Cassini: Mission to Saturn: Cassini Explores a Methane Sea on Titan News & Features | April 26, 2016 Cassini Explores a Methane Sea on Titan Preston Dyches and Markus Bauer Sunlight glints off of Titan's northern seas this near-infrared, color mosaic from NASA's Cassini spacecraft. More › Key Points ♦ A new study finds that a large sea on Saturn's moon Titan is composed mostly of pure liquid methane, independently confirming an earlier result. Key Points ♦ The seabed may be covered in a sludge of carbon- and nitrogen-rich material, and its shores may be surrounded by wetlands. Of the hundreds of moons in our solar system, Titan is the only one with a dense atmosphere and large liquid reservoirs on its surface, making it in some ways more like a terrestrial planet. Both Earth and Titan have nitrogen-dominated atmospheres -- over 95 percent nitrogen in Titan's case. However, unlike Earth, Titan has very little oxygen; the rest of the atmosphere is mostly methane and trace amounts of other gases, including ethane.

And at the frigid temperatures found at Saturn's great distance from the sun, the methane and ethane can exist on the surface in liquid form. It's a marvelous feat of exploration that we're doing extraterrestrial oceanography on an alien moon. - Steve Wall, Cassini radar team deputy lead. For this reason, scientists had long speculated about the possible existence of hydrocarbon lakes and seas on Titan, and data from the NASA/ESA Cassini-Huygens mission does not disappoint. Since arriving in the Saturn system in 2004, the Cassini spacecraft has revealed that more than 620,000 square miles (1.6 million square kilometers) of Titan's surface -- almost two percent of the total -- are covered in liquid. There are three large seas, all located close to the moon's north pole, surrounded by numerous of smaller lakes in the northern hemisphere. Just one large lake has been found in the southern hemisphere. The exact composition of these liquid reservoirs remained elusive until 2014, when the Cassini radar instrument was first used to show that Ligeia Mare, the second largest sea on Titan and similar in size to Lake Huron and Lake Michigan combined, is methane-rich.

A new study published in the Journal of Geophysical Research: Planets, which used the radar instrument in a different mode, independently confirms this result. "Before Cassini, we expected to find that Ligeia Mare would be mostly made up of ethane, which is produced in abundance in the atmosphere when sunlight breaks methane molecules apart. Instead, this sea is predominantly made of pure methane," said Alice Le Gall, a Cassini radar team associate at the French research laboratory LATMOS, Paris, and lead author of the new study. The new study is based on data collected with Cassini's radar instrument during flybys of Titan between 2007 and 2015. A number of possible explanations could account for the sea's methane composition, according to Le Gall. "Either Ligeia Mare is replenished by fresh methane rainfall, or something is removing ethane from it. It is possible that the ethane ends up in the undersea crust, or that it somehow flows into the adjacent sea, Kraken Mare, but that will require further investigation." In their research, the scientists combined several radar observations of heat given off by Ligeia Mare.

They also used data from a 2013 experiment that bounced radio signals off Ligeia. The results of that experiment were presented in a 2014 paper led by radar team associate Marco Mastrogiuseppe at Cornell University, Ithaca, New York, who also contributed to the current study. During the 2013 experiment, the radar instrument detected echoes from the seafloor and inferred the depth of Ligeia Mare along Cassini's track over Ligeia Mare -- the first-ever detection of the bottom of an extraterrestrial sea. The scientists were surprised to find depths in the sea as great as 525 feet (160 meters) at the deepest point along the radar track. Le Gall and her colleagues used the depth-sounding information to separate the contributions made to the sea's observed temperature by the liquid sea and the seabed, which provided insights into their respective compositions. "We found that the seabed of Ligeia Mare is likely covered by a sludge layer of organic-rich compounds," adds Le Gall. In the atmosphere of Titan, nitrogen and methane react to produce a wide variety of organic materials. Scientists believe the heaviest materials fall to the surface.

Le Gall and colleagues think that when these compounds reach the sea, either by directly falling from the air, via rain or through Titan's rivers, some are dissolved in the liquid methane. The insoluble compounds, such as nitriles and benzene, sink to the sea floor. The study also found that the shoreline around Ligeia Mare may be porous and flooded with liquid hydrocarbons. The data span a period running from local winter to spring, and the scientists expected that -- like the seaside on Earth -- the surrounding solid terrains would warm more rapidly than the sea. However, Cassini's measurements did not show any significant difference between the sea's temperature and that of the shore over this period. This suggests that the terrains surrounding the lakes and seas are wet with liquid hydrocarbons, which would make them warm up and cool down much like the sea itself. "It's a marvelous feat of exploration that we're doing extraterrestrial oceanography on an alien moon," said Steve Wall, deputy lead of the Cassini radar team at NASA's Jet Propulsion Laboratory in Pasadena, California.

"Titan just won't stop surprising us." The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate in Washington. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the US and several European countries. Preston Dyches What causes the Cassini division in Saturn's rings? | Reference.com What causes the Cassini division in Saturn's rings? A: Quick Answer The Cassini Division, a gap in the rings of Saturn, is caused by gravitational pull from Saturn’s moon Mimas. The moon’s gravity affects the tiny particles that make up the rings, creating what looks like empty space. Other divisions in Saturn’s rings are the result of similar interactions with the planet’s moons. Full Answer The Cassini Division, at about 3,000 miles or 4,800 kilometers wide, is the largest of several gaps in the rings of Saturn. The area is not completely empty, but the scarcity of ring material makes it look like a dark, empty space.

