Lost on the pizza moon

By Phil Plait | March 20, 2012 8:00 am

Speaking of Io… Oh man, do I remember that time I was cavorting around on that little moon of Jupiter, and took a left instead of a right at the flank of Tvashtar Paterae! That was so embarrassing. If only I’d had this really cool global geological map of Io’s surface:

[Click to enjovianate.]

This map was made by combining data from Voyagers 1 and 2 as well as high-resolution images from Galileo, which orbited Jupiter for nearly eight years starting in 1995. The map is the result of painstaking work piecing together data from the different missions.

This task was made harder by the fact that Io is the most geologically active object in the solar system, with constantly erupting volcanoes — the surface changed significantly between the eras of Voyager and Galileo. Io is so volcanic because it’s getting squeezed by tidal forces from Jupiter and the other large moons orbiting the huge planet.

The colors of Io come mostly from sulfur deposits spewed from volcanoes. The big orange ring to the lower left is the volcano Pele, for example. Prometheus is another volcano located smack on Io’s equator just to the right of the map’s center; Prometheus is a busy little mountain, which has essentially been erupting since it was first discovered in Voyager pictures in 1979!

I’ve seen Io literally hundreds of times through telescopes; it’s bright enough to easily be seen next to Jupiter, and was in fact discovered by Galileo shortly after he first pointed his telescope at the planet! It’s easy to forget that these are not just points of light in the sky, but actual worlds. Look at that picture again: when Galileo observed Io for the first time, we didn’t have maps of Earth that were this detailed. Four centuries is a long time, and we’ve learned a lot, of course. That’s what happened when you keep your hands on the guiding wheel of science. It’s a lot harder to get lost, and just look how far it’s taken us.

Image credit: U.S. Geological Survey

Related Posts:

The Galilean Revolution, 400 years later
Io’s footprint on Jupiter takes the lead
Jupiter’s moons light up aurora borealis
New Horizons at Jupiter

CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures

Comments (23)

  1. Chris

    Io is so volcanic because it’s getting squeezed by tidal forces from Jupiter and the other large moons orbiting the huge planet.

    I wonder if “squeezed” is the right word to use here. Perhaps “flexed” would more accurately portray the dynamics.

  2. Anders

    How long will the map remain current? Doesn’t Io resurface itself once a month or something crazy like that?

  3. The Mutt

    That’s amore.

  4. ceramicfundamentalist

    i like these world maps of other worlds but i really don’t like the map projections that are commonly used. the equirectangular projection makes everything above 30 degrees look really distorted, and everything beyond60 degrees is a totally incomprehensible smudge. surely there must be better solutions out there.

  5. The square, fourth down from the top, fourth from the left side… Yeah, I claim that.

    Techskeptistan. Enter at your own risk.

  6. Jay

    Pizza the Hut?!?

  7. Chris

    @4 ceramicfundamentalist

    You need to see http://xkcd.com/977/

  8. Aren’t the Moons of Jupiter named after the God’s various lovers? ‘Squeezed’ sounds like a good word to me.

  9. ceramicfundamentalist

    @7 Chris – thanks for that!

  10. Darren

    In the image of Io & Jupiter posted earlier we can see a volcano erupting on the surface of Io, is it possible to say which volcano that is on this map? Or are there too many active areas to be certain?

  11. Karen

    Yes, Zeus and Io. Wasn’t Io Zeus’s favorite lovey?? Io is certainly my favorite moon!

  12. Jason Perry

    That erupting volcano was Tvashtar Paterae. On the map in this post, look at the grid on it. Go to the first line down from the top edge and four lines over from the right edge. That’s Tvashtar. Tvashtar is actually a line of volcanoes bounded by a pair of broad mesas. The volcano in Tvashtar that was actually erupting in 2007 (and thus in the image Phil posted earlier) is just a little above and to the left of that grid intersection.

