Asteroid Collision May Have Shifted Saturn Moon’s Poles

Posted: May 31 2017, 4:03pm CDT | by , Updated: May 31 2017, 11:04pm CDT, in News | Latest Science News

 
Asteroid Collision may have Shifted Saturn Moon’s Poles
Credit: NASA/JPL-Caltech/ Space Science Institute

Shift in spin axis helps to explain why Enceladus' north and south poles appear quite different.

Saturn’s moon Enceladus is an unusual object. It is considered to be one of the few likely places in our solar system, other than Earth, to harbor life.

Enceladus appears extremely cold and icy but Cassini mission has revealed intense geological activity at the southern pole of the icy moon. Warm,linear fractures across the south pole known as “tiger stripes” contain over a hundred geysers which ejects plumes of gas and dust miles into the moon’s atmosphere. These active geysers hint at an ocean underneath the surface of Enceladus. On the other hand, the north polar region of Enceladus is heavily cratered, indicating that the surface has not been renewed since quite long ago.

Now researchers speculate that the geological activity in its south polar region is unlikely to have been initiated by internal processes. The moon may have tipped over long time ago.

Examining the moon’s features, researchers have found that Enceladus appears to have moved from its original axis by about 55 degrees -- more than halfway toward rolling completely onto its side. And the moon's spin axis -- the line through the north and south poles – changed its direction possibly due to a collision with a smaller body, such as an asteroid.

“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.” Lead study author Radwan Tajeddine, a Cassini imaging team associate at Cornell University said in a statement.

The disruption and creation of the tiger stripes on southern pole have caused changes in the distribution of weight on Enceladus, making the moon's rotation unsteady and wobbly. While researchers say rotation would have eventually stabilized, Enceldaus will continue to change its spin axis until then. This phenomenon is known as “true polar wanderer.” The rotation is expected to settle down somewhat over a million of years.

The polar wander idea helps to explain why Enceladus' current north and south poles look quite different. The south is geologically active and young, while the north is cluttered with craters and cracks and appears much older.

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