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Thread: zones for life just got narrower

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    Default zones for life just got narrower



    it's not just the water "Goldilocks" zone, there is an ultraviolet "Goldilocks" zone as well. you need to get lucky twice....

    UV Habitable Zones Further Constrain Possible Life

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    Default Re: zones for life just got narrower

    That's a significant constraint on possible life out there. Thanks for pointing this out not_Fritz.
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    Default Re: zones for life just got narrower

    Quote Originally Posted by not_Fritz_Argelander View Post
    it's not just the water "Goldilocks" zone, there is an ultraviolet "Goldilocks" zone as well. you need to get lucky twice....

    UV Habitable Zones Further Constrain Possible Life
    Is it worth mentioning that the Earth is not in the Suns UV inhabitable zone?
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    Default Re: zones for life just got narrower

    Quote Originally Posted by MG1692 View Post
    Is it worth mentioning that the Earth is not in the Suns UV inhabitable zone?
    It would be worth mentioning that if it were true. However it is not. The location of the habitable-UV zone depends on the metallicity of the star. For the solar metallicity the Earth is in the water and UV habitable zone. Figure 3 of the paper shows this.
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    Default Re: zones for life just got narrower

    Quote Originally Posted by not_Fritz_Argelander View Post
    It would be worth mentioning that if it were true. However it is not. The location of the habitable-UV zone depends on the metallicity of the star. For the solar metallicity the Earth is in the water and UV habitable zone. Figure 3 of the paper shows this.
    But I would suggest they are offering a self defeating argument. The goldilocks zone means liquid water. The same liquid water that can protect life against excessive UV rays until an ozone layer can be formed around the planet
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    Default Re: zones for life just got narrower

    Popcorn please
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    Default Re: zones for life just got narrower

    Quote Originally Posted by MG1692 View Post
    But I would suggest they are offering a self defeating argument. The goldilocks zone means liquid water. The same liquid water that can protect life against excessive UV rays until an ozone layer can be formed around the planet
    No. They aren't offering a self contradictory argument.

    They are saying there are two "Goldilocks zones". One is for liquid water, ZoneH2O. The second is for the right amount of UV, ZoneUV. Life can be found at the intersection of the two zones: those places that are in both ZoneH2O and ZoneUV.

    Water provides little protection down to about 200 nanometers. So a strong enough UV source can wreak havoc.

    https://en.wikipedia.org/wiki/Electr...quid_water.png

    The full article
    https://en.wikipedia.org/wiki/Electr...ption_by_water

    shows that as a vapor there are many transparency gaps at short wavelengths.

    What was the basis for your claim that the Earth was not in the Sun's UV habitable zone? I cannot understand that unless you were reading the low metallicity chart. Was that your error?
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    Default Re: zones for life just got narrower

    Quote Originally Posted by not_Fritz_Argelander View Post
    What was the basis for your claim that the Earth was not in the Sun's UV habitable zone? I cannot understand that unless you were reading the low metallicity chart. Was that your error?
    Because the chart does not hold up against the one biosphere we have access to. Ours. Without the ozone layer all life composed of DNA and RNA is gone. It only takes a dose of 254nm to start damaging the strings but the ozone layer blocks between 300 and 500nm. More than enough to toast anything trying to live. So prior to the GOE, life had only one potential habitat to survive in, and that is water
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    Default Re: zones for life just got narrower

    Quote Originally Posted by MG1692 View Post
    Because the chart does not hold up against the one biosphere we have access to. Ours. Without the ozone layer all life composed of DNA and RNA is gone. It only takes a dose of 254nm to start damaging the strings but the ozone layer blocks between 300 and 500nm. More than enough to toast anything trying to live. So prior to the GOE, life had only one potential habitat to survive in, and that is water
    I think you misread the chart. The chart, when read correctly, says that Earth is fine. Please reread the chart. Figure 3.

    Also the statement that "it only takes a dose of 254" for damage is physically wrong. The wavelength of 254nm needs an intensity to specify a damaging dose. The paper takes both wavelength and intensity into account. The blanket statement that any level of 254nm radiation is 100% lethal is erroneous.
    Last edited by not_Fritz_Argelander; 01-31-2017 at 02:35 AM.
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    Default Re: zones for life just got narrower

    Quote Originally Posted by not_Fritz_Argelander View Post
    The wavelength of 254nm needs an intensity to specify a damaging dose. The paper takes both wavelength and intensity into account. The blanket statement that any level of 254nm radiation is 100% lethal is erroneous.
    The good and correct methodology of the paper is that they use a probability distribution that describes the probability of bond breaking which depends on both the wavelength and the intensity of the radiation at that wavelength. Saying that radiation at 254 nm is 100% efficient at breaking bonds regardless of intensity is not a good physical model.
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