Life on Europa - an Essay by Ricky Leon Murphy:
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frozen surface of Europa for the first time must have been an
extraordinary event. Telescopic observation and Voyager data reveal what
is to be a frozen water-ice surface. Could liquid water exist below this
surface? Liquid water is an essential ingredient for life, and water
seems to be located in more and more places as we explore the solar
system. Data from the Galileo probe indicate what might be some geologic
activity on Europa, and with activity comes the possibility of organic
material. Meteorites like ALH 84001 raise the question that organic
material may exists outside the Earth. Further exploration of Europa
could prove that water and organic material exist under the frozen
surface. Information gathered from Europa and its possible evidence of
life can give us further insight as to how life on Earth evolved, and
further advance our current knowledge of how the solar system formed.
Earth is a
special case since life already exists here. We have an atmosphere that
sustains life, and we see living organism in a variety of environments.
The formation of Earth and its ocean of water are still not clearly
understood, but the most accepted theory is water being introduced by
comet impacts as our planet continued to evolve. With a predominantly
carbon dioxide atmosphere and a liquid ocean – thanks to the size and
location of Earth – atmospheric evolution was able to begin. Volcanic
activity introduced carbon dioxide as the oceans absorbed the carbon
dioxide to create carbon containing minerals (Beatty, et. al., page
187). With active plate tectonics and underwater volcanic activity,
carbon material with water and methane – expelled by under water
volcanoes – were able to evolve and form complex amino acids as shown by
the Miller-Urey experiment (Freedman, pg 691). Carbon is capable of
conglomerating into larger molecules, and as carbon material began to
form more complex molecules, life was able to begin (Beatty, et. al., pg
690). Eventually, plant life evolved and began to absorb carbon dioxide
and release oxygen in the atmosphere in a process called photosynthesis.
Liquid water on Earth plays a key role since water is required for life.
Water is a part of a living organism and is responsible for transporting
and combing nutrients and controls metabolic break down and facilitates
waste removal (Microsoft Encarta Reference Library 2003). This process
is called hydrolysis.
commonly believed that comets provided the water on Earth. This seems to
be the case since water is being found in surprising locations. In an
effort to fill the gap of missing data left by the Magellan space probe
of the surface of Mercury, radar imagery from Earth has discovered what
appears to be water-ice within the craters of the north and south poles
of Mercury (Beatty, et. al., pg 95). The Clementine probe scanning the
surface of the moon has found similar water-ice on its poles (Beatty,
et. al., pg 77). The polar caps of Mars are a familiar site, and with
the sublimation of the frozen carbon dioxide during seasonal changes,
the water-ice north pole is revealed (Freedman, pg 268, 269). A
meteorite originating from Mars has shown to include some water, though
not that much (http://www.jpl.nasa.gov/snc/nasa2.html).
Comets have formed at the same time as the solar system, and comet
impacts on the planetesimals were fairly common. These water-ice balls
may show a higher deuterium level than the water here on Earth (Beatty,
et. al, pg 335), however with water seen on other bodies as well as
Earth lead to the speculation that water originated from this source.
Enough carbon material could have also been introduced by comet impacts
as well (Freedman, pg 690). These carbonaceous chondrites have shown the
presence of enough carbon material to possibly allow the catalyst to
begin the cycle of life. Europa, with a water-ice surface, has also been
subjected to comet impacts as the other planets. The appearance of few
impact craters today give evidence to some geologic activity (Beatty,
et. al., pg 253).
material does exist here on Earth deep in the ocean. However, new
discoveries of previously unseen organisms thrive in locations where we
would least expect them. Lithoautrophic organisms have been discovered
near volcanic vents deep in the ocean where sunlight fails to penetrate
(Beatty, et. al., pg 369). The volcanic vent provides the energy and
carbon material. It was initially thought that sunlight was a key factor
on the formation of life, but these organisms prove otherwise. More
extreme environments have also revealed some strange life signs.
