My Favorite Moon: Io

November 14, 2018

Some of you may remember a post I did awhile back declaring Europa to be my favorite moon.  It’s a beautiful and mysterious world, a world that may have an incredible secret hidden beneath its icy crust.  Europa frequently tops the list of most likely places where we might find alien life.

But as I’ve learned more about the Solar System, I’ve developed a deeper affection for another moon, one of Europa’s neighbors, a world that is neither beautiful nor likely to support life.  I’m talking about Io.

Io is the innermost of Jupiter’s four big moons (Io, Europa, Ganymede, and Callisto).  As such, it gets pushed and pulled around pretty hard. Between Jupiter’s enormous gravity and the combined gravitational forces of the other three Galilean moons, it’s enough pushing and pulling to make anyone queasy.  And Io is a notoriously queasy planetoid.

Due to tidal forces, Io’s sulfur-rich interior is constantly boiling and churning.  And Io keeps literally spewing out its guts, making it the most volcanically active object in the whole Solar System.

Like Venus, my favorite planet, Io is a great chemistry professor, especially when it comes to sulfur chemistry.  Io’s also a pretty decent physics professor.  While most of the sulfur from Io’s volcanic eruptions settles back onto the moon’s surface, plenty of it escapes into space. The result: crazy dangerous games of particle physics in the vicinity of Jupiter.

Io’s ionized sulfur has a lot to do with controlling the intense radio emissions coming from Jupiter.  It’s also a major factor contributing to Jupiter’s insanely dangerous (to both humans and our technology) radiation environment. We recently learned that Jupiter has a third magnetic pole, located near the planet’s equator; while I haven’t read anything yet to back me up on this, I have a feeling Io is somehow responsible for that.

And lastly, Io’s ionized sulfur is partially (mainly?) responsible for the magnificent auroras that have been observed on Jupiter. And that’s my favorite bit about my favorite moon.  I love the idea that Io—the ugliest ugly duckling in the Solar System—plays such a crucial role in creating something beautiful.

But of course picking a favorite anything is a purely subjective thing.  Do you have a favorite moon?  If so, what is it?  Please share in the comments below!


Which Planet Has the Weirdest Magnetic Field?

October 23, 2018

When I did my yearlong Mission to the Solar System series back in 2015, the planet Neptune stood out as having the weirdest and wackiest magnetic field.  Here’s a totally legit photograph from 1989 taken by the Voyager 2 space probe.  As you can see, Neptune is really confused about how magnetic fields are supposed to work.

But since 2015, science has learned more about the other three gas giants in our Solar System.  Neptune’s magnetic field is still really weird, but it’s no longer clear that it is the definitive weirdest.

  • Jupiter: Based on data from the Juno mission, it looks like Jupiter has three poles instead of two.  There’s a north pole, right about where you’d expect it to be.  Then the magnetic field lines emanating from the north pole connect to two separate south poles.  The first south pole is about where you’d expect a south pole to be. The other one is near the equator. Click here for more about Jupiter’s “non-dipolar” magnetic field.
  • Saturn: As Sherlock Holmes says in one of his many adventures, “Depend upon it, there is nothing so unnatural as the commonplace.” According to data collected during the Cassini mission’s Grand Finale, Saturn’s magnetic field is almost perfectly aligned with its rotation.  At first blush, that might seem quite normal.  Commonplace, even. Except no other planet’s magnetic field is so perfectly aligned.  Not even close.  Apparently planetary scientists didn’t think such a thing was even possible.  Click here for more about the “negligible tilt” of Saturn’s magnetic field.
  • Uranus: The planet Uranus is tipped over sideways, and its magnetic field is tipped over further still.  According to recent computer simulations, these two factors combine to cause Uranus’s magnetic field to tumble over itself “like a child cartwheeling down a hill,” as one researcher put it. This leads to a “periodic open-close-open-close scenario” where the solar wind can flow in toward the planet then suddenly be blocked, then suddenly flow in again, and then suddenly be blocked.  If these simulations are correct, the Uranian aurora may flick on and off like a light switch. Click here for more about the “topsy-turvy motion” of Uranus’s magnetic field.
  • Neptune: In 1989, Voyager 2 discovered that Neptune’s magnetic field is lopsided. The magnetic field doesn’t run through the planet’s core. Instead it runs through a seemingly random point about halfway between the core and the “surface” (by which I mean the topmost layer of the atmosphere).  Also, only one of the poles ends up being near the planet’s “surface.”  The other pole is buried somewhere deep in the planet’s interior.  For more about Neptune’s “badly behaved” magnetic field, click here.

If I had to choose, I’d probably still give Neptune the award for weirdest magnetic field.  But the competition is a lot tighter than it used to be.  Maybe the real lesson here is that gas giants in general have wild and crazy magnetic fields.

So if you had to pick, based on all this new info, which planet do you think deserves the award for the weirdest magnetic field?

P.S.: Also, the Cassini mission discovered there’s an electric current flowing between Saturn and its innermost ring.


