A question about Europa

zeldun · Nov 30, 2007

Hi, I am not new to this forum, I read it a lot. This is, however, my first post. Well, to my question. What if, say in a parallel universe or something, Europa would have became Earth moon instead of the one we know of today orbiting our planet. Given this, how would Europa be like? I think reading an answer to this question could be a fun way to learn more about Europa. So, given what you know about this moon, how do you think it would have been constituted if orbiting Earth instead of Jupiter? Maybe, in answering this post, you could also tell which moon you would rather have orbiting Earth than the dead rock orbiting our planet right now, and what your reason behind your choice is. And please excuse my bad spelling, I will be happy to read your answers if anyone got any. /Tobias from a cold and wet Sweden

3488 · Nov 30, 2007

Hi Zeldun, Still welcome to SDC. A few basic facts first, before I raise my points. Europa has diameter of 3,130 KM & has an average density of 3.08 grammes per cubic centimetre. Europa orbits Jupiter at a distance of only approx 671,000 KM, once every 3 days, 12 hours & 30 minutes (approx), & rotates at the same period *(see note below)*, therefore like our own moon (with respect to Earth), Europa keeps the same face turned towards Jupiter. Europe is a highly differentiated body, with a small metal core, likely Iron or Iron Sulphides, overlain by a very deep silicate rock mantle, much of which, is likely to be molten, above which a H2O layer, which is suspected of being at least double layered, a frozen hard outer crust, with an ocean beneath, maybe 100 KM deep. Much of Europa's surface appears to be less than 30 million years old, using the crater counting method, though the current cratering rate within the Jupiter system is not well known, so the surface of Europa could be older. Even so, it is not primordial like Callisto, the giant outermost Galilean moon. Europa experiences approximaetly 10% if the tidal heating that its inner larger neighbour Io experiences. This is still more than sufficient to power volcanoes on the suspected ocean floor, if it exists, & to maintain a large amount of magma in the mantle. *Note reffered to from above* One piece of evidence of a subsurface ocean is the fact, that there arctuate scarps on the ice surface, suggesting that the outer ice crust of Europa is not physically attached to the silicate mantle, that in fact the surface of Europa completes an extra turn, once every 500,000 years, so every 250,000 years, Europa presents alternate hemispheres to Jupiter, whilst the main body of Europa does not do this, hence a liquid layer to decouple the surface from th <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

3488 · Nov 30, 2007

Hi Zeldun, Still welcome to SDC. A few basic facts first, before I raise my points. Europa has diameter of 3,130 KM & has an average density of 3.08 grammes per cubic centimetre. Europa orbits Jupiter at a distance of only approx 671,000 KM, once every 3 days, 12 hours & 30 minutes (approx), & rotates at the same period *(see note below)*, therefore like our own moon (with respect to Earth), Europa keeps the same face turned towards Jupiter. Europe is a highly differentiated body, with a small metal core, likely Iron or Iron Sulphides, overlain by a very deep silicate rock mantle, much of which, is likely to be molten, above which a H2O layer, which is suspected of being at least double layered, a frozen hard outer crust, with an ocean beneath, maybe 100 KM deep. Much of Europa's surface appears to be less than 30 million years old, using the crater counting method, though the current cratering rate within the Jupiter system is not well known, so the surface of Europa could be older. Even so, it is not primordial like Callisto, the giant outermost Galilean moon. Europa experiences approximaetly 10% if the tidal heating that its inner larger neighbour Io experiences. This is still more than sufficient to power volcanoes on the suspected ocean floor, if it exists, & to maintain a large amount of magma in the mantle. *Note reffered to from above* One piece of evidence of a subsurface ocean is the fact, that there arctuate scarps on the ice surface, suggesting that the outer ice crust of Europa is not physically attached to the silicate mantle, that in fact the surface of Europa completes an extra turn, once every 500,000 years, so every 250,000 years, Europa presents alternate hemispheres to Jupiter, whilst the main body of Europa does not do this, hence a liquid layer to decouple the surface from th <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

