Download Europalife - Denise Jacobs

I: Introduction
The search for extra-terrestrial life has been one of the major driving forces of
planetology. Many of planetology's major figures, from Sir William Herschel, to Percival
Lowell, even up to Carl Sagan, have believed in a plurality of worlds. Yet, despite the
optimism of all the searchers, not one of the terrestrial planets have been found to harbor
life, save our own planet Earth.
Yet the possibilities for life elsewhere in our Solar System have been poorly explored. In
the sixties, Carl Sagan postulated the existence of life under and among Jupiter's clouds.
Unfortunately, the proposal seemed to lack merit when it came time to design Galileo's
atmospheric probe. However, it is not Jupiter, nor is it any of the other Jovian planets that
I believe to be the abode of fellow creatures, but instead, two of the icemoons I wrote
about in my March 1990 article in the EJASA entitled "Ice Moons of the Jovian Worlds":
Enceladus and Europa.
In this article I will first describe what life need in order to get started on a world. Next, I
will desribe the conditions on Europa and Enceladus in both the past and present. Finally,
I will compare the five described conditions, and thereby discover if, indeed, Enceladus
and Europa are harbors for life, or dead lumps of ices.
II: Conditions for the Birth of Life
Life is a delicate thing, yet it arose on Earth under conditions that might seem harsh to us
here nearly three billion years after the fact. Earth's atmosphere was nothing then like it is
now. Instead of the familiar oxygen and nitrogen that we all breathe, Earth's atmosphere
was mainly composed of steam, carbon di-oxide, methane, and ammonia. Thanks to
experiments made in 1953 by Stanley Miller, it has been shown that if these chemicals
are exposed to electric sparks or ultra-violet light, most of the known amino acids and
some of the simpler proteins will form. In 1936, A.I. Oparin found that these amino acids
and protein would form globules in water. These he believed were the progenitors of
protozoa, the lowest forms of life. Thus life was started on Earth. But what about the
main subjects-Enceladus and Europa?
III: Primeval Conditions on Europa and Enceladus
It has been shown that Jupiter and Saturn are both warmer now than can be accounted for
by solar radiation. It seems to be the general consensus that this heat is the remnant of the
original energy that was the result of the respective planet's collapse into a dense ball of
rock, metal, and liquid metal hydrogen. If the heat is enough to show up signifigantly
now, what must it have been like four or five billion yers ago? Terence Dickinson claims:
"Near the origin of the solar system [sic] Jupiter was more like a miniature sun than a
planet, shedding enough heat that... would have allowed [Europa's] surface to be covered
in an ocean..."{1} I am including Saturn in this as well, in light of its similar size and
composition. During this time, there also were other processes that could have given
Enceladus and Europa open oceans for the Sun to shine on: heat of accretion and heat of
differentiation could have had melted the crusts of both moons. Meteorite impacts could
have opened pits in their icy crusts. However, do the moons have organic material for the
Sun's ultra-violet rays to shine on?
Let us look at the composition of the typical ice moon. In this "typical" ice moon, we
find, in addition to some rock and metal, water ice, dry ice, and frozen ammonia and
methane. Despite their frozen state today, at the time, if water was in liquid form then,
most, if not all of the chemicals listed above were also in liquid or vapor form. Plus, with
the exposure of these vapors and liquids to the young Sun's more energetic ultra-violet
rays, life's components would have formed on the far-off surfaces of Enceladus and
Europa. But what of the present day? How could protozoa formed then somehow survive
to the present?
IV: Present Conditions on Europa and Enceladus
Protozoa on Earth seem to tolerate many different environments, but one thing seems
clear. All life needs water, and all life needs an energy source, be it sunlight or plants or
geothermal energy. Do the present conditions on Europa and Enceladus give these
conditions to the hypothetical protozoa?
I say yes. There is a good chance that both Europa and Enceladus have liquid water under
their ice crusts. The heat generated by tidal interactions between Io, Europa and Jupiter,
according to Lucchita and Soderblom, was enough to melt the ice under the crust of
Europa. Enceladus has been observed to send out plumes of water by Voyager II. So we
can assume that at least there is water to sustain subterranean life on the two moons. But
is there an energy source? Considering that most estimates of the thickness of Europa's
crust, and it seems to be the warmer of the two moons, being both larger and less
cratered, lie around a figure of twenty-five miles, I think one can rule out sunlight as a
source of energy. But geothermal energy on such active moons is quite possible, to say
the least. It has certainly been shown on Earth that geothermal heat sources can sustain
life.
V: Life?
Let us compare the five conditions described above. For life's founding, we need
ammonia, methane, carbon di-oxide, steam, and either lightning or ultra-violet rays.
Europa and Enceladus had, and still have, the chemicals necessary. If one considers likely
the scenario I have described above for the Saturn and Jupiter, then ultra-violet light was
present as well. Life had a good chance of starting. For life's continuance, we need an
energy source and liquid water. Due to their tidal interactions with their neighbors,
Enceladus and Europa have liquid water and geothermal energy. This leads me to belive
that our first aliens are to be found as Europans and Enceladians, fellow members of the
Solar system of which we ourselves are a part.
{1} Terence Dickinson, _The Universe and Beyond_ (Camden East: Camden House
Publishing, Ltd., 1986), p. 54
List of References
Baugher, Joseph F.. _The Space-Age Solar System_. New York: John Wiley and Sons,
Inc., 1988.
Briggs, G.A. and F.W. Taylor. _The Cambridge Photographic Atlas of the Planets_. New
York: Cambridge University Press, 1988.
Dickinson, Terence. _The Universe and Beyond_. Camden East: Camden House
Publishing, Ltd., 1986.
Hartmann, William K.. _The Grand Tour_. Toronto: Saunders of Toronto, Inc., 1981.
Hartmann, William K.. _Out of the Cradle_. New York: Workman Publishing Company,
Inc., 1984.
Morrison, David, ed. _Satellites of Jupiter_. Tucson: The University of Arizona Press,
1982.
Acknowledgements
To Arthur Clarke, for inspiring in me the idea of life on Europa and Enceladus from his
book _2010_, and to John Novak, who helped find and patch some holes of the first draft.