BAN #468: BAN update, Europa up very, very close

October 3, 2022 Issue #468

October 03, 2022

About this newsletter

Ooo, meta

First, let me welcome the literally thousands of new subscribers I have to the BAN! I hope you enjoy this newsletter. I’ll be throwing space, astronomy, opinions, stories, fun photos, jokes, recipes, and more at you here; once a week for free subbies and three times a week for paid ones.

Having said that, holy cripes, what a week. It’s been a minute since I announced my departure from SYFY Wire and that I’ll be giving more dedicated attention to this newsletter, and oh my, things have happened.

For one the support I got on social media was nothing short of heart-exploding. So many people signed up, retweeted, and said nice things about my writing, and there was so much of it I had a hard time keeping up. If I didn’t respond to you personally my apologies but I’m sure I must have missed some.

I mean, come ON:

[Graph of free and paid BAN subscribers for the past 30 days as of Saturday, Oct. 1, 2022.]

Wow. The second jump in numbers after the plateau is mostly due to my old friend Fraser Cain from Universe Today; he mentioned all this in his own newsletter and many hundreds of his readers signed up as well. His weekly newsletter has a roundup of astronomy and space stories, so if you can’t get enough of stuff like that then go sign up!

As for Galaxy Class subscribers, I was expecting maybe a couple of dozen folks would sign up for that, but instead I got, um, significantly more. I promised y’all a meteorite, a personal video message, and a link to your site in one free issue a month if you wanted, and I plan on delivering, but the logistics are more complicated than I expected. Stay tuned, because I’ll be sending an email out in a week or two to get your info for all that.

Again, thank you to everyone for your support. This could’ve been a very rough time for me, but you have made it much, much smoother.

Pic o’ the Letter

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

Oh, Jupiter.

Well, more specifically, Europa.

Last week, the spacecraft Juno flew extremely close to the surface of that moon of Jupiter, taking incredible images. Incredible.

[Europa, as seen by the Juno spacecraft on September 29, 2022. This image was processed by the amazing Kevin Gill, a software engineer who does amazing work putting together planetary images from spacecraft. Credit: NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill]

The detail is staggering. All those crisscrossing long features are called lineae, and are likely due to warm water upwelling when the surface ice cracks due to stress. That in turn happens because of Jupiter’s very strong gravity. Europa’s orbit is very slightly elliptical and tilted, so sometimes it’s closer to Jupiter than others, so it experiences changes in the strength of the gravity it feels from the enormous planet. This change is called the tidal force, and it strains the ice, cracking it. As water wells up from the interior it can form ridges, and this obviously happens a lot on Europa.

I love the little depression about a quarter of the way in from the left, near the day/night line (which is called the terminator). I’d guess that’s a crater that’s sagging over time. The surface has very few impact craters because they fade rapidly as the ice deforms under the pressure, so any crater you see is relatively young.

[Close-up of a crater on Europa. Credit: NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill]

This view of Europa is mostly the sub-Jupiter hemisphere: Europa spins once per orbit, so it’s tidally locked to Jupiter, showing only one face to it like the Moon does to Earth (and for exactly the same reason). This part of Europa wasn’t seen well by Voyagers 1 and 2 when they passed by in 1979, or by the Galileo mission in the 1990s. In fact this is the best image of Europa taken in about 20 years!

I’ll note Juno took a close swing by Ganymede (the largest moon in the solar system!) in 2021 and will pass the volcanic moon Io twice in 2024. I’m very excited about that Io is a mess and the images should be amazing.

Juno is a mission that launched in 2011 to Jupiter. Built like a tank to resist the intense radiation near the giant planet due to its powerful magnetic fields (which accelerate subatomic particles to ferocious speeds), Juno’s goal was — and is — to examine Jupiter beneath its deep cloud layers and try to help us understand better the interior of the huge world and how it formed.

Juno is on a long, looping, elliptical orbit that takes it out as far as 8 million kilometers from Jupiter and as close as 4,200 km above its poles — and holy crap is that terrifyingly close — where it screams past at a soul-freezing 200,000 kilometers per hour. The whole point was to measure what’s going on inside Jupiter, so it has to get close. The radiation is so intense there, though, that it can’t stay in that close, which is why the orbit takes it so far out.

It’s not designed to observe the moons, but it can. In late September, it passed an incredible 352 kilometers above the surface of Europa, the third closest pass under 500 kilometers of any spacecraft. Europa is an icy moon, about 3,100 km wide (a little smaller than our own Moon) and the smallest of the four big Galilean moons. It likely has a core of metal and a mantle of rock, and we know it has a water ocean probably about 100 km deep topped by a crust of ice a dozen or more kilometers thick. All these interact to make it a very interesting moon indeed.

Obviously.

And I have to add this: JunoCam, the camera that takes these incredible shots, was not originally a part of the mission! The science goals of Juno don’t need a visible light camera, so at first it wasn’t designed to have one. But scientists and engineers realized that the images it returned would be stunning, so they commissioned Malin Space Science Systems to build one. My friend Emily Lakdawalla has more info on that and the camera, but the point here is that the camera was added solely for public outreach. Seriously, they put it in there so that the public could share the joy of seeing this extraordinary planet up close.

And the wonders it has shown us! Jupiter up very very close, its tempests and Earth-sized monster storms, aurorae, and now its moons. Juno won’t last forever; the radiation really should’ve already zapped JunoCam but it’s stubbornly kept working. Eventually though it’ll have acquired enough data and run low enough on fuel that the mission will end, and engineers will command it to fall into Jupiter, burning up as it plunges into the dense atmosphere, and becomes a part of the world its studied for many years. But there’s much to see and much more to learn before then.

[Jupiter’s swirling cloud tops, from a Juno image taken in October 2018. Credit: NASA/JPL-Caltech/SwRI/MSSS/Gerald Eichstád/Seán Doran.]

The Last Blog Jam

[Starfleet right to the end. From Friday’s last article. Credit: Phil Plait]

Friday 30 September, 2022: All Good Things…

Et alia

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