Lecture Series of the Week
- From: Wirt Atmar <atmar@xxxxxxxxxxxxxxxxx>
- Date: Mon, 13 Mar 2006 15:46:16 -0700
Beginning today, AICS Research, Inc. is launching a new service: a
Lecture of the Week, and you're welcome to subscribe to a weekly
announcement newsletter if you wish. The talks will center primarily
around evolutionary biology, in all of its aspects: cosmology,
astronomy, planetology, geology, astrobiology, ecology, behavior,
phylogenetics and evolutionary biology itself, and are presented at a
professional level, that of one scientist talking to another.
For the past 30 months AICS Research has been recording the highest
quality conferences in these fields and now has 200 excellent
presentations in its vault.
The webpage for the lectures is:
http://aics-research.com/lotw/
Instructions on subscribing to the weekly notice are given on the page.
Because of the recent, quite extraordinary news released last Friday
regarding the discovery of water geysers on Enceladus, a small moon of
Saturn, the inaugural lecture will be given by Reta Beebe, an archivist
of the Cassini mission that discovered this phenomenon. Reta's talk was
given last March, before the discovery, but as you will see, while the
discovery is surprising, it wasn't unexpected either.
An introduction to Reta's talk is presented below.
Wirt Atmar
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March 13, 2006
Looking for Life in All The Wrong Places
Cassini and Huygens at the Saturn System
Reta Beebe, New Mexico State University
54 min. (requires QCShow Player)
In our search for a second genesis of life in the solar system, Mars has
been the perennial favorite for more than a century. But life appears to
require liquid water, and Mars has been a dry and desolate, at least on
its surface, for 3 billion years or more, and thus its prospects are
fading.
Our hopes for discovering life in this solar system began unexpectedly
turning to the moons of the outer planets 25 years ago, following the
twin Voyager missions. The gas giant planets are composed primarily of
hydrogen and helium, and are thus they're made of the stuff of the
primordial universe. But these low atomic weight gases also make them
rich in water. The problem? They're cold. Indeed many of the moons of
these planets are so cold that water ice becomes the geologic rock of
the planetary body.
But a few of the moons are hot. The mechanism? Tidal heating. As Reta
Beebe explains in this talk, several of the larger inner moons of both
planets are synchronously locked forever with a twin, orbiting at
exactly half its speed. This is true for the Jovian moons, Io, Europa
and Ganymede and for the two Saturnian twins, Enceladus and Dione and
Mimas and Tethys. For every trip around Jupiter that Ganymede makes,
Europa makes two trips and Io makes exactly four. These resonances will
occur forever. Their orbits are gravitationally bound to one another.
But because their orbits are not exactly circular, tidal heating occurs,
sufficient to the point that the surface of Io is nearly molten and
Europa and Ganymede appear to have liquid water oceans under thick and
thicker crusts of ice.
The tidal heating in these moons provides precisely the two things that
we suspect that life requires: energy and liquid water. Following the
Voyager missions in the early 1980's, attention turned to Europa as
possibly the second best hope for finding life in the solar system, but
Europa also lies in a terrible neighborhood: Jupiter's radiation belt.
The radiation levels are so high at Europa that the most
radiation-hardened spacecraft could only spend a month or so orbiting
Europa before it was fried. No complex biochemical molecule, much less
life, could exist on its surface. If life exists, it will have to have
been protected by Europa's ice cap, deep in its interior ocean.
Enceladus, in contrast, resides in a much more benign environment, and
it now appears that it may be warmer in its interior than Europa. Just
this week, a new report by Carolyn Porco et al. in Science reports that
geysers of liquid water appear to breaking through Enceladus' much
thinner ice crust and are venting into space.
"We realize that this is a radical conclusion, that we may have evidence
for liquid water within a body so small and so cold. However, if we are
right, we have significantly broadened the diversity of solar system
environments where we might possibly have conditions suitable for living
organisms," Porco said.
The discovery of liquid water in Enceladus so near the surface was
unexpected, but it wasn't a complete shock either. The four- or six-year
Cassini mission currently orbiting Saturn represents only our second
trip to Saturn in 25 years, but this discovery of water at Enceladus is
likely to foster a quick return to the moon, but the next time now with
instruments more suited for biological exploration.
If there is life in Enceladus' oceans, it should be very easy to detect.
We can sample that water from space, using a low-orbiting spacecraft
flying over Enceladus' south pole.
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