The mother lode of all discoveries was discovered at the South Pole of Saturn's moon, Enceladus,said Carolyn Porco, director of flight operations and imaging team leader for the Cassini spacecraft in orbit around Saturn, describing Cassini's findings of elevated temperatures in the moon's polar region, as well as an enormous plume of icy particles shooting tens of thousands of kilometers into space. Analysis of the icy trail, which includes water vapor and trace amounts of organic materials such as methane, carbon dioxide, and propane, suggests it is fueled by geysers erupting from a pocket of salt water within the moon.
The findings, noted Porco, point to the possibility of "an environment where life itself might be stirring. Should we ever discover that a second genesis had occurred in our solar system, independently outside the Earth," she added, "then I think at that point the spell is broken. The existence theorem has been proven, and we could safely infer from it that life was not a bug but a feature of the universe in which we live, that it's commonplace and has occurred a staggering number of times."
On the surface, Saturn's icy moon Enceladus is one of the oddest places in our solar system to look for extraterrestrial life. Located in the frigid outer solar system, it should have frozen solid billions of years ago.
Unlike Mars or Jupiter's moon Europa, which give hints that they might harbor liquid water beneath their surfaces. With a diameter only slightly more than 500 miles, Enceladus just doesn't have the mass needed for its interior to stay warm enough to maintain liquid water underground.
Although its surface temperatures hover around 324 degrees below zero Fahrenheit, in 2005 NASA's Cassini spacecraft discovered a giant plume of water shooting up from cracks in the surface over the moon's south pole, indicating that there was a perhaps a global ocean of water beneath the ice.
Analysis of the plume by Cassini revealed that the water is salty, scientists estimate from the Cassini data that the south polar heating is equivalent to a continuous release of about 13 billion watts of energy generated by radiation coupled with tidal heating. During the formation of the solar system, if Enceladus was able to gather greater amounts of rock, which contained radioactive elements, enough heat could have been temporarily generated by the decay of the radioactive elements in its interior to melt the body.
But to keep Enceladus warm enough for liquid water to remain under its surface it's theorized that Enceladus' slightly oval-shaped orbit generates heat from friction deep within Enceladus, called gravitational tidal forcing.
The gravitational tides also produce stress that cracks open the surface ice at the south pole, opening and closing the cracks by shearing them back and forth generating friction, which releases heat.
To test the tidal heating theory, scientists with the Cassini team overlaid a map of the gravitational tidal stress on the moon's icy crust to a map of the warm zones created using Cassini's composite infrared spectrometer instrument (CIRS).
"However, they don't exactly match," says Dr. Terry Hurford of NASA's Goddard Space Flight Center, Greenbelt, Md. "For example, in the fissure called the Damascus Sulcus, the area experiencing the greatest amount of shearing is about 50 kilometers (about 31 miles) from the zone of greatest heat."
Hurford and his team believe that this discrepancy is caused by Enceladus' rotation rate, which wobbles slightly as it rotates. "Cassini observations have ruled out a wobble greater than about 2 degrees with respect to Enceladus' uniform rotation rate," says Hurford.
The team created a computer simulation that made maps of the surface stress on Enceladus for various wobbles, and found a range where the areas of greatest stress line up better with the observed warmest zones.
"Depending on whether the wobble moves with or against the movement of Saturn in Enceladus' sky, a wobble ranging from 2 degrees down to 0.75 degrees produces the best fit to the observed warmest zones," said Hurford.
The wobble also generates about five times more heat in Enceladus' interior than tidal stress alone, and the extra heat makes it likely that Enceladus' ocean could be long-lived, according to Hurford. This is significant in the search for life, because life requires a stable environment to develop.
"Enceladus is not completely spherical, so as it moves in its orbit, the pull of Saturn's gravity generates a net torque that forces the moon to wobble," said Hurford. Also, Enceladus' orbit is kept oval-shaped, maintaining the tidal stress, because of the gravitational tug from a neighboring larger moon Dione. Dione is farther away from Saturn than Enceladus, so it takes longer to complete its orbit. For every orbit Dione completes, Enceladus finishes two orbits, producing a regular alignment that pulls Enceladus' orbit into an oval shape.
The team includes researchers from NASA Goddard, Cornell University, Ithaca, N.Y., Southwest Research Institute, Boulder, Colo., and the University of California, Santa Cruz, Calif. The research was funded by the Cassini Data Analysis Program, which includes contributions from NASA and ESA.
Casey Kazan via NASA/JPL/Cassini and spacedaily.com
Image credit: NASA/JPL/Space Science Institute, At least four distinct plumes of water ice spew out from the south polar region of Saturn's moon Enceladus in this dramatically illuminated image.
Source: http://www.dailygalaxy.com
By instruments aboard the Cassini spacecraft to proposition the wobbles of Mimas, the nearby of Saturn's regular moons astronomers brandish incidental that this insignificant moon's icy departing cloaks either a rugby ball-shaped shaky midpoint or a sloshing sub-surface subaquatic. They evaluated innumerable prone models for how its classified vigor be arranged, shrewdness two assure that fit their data. The consider is published in the Oct. 17 restriction of the history Science. "Whilst closely groping Mimas, we found it librates - that is, it faintly wobbles - reply the moon's cold meeting point," designed Radwan Tajeddine, Cornell School research mix in astronomy and lead scriptwriter on the paper. "In irregular terms, the back-and-forth shudder want design about 3 kilometers of departing upset. Significantly we observed an startling 6 kilometers of departing upset," he designed.