Sciency Words: Nice Model

May 18, 2018

Today’s post is part of a special series here on Planet Pailly called Sciency Words.  Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together.  Today’s term is:

NICE MODEL

I recently assembled Lego’s Saturn V rocket set, and I have to say it’s a really nice model.  It even has these little orange pieces to represent the floaty things for when the Apollo capsule returns to Earth and splashes down in the ocean. That, I thought, was a really nice touch!

But as nice as that Lego model is, that’s not the model we’re talking about today.  Nope, today we’re talking about the Nice model, with a capital N.

In May of 2005, three papers were published in the journal Nature which did a nice job explaining some of the big mysteries of our Solar System.

  • First (in order of page number) was a paper on the anomalous orbital eccentricities and inclinations of the four gas giant planets.
  • Next came a paper on the Trojan asteroids which hang out around Jupiter’s Lagrange points, 60º ahead and 60º behind Jupiter in its orbital path.
  • And lastly, there was a paper on the Late Heavy Bombardment, a period of time when the Moon (and also the four inner planets) got pummeled with asteroids.

All three of these papers share a common idea: that the four gas giants of our Solar System must have started out much closer together, with a broad disk of rocky and icy debris beyond them, like a super-sized Kuiper belt.  Then, approximately 700 million years after their initial formation, three of those gas giants (Saturn, Uranus, and Neptune) started drifting farther and farther away from the Sun and away from each other.

Jupiter seems to have drifted slightly closer to the Sun, but stopped short of entering and demolishing the inner Solar System thanks to a last minute gravitational interaction with Saturn (thanks, Saturn!).

As the gas giants spread out, they threw that super Kuiper belt into chaos.  Some of that rocky and icy debris was hurled toward the inner planets, causing the Late Heavy Bombardment.  Some of the debris got stuck around Jupiter’s Lagrange points, becoming the Trojan asteroids.  And with so many complicated gravitational interactions happening at once, it’s no wonder the four gas giants ended up with some anomalies in their orbital paths.

This one idea—that the gas giants drifted apart after they formed—does a pretty nice job explaining three of the biggest mysteries about our Solar System.  But sadly, that’s not why it’s called the Nice model.  The name actually isn’t pronounced like the English word “nice” but rather like the French city of Nice (which rhymes with geese or fleece).  That’s because the model was originally formulated at an observatory in Nice, France.

Unfortunately, I didn’t find that out until I’d already sprinkled a bunch of nice puns into this post, and I don’t feel like taking them out.


The End for Juno?

May 15, 2018

We’ve always known the Juno Mission to Jupiter would be a short one.  Often times planetary science missions like Juno will get extra funding for extended missions, because it costs less to keep using a spacecraft you already have than it does to design, build, and launch a new one.  But as I wrote two years ago, this really wouldn’t be an option for Juno.

The reason is that Jupiter has at least one moon (Europa) and perhaps two others (Ganymede and Callisto) which may be home to alien life.  Based on everything I’ve read about Europa in particular, I think it would be a bigger surprise if we didn’t find life there; that’s how promising the place looks.

NASA absolutely cannot risk letting Juno crash into and contaminate any of those moons (especially Europa).  So after completing its scheduled mission, which was meant to take about two years, Juno would do a suicide run into Jupiter’s atmosphere, destroying itself to ensure there are no future accidents, and also collecting a little extra atmospheric data in the process.

Except shortly after Juno arrived in Jupiter orbit, it ran into some engine trouble, something to do with a pressure valve opening too slowly. As a result, Juno wound up stuck in a much wider and much longer orbit than originally planned.  Rather than getting a science pass every 14 days, we’re getting them every 53 days, which has dramatically slowed down Juno’s progress.

Juno’s two years are almost up, but because of that pressure valve malfunction its mission is only half complete.  So now Juno needs that mission extension that it was never supposed to get.  A planetary scientist working on the Juno Mission was recently quoted as saying: “I think for sure the continuation mission will go on.”  He then added: “I’m hopeful but nervous.”

Funding for the Juno mission (for ground operations, mission control stuff, etc) will run out in July of this year. Given the circumstances, I have to assume NASA will grant Juno an extension, but as of this writing they have not done so.  Navigating the bureaucracy here on Earth can be just as nerve-wracking as all the hazards of space.

I’m not sure how much Congress is involved in the decision making process here, so maybe that’s what’s holding things up. Or maybe Juno has run into other technical issues which NASA hasn’t made public yet.  I don’t know, but if anything else went wrong with the spacecraft during its extended mission, we might lose control of it, and we really, really do not want it crashing into those icy-on-the-outside, watery-on-the-inside moons.

So fingers crossed.  Hopefully everything works out okay and Juno can get its extended mission.


Going Up: Jupiter’s Auroras Get Weirder Than Ever

July 17, 2017

Last week, the Juno mission flew over Jupiter’s Great Red Spot and sent back some spectacular close-ups. But I’m not ready to talk about that. Not yet. I’m still catching up on the Juno news from two months ago.

