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Space Science

Galileo's Flyby of Almathea 169

Posted by michael
from the diana-gallagher-songs dept.
An anonymous reader writes "The spectacular Galileo flybys of Jupiter, Europa and Io are largely credited with the discovery of frozen water ice and some of the earliest examples of non-solar (tidal) heating anywhere in our solar system. For the next 10 days, Galileo scientists are preparing for their next target: probing one of Jupiter's moons, Almathea, at the close-up range of 100 miles. Almathea is one of the most unusual moons in the solar system, because it gives off more heat than it receives from the Sun."
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Galileo's Flyby of Almathea

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  • by deaton (616663) on Friday October 25, 2002 @08:40AM (#4528743)
    is that anything like unfrozen ice water?
    • Re:frozen water ice? (Score:4, Informative)

      by Alain Williams (2972) <addw@phcomp.co.uk> on Friday October 25, 2002 @08:46AM (#4528773) Homepage
      The point is that 'ice' can be made from all sorts of liquids - water is just one of them.
      • Re:frozen water ice? (Score:1, Informative)

        by Blackneto (516458)
        But all ice is in a frozen state no matter what it's made out of. I just thing he was pointing out the redundancy of saying "Frozen Ice"
        • Re:frozen water ice? (Score:4, Informative)

          by comic-not (316313) on Friday October 25, 2002 @10:27AM (#4529539) Homepage
          Well, ices can exist in the crystalline or amorphous phase. E.g. the water ice inside cometary nuclei is in amorphous form, and one can argue that it is technically not frozen, because it has originally been built from such tiny particles that there hasn't been a meaningful macrostate (BTW, did you ever create amorphous sulphur in the chemistry class?) to call it such. When amorphous ice is heated, it turns to the 'normal', crystalline phase, which more closely resembles our concept of 'frozen'. I don't know, however, whether the original poster tried to express this distinction.
    • I think they were talking about italian water ice. [ritasice.com]

  • by Anonymous Coward on Friday October 25, 2002 @08:41AM (#4528750)
    Lisa, In this house we obey the laws of thermodynamics.

    Yes i know there are other explainations
    • Yet another law to disobey... http://news.bbc.co.uk/1/hi/sci/tech/2135779.stm
    • by verag (617874) on Friday October 25, 2002 @09:00AM (#4528860)
      The planet itself does this as well... "...Jupiter radiates nearly twice as much heat as it receives from the Sun." Found here [thinkquest.org]

      Jupiter is by far the most interesting planet (with it's moons) to me, other than the Earth. More information as well as pictures can be found on NASA's site [nasa.gov] for the planet itself.

      • by Jugalator (259273) on Friday October 25, 2002 @09:25AM (#4528998) Journal
        I think at least Io was so volcanic and active because of the extreme "tidal waves" from Jupiter. The "waves" are, due to the huge gravitation of Jupiter, so strong they pull solid matter and this of course cause quite a bit of friction. And friction cause heat. Not really surprising, since such a small object as our Moon does funny things to our seas. :-)

        Anyway, to my point, perhaps the same applies to Amalthea?
        • Our moon pulls earth's solid surface out of shape too. The amount of motion is much smaller than the ocean's but it is not inconsiderable. Can anyone closer to their Geology 101 class or Astronomy 101 class remember how many inches the crust moves tidally? (Okay, cm's?)
        • I think at least Io was so volcanic and active because of the extreme "tidal waves" from Jupiter. The "waves" are, due to the huge gravitation of Jupiter, so strong they pull solid matter and this of course cause quite a bit of friction. And friction cause heat. Not really surprising, since such a small object as our Moon does funny things to our seas. :-)

          IIRC Io being heated is part of an interaction with the other Jovian moons. What happens is that a moon generating tides also transfers energy to the moon, so that it moves away from the planet it orbits. This is what happens here on Earth.
          With Io the interaction of the other large moons keeps in in orbit, so the energy shows up as vulcanism.
    • "That's no moon... It's a space station!"
  • by phpinfo() (588642) on Friday October 25, 2002 @08:44AM (#4528758)
    Doesn't anyone make a good cooling system for moons?
  • by ksplatter (573000) on Friday October 25, 2002 @08:44AM (#4528760)
    I thought this Galileo guy died a long time ago. And with him being so busy with Astronomy how did he ever find the time to learn how to Fly?

