An amazing image of Io, Jupiter’s tortured hell-moon

We can get pretty cool shots of tiny, distant objects from Earth sometimes

June 10, 2024 Issue #732

Pic o’ the Letter

A cool or lovely or mind-bending astronomical image/video with a description so you can grok it

Jupiter’s moon Io is the most volcanic object in the solar system. There may be as many as 400 — four hundred! On a moon only a little bit bigger than our own! — and 150 are active at any one time. It’s a hellscape there, with sulfur compounds spewed everywhere, a haphazard mix of hot spots from the internal volcanism and the cold landscape due to it being so far from the Sun. 

That distance is an issue for scientists. At best it’s only about 1 arcsecond in size as seen through a telescope, which is small. The full Moon is 1,800 arcseconds across, so Io looks teeny. The only way to see it in any detail is to send spacecraft there. And while that’s great, the problem is they can’t just observe Io whenever scientists want; the craft is usually busy looking at a hundred other things, and you can’t get the time coverage needed to see changes in the landscape due to eruptions.

… until recently. There are some telescopes that can see it pretty well; the Keck 10 meters, for example, are huge telescopes so they have good resolution (ability to see details) and also sports adaptive optics, an internal mechanism that compensates for the distortions due to the roiling atmosphere above our heads that causes stars and small objects to twinkle. However, Keck sees in the infrared, but it helps to be able to see things in visible light, the kind our eyes see.

Enter the Large Binocular Telescope (or LBT), a pair of immense 8.4-meter telescopes mounted side-by-side in Arizona. The combo provides a fantastic view of the heavens, and just got a new instrument called SHARK-VIS. Aside: I searched high and low, and it took a long time to finally find out what the acronym stands for: System for coronagraphy with High order Adaptive optics from R to K band. This unwraps to mean is it has a metal mask to block out bright sources to see faint things near them (the coronagraph), adaptive optics is explained above, and the R and K bands are regions in the infrared spectrum. SHARK-NIR (for near-infrared) was the first camera, and the new one looks in visible light, so it’s SHARK-VIS*.

Io looks a bit like a pale pizza, covered in weird splotches that turn put to be volcanoes, surrounded by the black of space.

Io, via the Large Binocular Telescope. Credit: INAF/Large Binocular Telescope Observatory/Georgia State University; IRV-band observations by SHARK-VIS@LBT [P.I. F. Pedichini]; processing by D. Hope, S. Jefferies, G. Li Causi


Yowza! All those blotches on it are volcanoes, many of which are active (Io is relentlessly squeezed by Jupiter’s immense tidal force, which create internal friction which melts the moon’s interior and cracks the outer layers, allowing that material to reach the surface). In fact the paper notes that the observations show some changes on the surface. The volcano Pele is the oddly shaped dark blob just below and to the right of center, surrounded by a red ring of erupted material. There are two volcanoes just to the right of it; the left one is Pillan Patera, and the scientists note that the red ring looks overlaid by newer lighter material right where Pillan sits. That’s likely from a powerful eruption that occurred in 2021. 

This image is the highest resolution visible light image taken from Earth of Io, and is better even than what Hubble can do. The scientists hope to get simultaneous observations of Io using LBT and infrared telescope, the latter of which can trace hot spots better. Images in different wavelengths really help planetary scientists get a better grip on the processes going on with the small moon (and, really, with any astronomical object; physical processes are produced by a variety of mechanisms that can reveal themselves in widely different parts of the electromagnetic spectrum).

This image is really tremendous, and I’m excited to see what else this amazing SHARK-VIS camera can do. Being able to monitor Jupiter’s moons, and those of the other outer planets, on a more routine basis could reveal a lot of very interesting behaviors. I’m really looking forward to seeing what else this machine can do.

 * NOTE TO SCIENTISTS: Define your danged acronyms in every paper, please.

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