thalion · Nov 30, 2007

3488 has it about right... Europa is so water-rich in large part *because* of where it formed: in the volatile-rich outer solar nebula, where Europa's low gravity was more than compensated by their abundance (Jupiter's own formation probably figures into it in some way, as well). Placed around Earth, Europa's ice would melt, and the water vapor would be lost to space, and a geologic eyeblink later, it would end up looking...well...pretty much like our Moon does now. Then again, Europa has an awful lot of water, and I think it's safe to say that there's enough we don't know about planet and satellite formation to prevent it from being impossible. That said, if Europa formed around Earth it would probably still be pretty dry, perhaps with a *very* thin atmosphere that would dissipate rapidly without a steady trickle of volatiles from the interior. Aside from thin or patchy ice in polar regions, I'm guessing all other differences from our Moon would be relatively minor.

kelvinzero · Nov 30, 2007

Ok so Europa wouldnt have water on the surface, but what about hydrogen and carbon chemically bonded to the rocks? I read somewhere that the undifferentiated geology of the moon was related to the odd way it had formed from some collision with the earth. It is a real pity that the moon appears to have basically no hydrogen, carbon, nitrogen or phosphuros in useful amounts. ie all the key elements of life except for oxygen. Can anybody correct me on that? When will we know more about the poles and the possibility of useful elements there? One thing is.. not having at atmosphere may actually be a bonus. The thin mars atmosphere apparently makes landing on it much trickier than either earth's thick atmosphere or the moons vacuum.

3488 · Nov 30, 2007

Hi KelvinZero. The Moon is not undifferentated. The Moon has a definate core, mantle & crust. In fact the Moon, is more like a small planet, than a stereotypical unevolved 'moon' object. I do not personally buy into the collision theory for the moon's formation, as I think it formed in one of the langrangian points with Earth, & over time, the moon drifted close enough for capture. It is my opinion only. Maybe the moon DID form by impact, but I do not know & have serious doubts about that theory. Yes if Europa had formed around Earth, than there would be no water there, in fact we would have a smaller moon, approx 63% that of our own Moon. It would still be a large object & would still be one of the largest moons in our Solar System, but not quite the giant moon we do have. I would still expect some hydrogen & carbon to be chemically bonded to the rocks. There was (in the proto solar nebula) & still is an ample supply of both (comets & asteroid impacts), that this would not be an issue. Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

3488 · Nov 30, 2007

Cheers Thalion, Your take is identical to mine. I have studied the Jupiter system & also had extensive contact with people involved in the Galileo mission & a little contact with the New Horizons team. Europa obviously was a major talking point as was Io. One thing that is noticable is that the infant Jupiter did have a bearing on how the Galileans turned out. Io is the densest known planetary moon in the solar system, @ about 3.55 Grammes P C CM, Europa @ 3.08, Ganymede @ 1.93 & Callisto @ 1.81. A definate trend is apparent here, the density falls off as one moves away from Jupiter. Jupiter must have given off immense heat when forming, thus driving out many of the volatiles close in. The Saturn system, BTW does not have this density drop off. When the Galileo spacecraft encountered Amalthea, that encounter seemed to throw a spanner in the works with that neat model, revealing Amalthea to be about the same density as ice!!!! Hovever, Amalthea may not have formed in that orbit & there are suggestions that the four inner smaller moons, may actually be captured asteroids / comets, that were place inthose orbits through interactions with Io. If so, than the previous model of the reasoning behind the density fall off withing the four giant moons remains correct & that Io indeed is the innermost genuine Jupiter moon. Also tidal influences appear to play a part too. Io is very active, Europa less so, Ganymede less so again (probably inactive now, but cannot be too sure) & Callisto definately so. Ganymede though appears to have had a temporary resurgence of activity approx 1GYA, for reasons that are currently unknown. Ganymede appeared to had temporarily taken up a more eccentric orbit, thus tidal heating started, but then after a while, the orbit settled back into a more stable configu <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

kelvinzero · Nov 30, 2007

Oops, yes. Wrong word. Maybe hetrogeneous? But again that doesnt seem to explain what I thought.. What is the reason the moon is so lacking in carbon? (hey look! (off topic)pure carbon stars. I found that while trying to discover how common carbon is. Apparently very common.)

