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Location: UFOUpDatesList.Com > 1999 > Feb > Feb 1

Re: Greek Legend Becoming Fact: Charon Prime Target

From: Stig Agermose <stig.agermose@get2net.dk>
Date: Sun, 31 Jan 1999 07:56:59 GMT
Fwd Date: Mon, 01 Feb 1999 10:08:48 -0500
Subject: Re: Greek Legend Becoming Fact: Charon Prime Target





'Charon was supposed to be the boatman who brings life between
this world and the underworld. If there is indeed life on
Charon, it seems very fitting with these legends.'


Lick Observatory

[Image: This is the clearest existing image of Pluto and Charon,
captured by the Hubble Space Telescope. The moon, at upper
right, was discovered in 1978. Before that, astronomers could
not make out the satellite as separate from the planet.]

Charon: Dark horse in search for life

Could there be water and energy under ice of Pluto's moon?

By Alan Boyle


MSNBC -  Jan. 28 - It's the most distant moon known, out where
our sun is a cold point of light. But scientists say Charon, the
icy satellite of the planet Pluto, ranks as a prime target in
their study of the conditions that could sustain life.

Planetary scientists have a short list of worlds in our solar
system that could have sustained life at some point in their
development. "There have been as many as five habitable worlds,"
including Earth, said David Des Marais of NASA's Ames Research

He said his list included Mars, which scientists believe was
once warmer, wetter and Earthlike; Venus, which may have had a
more hospitable climate before its atmosphere fell victim to a
runaway greenhouse effect; Europa, which may have the solar
system's biggest ocean of water beneath its outer shell of ice;
and Charon.

Charon? The cold moon that whirls around Pluto at a distance of
3.7 billion miles (5.9 billion kilometers) from the sun? The
puny world discovered only in 1978, with a mass just 0.03
percent of Earth's, with a diameter roughly equal to the
distance from New York to Chicago?

Although it seems unlikely, Charon (generally pronounced like
the name Karen) just might be capable of harboring life, said
Douglas Lin, an astrophysicist at the Lick Observatory. The
possibility was raised by data from the Hubble Space Telescope,
indicating that Charon's orbit around Pluto is slightly

Lin theorized that the orientation of Charon's orbit to Pluto's
orbit introduced a wobble, analogous to the wobble of a spinning
top as it starts to slow down. Whatever the cause, the eccentric
orbit means both Pluto and Charon are subject to gravitational
tides as they spin around each other.

The tides warp both worlds, leading to internal heating. But
since Charon is 10 times less massive than Pluto, the tides
create more stresses and strains within the interior of the

"We estimate that the interior of Charon could be molten," Lin
said. "Now, do we have any evidence to suggest this is in fact
what's happening? For the time being, we don't have any
information. We don't have a very good picture of what's going

If Charon does have a molten core, scientists say that could
provide the energy source required for sustaining life. After
all, there are organisms that survive around hydrothermal vents
in the sunless depths of Earth's oceans, which are as dark as

Scientists also say life requires liquid water and organic
materials and Lin contends that those might be present on Charon
as well.

"You see plenty of organic material in comets, and comets come
from the outer part of the solar system," Lin said. "There
probably is no shortage of organic material in the outer solar

As for water, Lin noted that Charon's surface was apparently
more reflective and had "a little bit more of water frost" than
Pluto's surface leading scientists to speculate that the moon
was covered with ice. If Charon's interior is warm enough, there
may be liquid water beneath the ice, Lin theorized. And if
that's the case, such waters might be suitable for life, at
least on the microbial level.

"Pluto, it turns out in Greek legend, was the god of the
underworld, and Charon was supposed to be the boatman who brings
life between this world and the underworld," Lin mused. "If
there is indeed life on Charon, it seems very fitting with these

Charon and Pluto are both on the itinerary for a probe known as
the Pluto-Kuiper Express, currently on the drawing boards at
NASA. The space agency intends to launch the spacecraft in about
2004. It would take 10 years for the probe to fly by Pluto, and
then it would continue even farther out, into a ring of ice
worlds known as the Kuiper Belt. The data sent back during that
flyby could answer at least some of the questions posed by Lin.

