Re: Europa life papers for europeans

[Edwin Kite]

> HOWEVER: the analyses of Europan impact-gardening rates conducted since
this
> paper by Chyba and others strongly suggest that the oxidants and organics
> created in Europa's upper film of ice by Jovian particle radiation ARE
> mostly buried safely before solar UV light can break them back down again.
> I am not -- I hope -- wildy optimistic about the possibility of life on
> other worlds, but I find these new papers on Europan ocean oxygenation
> nothing short of electrifying.  If the theory is true, the chances of
> Europan life may actually be INCREASED if Europa has little geological
> activity on its ocean floor, since this would expose less fresh reduced
> rocks and gases to eat up much of the ocean's oxygen.

Interesting! But isn't there a basal layer of MgSO4.7 H20 insulating the
ocean from reducing agents on the seafloor in any case?

Riff => to be taken with a pinch of epsomite ;-)

If the upper limit of 10^12 mols/year is continuously produced and
transported, and there are no sinks - animal, vegetable, microbial (call me
prejudiced) or mineral (see above) - the ocean will become DO-saturated in a
geologically short time. If the ocean is well-mixed this'll take 400 Ma.

At ice + water depths of 42 km (if my shums are straight), bubbles will rise
to the top of the ocean; below 42 km they will sink.* More to the point, so
long as the rate of O2 removal at the base of the ocean is less than the
rate of addition (assuming water diapirism is negligible and fresh ice
crystallises slowly), O2 will accumulate in a layer at the water-ice
interface. The maximum rate, with a 20 km thick shell, would be 2.8 microns
per year. Leave that kind of process running for a few million years and
you've partially decoupled the ice lid from the ocean, which should cause
some iffy stress patterns.

So will the first smoker on Europa please light up outside?

Ed Kite

* If the ocean is extremely well-stratified and convection rare - which is
unlikely - K40-generated oxygen will eventually create a "bubble raft" at
this depth.



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Re: Europa life papers for europeans

[Bruce Moomaw]

- Original Message -
From: "Edwin Kite" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Friday, June 21, 2002 7:40 AM
Subject: Re: [jupiter_list] Re: Europa life papers for europeans


> Hi Cynthia,
>
> I'm a high-school student in Newcastle, England interested in Europa. I
> don't thing OLEB is obscure, but I do think its expensive ;-o
>
> I'd be very grateful if you could send me the pdf of your paper.
>
> Cheers,
>
> Ed Kite.
>
> > You can get our PNAS paper free online at:
> >
> > http://www.pnas.org/cgi/content/full/98/3/801
> >
> > We also published an updated, fuller version recently in Origins of Life
> > and the Evolution of the Biosphere, in the February 2002 issue (sorry,
> > another obscure journal I guess :).  Abstract available here:
> >
> > http://www.kluweronline.com/issn/0169-6149/current
> >
> > Email me if you need a pdf of the paper.
_

One important point: that PNAS paper (Jan. 30, 2001) contains the following
passage:

"It is natural to wonder whether analogs to giant squid or other macrofauna
might exist in the Europan ocean.  Terrestrial metazoa require high levels
of dissolved oxygen.  For example, benthic macrofauna require O2
concentrations above ~20 millimoles/liter.  Even in a complete absence of O2
sinks in Europa's ocean, the production rate of O2 from H2O2 derived above
would require ~200 million years to oxygenate Europa's entire ocean to this
level.  Calculating H2O2 via n=FGt would decrease this time to ~50,000
years, but this requires significant recycling of the upper meter of
Europa's ice.  If this does not occur, and if we assume that Europen
macrofauna would face the same high-energy respiration requirements as
terrestrial macrofauna, we are challenged to find a sufficient source of O2
production in the absence of photosynthesis."

HOWEVER: the analyses of Europan impact-gardening rates conducted since this
paper by Chyba and others strongly suggest that the oxidants and organics
created in Europa's upper film of ice by Jovian particle radiation ARE
mostly buried safely before solar UV light can break them back down again.
I am not -- I hope -- wildy optimistic about the possibility of life on
other worlds, but I find these new papers on Europan ocean oxygenation
nothing short of electrifying.  If the theory is true, the chances of
Europan life may actually be INCREASED if Europa has little geological
activity on its ocean floor, since this would expose less fresh reduced
rocks and gases to eat up much of the ocean's oxygen.  (Of course, it's
quite possible that, if the ocean is highly oxygenated -- unlike early
Earth's bodies of water -- this might actually prevent the evolution of life
from prebiotic molecules there.)

Really, every new look we take at this world simply seems to increase its
biological interest further.  We'd be fools not to follow this up with
further examinations.

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