NASA’s Cassini spacecraft has returned images from its final close approach to Saturn’s oddball moon Hyperion, upholding the moon’s reputation as one of the most bizarre objects in the solar system. The views show Hyperion’s deeply impact-scarred surface, with many craters displaying dark material on their floors.
During this flyby, Cassini passed Hyperion at a distance of about 21,000 miles (34,000 kilometers) at closest approach. Cassini’s closest-ever Hyperion flyby took place on Sept. 26, 2005, at a distance of 314 miles (505 kilometers).
Hyperion is the largest of Saturn’s irregular, or potato-shaped, moons and may be the remnant of a violent collision that shattered a larger object into pieces. Cassini scientists attribute Hyperion’s peculiar, sponge-like appearance to the fact that it has an unusually low density for such a large object — about half that of water. Its low density indicates Hyperion is quite porous, with weak surface gravity. These characteristics mean impactors tend to compress the surface, rather than excavating it, and most material that is blown off the surface never returns.
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The NASA and European Space Agency Cassini mission has revealed hundreds of lakes and seas spread across the north polar region of Saturn’s moon Titan. These lakes are filled not with water but with hydrocarbons, a form of organic compound that is also found naturally on Earth and includes methane. The vast majority of liquid in Titan’s lakes is thought to be replenished by rainfall from clouds in the moon’s atmosphere. But how liquids move and cycle through Titan’s crust and atmosphere is still relatively unknown.
A recent study led by Olivier Mousis, a Cassini research associate at the University of Franche-Comté, France, examined how Titan’s methane rainfall would interact with icy materials within underground reservoirs. They found that the formation of materials called clathrates changes the chemical composition of the rainfall runoff that charges these hydrocarbon “aquifers.” This process leads to the formation of reservoirs of propane and ethane that may feed into some rivers and lakes
“We knew that a significant fraction of the lakes on Titan’s surface might possibly be connected with hidden bodies of liquid beneath Titan’s crust, but we just didn’t know how they would interact,” said Mousis. “Now, we have a better idea of what these hidden lakes or oceans could be like.”
A combined NASA and European Space Agency (ESA)-funded study has found firm evidence that nitrogen in the atmosphere of Saturn’s moon Titan originated in conditions similar to the cold birthplace of the most ancient comets from the Oort cloud. The finding rules out the possibility that Titan’s building blocks formed within the warm disk of material thought to have surrounded the infant planet Saturn during its formation.
The main implication of this new research is that Titan’s building blocks formed early in the solar system’s history, in the cold disk of gas and dust that formed the sun. This was also the birthplace of many comets, which retain a primitive, or largely unchanged, composition today.
An unusual structure with a hexagonal shape surrounding Saturn’s north pole was spotted on the planet for the first time thirty years ago. Nothing similar with such a regular geometry had ever been seen on any planet in the Solar System. The Planetary Sciences Group has now been able to study and measure the phenomenon and, among other achievements, establish its rotation period. What is more, this period could be the same as that of the planet itself. Saturn is the only planet in the Solar System whose rotation time remains unknown. The research illustrates the front cover of the journal Geophysical Research Letters and has been highlighted by the publication’s editor.
In 1980 and 1981 NASA’s Voyager 1 and 2 space probes passed for the first time over the planet Saturn, located 1,500 million km from the Sun. Among their numerous discoveries they observed a strange, hexagon-shaped structure in the planet’s uppermost clouds surrounding its north pole. The hexagon remained virtually static, without moving, vis-à-vis the planet’s overall rotation that was not accurately known. What is more, the images captured by the Voyager probes found that the clouds were moving rapidly inside the hexagon in an enclosed jet stream and were being dragged by winds travelling at over 400 km/h.
NASA’s Cassini spacecraft and Deep Space Network have uncovered evidence Saturn’s moon Enceladus harbors a large underground ocean of liquid water, furthering scientific interest in the moon as a potential home to extraterrestrial microbes.
Researchers theorized the presence of an interior reservoir of water in 2005 when Cassini discovered water vapor and ice spewing from vents near the moon’s south pole. The new data provide the first geophysical measurements of the internal structure of Enceladus, consistent with the existence of a hidden ocean inside the moon. Findings from the gravity measurements are in the Friday, April 4 edition of the journal Science.
“The way we deduce gravity variations is a concept in physics called the Doppler Effect, the same principle used with a speed-measuring radar gun,” said Sami Asmar of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., a coauthor of the paper. “As the spacecraft flies by Enceladus, its velocity is perturbed by an amount that depends on variations in the gravity field that we’re trying to measure. We see the change in velocity as a change in radio frequency, received at our ground stations here all the way across the solar system.”
NASA trained several pairs of eyes on Saturn as the planet put on a dancing light show at its poles. While NASA’s Hubble Space Telescope, orbiting around Earth, was able to observe the northern auroras in ultraviolet wavelengths, NASA’s Cassini spacecraft, orbiting around Saturn, got complementary close-up views in infrared, visible-light and ultraviolet wavelengths. Cassini could also see northern and southern parts of Saturn that don’t face Earth.
The result is a kind of step-by-step choreography detailing how the auroras move, showing the complexity of these auroras and how scientists can connect an outburst from the sun and its effect on the magnetic environment at Saturn. A new video showing aurora images from Hubble and Cassini is available here.
“Saturn’s auroras can be fickle — you may see fireworks, you may see nothing,” said Jonathan Nichols of the University of Leicester in England, who led the work on the Hubble images. “In 2013, we were treated to a veritable smorgasbord of dancing auroras, from steadily shining rings to super-fast bursts of light shooting across the pole.”
NASA’s Cassini spacecraft is providing scientists with key clues about Saturn’s moon Titan, and in particular, its hydrocarbon lakes and seas.
Titan is one of the most Earth-like places in the solar system, and the only place other than our planet that has stable liquid on its surface.
Cassini’s recent close flybys are bringing into sharper focus a region in Titan’s northern hemisphere that sparkles with almost all of the moon’s seas and lakes. Scientists working with the spacecraft’s radar instrument have put together the most detailed multi-image mosaic of that region to date. The image includes all the seas and most of the major lakes. Some of the flybys tracked over areas that previously were seen at a different angle, so researchers have been able to create a flyover of the area around Titan’s largest and second largest seas, known as Kraken Mare and Ligeia Mare, respectively, and some of the nearby lakes.
“Learning about surface features like lakes and seas helps us to understand how Titan’s liquids, solids and gases interact to make it so Earth-like,” said Steve Wall, acting radar team lead at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “While these two worlds aren’t exactly the same, it shows us more and more Earth-like processes as we get new views.”