Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Life on moon rather than planet

  1. Mar 21, 2010 #1
    why planethunters and astrobiologists are concentrating on finding life on earth like planet with an orbit around host star rather than on jupiterlike planets moon

    i was browsing through the essentials of complex life to evolve on a planet. i am sure you all pretty much know that.

    plate tectonics,
    reasonable gravity (1/2 earth to 10 earth masses)
    massive magnetic field
    big moon to stabilize planets tilt
    certain degree of vulcanism
    habitable zone

    i was adding up probabilities for thease occations to happen on earthlike planet. and found out that this is very higly improbable.
    for e.g. for earthsize planet to have a big moon is almost imposible. it really involves two planet crash. wich means two planets have to form in same orbit. witch is close to impossible.
    to have a massive magnetic field is also very impossible for small planets.

    if a planet is a moon to a jupiter. its much much easier. - probable.

    you dont have to have your own magnetic field - solar winds are deflected by host planets magnetic field.
    host planet does not let its moon tilt go wild.
    it is cracking the planets core allowing vulcanism and plate tectonics to accure on much smaller objects than earth - sustaining rich atmosphere
    it is protecting against asteroids and comets.

    we have no reason to believe that jupiterlike planets will not have many big moons like it is here
    we see that facelocking threat is not an often case in solar system moons
    we know that gas gigants often drift inwords after planet formation and mey find its orbit near habitable zone.

    if we could put our gas giants in habitable zone i have at least 2 moons airing for life - europa and titan, maybe titania... but it could be more than that

    it is easy to detect jupiterlike planets. wich means we know exact points where to concentrate our efforts in order to find the moons rather than looking for planets everywhere
  2. jcsd
  3. Mar 21, 2010 #2

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2017 Award

    They aren't. But planet hunters can only see extrasolar planets, not moons.
  4. Mar 21, 2010 #3
    and not just any planets, they have to be relatively large compared to their star. basically, we're only seeing the "jupiters" of other stars.
  5. Mar 21, 2010 #4
    keppler mission (loounched march 2009) wich is the most expensive and promising planethunting device... is built to detect earthlike planets in an area as big as two constilations.

    it is not explicitly pointed to known jupiters in habitable zone.

    1. so i guess we are concentrating on planets rather than moons
    2. yes we can detect earthsize objects (data is flowing in ever day)
  6. Mar 21, 2010 #5
    interesting. I wasn't aware of that.
  7. Mar 21, 2010 #6


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Kepler works by measuring a dip in the brightness of a star as a planet passes in front of it. This is not very conducive to detecting moons circling a gas giant.
  8. Mar 23, 2010 #7
    Yes that is what I am saying.
    It is built so that it can detect planets not moons.

    which in my opinion is incorrect.

    I dont know how a moondetecting instrument should work...probably the same way - measuring the dip in solar radiation (light) of a star made by host planet and see if that dip is not linear and has some periodical fluctuations. if the instrument would zoom in any known jupiterlike planet in any constellation, whenever it or the host star is eclipsing. then the data could maybe reveal something

    but anyhow the idea stays, living on moon is far more easier - in onther words - probable - in other words moons ought to be more frequently inhabited than planets.

    this graph shows that there are a lot of known jupiters in habitable zone

    we are all the time complaining that we keep finding only jupiters, but i believe - that is just what we need.
  9. Mar 23, 2010 #8


    User Avatar
    Gold Member

    Simply put: we are doing the absolute best we can. Planet detection is right at the very limits of our technology. Anything we see is a bonus.

    Wait another ten years, till planet detection is as common as dirt, then we'll start getting picky about what kinds we want to concentrate on.
  10. Mar 23, 2010 #9
    The variation in light between a large planet eclipsing a star is very, very small. And it would be very^5 smaller for a moon eclipsing a star. You would have to know the orbit of the planet, and be able to look at the star just before and just after the planet eclipses the star in order to detect a variation in light output.

    Heck the variation in light output is small for binary stars!
  11. Mar 24, 2010 #10

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2017 Award

    I find this very, very, very hard to believe. Do you have any evidence for your claim?
  12. Mar 24, 2010 #11


    User Avatar
    Gold Member

    Your arguments are way too Earth-centric, and flawed even at that.

    One example:
    No they don't.

    Dolphins are intelligent yet they live in an environment that is relatively opaque to visible light beyond a few dozen feet. They do quite well with sonar. Scorpions locate prey using vibrations through the ground. And, of course, bats...

    You are looking at the whole scenario backwards. Life does not get to choose the planet it evolves on. It's not like life is going to say to itself "hm, this atmosphere is opaque, I guess I won't bother evolving beyond the bacterial stage."

    If life got a start on a planet with an atmo that's opaque to visible light, it would just make do.
  13. Mar 24, 2010 #12


    User Avatar
    Gold Member

    What is not naturally evolved about dolphins, scorpions or bats?

    OK, now you're talking about technologically advanced. You're changing the goal posts.

    On what do you base this?

    On what do you base this?

    TESLACOILZAP, you are simply saying stuff that makes sense to you and claiming it as obvious or inevitable. This is not how science works.
    Last edited: Mar 24, 2010
  14. Mar 24, 2010 #13


    User Avatar
    Gold Member

    Yes we all have good imaginations. What does 'imagination' have to do with 'doable'?

    This is a rhetorical question. You are not answering a question asked, you are off on a philosophical tangent.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook