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.


Sciency Words: Decametric Radio Emissions

June 30, 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:

DECAMETRIC RADIO EMISSIONS

The decameter doesn’t get as much love as the meter or the kilometer, but it’s still a perfectly legitimate S.I. unit of measure. It equals ten meters.

In 1955, astronomers Bernard Burke and Kenneth Franklin detected radio emissions coming from the planet Jupiter, radio emissions with wavelengths long enough to be measured in decameters. Thus these emissions came to be known as the decametric radio emissions.

Surprisingly, the decametric radio emissions don’t radiate out into space in all directions. Instead, they shoot out like laser beams. Or perhaps I should compare them to searchlights. As a result, we can only detect them here on Earth if they happen to be aimed right at us.

Now here’s the part that I find really interesting. There are currently seven known sources for the decametric radio emissions, and they’re classified into two groups: Io-dependent and Io-independent.

The Io-independent sources require Jupiter’s magnetic field to align with Earth just so in order for us to hear them. And the Io-dependent sources? Well, they depend on Io, one of Jupiter’s moons. Jupiter’s magnetic field has to align with Earth, and Io has to be in the proper phase of its orbit.

I’m not sure why I think the decametric radio emissions would sound like dubstep. Click here, here, or here to find out what they actually sound like.

In next week’s edition of Sciency Words, we’ll take a closer look—a much closer look—at Io. It seems this humble little moon does more than adjust Jupiter’s radio emissions. Io wields enormous power and influence over the entire radiation environment surrounding Jupiter.

P.S.: Okay, on second thought, maybe we shouldn’t get too close to Io.


Sciency Words: Patera

September 23, 2016

Sciency Words PHYS copy

For the last few weeks, we’ve been touring the moons of Jupiter and learning about some of the scientific terms used to describe the weird geological features we’ve found there. Today, we conclude this Jovian moons series with the term:

PATERA

Meet Io, Jupiter’s fifth moon and the inner-most of the Galilean moons. Io, say hello to the nice blog readers.

sp23-queasy-io

Oh jeez. I’m sorry you had to see that. Io is sort of caught in a gravitational tug of war between Jupiter and the other Galilean moons. You’d feel queasy too if you were constantly being yanked back and forth by all that gravity.

The result is that Io is the most volcanically active object in the Solar System. Just about any time you look at Io, its sulfur volcanoes are erupting.

A Caldera by Any Other Name…

Astronomers use the word patera (plural, paterae) when discussing Io’s volcanoes. The term comes from the Latin word for flat dish, and the name is appropriate.

Paterae don’t look much like the kind of volcanoes we typically imagine. They aren’t raised, mountain-like features but rather flattened, crater-like depressions. If you know what a caldera is, a patera is basically the same thing.

How Calderas… I Mean, Paterae… Form

Picture this: somewhere on Io, we find an underground chamber full of a nasty, sulfur-rich brew. The temperature in this chamber rises, and the pressure builds up. Suddenly, an eruption occurs, and Io spews that sulfur mixture all over its surface.

As that subterranean chamber empties, the ground above it starts to sink. The resulting pit-like surface feature is a patera. Or a caldera. They really are the exact same thing. (Here’s a short video demonstrating the caldera/patera formation process).

Paterae are not unique to Io. They’ve also been observed on Mars, Venus, and Titan, among other places. They’re also found on Earth, except you’re not supposed to call it a patera if it’s on Earth.

Patera vs. Caldera: What’s the Difference?

If you really want to, you can use the word caldera when referring to Io’s volcanoes, or similar volcanoes on other worlds. That usage seems to be acceptable. But it is unlikely that you will ever see the word patera used for such features here on Earth.

I think there’s a bit of geocentrism at work here. A lot of planetary features have one name on Earth and some other name everywhere else. You’ll sometimes find Earthly terminology used off-world, because Earth terms are more familiar to the average reader; the reverse is rarely if ever true.

Which is fine. I’m not judging. A little linguistic geocentrism makes sense to me, at least at present. In some distant Sci-Fi future where humanity has spread across the Solar System and beyond… at that point, things like the caldera/patera distinction might seem a bit silly.