[meteorite-list] 'Shocking' Discovery Boosts Chance Of Life On Europa

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:18:29 2004
Message-ID: <200302211630.IAA27476_at_zagami.jpl.nasa.gov>

http://www.newscientist.com/news/news.jsp?id=ns99993421

'Shocking' discovery boosts chance of life on Europa
Jenny Hogan
New Scientist
21 February 03
 
Scientists simulating meteorite impacts on the frozen oceans of Europa
have made an electrifying discovery, which raises the chances of finding
life on Jupiter's moon.

Jerome Borucki, at the NASA Ames Research Center in California, and
his colleagues fired aluminium bullets into a block of ice. They found that
when the bullet impacted, sensors embedded in the ice detected an
electric shock. A second, and much larger, electrical discharge was
observed a few moments later.

A shell of ice many kilometres thick encases the surface of Europa and
scientists speculate that liquid water - and therefore life - might lie
beneath. Evidence for the presence of the molecular building blocks for life
comes from the yellow-brown stains seen on the ice by the Galileo probe.

"Europa is a high priority target for exploration because the key
ingredients for life seem to be there. But even if you have the ingredients,
the question is, is there a spark that creates the first organic molecules?"
says Ron Greeley, a planetary scientist at the Arizona State University.

Borucki's bullet experiments suggest meteorite impacts might have
provided that spark. The electric shock had gone undetected because
no-one had put sensors below an impact crater before, he told New
Scientist. The team think the current is caused by the movement of
protons as the ice cracks.

Methane and ammonia

In the 1950s, Stanley Miller, now at the University of California in San
Diego, showed that shooting an electric current through a mixture of
water, methane and ammonia created complex organic molecules. Amino
acids, the building blocks of proteins, were among the products.

Methane and ammonia are likely to be present in Europa's ice and the
energy pumped into the ice by a meteorite impact will melt it. Shock this
mixture with electricity, says Borucki, and complex molecules should
form.

But this still needs to be tested in the laboratory. So far the experiments
have used only pure water ice, cooled to a chilly -196°C to simulate
conditions on Europa.

The bullets used are about a centimetre across and were fired
at the ice at a speed of six kilometres per second. This is the
equivalent to a kilometre-sized asteroid crashing into the moon at
about 24 km/s.

"We do see a handful of very large craters on Europa, and there would
have been a lot of energy associated with those," comments
Greeley. "These new results are exciting."

Greeley has been appointed by NASA to set the scientific
priorities of Jupiter's Icy Moon Orbiter. This probe, which has
recently been allocated funding, will visit Europa and two of
Jupiter's other moons, Callisto and Ganymede. A lander may be sent
to the surface of the Europa to look for organic matter. But it
will be a long wait - Greenley estimates the earliest launch date
for the mission to be 2011.

Journal reference: Journal of
Geophysical Research - Planets (Vol 107, p 24)
 
Received on Fri 21 Feb 2003 11:30:25 AM PST