Toward the end of May, NASA released a ton of fresh data from Juno, including new information about Jupiter’s auroras. Astro-scientists had previously known about two sources contributing to these auroras: the solar wind and the Io plasma torus. Now Juno may have discovered a third.

As Juno flew over Jupiter’s poles, it detected electrically charged particles flying up.

I can’t emphasize enough how weird this is. I wanted to write about it right away, but I held off doing this post because I was sure I must have misunderstood what I was reading.

Auroras are caused by electrically charged particles accelerated down toward a planet’s magnetic poles. These particles ram into the atmosphere at high speed, causing atmospheric gases to luminesce. At least that’s how it’s supposed to work. I guess nobody told Jupiter that.

In addition to the “normal” downward flow of particles from the Sun and Io, Jupiter’s magnetic field apparently dredges charged particles up from the planet’s interior and hurls them out into space. So Jupiter’s auroras are triggered by a mix of incoming and outgoing particles.

This definitely falls under the category of “further research is required.” Even now, I still feel like I must have misunderstood something. This is just too weird and too awesome to be true.

P.S.: As for the Great Red Spot, I’m waiting to hear something about the microwave data. We’re going to find out—finally!—just how far down that storm goes.


Io: Jupiter’s Ugliest Moon

July 11, 2017

For today’s post, I hopped in my imaginary spaceship and flew all the way out to Io, one of Jupiter’s moons. Without a doubt, Io is the ugliest object in the Solar System.

I know, that’s mean. I shouldn’t say things like that. But come on, just look at it. Seriously, look at it. It’s like some moldy horror you might find in the back of the fridge.

So yeah, Io’s hideous. Let’s go look at something else instead. Something pretty, like Jupiter’s auroras.

We have auroras back on Earth, of course, but Jupiter’s are a whole lot bigger, a whole lot more powerful, and when viewed in ultraviolet, a whole lot brighter. Also, unlike Earth’s auroral lights which come and go, Jupiter’s are always there. They may vary in intensity, but they never stop, never go away.

Auroras are caused by charged particles getting caught in a planet’s magnetic field, directed toward the magnetic poles, and colliding at high speed with molecules in the planet’s atmosphere.

On Earth, those charged particles come mostly from the Sun in the form of solar wind. No doubt the solar wind contributes to Jupiter’s auroras as well, but the greater contributing factor is actually—believe it or not—Io. That’s right: ugly, little Io causes Jupiter’s auroras. I guess spreading ionized sulfur all over the place is good for something after all!

In fact if you ever get to see a Jovian aurora, you’ll notice little knots in the dancing ribbons of light. These knots correspond to the positions of several of Jupiter’s moons. And the largest, brightest, most impressive of these knots… that one belongs to Io.

Jupiter.Aurora.HST.mod.svg

Image courtesy of Wikipedia.

So I guess today’s lesson is that even the ugliest object in the Solar System can still help make the universe a more beautiful place.


Sciency Words: Plasma Torus

July 7, 2017

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:

PLASMA TORUS

Saturn may have the most beautiful rings in the Solar System, but Jupiter’s got the most impressive plasma torus. Torus is the proper mathematical term for a donut shape, and plasma refers to ionized gas. Put the two words together and you get a giant, donut-shaped radiation death zone wrapped around a planet’s equator.

Jupiter’s plasma torus is faint, almost invisible; but if we take the totally legit Hubble image below and enhance the sulfur emission spectra, you’ll see what we’re talking about.

Ever since the discovery of Jupiter’s decametric radio emissions, astronomers have known there must be a relationship between Jupiter’s magnetic field and its moons. Well, I say moons plural, but it’s really only one moon we’re talking about: Io.

It wasn’t until the Voyager mission that we figured out why Io has so much influence over Jupiter’s magnetic field. In 1979, the Voyager space probes discovered active sulfur volcanoes on Io. They also detected ionized sulfur and oxygen swirling through space conspicuously near Io’s orbital path.

It seems that due to Io’s low surface gravity, Io’s volcanoes can easily spew a noxious mix of sulfur dioxide and other sulfur compounds up into space. Jupiter’s intense and rapidly rotating magnetic field acts as a sort of naturally occurring cyclotron, bombarding these sulfur compounds with radiation, breaking them apart into ionized (electrically charged) particles and accelerating those particles round and round the planet.

The result is a giant, spinning, donut-shaped cloud of ionized gas. We’re talking about a lot of radiation here—seriously, keep your distance from the Io plasma torus! We’re also talking about a lot of electrically charged, magnetically accelerated particles moving through a planetary magnetic field.

One source I read for today’s post described Io as “the insignificant-looking tail that wags the biggest dog in the neighborhood.” Jupiter has by far the largest, strongest magnetic field of any planet in the Solar System, but thanks to this plasma torus, it’s Io—tiny, little Io—that has the real power in the Jovian system.

Next week, we’ll go take a look at Jupiter’s auroras. They’re rather different from the auroras we have here on Earth, and SPOILER ALERT: Io has a lot of control over them.