Possibilities for complex life on Europa.

[Robert Clark]

An article in Science of 1999 suggested that the lack of
photosynthesis and therefore probable lack of oxygen at the depths of
the Europan ocean make life more complex than single-celled organisms
on Europa unlikely:

Lack of Energy Makes Europan Life Unlikely
"Pasadena - June 3, 1999 - Future space travelers to the watery Jovian
moon Europa should probably leave their fishing tackle at home. A new
study conducted by California Institute of Technology and Jet
Propulsion Laboratory scientists shows that the Europan ocean is
unlikely to harbor any life form more complex than single-celled
organisms -- and maybe not even that."
http://www.spacedaily.com/news/europa-99b.html

Life in Ice-Covered Oceans. E. J. Gaidos, K. H. Nealson, and J. L.
Kirschvink, 1999 Science 284: 1631-1633,
http://www.gps.caltech.edu/~gaidos/REPRINTS/science284.pdf [full text]

I proposed a possible method by which oxygen might be able to reach
the ocean depths in a post to sci.astro copied below. Chris Chyba has
also proposed a method by which oxidants can reach the ocean depths
that could power a possible Europan biosphere:

Jupiter's Deadly Radiation Could Power Life On Europa
http://www.space.com/scienceastronomy/solarsystem/europa_life_000126.htm
l

Another possibility arises from the discovery of a curious glow coming
from some hydrothermal vents:

The Light at the Bottom of the Ocean
Oceanographers struggle to explain a strange glow from seafloor vents
http://www.sciencenews.org/sn_arch/9_7_96/bob2.htm

Variations in Ambient Light Emission from Black Smokers and Flange
Pools on the Juan de Fuca Ridge, S.N. White, A.D. Chave, G.T. Reynolds,
E.J. Gaidos, J.A. Tyson, and C.L. Van Dover, 2000, Geophysical Research
Letters 27: 1151-1154,
http://www.gps.caltech.edu/~gaidos/REPRINTS/grl27b.pdf [full text]

It was found the light detected is greater than that which would be
produced from the heat of the vent systems alone. Indeed there is
sufficient light to produce photosynthesis. Then this might provide a
means to produce photosynthesis and oxygen at the depths of the Europan
ocean.

However, it should be noted that a recent theory has proposed that the
glow arises from the oxidation of the sulfides that originate from the
hydrothermal vents. If so, then the water would already have to be
oxygenated for the light to be produced:

Seeing the light,
New Scientist, 20 March 1999,
http://www.newscientist.com/ns/19990320/newsstory3.html

Free radicals and chemiluminescence as products of the spontaneous
oxidation of sulfide in seawater, and their biological implications,
DAVID W. TAPLEY, GARRY R. BUETTNER, and J. MALCOLM SHICK . The
Biological Bulletin, v. 196 (1) 1999 pp. 52-56,
http://zeus.mbl.edu/public/citations/citations/php3?
func=detail&par=cit_id=525 [abstract]

--
_______________________________________________________

"The statement: 'Sig file on vacation' IS a sig file."
- Bob Clark
_______________________________________________________

********************************************************
Forum: sci.astro
Subject: Re: Lack of energy makes life on Europa unlikely, Caltech
study concludes (Forwarded)
Date: 06/09/1999
Author: Robert Clark <rcl...@op.net>

In article <Pine.LNX.4.05.9906050311010.29056-
100...@nova.astro.utoronto.ca>,
Andrew Yee <ay...@nova.astro.utoronto.ca> wrote:
> Media Relations
> Caltech
>
> Contact:
>
> Joseph Kirschvink, (626) 395-6136, krsc...@caltech.edu
> Kenneth Nealson, (626) 395-6143, Knea...@gps.caltech.edu
> Eric Gaidos, (626) 395-2949, gai...@gps.caltech.edu
> Sue McHugh, (626) 395-3227, smc...@caltech.edu
>
> Embargoed for Release at 3 p.m. Thursday, June 3, 1999
>
> Lack of energy makes life on Europa unlikely, Caltech study concludes
>
> PASADENA -- Future space travelers to the watery Jovian moon Europa
> should probably leave their fishing tackle at home. A new study
conducted
> by California Institute of Technology and Jet Propulsion Laboratory
> scientists shows that the Europan ocean is unlikely to harbor any
life form
> more complex than single-celled organisms -- and maybe not even that.
>
> In this week's issue of the journal Science, Caltech geobiologist
Eric Gaidos
> and coauthors Kenneth Nealson and Joseph Kirschvink show that nearly
all
> forms of energy used by life on the Earth are unavailable to the
organisms
> that might live beneath Europa's surface ice layer.
>
> According to Gaidos, "One must be careful when doing comparative
> planetology. It is not a safe assumption to use Earth as an analogy.
A liquid-
> water ocean on Europa does not necessarily mean there is life there."
>
> On Earth, chemical energy is derived either from sunlight by means of
> photosynthesis or from the oxygen that is a byproduct. This oxygen
reaches
> even the exotic animals inhabiting the super-hot volcanic vents in
the deep
> sea that were discovered 20 years ago.
>
> Even for the organisms living under ice sheets on Earth, the system
is not
> closed. Energy from outside is available for the organisms underneath.
>
> Unlike Earth, Europa is a closed system. The ice layer cannot be
penetrated
> by sunlight and the only available energy in the system comes from
within.
>...

Lake Vostok in Antarctica has been compared to the oceans of Europa.
This is the lake covered by ice kilometers thick. It is believed to
have been cut off from the rest of the Earth for several hundreds of
thousands of years. There are plans to send robot explorers into the
lake as a testing ground for the future exploration of Europa. The
same problem of lack of oxygen should apply to the lake. Fish for
example do not chemically separate oxygen from water with their gills,
but rather take the oxygen that diffuses through the water from the
atmosphere. This would not be available in Lake Vostok or on Europa. If
complex life forms did develop in such an environment they would have
to be very different from all the animal life currently known on Earth.

"Alien creatures in Antarctica’s ice"
http://www.msnbc.com/news/148732.asp

"Clues to possible life on Europa"
http://science.msfc.nasa.gov/newhome/headlines/ast04mar98_1.htm

"Life in Ice-Covered Oceans"
http://www.sciencemag.org/cgi/content/summary/284/5420/1631

Another possibility occurs to me for how oxygen could be produced in
Europa's oceans. Recent research shows Europa to possesss a very
tenuous oxygen atmosphere: "Production of O2 on icy satellites by
electronic excitation of low-temperature water ice",
http://www.nature.com/server-java/Propub/nature/394554A0.abs_frameset.
The mechanism of production of the oxygen is by interaction by high
energy particles in the jovian magnetosphere with the ice on Europa's
surface. Could sufficiently energetic particles cause oxygen to be
produced in Europa's oceans? The particles themselves need not
penetrate the ice. It may be necessary for only the secondary showers
to penetrate. Also, the thinness of the surface oxygen is probably due
to Europa's weak gravity. Oxygen generated in the oceans would be
trapped by the ice above. A recent article shows that high energy
electrons regularly bombard the Earth from Jupiter: "Earth Bombarded by
Sun and Jupiter",
http://www.spacer.com/planetary/sunjupearth.html. According to the
report these electrons are even higher energy than generated by the
Sun. The much closer Europa would take a much greater hit from such
electrons.

________________________________________

"In science, everything is significant"
-- Bob Clark
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