    Boy you sure learn something new everyday reading Slashdot!
  • by scrod98 (609124) on Friday October 25, 2002 @08:44AM (#4528761)
    because it gives off more heat than it receives from the Sun

    And NASA releases a picture of the Intel Inside logo on the surface...

  • by Transient0 (175617) on Friday October 25, 2002 @08:45AM (#4528767) Homepage
    a civilization of alien potheads who have hotboxed an entire atmosphere?

    or maybe the worlds biggest overclocked processor.

    I can't think of any other reasonable theory to account for this moon radiating so much heat.
  • by Zech Harvey (604609) on Friday October 25, 2002 @08:45AM (#4528769)

    I mean, that's the only explanation I can come up with. Ours just...you know, sits there. We go there once, get bored and come back. So we spend our time looking at other planets' moons instead of making it back to ours. I mean really. Give our moon some lubbin'!
    • by edremy (36408) on Friday October 25, 2002 @10:11AM (#4529408) Journal
      Nah. Ours is the biggest, at least in relation to our size. (Forget Pluto+Charon; they're just comets that took a wrong turn.)

      It's not the number, it's the size, baby.

      (And in seriousness, there's a fair number of theories that think life would not have come about without the large tides raised by the moon.)

  • by Dark Lord Seth (584963) on Friday October 25, 2002 @08:45AM (#4528771) Journal

    For those of us who aren't very much at home in astronomy and it's terms and who just want to see (relatively) pretty pictures; Celestia [sourceforge.net] also has Almathea available for your viewing pleasure, along with allot of different stuff in our solar system and even beyond there. Besides, it's a pretty proggy... :)

  • Almathea? (Score:4, Funny)

    by CommandNotFound (571326) on Friday October 25, 2002 @08:46AM (#4528774)
    ...isn't that the planet where they used to build luxury planets for the super-rich?
  • by Drunken Coward (574991) on Friday October 25, 2002 @08:46AM (#4528776)
    Spending all these resources investigation such distant objects in outer space when there is so much [slashdot.org] so close [slashdot.org] to us that we have yet to get a good view of. Walk before we run people!
    • It's not distant at all - in the same solar system, roughly a light-hour away. How close do you need it?

    • Um, Galileo has been orbiting Jupiter for 7 years. It's not like it's costing them a lot more to do this.
      Think and read before we post people!
    • by ChuckDivine (221595) <charles.j.divine@gmail.com> on Friday October 25, 2002 @09:24AM (#4528994) Homepage

      While I strongly support looking for close in objects, it's not like it's an either/or situation. The world has lots of astronomers (and other kinds of scientists as well). We also have resources sufficient to do research into a wide variety of astronomical phenomena.

      Those of us who have actually done some political work in support of looking for earth approaching asteroids only ask for a few millions of dollars to finance such work. Focusing all of our attention on nearby objects would be foolish and wasteful in the extreme.

  • by MrFenty (579353) on Friday October 25, 2002 @08:47AM (#4528778)
    This sort of place is exactly the sort of reason I think, if we find life elsewhere in the universe (intelligent or otherwise) then it won't have to be on a planet that looks exactly like Earth and at roughly 1 AU from its local star. Here we have a moon that gives off heat, at a very large distance from its sun. There is no reason for us to be arrogant enough to assume that life can only exist on a place that looks identical to our place. This really bugs me, when I see people say "life can't exist there, that planet is twice Earth's distance from its star..." and rubbish like that. Aarrgghh !

    Sorry, I needed that rant.

    • by FortKnox (169099) on Friday October 25, 2002 @08:58AM (#4528848) Homepage Journal
      To continue your rant philosophically...

      We are ignorant when it comes to life. What exactly is life? We only know what life is within our world.
      Astronomers get excited at the fact that we can find water on Mars and Europa, meaning they could have life, because our knowledge of life involves water. But, as far as we know, there could be life on the moon, we just aren't looking for it correctly.
      If (or when, depending on your philosophy) we find extraterrestrial life, it will be when we aren't looking for it, IMHO.
      • We are ignorant when it comes to life. What exactly is life?


        Isn't this why there are plans to retrieve some of the upper atmosphere of Venus? There have been several articles on /. recently describing how there could be life in Venus's upper atmosphere ... just floating around, using carbon monoxide and the energy from the sun as a means of sustaining life.

        BTW: I doubt you're going to find water on a planet as hot as Venus :)

        This is why I REALLY hope there is life on Venus ... it will make everyone take a hard look at where we should be looking for life. These "aliens" won't have arms and legs as we think of them, which would also be excellent!

