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Thread: What if, Earth was orbiting a Gas Giant closer to the Sun?

  1. #1 What if, Earth was orbiting a Gas Giant closer to the Sun? 
    Forum Cosmic Wizard icewendigo's Avatar
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    What kind of atmosphere and climate could we expect if Jupiter was orbiting the sun somewhere between Venus and the current orbit of Earth, and Earth was orbiting that Jupiter?

    Would the temperature rise along with sea levels, and would their be more cloud cover and rain?

    Would it be more suitable for plants to proliferate on land (less desserts)?


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  3. #2  
    Time Lord
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    I think more detail would help. Is the Earth's orbit around Jupiter mostly circular or highly elliptical? Does Jupiter get to keep it's other moons? How close is Earth's orbit around Jupiter. This is important because Jupiter emits a lot of radiation (slightly more heat than it receives from the Sun), and if the Earth's orbit were like say that of IO, very close with some variation in how close it gets over time due to an elliptical orbit, the tidal forces would cause it to have a lot of geological activity.

    Io (moon) - Wikipedia, the free encyclopedia


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    Forum Cosmic Wizard icewendigo's Avatar
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    Ok lets say it has all its moons except Io, and Earth is in an orbit as close to that of Io as is possible (ex: slightly farther and faster than Io)


    I just thought that when on the sun exposed arc, given the proximity of jupiter to the sun and the massive amount of light that would be bouncing back to the night side on earth, there would be periods with not-that-dark nights, and when on the other side of jupiter there would be a lot of eclipses, so you might have a cycle of more heat(bright nights) and more cold (dark days), then our present day night cycle.
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  5. #4  
    Moderator Moderator Janus's Avatar
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    Quote Originally Posted by icewendigo View Post
    Ok lets say it has all its moons except Io, and Earth is in an orbit as close to that of Io as is possible (ex: slightly farther and faster than Io)
    Slightly further would mean slower not faster.

    One thing would be sure, the Earth would be tidally locked to Jupiter keeping one face to it at all times, and with Jupiter's immense tides, the oceans would be all piled up on the Jupiter and anti-Jupiter sides. This also means that a day would be equal in length to one orbit around Jupiter (~42 hrs for Io)

    I just thought that when on the sun exposed arc, given the proximity of jupiter to the sun and the massive amount of light that would be bouncing back to the night side on earth, there would be periods with not-that-dark nights, and when on the other side of jupiter there would be a lot of eclipses, so you might have a cycle of more heat(bright nights) and more cold (dark days), then our present day night cycle.
    Jupiter would reflect a lot of light onto the side facing it when it is full, but the other side would never see Jupiter. So one side would have a ~20 hr day lit period followed by ~20 hrs of dark. The other would have a ~20 hr day lit period broken up by a 2 hr eclipse (assuming the plane of the orbit aligns with the ecliptic), followed by a Jupiter lit night with the light levels peaking at around the same as an overcast day.
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  6. #5  
    Forum Cosmic Wizard icewendigo's Avatar
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    Wow, thats quite a difference from what we have today.
    1-Would cloud cover be less, the same or greater?
    2- Would the air and sea water temperatures on earth stay the same (but with greater peaks of day warmth and night cold)? Or is there some mechanism I'm missing that would increase (or decrease) the temperature?
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  7. #6  
    Moderator Moderator Janus's Avatar
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    Quote Originally Posted by icewendigo View Post
    Wow, thats quite a difference from what we have today.
    1-Would cloud cover be less, the same or greater?
    2- Would the air and sea water temperatures on earth stay the same (but with greater peaks of day warmth and night cold)? Or is there some mechanism I'm missing that would increase (or decrease) the temperature?
    There is just not enough information to say. Over all cloud cover and temperatures rely on so much. Ocean currents for one. With the oceans all piled up on opposite sides of the planet and the two sides not connected, climate patterns will be different, but in what way would take a pretty complicated model to figure out.
    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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  8. #7  
    Forum Cosmic Wizard icewendigo's Avatar
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    I see, thanks
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    Jupiter would add a lot of heat in general, regardless of what side we were on, because it radiates slightly more energy than it absorbs (due to internal mechanisms) and at so near an orbit to the Sun it would absorb quite a lot of Sunlight due to its size.

    It works like this:

    1) - Sunlight hits Jupiter and heats it up.

    2) - The very hot Jupiter radiates black body radiation into space due to its internal temperature (not necessarily visible light, but we still feel it. Think about how your body feels when you sit near a hot fireplace.) The amount of this radiation it sends out must be equal to the amount it absorbs, or it must have some internal process eating the heat up. Otherwise it would continue to get hotter and hotter forever.

    3) - Earth being very near this very hot Jupiter gets a lot of that black body radiation.

    I'm not sure quite how hot Jupiter would get, though. Maybe it only gets as hot as Earth, or maybe a lot hotter, or cooler. It depends on how well it absorbs/reflects heat. Part of what keeps Earth cool is the reflective nature of the polar ice caps, directing some sunlight away before it can be absorbed.
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    Forum Bachelors Degree dmwyant's Avatar
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    A better orbital distance would probably be on the lines of Europa over Io. If your gas giant was closer than the current Earth orbit I don't know that life would be able to exist. When you add the radiation of Jupiter to the increased distance to Sol I think that it would make the planet inhospitable for life. Maybe you could have deserts and such. However if you moved it back say closer to a Mars orbit, you may be able to achieve a biosphere. I love theoretical stuff like this.

    A question Janus. Why would the planet be in a tidal lock. I thought a few of Jupiter's moons have their own rotation.
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  11. #10  
    Moderator Moderator Janus's Avatar
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    Quote Originally Posted by dmwyant View Post

    A question Janus. Why would the planet be in a tidal lock. I thought a few of Jupiter's moons have their own rotation.
    The time it takes to tidal lock a satellite to its primary is proportional to the Average distance to the 6th power and directly proportional to the mass of the satellite. However, it is inversely proportional to the mass of the primary squared and the radius of the satellite cubed.

    IO's orbit is 1.099 the radius of the Moon's
    Earth is 81 times more massive than the Moon
    Jupiter is 317 times more massive than the Earth
    Earth's radius is 3.67 times that of the moon.

    So if we compare the time it would take Jupiter to tidal lock the Earth at Io's orbit compared to the time the Earth took to tidal lock the Moon we get roughly:



    = 0.000029

    meaning it should take Jupiter about 1/34800 the time to tidally lock the Earth as it took the Earth to tidally lock the Moon.

    Yes, there are some moon's that are not tidally locked, but you have to go out to Himalia, and it orbits over 11 million km away from Jupiter. At that distance, Jupiter's angular size would only be ~1.4 times that of the Moon as seen from Earth. It orbital period would be ~250.5 days. This in turn would make the synodic period (full Jupiter to full Jupiter) 797.3 days ( assuming Jupiter orbited at Earth distance).

    We are not sure about a couple of the inner moon's like Metis. Since tidal locking is so dependent on the satellite radius, and Metis is so small, it may have avoided having been tidally locked yet. it would depend on what its initial rotation rate was.
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