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Location: UFOUpDatesList.Com > 1998 > Jul > Jul 17

Galileo Reveals Hints Of Ganymede's Past Ocean

From: Stig_Agermose@online.pol.dk (Stig Agermose)
Date: Fri, 17 Jul 1998 05:35:42 +0200
Fwd Date: Fri, 17 Jul 1998 09:21:04 -0400
Subject: Galileo Reveals Hints Of Ganymede's Past Ocean

AP via CNN. URL:

http://cnn.com/TECH/space/9807/15/galileo.ganymede.ap/index.html

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Jupiter's moon Ganymede has crater chain, hints of past ocean


July 15, 1998
Web posted at12:37 PM ET

LOS ANGELES (AP) -- New images show Jupiter's giant moon Ganymede has
geologic hints of an early subsurface ocean and a chain of 13 craters
that could have come from a broken-up comet.

But scientists still can't say whether life ever existed there.

"We don't know and that's why we're out there looking," said James
Head, a Brown University planetary scientist. "You have heat, liquid
water, organic material coming in from impacts from meteorites. The
ingredients are there."

The close-ups of Ganymede's rich geology were being released today by
NASA. The unmanned Galileo spacecraft captured them during several
flybys, some within just a few hundred miles of the surface, in June
1996 and June 1997.

Ganymede, the largest moon in the solar system, is 3,269 miles in
diameter -- bigger than Mercury and three-quarters the size of Mars.
About half its surface is bright, clean ice and half dark,
heavily-cratered terrain made up of "dirty" ice and rocks. Scientists
are looking for signs of liquid water.

The new images suggest that icy volcanoes spewed water instead of the
rocky lava seen on Earth, Head, a member of the Galileo imaging team,
said Tuesday from his office in Providence, R.I.

Because much of the moon is icy, scientists have wondered whether there
is a warmer liquid layer beneath.

"The Galileo images show us quite dramatically that about half of the
surface has been renewed by some process that put bright terrain out
onto 50 percent of the surface," Head said.

>From images snapped by the Voyager missions of the late 1970s,
scientists suspected this was water, Head said. The water-spewing
volcanoes suggested by the latest photos could provide the mechanism
for how the ice was deposited.

At least 1 billion years into its history, Ganymede very likely had a
global ocean, like the one that scientists suspect lies beneath the
frozen expanses of another of Jupiter's moons, Europa.

Europa, one of the major targets of the search for life in the solar
system, is the focus of the two-year Galileo mission extension.

Galileo is teaching scientists that Ganymede "probably had a global
ocean earlier in its history, but didn't continue on with the kind of
activity Europa had and has still today," Head said.

Still, he said the new Ganymede images show several signs of water:
large valleys, where it appears water flowed down into surrounding
lowlands. Hot water from volcanoes may have melted ice and created the
channels.

The images show remains of old craters and basins in dark terrain,
believed to date from early in the history of the 4.5 billion-year-old
solar system.

Head described the chain of craters, spread over about 93 miles, as
like Shoemaker-Levy, the "string of pearls" comet that struck Jupiter
piece by piece in 1994.

The Galileo spacecraft, which spent two years orbiting Jupiter and its
major moons -- Ganymede, Europa, Io and Callisto -- is more than six
months into the Galileo Europa Mission.


Copyright 1998 =BF The Associated Press.