Even if Charon turns out to be barren, Lin said that each
expansion to our solar system's "habitable zone" increases the
odds of finding life elsewhere in the universe.

"If you took literally our old concept (of habitable zones), you
would be very pessimistic indeed to think there would be the
possibility of life existing anywhere in the universe," he said.


Over the past few weeks, Pluto has been in the news because of a
controversy over its classification. Some leading astronomers
said they were a bit miffed over reports that Pluto might be
"demoted" from its status as a major planet.

"It's not been demoted," said Brian Marsden of the International
Astronomical Union's Minor Planet Center. "That never really was
the situation."

But Marsden acknowledged that the debate was confusing even for
some of his scientific colleagues. Pluto facts

Average orbit: 3.7 billion miles, or 5.9 billion kilometers.

Diameter: 1,430 miles, or 2,301 kilometers.

Length of day: 6 Earth days, 9 hours.

Length of year: 248 Earth years.

One known satellite, named Charon.

Ever since Pluto was discovered in 1930, astronomers have
acknowledged that it was a breed apart: Pluto is less than half
the size of any other planet. Its orbit is much more inclined
and eccentric than those of the other eight. In fact, for the
past 20 years it's been closer to the sun than Neptune but will
reclaim its title as the farthest planet next month.

"We've known for a long time that Pluto didn't fit," said
University of Maryland astronomer Mike A'Hearn, who heads the
Planetary Systems Sciences Division of the International
Astronomical Union.

The dilemma deepened in 1992 when astronomers discovered other
objects similar to Pluto, balls of ice on the fringes of the
solar system that have been dubbed Trans-Neptunian Objects. More
than 90 such objects have been identified, and although none of
them is as big as Pluto, their existence led A'Hearn and his
colleagues to wonder about changing Pluto's classification.

"There is no doubt that Pluto is a Trans-Neptunian Object, all
the experts agree that dynamically that's what it is," A'Hearn

That led to the next question: Should Trans-Neptunian Objects be
classified formally as minor planets, a category that also
includes asteroids such as Ceres, Vesta and Eros? If so,
shouldn't Pluto be lumped in with the others of its ilk?

A'Hearn canvassed other astronomers by e-mail, hoping that the
deliberations would result in a formal decision by the
International Astronomical Union. But so far there has been no
consensus on whether Pluto should be put on the list or

Marsden said he favored giving Pluto "dual status": It would
continue to be recognized as one of the nine major planets, and
also take a place of honor among Trans-Neptunian Objects as the
10,000th minor planet.

He acknowledged that "there have been movements afoot to try and
not do this." But he said it was important to come up with a
classification system that made sense.

"We've reached the state where (Trans-Neptunian Objects) need to
have a permanentization of their status. ... If we're going to
start doing that, the whole point is that if you exclude Pluto
from consideration in the same sense, it looks rather funny,"
Marsden said. "You can understand astronomers saying 50 years
from now, 'Well, that looks pretty stupid.'"

Astronomers on both sides of the debate said the controversy was
ultimately about the definition of planethood. Is that
definition dependent on mass, or shape, or the way it behaves in
a solar system? Depending on the criteria, our solar system
could contain eight, 10 or even more planets.

"There has just never been a need to make that definition in the
past," A'Hearn said.

He said the fact that scientists were rethinking Pluto's status
was a healthy sign.

"I view this as an opportunity to show the public that the whole
point of studying the solar system is to explain how it came
into being, and as we do that we uncover things that lead us to
have to rethink some of these issues," he said. "If we're never
revisiting some of these issues, that's a good indicator that
our knowledge is not advancing."

*IAU Planetary Systems Sciences: Pluto
*Pluto-Kuiper Express
*Pluto, the Ninth Planet
*The Nine Planets
*Views of the Solar System
*Planetary Photojournal
*Your Weight on Other Planets
*Planet or Trans-Neptunian Object? Discuss it on the Space News BBS

*Looking for life? Look down deep
*Dark cave may hold secrets of life
*Space station plan in flux again
*First images from Subaru Telescope
*Gamma ray burst caught on tape
*Tour the solar system

Should Pluto's status as a major planet be changed?

*Yes    *No

Vote to see results

MSNBC =A9 1999

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