NASA Spacecraft's Data Reveal Magma Ocean Under Jupiter Moon

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May 12, 2011

Dwayne C. Brown 
Headquarters, Washington 
202-358-1726 
dwayne.c.brown@xxxxxxxx 

Jia-Rui Cook 
Jet Propulsion Laboratory, Pasadena, Calif. 
818-354-0850 
jccook@xxxxxxxxxxxx   


RELEASE: 11-144

NASA SPACECRAFT'S DATA REVEAL MAGMA OCEAN UNDER JUPITER MOON

WASHINGTON -- New data analysis from NASA's Galileo spacecraft reveals 
a subsurface ocean of molten or partially molten magma beneath the 
surface of Jupiter's volcanic moon Io. 

The finding heralds the first direct confirmation of this kind of 
magma layer at Io and explains why the moon is the most volcanic 
object known in the solar system. The research was conducted by 
scientists at the University of California, Los Angeles, the 
University of California, Santa Cruz, and the University of Michigan. 
The study is published this week in the journal Science. 

"Scientists are excited we finally understand where Io's magma is 
coming from and have an explanation for some of the mysterious 
signatures we saw in some of the Galileo's magnetic field data," said 
Krishan Khurana, lead author of the study and former co-investigator 
on Galileo's magnetometer team at UCLA. "It turns out Io was 
continually giving off a 'sounding signal' in Jupiter's rotating 
magnetic field that matched what would be expected from molten or 
partially molten rocks deep beneath the surface." 

Io produces about 100 times more lava each year than all the volcanoes 
on Earth. While Earth's volcanoes occur in localized hotspots like 
the "Ring of Fire" around the Pacific Ocean, Io's volcanoes are 
distributed all over its surface. A global magma ocean about 20 to 30 
miles (30 to 50 kilometers) beneath Io's crust helps explain the 
moon's activity. 

"It has been suggested that both the Earth and its moon may have had 
similar magma oceans billions of years ago at the time of their 
formation, but they have long since cooled," said Torrence Johnson, a 
former Galileo project scientist based at NASA's Jet Propulsion 
Laboratory (JPL) in Pasadena, Calif. He was not directly involved in 
the study. "Io's volcanism informs us how volcanoes work and provides 
a window in time to styles of volcanic activity that may have 
occurred on the Earth and moon during their earliest history." 

NASA's Voyager spacecraft discovered Io's volcanoes in 1979, making 
that moon the only body in the solar system other than Earth known to 
have active magma volcanoes. The energy for the volcanic activity 
comes from the squeezing and stretching of the moon by Jupiter's 
gravity as Io orbits the largest planet in the solar system. 

Galileo was launched in 1989 and began orbiting Jupiter in 1995. 
Unexplained signatures appeared in magnetic field data from Galileo 
flybys of Io in October 1999 and February 2000. After a successful 
mission, the spacecraft intentionally was sent into Jupiter's 
atmosphere in 2003. 

"During the final phase of the Galileo mission, models of the 
interaction between Io and Jupiter's immense magnetic field, which 
bathes the moon in charged particles, were not yet sophisticated 
enough for us to understand what was going on in Io's interior," said 
Xianzhe Jia, a co-author of the study at the University of Michigan. 

Recent work in mineral physics showed that a group of rocks known as 
"ultramafic" rocks become capable of carrying substantial electrical 
current when melted. Ultramafic rocks are igneous in origin, or form 
through the cooling of magma. On Earth, they are believed to 
originate from the mantle. The finding led Khurana and colleagues to 
test the hypothesis that the strange signature was produced by 
current flowing in a molten or partially molten layer of this kind of 
rock. 

Tests showed that the signatures detected by Galileo were consistent 
with a rock such as lherzolite, an igneous rock rich in silicates of 
magnesium and iron found in Spitzbergen, Sweden. The magma ocean 
layer on Io appears to be more than 30 miles (50 kilometers) thick, 
making up at least 10 percent of the moon's mantle by volume. The 
blistering temperature of the magma ocean probably exceeds 2,200 
degrees Fahrenheit (1,200 degrees Celsius). 

The Galileo mission was managed by JPL for NASA's Science Mission 
Directorate in Washington. For more information about the Galileo 
mission and its discoveries, visit: 


http://solarsystem.nasa.gov/galileo   



and 







http://www.jpl.nasa.gov/galileo-legacy   

	
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