to take photos of this volcanic moon and its features. There are hundreds of volcanic craters, called paterae, on Io, but one in particular is pretty hard to miss. Loki Patera, named after the norse god, is an enormous lava lake and researchers at UCLA Berkeley seized this rare opportunity to capture images of this mysterious molten feature. Izzie Clarke spoke to astrobiologist Katherine De Kleer to find out more…

Katherine - It’s, in fact, the most volcanically active object anywhere in the solar system, even more so than Earth itself. It has some very dramatic and enormous volcanoes and the one that we were focused on in this study was Loki Patera, which is a massive volcanic feature on Io.

Izzie - We have lava on Earth and do these volcanoes have that same lava - is it all the same thing effectively?

Katherine - Well, that’s a good question and it’s one that we don’t necessarily know the answer to. It’s at least similar in composition to lava on Earth but possibly different, possibly a more exotic, higher temperature composition of magna - we’re actually not sure.

Izzie - And looking at that, what did you find exactly?

Katherine - Within Loki Patera, this massive lava lake, we saw a fairly smooth distribution of temperatures. There had been some waves of magna that were resurfacing the patera that started at different points, moved in opposite directions around the volcano, and then converged in the southeast corner.

Izzie - Gosh. That’s a wave you would not want to go surfing on but do you know what’s causing that wave?

Katherine - Well, we don’t know for sure but there are some good hypotheses out there that this wave may represent basically an overturned front on the crust that’s on the surface of this lava lake. So we have crust that over time becomes cool, and thick, and eventually stable and it sinks down back into the lava lake when it becomes unstable. So we have this wave of sinking that then propagates all the way across the patera.

Izzie - Now Io is one of Jupiter’s moons - this is really far away. How are you even able to measure this and find this out?

Katherine - That's a great question because from direct telescope observations we’re really not able to get this level of spatial resolution at all. We were able to get this kind of resolution when Europa, another of Jupiter’s satellites, was moving across Io. So we have Europa passing in front of Io from the point of view of Earth and it systematically blocked light from Loki Patera. And by looking at how the emission from Loki decreased as Europa slowly moved across it, we could reconstruct the distribution of emission from within.

Izzie - What is so important about Europa crossing Io that has made this possible?

Katherine - Europa crossing Io is a fairly rare occurrence. This only happens once every six years, when the orbital geometry of Jupiter’s satellites lines up just right from the perspective of Earth’s that we see these satellites cross one another. But something else that makes it possible to get out the intensity of these volcanoes is that while Io is very bright, Europa is almost completely dark at the infrared wavelengths that we observed at because Europa is covered in water ice, which absorbs all of the sunlight that’s incident on it, so it’s almost invisible.

Izzie - How precise can we get in terms of imaging this effect?

Katherine - Loki Patera covers a total area of 20,000 sq. kilometres, so it’s about the size of the state of Massachusetts or of Wales. The image we reconstructed has a resolution of somewhere around 10 kilometres, maybe a little bit better than that. So you’re talking about a resolution of 10 kilometres across all of Wales or all of Massachusetts.

Izzie - Gosh. So that’s quite high detail.

Katherine - Yes.

Izzie - Why is this study important?

Katherine - In general, what we’d like to do is construct a very generalised understanding of how volcanic activity works. Not just on Earth, but everywhere in the solar system. We’d like to know in different environments how does geological activity differ, and how Earth and Io are different from one another? Then we can start to speculate about the full range of styles of geological activity that might be present throughout our solar system as well as elsewhere in the galaxy.