Organic Molecules on Jovian Moons
By Sean Henahan, Access Excellence
Europa, Jupiter (10/10/97)- Having previously discovered
water on the Jovian moon Europa, the Galileo spacecraft now reports the
presence of organic molecules on two other moons, Ganymede and Callisto.
The Galilean Moons
Ganymede, Callisto, Io and Europa
Because Europa shares common characteristics with the other Galilean moons,
researchers believe it is reasonable to expect that organic molecules will
also be found on Europa. Europa, with water and heat energy provided by
the moon's core, is now considered the leading contender for a second source
of life in the solar system.
The Galileo spacecraft's near-infrared mapping spectrometer sent back
data indicating the presence of combinations of oxygen, carbon, sulfur,
hydrogen and nitrogen on the two moons. The data also included a suggestion
of the presnece of tholins, complex organix compounds.
"This doesn't mean there is life on Europa. The exciting thing now
is the evidence that Europa may have all three of the ingredients," University
of Hawaii geophysicist Thomas McCord told the press.
The next goal will be to determine if organic molecules also exist on
Europa. The researchers sould have this answer by December of this year.
Much of the current search for primitive life forms in the solar system
hinges on research originally conducted by biochemist Stanley Miller, who
demonstrated in the 1950's that sending electric current through a chamber
containing a combination of methane, ammonia, hydrogen and water produced
organic compounds including amino acids- the building blocks of life. This
was the foundation of a new field of study called exobiology, the search
for prebiotic and biotic conditions on other planets. The announcement
of a bacterial fossil originating on Mars, along with new data sent by
Pathfinder, have brought new attention to the study of life's origins.
The four largest moons of Jupiter, Ganymede, Callisto, Io and Europa
are known as the Galilean satellites, after Galileo who discovered them.
Io, the innermost, is the most volcanically active body in the solar system.
Europa, is now known to have a dense core and an ice crust, which may be
floating on a water ocean.Ganymede shows scars from giant impacts and complete
resurfacing. Callisto, the fourth satellite, is heavily cratered and undifferentiated.
"The Galilean satellites are located in the temperature region of the
solar system where water ice and other volatiles become stable over the
age of the solar system . The composition and chemistry of the surfaces
of these objects is of interest because they provide clues to the origin
of our solar system and because they contain water ice and may contain
organic molecules that are essential for the initiation of life," notes
McCord.
The findings are reported in the October 9, 1997 issue of Science
|
Science Updates Index