        But it would definately be cooler if we found something a bit more advanced than floating bacteria on Almathea, Europa or IO.

        If there was life that was slightly more advanced, it is only a matter of time before someone from N*Sync will want to take a field trip out there ...

    • Planet hunters don't assume that life can only exist on earth-like planets. However they do assume that life might be more likely to be found on earth-like planets. hence it's worth looking for them.
      • Also, that "Class M" planets will be more likely to sustain human life, making their discovery not just of interest to the scientific community in a "we hope to find alien life here" kind of way, but also intensely personal to the human race in a "we hope to someday live here" kind of way.
    • by overunderunderdone (521462) on Friday October 25, 2002 @10:35AM (#4529599)
      This really bugs me, when I see people say "life can't exist there, that planet is twice Earth's distance from its star..." and rubbish like that. Aarrgghh !

      If you are ranting about the "rare earth hypothesis" [amazon.com] you should remember that the authors believe that life is MUCH more common than was previously believed. However they believe that advanced life and advanced civilizations are MUCH rarer than previously believed and do require conditions substantially similar to earths. Even you own post basically makes some of the same assumptions - you see the heat from this moon as promising because that heat is one of the prerequisites for life, the rare earth hypothesis adds additional prerequisites which must be present for *advanced* life. There are those that simply assume without thinking that life must evolve on a planet substantially similar to earth. The rare earth hypothesis arrived at pretty much the same conclusion through serious thought on the subject. They may be wrong (we simply don't have enough data) but their reasoning is sound and not based on simple prejudice or ignorance.
  • by igotmybfg (525391) <slashdot@@@danielthompson...net> on Friday October 25, 2002 @08:48AM (#4528787) Homepage
    Two summers ago, one of my friends in University here asked me to come outside with her and look at something which she described as 'cool'. Thinking I might get some :) I went with her, and we set up a tripod and telescope and ended up watching the stars all night long. For a time we focused on Jupiter, and though I couldn't see Almathea, I did see Jupiter, Callisto, Io, Europa, and Ganymede. The thought that there was nothing (well, almost nothing) in between me and those huge, huge objects that were so very far away still sends tingling down my spine whenever I think about it. It reminds me, when I think that there is pretty much nothing left to do or discover, that there is indeed a whole universe out there, waiting for (or perhaps indifferent to) us.

    Cheers!

    • by allanj (151784) on Friday October 25, 2002 @08:54AM (#4528820)

      Well, I think I speak (type?) for all of us here - did you, in fact, get some?

    • Better than sex huh?
    • by vinlud (230623) on Friday October 25, 2002 @10:21AM (#4529485)
      The thought that there was nothing (well, almost nothing) in between me and those huge, huge objects that were so very far away still sends tingling down my spine whenever I think about it. It reminds me, when I think that there is pretty much nothing left to do or discover, that there is indeed a whole universe out there, waiting for (or perhaps indifferent to) us.

      You're talking 'bout the girl now right?
    • Whether you got some or not aside, I know what you mean. When I think of things like this, the fact that we humans actually have the tech to perform such feats - probes to other planets, men on other worlds - it causes within me the same kind of reaction.

      Then tears come to my eyes...

      For I know that despite all of this, despite the facts, despite the wonder, despite the possibilities - the majority of humans do not care one way or the other about it. They would rather war, rape, pillage, and plunder to death a world which currently is the only one we have - yet they seem unable to grasp this simple concept. These same humans continue to believe in the idea of an invisible being "in the sky", a being who apparently hates other invisible beings, who insists that those invisible beings be destroyed, along with those who believe in that being, or don't believe in his being. Yet these same humans consider such concepts as the "easter bunny" and "santa claus" to be fantasy imaginings of children's fairytales.

      These people continually fight, some for their invisible men, most for more space - when with a little solidarity, and the realization that humans really do only get one life, and that death shouldn't be feared (do those who fear the consequences of a fictional afterlife wonder what came before their birth - also, if they don't remember what came before, what logic says they will know what comes after?), and that by there only being one life per each living thing, makes that life ALL THE MORE PRECIOUS. This logic doesn't destroy morality, but affirms it in a great way. With this realisation, working together to explore all of these other worlds would expand the space available for mankind, while furthering our wonder and the workings of the universe. Why does it seem so few can get these rather simple concepts?

      Perhaps we really are nothing more than "advanced animals", and really don't deserve all of what is out there..

    • When the female friend in HS pulled me outside to "show [me] something", all I got was sex.