Worm-like organisms deep in the Gulf of Mexico survive from the
underwater source of methane and without sunlight. These organisms are
dubbed “extremophiles” (Beatty, et. al., pg 368). Even more surprising
is the recent discovery of organisms that do not need volcanic heat to
survive, and live by processing methane instead of carbon dioxide or
These hydrogen-oxide bacteria evolve and survive in temperatures of only
40C to 75C, far below the heat of a volcanic source.
of a meteor in Antarctica dubbed ALH 84001 has brought forth questions
of the possibility of life from a source other than the Earth. While
controversy surrounds this meteorite, proponents of ALH 84001 maintain
the microscopic fossils of bacteria found on this meteorite originated
from Mars. Skeptics have shown the microscopic bacteria resemble
bacteria found under the ice of Antarctica (Beatty, et. al, pg 371,
372), and therefore was introduced on this meteor upon impact thousands
of years ago. While the data remains controversial and inconclusive,
this teaches us three very important lessons. The first lesson is life
is possible (in this case on Mars) although the possibility is remote
and unconfirmed. The second lesson is that scientific scrutiny plays a
vital role in the evaluation of data. And the third lesson is to create
a list of standards when evaluating the possibility of life. A standards
organization can be organized to draw on disciplines such as medical
science and research, pharmaceutical companies, and the biological
sciences. These groups deal with life on a daily basis, and can provide
valuable data in generating a list of standards. It is clear in the case
of ALH 84001, contamination from an outside source is certainly
possible. Every effort must be made to remove any outside influence,
conscious or unconscious, when evaluating organic material. Gravity
influence, heat, radiation, and bacteria from other sources could
dramatically affect the outcome of data.
Galileo data shows there is some internal heating emanating from Europa.
With this heat as an energy source, the prospect of life becomes
exciting. Such heating can be attributed to several sources, such as the
normal decay of radioactive material; however, the majority of heating
is thought to occur from tidal flexing as a result of Jupiter’s enormous
gravity pull (Beatty, et. al., pg 254). Using the moon Io as a model, we
see prominent volcanism as a result of this tidal energy from Jupiter
(Beatty, et. al., pg 245). The same effects of tidal flexing may also
cause volcanism on Europa, called cryo-volcanism (Beatty, et. al, pg
254). The friction heat caused by this flexing will also allow the
water to remain liquid under the icy surface. The smooth surface and the
presence of bulging and fractures point to some active geology that
could indicate cryo-volcanism. Further evidence of cryo-vulcanism is
present in the form of localized bulging, triple fracture bands and
resurfacing (Beatty, et. al., pg 260, 261). Reddish material seen in
photography from Galileo could indicate material from the mantle being
stirred up in the presumed liquid ocean by the active geology. With a
water-ice surface and the presence of a heat source, a liquid ocean
almost seems very likely. Knowing that organic life can exist in some
extreme environments and knowing that volcanism can release carbon
material make the prospect of life on Europa more likely. Even more
remarkable is the discovery of a tenuous oxygen atmosphere. This data
provided by the Hubble Space Telescope (http://jpl.nasa.gov/galileo/europa/hst.htm)
could be the result of liberated oxygen from the magnetosphere of
Jupiter; however this new information is added to the list of questions
to be answered by further exploration. With the Europa Orbiter scheduled
to arrive in the year 2008 (http://www.jpl.nasa.gov/europaorbiter/EO_info.htm),
our answers to the presence of liquid water and geological activity will
be revealed. It is clear that given the questions of life Europa,
further exploration is necessary.
important to life. Life in our deep oceans should become a template in
which we evaluate the possibility of life on Europa. Organisms can
survive in extreme environments, and organic material in our solar
system is available either by comet impact or active volcanism. With the
possibility of a liquid ocean and the presence of internal heat, and
evaluating the presence of life in our own deep oceans and recognizing
alternate sources of energy and organic material, the possibility of
life on Europa is likely. Further exploration will continue to answer
our questions and may generate more questions to be answered. The key to
unlocking the origin of life on Earth may exist deep in the sub-surface
oceans of Europa. We may have a chance to witness the early stages of
life that was once present on Earth millions of years ago. Only by
continuing our exploration of our solar system will we begin to
understand our own humble beginnings. However, great care must be given
when evaluating the possible presence of life. Every effort must be made
to scrutinize the results of exploration so controversy can be avoided.
Beatty, Kelly J.,
Petersen, Carolyn C. and Chaikin, Andrew, ed. The New Solar
Cambridge: Sky Publishing Corp, 1999.
Freedman, Roger A.
Universe 6th Edition. W.H. Freeman and Company, 2002
Reference Library 2003. 1993 – 2002 Microsoft Corporation
NAI Features Archive.
“Life without Volcanic Heat.” Internet. 11 Jan 2002.
Office, Jet Propulsion Laboratory. “Europa Orbiter: Mission
At a Glance.”
Internet. 11Sep 2002.
Office, Jet Propulsion Laboratory. “Hubble Finds Oxygen
Europa.” Internet. 23 Feb 1995.
Office, Jet Propulsion Laboratory. ”Water Extracted From Mars
Provide Clue to Red Planet’s Past.” Internet. 13 Mar 1992.
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