3488 · Nov 30, 2007

I wonder when the surface of the Moon, was a Magma Ocean, that drove it off?? Clearly the lunar surface was subjected to very high temperatures in its youth. Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

brellis · Nov 30, 2007

A question stirs in my head: if our Moon once had water, would some of it have fallen to earth? <div class="Discussion_UserSignature"> I'm a recovering optimist - things could be better. </div>

kelvinzero · Nov 30, 2007

I wonder when the surface of the Moon, was a Magma Ocean, that drove it off?? Oh. You mean combining with oxygen to form a gas which escapes?

alokmohan · Dec 1, 2007

It would be evaporated I think.

3488 · Dec 3, 2007

Alokmohan is correct. If a water rich world like Europa, formed as our Moon instead, any transfer of H2O would evaporate. The long & short of the situation is that Europa, in its current form, could not form near Earth. Sunday 2nd December 2007 . Europa APOD. Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

zeldun · Dec 3, 2007

Thanks for all your answers! I also would like to know how Titan would be like if it were to orbit Earth. Would Titan also turn into a dead rock?

3488 · Dec 3, 2007

Hi Zeldun, Yes, I am afraid so. Although Titan is considerably larger & more massive than Europa, the outcome would still be the same. Really, what would be required would be something at least the mass of Mars, to have enough gravity to prevent the volatiles from boiling away @ this distance from the Sun. Even saying that, even Mars may not be massive enough, with only 11% of the Earth's mass. Even giant moons like Ganymede, Titan & Callisto, would not survive long term @ 1 AU from the Sun. They are made from too many volatiles. Io would manage nicely as Io is made from rock & metal, like our own moon. Ganymede's ice crust would go, but the mantle & core would survive, as once again, they are silicate rock & metals. The bottom line is, unless the object has a strong gravitational field, like Earth, that can hold down a dense atmosphere, that can raise the boiling point of water to a high temperature, then forget it, I'm afraid. Glad to be of some help here. I do find this sort of thing most interesting. Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

jasonpply · Dec 3, 2007

have any sort of drilling or inner surface studies been performed on our moon to see if any type of rich metals or resources ie;neuclear or say gas or oil lie within? i think drilling on the moon or on mars could be an asset to our own world by preventing us to destroy it further.

alokmohan · Dec 4, 2007

Whenever Europa is discussed I remembe Patrick moore who inspired so many like us to Europa.He told us to fish in Europa.Patrick Moore: They're eruptions of hydrogen gas from the sun's surface. You can't see them, you need specialist equipment for it. Don't turn your binoculars towards the sun, be very careful. Question from Esther, Netherlands: Why do some stars twinkle red and blue-ish instead of staying just red or just blue? Patrick Moore: Entirely due to the earth's atmosphere. Go to the moon and the stars won't twinkle. Question from George Moore: I believe that aliens - if they exist - would probably not be little green men, but very like humans. Do you agree? Patrick Moore: I think you're probably right. I see no reason why life would be different to ours. It may be different though, there's no positive proof there yet. Depending on how advanced they are, they might be looking for life elsewhere, like we are doing. Question from Mike Proctor: What is gravity? Patrick Moore: A curviture of space time. It's not a simple thing at all. In plain English I can't do, neither could Einstein! Question from John B: What made you want to become an astronomer? Patrick Moore: When I was 6, I picked up a book called 'The Story of the Solar System'. I read that and was fascinated, and went on from there. When I should have been going to university, I went into the RAF instead though. Question from Mike Banks: Do you believe the first moon landing took place? Patrick Moore: Of course I do. The idea that it was a fake came from a film and how anybody can believe that I do not know. If people believe the moon landings were fake, if ignorance is bliss you must be very happy. Question from Axe9: What was your most memorable stellar event? Patrick Moore: A total eclipse of http://www.bbc.co.uk/communicate/archive/patrick_moore2/page2</safety_wrapper

A question about Europa

zeldun

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thalion

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brellis

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