https://www.jpl.nasa.gov/news/news.php?feature=6860

Cassini Finds Saturn Moon May Have Tipped Over
Jet Propulsion Laboratory
May 30, 2017

Saturn's icy, ocean-bearing moon Enceladus may have tipped over in the 
distant past, according to recent research from NASA's Cassini mission. 
Researchers with the mission found evidence that the moon's spin axis 
-- the line through the north and south poles -- has reoriented, possibly 
due to a collision with a smaller body, such as an asteroid.

Examining the moon's features, the team showed that Enceladus appears 
to have tipped away from its original axis by about 55 degrees -- more 
than halfway toward rolling completely onto its side. "We found a chain 
of low areas, or basins, that trace a belt across the moon's surface that 
we believe are the fossil remnants of an earlier, previous equator and 
poles," said Radwan Tajeddine, a Cassini imaging team associate at Cornell 
University, Ithaca, New York, and lead author of the paper.

The area around the icy moon's current south pole is a geologically active 
region where long, linear fractures referred to as tiger stripes slice 
across the surface. Tajeddine and colleagues speculate that an asteroid 
may have struck the region in the past when it was closer to the equator. 
"The geological activity in this terrain is unlikely to have been initiated 
by internal processes," he said. "We think that, in order to drive such 
a large reorientation of the moon, it's possible that an impact was behind 
the formation of this anomalous terrain."

In 2005, Cassini discovered that jets of water vapor and icy particles 
spray from the tiger stripe fractures -- evidence that an underground 
ocean is venting directly into space from beneath the active south polar 
terrain.

Whether it was caused by an impact or some other process, Tajeddine and 
colleagues think the disruption and creation of the tiger-stripe terrain 
caused some of Enceladus' mass to be redistributed, making the moon's 
rotation unsteady and wobbly. The rotation would have eventually stabilized, 
likely taking more than a million years. By the time the rotation settled 
down, the north-south axis would have reoriented to pass through different 
points on the surface -- a mechanism researchers call "true polar wander."

The polar wander idea helps to explain why Enceladus' modern-day north 
and south poles appear quite different. The south is active and geologically 
young, while the north is covered in craters and appears much older. The 
moon's original poles would have looked more alike before the event that 
caused Enceladus to tip over and relocate the disrupted tiger-stripe terrain 
to the moon's south polar region.

The results were published in the online edition of the journal Icarus 
on April 30, 2017.

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European 
Space Agency) and the Italian Space Agency. NASA's Jet Propulsion Laboratory, 
a division of Caltech in Pasadena, California, manages the mission for 
NASA's Science Mission Directorate, Washington. JPL designed, developed 
and assembled the Cassini orbiter.

More information about Cassini:

https://www.nasa.gov/cassini

https://saturn.jpl.nasa.gov

News Media Contact
Preston Dyches
Jet Propulsion Laboratory, Pasadena, Calif.
818-394-7013
preston.dyc...@jpl.nasa.gov

2017-155 
______________________________________________

Visit our Facebook page https://www.facebook.com/meteoritecentral and the 
Archives at http://www.meteorite-list-archives.com
Meteorite-list mailing list
Meteorite-list@meteoritecentral.com
https://pairlist3.pair.net/mailman/listinfo/meteorite-list

Reply via email to