      Dammit!
  • heat (Score:1, Interesting)

    by Anonymous Coward
    Is it in any way possible that Amalthea recieves additional energy from the radiation and gravity in the Jupiter system?
  • Monolith? (Score:5, Funny)

    by alexc (37361) <alexc@spo[ ].org ['rks' in gap]> on Friday October 25, 2002 @08:57AM (#4528837)
    Did Galileo find a Black Monolith yet?
    • It'd have to go to Saturn to find that... Japetus (or maybe Iapetus) is the place to go.
    • I'm sorry, Dave. I'm afraid I can't do that.
    • Re:Monolith? (Score:3, Informative)

      by khendron (225184)
      No no no. Clarke envisioned Amalthea (a.k.a Jupiter V) as great big a spaceship, used by an extinct alien race to move to our solar system. See here. [sfsite.com]
    • "Did Galileo find a Black Monolith yet?"

      Wrong system. You'll have to look at what's in orbit around Saturn. It doesn't teleport to the Jovian system until Kubrick gets involved, and since he's now dead...
    • > Did Galileo find a Black Monolith yet?

      The sad thing is we'll never know, because for want of $100,000 - or rather, because of a bureaucratic culture at NASA - we won't be taking any pictures as we fly by it at 100 km range.

      So for anyone that wondered exactly what's in that red stuff that Io's splattered all over Amalthea's surface over the past few million years, tough. Wait for the next Jupiter probe. What's another 20-30 years, huh? But at least we've got a useless space station in a useless orbit!

  • Almathea? (Score:3, Funny)

    by Kierthos (225954) on Friday October 25, 2002 @08:57AM (#4528838) Homepage
    "All these are yours, save Io. Attempt no landing there."

    No problem, guv. These other moons look much more interesting.

    Kierthos
  • by Anonymous Coward on Friday October 25, 2002 @09:00AM (#4528857)
    Hell, has nobody noticed that the real name is Amalthea [arizona.edu]?
    Where are your classics!?
    She was the goat that nurtured baby Zeus = Jupiter!
  • Isn't the extra heat because of all the other planets being built there?

    Oh wait, that's Magrathea...
  • Amalthea (Score:5, Informative)

    by Blackneto (516458) on Friday October 25, 2002 @09:02AM (#4528870) Journal
    The Correct spelling is Amalthea.
    It says so on the JPL's website.
    Also Amalthea was a nymph that nursed Jupiter in mythology. This fits in with the naming of the other moons.
    It looks like it was only misspelled once on the astrobio site which may be the cause of the confusion.
  • by Njoyda Sauce (211180) <jnjpepper.hotmail@com> on Friday October 25, 2002 @09:07AM (#4528901)
    Seriously, as interesting as it would be to find alien life on one of these moons, the more probable scientific interest here would be unlocking a new method of heat creation.

    In the future as we attempt to colonize anything other than earth, we might find it's a bit chilly out there. Generating long-term, sustaining heat on a planetary scale without a nearby sun would be a feat indeed! Through closer study we may learn how to artificially introduce these systems to climates that are less hospitable.
    • The fact that it radiates more heat than it receives implies that there's some kind of heat source within the planet, something like a metal core not unlike earth's.

      When we're capable of artificially introducing something like that into a planet most likely, we're capable of building our own (planets, that is ;).
  • by El Jynx (548908) on Friday October 25, 2002 @09:14AM (#4528936)
    "Almathea is one of the most unusual moons in the solar system, because it gives off more heat than it ceives from the Sun."

    Funny. My girl does the same thing during the more active cycles.
  • by Qbertino (265505) on Friday October 25, 2002 @09:18AM (#4528958)
    ..I just imagined they find an abandoned settlement/station or reactor or something on/in that moon. I mean really. Just imagine.
    That would render all that debating about economy, sadam, snipers and all that stuff irrelevant, wouldn't it?
    Funny to imagine. Things shure would change. For a while that is.

    *sigh* Gotta get that code done... :-)
    • I thought of the same thing. On the other hand; I wondered if one of the last pictures Gal sent was of it being picked up by whatever was out there. One can still hope; especially with some of the long-range viewing activities noticing stars and objects in deep space that seem to have water or life-supporting environments on them. Again, one can only hope.
  • by Anonymous Coward on Friday October 25, 2002 @09:32AM (#4529027)
    Every time I read stories on Galileo I get an incredable feeling of depression, not because the mission has been a failure, it has not. Rather that the craft never reached its full potentual. Early in the mission, the main arial to earth never opened meaning that the amount of pictures we get now are much lower then what we should have gotten, Sometimes I think that Galileo could have been the mission which found life on another planet besides earth. This would have changed everything, instead of planning wars today we would be planing probes to discover what the hell was out there.(a real long shot). Things like the pluto express would not have been cancelled, and millions would not be wasted on the ISS - a project which gets all its money just from the cool factor, and like the shuttle a complete waste of resources.

