Cracks in the icy surface of Saturn's moon Enceladus open and close daily under the pull of Saturn's gravity, according to new calculations by NASA-sponsored researchers.
"Tides generated by Saturn's gravity could control the timing of eruptions from cracks in the southern hemisphere of Enceladus," said Dr. Terry Hurford of NASA's Goddard Space Flight Center, Greenbelt, Md. Hurford is lead author of a paper on this research appearing in Nature May 17.
In 2005, the Cassini spacecraft flew by Enceladus and saw plumes of material erupting from the south pole of Enceladus. Scientists were surprised to see this because eruptions are powered by heat from an object's interior. Enceladus is tiny compared to most moons, only about 500 kilometers (310 miles) in diameter, so it should have lost its interior heat to the cold of space long ago.
A closer look by Cassini revealed a series of 120-kilometer (75-mile) long cracks in the south polar region of Enceladus, which were nicknamed "Tiger Stripes" because they resembled a tiger's distinctive marks. The stripes are warmer than their surroundings, so scientists believe they are the source of the eruptions. The Cassini observations also show the plumes consist of water vapor, so there is evidence for liquid water under the ice. Since liquid water is necessary to support known forms of life, Enceladus has become a promising place to look for extraterrestrial life.
Enceladus' 1.3-Earth-day orbit around Saturn is slightly elliptical (egg-shaped), so the moon's distance from Saturn changes regularly as it travels in its orbit. When Enceladus is closer to Saturn, the pull of Saturn's gravity is stronger, creating a larger tide; and when Enceladus is farther away, the pull is weaker, creating a smaller tide. Saturn's position in Enceladus' sky also changes slightly, moving the location of the tide on Enceladus' surface from east to west and back again with each orbit. These two effects combine to produce changing stress on the moon's icy surface. The team developed a computer model to calculate how the changing stress affects the Tiger Stripes.
"We found that because of the way the Tiger Stripes are oriented on the surface, when Enceladus is farthest from Saturn, the stresses in the region pull most of them open, and when Enceladus is closest to Saturn, the stresses force most of them to close," said Hurford. "Different stripes open at different times in the orbit. Assuming they erupt as soon as they open, exposing liquid water to the vacuum of space, we can predict which stripes will be erupting at certain times in the orbit. Also, because most of the stripes are open when Enceladus is farthest from Saturn, we expect the eruptive activity to be greatest at this time."
It has been hard to conclusively test the model so far because of the orientation of the stripes when Cassini took images of the eruptions. Cassini saw the eruptions when they appeared on the edge of Enceladus as they were backlit by the sun. From this viewpoint, the Tiger Stripes were lined up so that some were closer to the spacecraft and some were farther away. It is hard for the team to tell if an eruption was coming from a stripe in the foreground or from one in the background. However, future observations of the moon when Cassini is in a different location may provide a partial test by allowing the eruptions from one stripe to appear distinct from the rest.
Source: NASA/Goddard Space Flight Center
- PHYSICAL SCIENCES
- EARTH SCIENCES
- LIFE SCIENCES
- SOCIAL SCIENCES
Subscribe to the newsletter
Stay in touch with the scientific world!
Know Science And Want To Write?
- The Serious Physics Of Super Balls
- Mystery Of Morgellons - Disease Or Delusion - Scientific Hypothesis Of Connection With Lyme Disease
- Numenta And IBM To Build Biologically Inspired Intelligent Machines.
- Traditional Medicine: Thunder God Vine As Potential Obesity Treatment
- Grading The President's Strategy To Promote Bee Health
- "Boys With Toys" - Was It Sexist?
- Enjoy Sugar Again: High Carb Diet On Par With Caloric Restriction In Boosting Health
- "As a Christian I've always believed that there are no true atheists. We are created in God's image..."
- "The math realities are that the President's Strategy cannot possibly increase the amount of honeybee..."
- "Yes for sure. I'm at email@example.com. It's on loads of websites as that's my support..."
- "Good points, yes I think that's the way of it. I know it's rather long, some of the wikipedia articles..."
- "Well. This doesn't translate straightforwardly, given that to my knowledge Rats' natural composition..."
- How we make emotional decisions
- Racial Socialization May Help Minority Children Succeed in School
- Component in green tea may help reduce prostate cancer in men at high risk
- In battle of the sexes, a single night with a New York male is enough to kill
- Vulnerability found in some drug-resistant bacteria