[meteorite-list] Europa Has Right Stuff

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:04:51 2004
Message-ID: <200205221723.KAA13843_at_zagami.jpl.nasa.gov>

http://www.seti.org/general/press_release/europa_05_21_02.html

FOR IMMEDIATE RELEASE: May 21, 2002

Contact:

Diane Richards
Marketing and Communications Officer
(650) 960-4513
Email: drichards_at_seti.org

Taylor Bucci, Operations Manager
Center for the Study of Life in the Universe
(650) 960-4519
Email: tbucci_at_seti.org

Elisabetta Pierazzo
(520) 622-6300
Email: betty_at_psi.edu

                           Europa Has Right Stuff

Mountain View, CA - Compelling evidence for a liquid water ocean beneath its
icy crust makes Jupiter's moon Europa an attractive target for scientists
seeking life in distant regions of our solar system. Recent work by Dr.
Elisabetta Pierazzo, currently at the Planetary Science Institute, and Dr.
Christopher Chyba of the SETI Institute, sheds light on the question of
whether enough "biogenic elements," the raw ingredients for life, including
carbon, nitrogen, sulfur and phosphorus, could be present to support Europan
life.

Because Europa's formation conditions are uncertain, scientists do not know
the exact composition of the moon's ocean and overlying ice. Some models
suggest a Europa depleted of life-essential carbon and other important
biogenic chemicals at birth. Pierazzo and Chyba explored comets as an
alternate source for biogenic materials, applying complex modeling methods
to set the lower limits for a Europan inventory. In the May edition of the
journal Icarus, Pierazzo and Chyba present a paper that concludes the
Europan inventory to be "substantial."

"We now know that enough of the right materials should have been present to
support a Europan biosphere," says author Chyba, who in addition to studying
Europa, also oversees a broad spectrum of astrobiological research conducted
at the SETI Institute's Center for the Study of Life in the Universe.

"If these chemicals find their way into the ocean," said Pierazzo, "and if
there exists a mechanism that could take them through the formation of
increasingly complex organic molecules, those elements could ultimately
evolve into living cells."

In their model, Pierazzo and Chyba used typical cometary sizes, densities,
and impact velocities throughout Solar System history to calculate how much
biogenic material would remain on the moon's surface after impact events.
Unlike the more massive Earth, which has a much higher escape velocity and
can therefore retain a higher percentage of cometary impact material, Europa
has a very low escape velocity, thus losing a significant portion of
material from any projectile that hits its surface.

Earlier studies of cometary impacts on Earth and Mars by the authors
suggested substantial amounts of prebiotic chemicals including amino acids
would have survived cometary impacts, especially at very low, grazing
angles, and thus contributed to the planets' inventories of complex organic
materials. While Europan models also predict significant post-impact
survival rates for similar impacts, the low escape velocity of the moon
would allow the vast majority of this complex organic material to be lost;
with the rest of the projectile material, it would disappear in space.

Nevertheless, cometary impacts would provide billions of tons of carbon, and
somewhat less nitrogen, sulfur and phosphorus to the surface of Europa.
These amounts are significant, and correspond to about 1% of the biomass of
prokaryotic life (cells lacking nuclei and believed to be representative of
early life) in today's Earth oceans.

Knowing that, at a minimum, Europa has enough of the elements needed to
sustain a biosphere offers further reason for scientists to feel hopeful
about the search for extraterrestrial life within our own solar system.

Dr. Chyba is the Carl Sagan Chairholder and Director of the Center for the
Study of Life in the Universe at the SETI Institute in Mountain View,
California, and is also an Associate Professor of Geological and
Environmental Sciences at Stanford University in Stanford California.

The SETI Institute,a private nonprofit organization dedicated to scientific
research, education and public outreach, seeks to explore, understand and
explain the origin, nature and prevalence of life in the universe.

Dr. Pierazzo is a research scientist at the Planetary Science Institute of
Tucson Arizona where her work focuses on impact cratering of planetary
surfaces and their effects on the evolution of biospheres.

Complete information about the Planetary Science Institute can be found at
www.psi.edu
Received on Wed 22 May 2002 01:23:30 PM PDT