    Probes are the way to go, its just a pity that for every one sent few manage to survive the trip, the payoff is so great.

    • by raduga (216742) on Friday October 25, 2002 @11:38AM (#4530063)
      With the primary arial undeployed the primary effect has been a reduction in the total number of pictures, and the frequency at which they are captured and returned; since the low-gain antenna / tape recorder are still capable of bringing back images of the same quality, just not nearly as many.

      It's disappointing, sure, but even had the arial been fully deployed, we wouldn't have significantly greater resolution, and might not see substantially more detail of Europa's surface. Also, the change in mission priorities might (?) have meant fewer resources spent on magnetometric observations. Events don't seem to change frequently enough on Europa's surface that a few missing frames would have changed our view much.

      (Contrast with Io! What if we'd missed that eruption?)

    • New Horizons (Score:3, Informative)

      by Merk00 (123226)
      The "Pluto Express" you mentioned is named New Horizons. And it's yet to be canceled. In fact, I sat in on a technical discussion of all its subsystems over the summer. It's still on track to launch sometime around 2007. However, Congress has yet to approve funding for New Horizons so its up in the air whether or not it'll actually fly. That said, development for the probe is still on going.
    • What depresses me is that for the Almathea flyby they've left the camera off to save the expense of the photo team salaries. About the only science that's gonna happen is measuring doppler shift change of the carrier signal from the probe as it gets close to the moon to refine its mass estimate. This is a real shame; Almathea has some kind of interesting chemistry going on that creates unusual bright red and green patches on its surface we have glimpsed only from afar 20 years ago with Voyager...
  • by Big Mark (575945) on Friday October 25, 2002 @09:35AM (#4529051)
    Jupiter is so heavy that it's inner reigions are incredibly hot - some think it's actually a star that just wasn't big enough to have it's own mass crush it's innards to the point where nuclear fusion occurs and the star is born. It's big enough, though, that the innards are squished to to superheat. It's this heat from the inside that makes Jupiter warm up.

    The moon's heating is accounted for by tidal forces - Jupiter is just so flippin' MASSIVE that it's gravity stretches and squeezes the moon, and these tidal forces make it heat up.

    The surface of Amalthea (sp.?) will be interesting to look at. I think it will have pronounced cracks on the surface where aeons of tidal forces have had their way.
    • And possibly a big ol' breeder reactor might be sitting at the core, if there's enough uranium floating around in there.
    • by LMCBoy (185365) on Friday October 25, 2002 @11:04AM (#4529810) Homepage Journal
      It's this heat from the inside that makes Jupiter warm up.

      This parses to "Jupiter is hot because it is hot."

      You're correct that Jupiter's core is not hot enough for nuclear reactions (core temperature is about 20,000 K).

      Just to clarify, Jupiter gives off more heat than it receives because it is still collapsing! Sounds incredible, but the "heavier" elements are still slowly settling out toward its core. As they do, they release gravitational potential energy in the form of heat. This settling process must be incredibly slow, since it's presumably been happening steadily for the past 4.6 Gyr; the fact that it still produces a significant amount of heat demonstrates how damn BIG Jupiter is.

      See SEDS.org [seds.org] for more information (about halfway down the page, right after the section on the Great Red Spot).
    • some think it's actually a star that just wasn't big enough to have it's own mass crush it's innards to the point where nuclear fusion occurs and the star is born.

      And that makes it "actually a star" how, exactly?

      You pretty much just gave the definition for why it isn't a star.