  13. Infinite123Lifer

    @4 ceramicfundamentalist:

    I have been told there is no great way to accurately portray the surface of a world on a 2 dimensional flat map as Chris pointed towards :)

    @7 Chris

    that was cool, sort of a choose your own adventure of sorts or at least choose your less confusing

    @5 techskeptic

    have fun wrestling that away from the seductress Pele :)

    That must be Loki Patera 3 down from the top and 2 squares from the left?

    Wikipedia describes Loki as a lava lake with an episodically overturning crust.

    Dang, how amazingly intriguing is Io, and how spectacular to grind out these images and achievements over time.

    I owe I owe some really cool people are off to work on Io.

  14. Chris A.

    One of my favorite things about viewing Jupiter and Io in a telescope is when Io appears just off the planet’s limb. It’s when they are close that you can detect Io’s subtly yellowish hue, against Jupiter’s stark white. Immediately, I comprehend that I’m seeing a ball of partially molten sulfur (at least on the surface). You can almost smell the rotten eggs!

  15. Ah.

    If only there was a bump/displacement map to go with it. Image how many of us geeky computer nerds would be mapping that onto spheres in our favourite 3D software and making our own scenes.

  16. Chris

    For those interested there is the “Atlas of the Galilean Satellites”
    An absolutely beautiful compilation of all the info we have on them. A bit pricy, but maybe ask your local library for an interlibrary loan.

    Even got 5 stars from Emily Lakdawalla. High praise :-)

    Can’t wait for Google Io!

  17. Nobody

    Very cool, but won’t this only be good for a few months before Io’s volcanism totally repaves the surface?

  18. Luis Correia

    I’ve created a small interactive web app to visualize Io.
    You can see it here:

    www openprocessing org/sketch/56652

  19. Infinite123Lifer

    @17 Nobody

    I am not the expert here but Phil mentions in the article:

    “This map was made by combining data from Voyagers 1 and 2 as well as high-resolution images from Galileo, which orbited Jupiter for nearly eight years starting in 1995. The map is the result of painstaking work piecing together data from the different missions.”

    I am guessing that the major features of Io like Pele and Loki and Tvashtar Paterae and Prometheus (to mention the only ones I am familiar with) obviously change over time but don’t disappear completely through the reforming of the surface at least not in the time frame which we have been able to observe and not from the distance at which we see them. Perhaps these major features are the most active in the reforming and thus stay mildly constant from a distant view.

    To my understanding these areas are volcanoes and lava lakes which are constantly changing but from a distance these large features (speculation) continue to be recognizable, at least as was mentioned Prometheus has been, i guess, pretty steadily erupting since Voyagers first glimpse in 1979! as was also mentioned in the article.


    Ah, the next best thing to being a geeky computer nerd would be to marry one I suppose. I would love to understand how to use data sets to create my own 3D spheres or whatever else the cool guys and gals might contrive from the growing horde of information being collected.

    I need to check into those public science helper thingamajigs. Where the average Joe or Jill can lend a hand wading through the mega-tons of info and not get in the way. I have heard of 3 so far and cannot recall, one was a beta (which I think means: just testing out???) and the other 2 were mentioned here in Bad Astronomy but I cannot recall. I also have heard where you can “lend” your computer to help out. This is far from my understanding as I have a hard time understanding why my Bookmarks Toolbar wont allow me to bookmark anything under the folder I created for Science News. Sigh

    You may say
    I’m a dreamer, but I’m not the only one

  20. Infinite123Lifer

    DUDE! Luis Correia, that is awesome!

  21. Luis Correia

    @20 Infinite123Lifer


  22. I will always have a warm spot in my heart for Io. I was in on the first observation of sulfur ions in the Io torus (the nearby environment) and it led me into decades of planetary science including Voyager, Galileo and Cassini. Lovely place indeed.
    Detection of ionized Sulfur in the Jovian magnetosphere, I. Kupo, Yu.
    Mekler and A. Eviatar, Astrophysical Journal, 205, L51-L53,1976.
    Sorry, articles from before 1995 are not on line

  23. Matt B.

    Yeah, Io is Jupiter’s main squeeze. :)

    @0. Was Io’s prime meridian chosen to be the mean position of Jupiter in Io’s sky?


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