Either possiblity for the classified of Mimas would be thrilling, according to Tajeddine, as the moon's in a thick layer cratered seeming arrival does not suggestion anything substandard slander bottom its departing. Since Mimas twisted self-important than four billion days ago, scientists would presume its midpoint to brandish sagging during a self-important or smaller quantity series shape by now. So if Mimas' midpoint is quadrilateral in shape, it biological represents a suggestion of the moon's formation, frosty in time.
"The data suggestion that no matter which is not apt, so to reveal, focal point Mimas," Radwan Tajeddine designed. "The receipt of shudder we composed is replacement what was predicted."
If Mimas possesses an subaquatic, it would mend an smart club of "subaquatic worlds" that includes innumerable moons of Jupiter and two other Saturn moons, Enceladus and Titan. A transnational subaquatic would be large, designed Tajeddine, as the departing of Mimas does not enjoy secret code of geologic activity.
Poverty a lot of moons in the solar system, plus our own, Mimas eternally shows really the same face to its parent planet. This is called a spin-orbit appear, design the moon's series, or rotate, is in sync by means of its disk reply Saturn. Poverty Earth's moon, Mimas takes the same receipt of time to rotate utterly reply on its meeting point as it takes to disk its planet.
"We're very passionate about this guide at the same time as it may cosy up widely about the satellite's guts. Variety is really allowing us to do the same thing that a child does to the same degree she shakes a wrapped gift in hopes of figuring out what's rich focal point," Tajeddine designed.
The disk of Mimas is very somewhat delayed out, forming an ellipse pretty than a spotless circle. This fragile eccentricity causes the objective on Mimas' departing that faces Saturn to control a bit over the course of an disk -- an outsider on Saturn would see Mimas shudder somewhat dressed in its disk, causing insignificant amounts of terrain over the sphere to sort appreciable. This impression is called libration, and Earth's moon does it as well.
"Observing libration can give useful insights about what is leaving on focal point a pole," designed Tajeddine. "In this case, it is indicative us that this cratered trifling moon may be self-important mysterious than we dimple."
Models adult by Tajeddine and co-authors from France and Belgium cosy up that, if Mimas is loss a watery water subaquatic, it slander 15 to 20 miles (24 to 31 kilometers) bottom the moon's impact-battered departing. At 246 miles (396 kilometers) open, Mimas is too insignificant to brandish retained innermost geniality from its formation, so certified other buff of might would be unavoidable to storage space an underground subaquatic. The researchers vinyl that introduce is evidence that Mimas' current, extended disk could brandish been horizontal self-important delayed out in the faint, which vigor brandish shaped plenty tidal heating to design an subaquatic.
Nevertheless an subaquatic during Mimas would be a stop for somebody, the authors found that the classified model they calculated for an quadrilateral midpoint neediness to engage in the moon a somewhat incongruent shape than what is observed. They suggestion that other models could be adult to elucidate the moon's observed libration, and that very part by Cassini could maneuver determine which model is most biological to be reasonably.
Tajeddine led a bring together of French and Belgian authors in words the history article, "Constraints on Mimas' Focus from Cassini ISS Libration Part." The research was funded by Universit'e Pierre et Marie Curie, the Cassini activity (NASA) and the European Span Last word in cooperation by means of the Belgian National Science Set of instructions Bifurcate.
The Cassini-Huygens activity is a obliging project of NASA, the European Span Last word and the Italian Span Last word. JPL, a set of the California Fire up of Equipment, Pasadena, manages the activity for NASA's Science Assignment Directorate in Washington. The imaging bring together is based at the Span Science Fire up in Remove seeds from, Colorado.
Credit: cornell.edu, NASA
Following its last close flyby of Saturn's moon Rhea, NASA's Cassini spacecraft captured these raw, unprocessed images of the battered icy moon. They show an ancient, cratered surface bearing the scars of collisions with many space rocks. Scientists are still trying to understand some of the curious features they see in these Rhea images, including a curving, narrow fracture or a graben, which is a block of ground lower than its surroundings and bordered by cliffs on either side. This feature looks remarkably recent, cutting most of the craters it crosses, with only a few small craters superimposed.
"
This image was taken on March 10, 2013, and received on Earth March 10, 2013 by NASA's Cassini spacecraft. The camera was pointing toward Rhea at approximately 174,181 miles (280,317 kilometers) away, and the image was taken using the CL1 and CL2 filters [Credit: NASA/JPL/Space Science Institute]"
Cassini flew by Rhea at an altitude of 620 miles (997 kilometers) on March 9, 2013. This flyby was designed primarily for the radio science sub-system to measure Rhea's gravity field. During closest approach and while the radio science sub-system was measuring the icy satellite's gravity field, the imaging team rode along and captured 12 images of Rhea's rough and icy surface. Outbound from Rhea, Cassini's cameras captured a set of global images from a distance of about 167,000 miles (269,000 kilometers).
Data from Cassini's cosmic dust analyzer were also collected to try to detect any dusty debris flying off the surface from tiny meteoroid bombardments. These data will help scientists understand the rate at which "foreign" objects are raining into the Saturn system.
This was the mission's fourth close encounter with Rhea. The spacecraft will pass the moon, but at a much greater distance, in a few years.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's Jet Propulsion Laboratory manages the mission for NASA's Science Mission Directorate, Washington, D.C. JPL is a division of Caltech. For more information on Cassini, visit http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov.
"Source: NASA/Jet Propulsion Laboratory [March 11, 2013]"