    • ...some think it's actually a star that just wasn't big enough to have it's own mass crush it's innards to the point where nuclear fusion occurs and the star is born

      For nuclear fusion to start you need about 80 times the mass of Jupiter. (and that would be a really really tiny star. Our one is about 1000 times jupiter, and it's only average).
  • by peter303 (12292) on Friday October 25, 2002 @10:02AM (#4529330)
    Rescued from disaster- NASA figured out how squeeze data throught the 50 times slower backup attenna when the main one failed- the Galileo mission has extended five years beyond its planned lifetime. Exhaustion of nagivation fuel and other priorities for the Deep Space Network will eventually finish this mission.
  • It's *Amalthea* (Score:4, Informative)

    by notfancy (113542) <matias@@@k-bell...com> on Friday October 25, 2002 @10:16AM (#4529442) Homepage

    Sorry to pick nits, but the name is Amalthea (ah-mal-THEH-ah), it means "the Goddess Amal" (IIRC a Babylonian name for Astarte, the Moon goddess). She was the goat that nursed Jupiter (Zeus, actually) in Mount Ida, and whose horn the baby god pulled with his mighty force while playing with her. That horn is called the Cornucopia, or the Horn of Plenty, after Jupiter, ashamed at his own clumsiness, bestowed that gift on the goat as an apology.

  • by teridon (139550) on Friday October 25, 2002 @10:26AM (#4529529) Homepage
    From the article:

    Dimensions: The length of the spacecraft is 9 m and, with the high-gain antenna (HGA) deployed, is 4.6 m in diameter.

    Ha! That's great! Except that the high-gain antenna failed to deploy [google.com]. Fortunately, with some spacecraft reprogramming, Galileo will still acheive about 70% of its original science goals using the low-gain antenna.

    • I guess we'll never know, but I have this perverse feeling that the HGA will finally deploy as Galileo plummets into the denser layers of the Jovian atmosphere. (The spacecraft is being dropped into Jupiter at the end of its mission in order to eliminate the possibility that it might eventually crash into one of the Galilean satellites and contaminate it with terrestrial microorganisms.)
      • And the giant superintellegent Jovian gasbags who get whacked on the head by it will suddenly notice those insignificant 'big asteroids' closer to the sun and declare war on them..
    • Except that the high-gain antenna failed to deploy [google.com]. Fortunately, with some spacecraft reprogramming, Galileo will still acheive about 70% of its original science goals using the low-gain antenna.

      That 70% is kind of a fuzzy number. Who knows what they would have discovered if the antennas worked as planned? It is true that most instruments were able to be used at nearly their full potential because they generate low-bandwidth data sets to begin with. However, high-bandwidth consuming studies, such as close-up "movies" of Jupiter's weather patterns may have told us a lot about Jupiter.

      And with less compression needed on photos, we may have had clearer (more enhance-able) pictures of say Europa. But it is true that they got nice data from most instruments regardless of bandwidth problems.

      Antennas and instrument booms have a history of deployment problems on probes. One of the Voyagers had an instrument boom would not lock into place, ruining some gas giant moon cose-ups. A Viking had a seismometer (sp?) that would not work because a springed latch would not jog. Perhaps they should include a long lite robotic arm that can be remotely told what to push on or poke at. IOW, a way to emulate the famous hammer tap to a farky gizmo.

      It seems like moving parts don't like to move in space for some reason. The wide tempurature and pressure variations during the trip perhaps damage lubricants [1]. They can't get rid of all of the moving parts because launch packaging constraints often require "pop-up" equipment.

      [1] Galileo had to sit in storage for a while due to the launch backlog from the Challenger explosion. Some think that the sitting caused the antenna joint libricant to harden.
  • by erik_fredricks (446470) on Friday October 25, 2002 @11:30AM (#4529985)
    Almathea is one of the most unusual moons in the solar system, because it gives off more heat than it receives from the Sun."

    Actually, Triton (Neptune's largest) does, too, IIRC. All the gas giants do as well.

    In Amalthea's case (as well as Europa and Io), the moon is constantly being contracted and stretched by Jupiter's gravity, and those tidal forces generate heat in the moon's core. You can duplicate this effect by squeezing a piece of styrofoam in your hand and feeling it heat up.

    Of course, all the gas giants have internal heat sources due to the immense gravity in their highly contracted solid cores. Neptune gives off way more heat and light than it receives from the Sun.
  • by mraymer (516227) <mraymer@@@centurytel...net> on Friday October 25, 2002 @01:35PM (#4531267) Homepage Journal
    Celestia [shatters.net] is a 3D space simulator much like OpenUniverse. It's avaible for both Windows and *nix OSes. In it, you can view all the planets, some moons, asteroids, and a fair number of stars. Here's a shot of Almathea. [centurytel.net]They release add-ons every now and then-- you can even download the recently discovered Quaoar!
  • I wonder what sort of strange substance that is...

The universe seems neither benign nor hostile, merely indifferent. -- Sagan

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