Space for the day

The BBC has an article by Melissa Hogenboom about Io:

In 1610, Galileo first observed four of Jupiter's largest moons. Its innermost is Io (photow), which is only marginally bigger than our own Moon, but that is where the similarities end. It is an extremely volcanic body, the most geologically active in our solar system. Massive volcanoes regularly erupt plumes of silicate lava, sulphur, and sulphur dioxide. These emissions constantly remold Io's surface and appearance.
Now an extremely powerful telescope, aptly named the Large Binocular Telescope Interferometer (LBTI), has revealed images of one of Io's largest lava lakes in astonishing detail. And it did so from Earth, with the findings published in the Astronomical Journal.
Named after the chaotic Norse god Loki, the volcanic feature is what's called a patera. This is a lava lake with thick lava crust solidified onto it. This crust periodically sinks into the lake as it fills up with lava, and then it cools off again. The resulting radiating heat can often be spotted from Earth.
"It’s a very bright heat source, so people are curious how so much lava flows out a large caldera like this," says Chick Woodward of the University of Minnesota, one of the team members.
Though the images are a little blurry to our eyes, they are actually some of the highest resolution ground-based images that have ever been obtained. Each pixel is roughly equivalent to a hundred kilometer footprint.
The team were able to capture these images because the powerful, large aperture telescope combines its light from two large mirrors to form one image. It also has an advanced optics system which cancels out distortion from the atmosphere, such as the twinkling of stars. This has enabled the team to capture images showing varying levels of brightness of the Loki lake, which hint at the geological processes occurring there.
"At lower spatial resolutions we usually see a bright spot at Loki Patera, but just one spot," says Imke de Pater, of the University of California at Berkeley.
Now they can see several, whereas previously the team was not able to confirm how many bright spots were present, as the resolution was not high enough.  It could help redefine what makes an Earth-like planet habitable.
"These exquisite images from the LBTI show for the first time in ground-based images that emissions arise simultaneously from different sites in Loki Patera." This, de Pater says, strongly suggests that the horseshoe-shaped feature really is an active lava lake. "These new data only add to our curiosity of what really happens there."
The Loki lake had never been spotted in such detail from Earth, due to its small size: only two hundred kilometers wide. That is small, considering it is six hundred million kilometers from Earth. In addition to Loki, the LBTI has spotted two new hot spots of volcanic activity. These might be the remnants or lava flows of a massive eruption which took place a few months ago.
They also obtained an astonishing video (undownloadable, of course, this being the BBC). It shows a spectacular cosmic alignment, one of Jupiter's other moons, Europa, is passing in front of Io sort of like a solar eclipse. The reason Europa is so dark is because this cold icy body is absorbing Io's radiation.
The fact that there is even more volcanic activity than was previously known is astounding when you consider just how small this moon is, says Woodward. Studying volcanism on extra-terrestrial worlds is extremely interesting, he adds, as it can tell us more about the internal dynamics of volcanism on Earth. "It's becoming clear that volcanism on the Earth is part and parcel of what makes it a habitable planet, and so understanding how these processes work off-world helps us address a number of issues in exoplanetary science."
For example, it could help redefine what makes an Earth-like planet habitable. It's usually said that it needs to be in what's called a "goldilocks zone" where the temperature is not too hot and not too cold. But only considering bodies in this "perfect" zone may be too limiting when considering whether a planet could host life, Woodward told BBC Earth. "If you really want to understand how volcanism works on Io, you need to regularly monitor the activity, and that’s difficult to do with space craft missions," he says.  Studying Io's activity from the ground will therefore give the team better insights into the internal "structure and plumbing" of this tumultuous moon.

Rico says that Europa is the moon we were warned about in Asimov's book...