The Cassini Division marks the division between what scientists call Saturn's A and B rings. Other divisions, created by the gravitational pull of other moons, exist farther out from the planet and are not as wide. astronomy 2 - Astronomy 1010 with Song at University of Georgia - StudyBlue What gives Uranus its blue-green coloration? absorption of the red sunlight by methane gas On which other world in the Solar System do we find evidence of ice rafts (now apparently frozen) similar in many respects to ice rafts in the Arctic Ocean? in the icy surface of Jupiter's satellite Europa Why are the lunar maria concentrated almost entirely on the near side of the Moon? The crust is thicker on the far side of the Moon, restricting massive lava flows after asteroid impact. The major gaps in the rings of Saturn are most likely caused by the combined gravitational forces of Saturn and its major moons, which deflect the paths of particles which stray into the gaps. People on Earth see the same side of the Moon at all times. Which chemical or chemicals appear to play a prominent role in the eruptive plumes of Io? sulfur and sulfur dioxide What appears to have caused the extensive cracking and streaking of the surface of Europa?

tidal flexing by Jupiter A comet's tail points away from the Sun regardless of the comet's motion. The Oort cloud of comets, which surrounds the Solar System at a distance of about 50,000 AU, is believed to be material flung out of the inner Solar System by the gravity of the newly formed giant planets early in the Solar System history. In what way do Uranus and Neptune differ from Jupiter and Saturn? Hydrogen and helium make up a smaller fraction of the total mass of Uranus and Neptune. On Earth (and in the past, on Mars), volcanoes have been vital for keeping the planet warm. This is because they have replenished the CO2 (a greenhouse gas) that is washed out of the atmosphere by rain. The clouds in the atmosphere of Venus consist primarily of droplets of H2SO4 or sulfuric acid. What feature of the Saturnian moon Enceladus makes it a unique object in our Solar System? It has the most reflective surface of all objects in the Solar System. The reason Venus has very few impact craters compared to the Moon is believed to be that lava flows have covered all but the most recent craters.

Which of the following satellites of planets in our Solar System has a significant, dense atmosphere? Titan, a moon of Saturn What features dominate the surface of Callisto, one of Jupiter's satellites? craters, densely spread over the entire surface Most meteor showers occur when Earth moves through the orbit of a comet (or of a former comet). The Hawaiian Islands experience continuous volcanic activity because they lie directly above a hot-spot plume in Earth's interior. Uranus and Neptune are about the same size, yet Neptune shows spots and bands in its atmosphere while Uranus is almost featureless. Why this difference? Neptune is still contracting and giving out energy which warms the lower layers of its atmosphere while Uranus is not. It was originally thought questionable whether a manned lunar landing could take place because the lunar surface might be too soft to land upon. What is the dominant circulation pattern in Jupiter's atmosphere (i.e., at the visible “surface”)? alternating bands of eastward and westward flow parallel to the equator, with light and dark ovals between these flows Most of the craters on the Moon were formed by bombardment by interplanetary meteoritic material.

Based on their average densities, the six moderate-sized satellites of Saturn are believed to be composed mostly of ice, with perhaps a small, rocky core. The best images of the overall topology of Venus have been produced by reflection of microwave and short radio wave radiation from the surface by an orbiting spacecraft. Which of the following objects in the Solar System has the smoothest surface relative to its radius? Europa, a moon of Jupiter coated with water ice If you were standing on the Moon with Earth in view, how much time would elapse between two successive “Earthrises”? infinite time, because the same side of the Moon always faces toward Earth The white spots observed in Saturn's atmosphere are believed to be crystals of ammonia. What are the most abundant gases in the atmosphere of Uranus? hydrogen and helium Where are the asteroids located? Most asteroids have orbits between the orbits of Mars and Jupiter, but there are gaps caused by resonances with Jupiter. If the orbits of one of the large moons were somehow deflected so that it passed within the Roche Limit of Jupiter it would be torn to pieces by tidal forces. However, there are many artificial satellites orbiting Earth within Earth's Roche Limit, and these are not torn apart. Why not?

The Roche Limit applies only to objects held together by gravity. How would “Interplanetary Travel” advertise a holiday on Jupiter's satellite Io? Largest number of volcanoes for your travel dollar anywhere in the Solar System! The northern Martian polar cap decreases in size during the northern Martian summer but does not completely disappear. What is the explanation for this? The polar cap is composed partially of water ice. The four Galilean moons of Jupiter do not all have the same mean density because heat from Jupiter prevented ice from forming at the locations of the inner moons. The weak and variable magnetic field measured by the Galileo spacecraft on Europa is generated by electrical currents in the ocean water, induced by Europa's motion through Jupiter's intense magnetic field. The white ovals seen on Jupiter appear to be vortices (whirlpools) created between regions of oppositely directed winds. The ecliptic is the plane defining Earth's orbit around the Sun. The orbits of most other objects in the Solar System generally lie fairly close to the ecliptic. However, the orbits of which one of the following types of objects do not generally lie close to the ecliptic?

comets The dark markings near the equator of Mars show seasonal variations because of variations in the dust coverage of the surface. Titan is Saturn's largest satellite. It is unusual among all the planetary moons because of its dense atmosphere. The composition of the clouds that we see on Jupiter is similar to those of Earth (water droplets and crystals of frozen water) in the lower levels but very different (e.g., ammonia crystals and other chemicals) in the higher levels. What are zonal winds on Jupiter? winds blowing horizontally eastward and westward in the cloud layer Venus has no magnetic field. Why would you expect to see no craters, such as those on the Moon or Mars, on Io, the innermost Galilean moon of Jupiter? because volcanoes are continuously depositing new material on the surface The material in the interiors of Jupiter and Saturn thought to be responsible for their powerful magnetic fields is liquid metallic hydrogen. What is the Cassini division? a wide, dark gap in Saturn's rings. Compared to that of Earth, the mass of Jupiter is about 300 times larger. The lifetime of the Great Red Spot appears to be at least 300 years, from visual records.

Mercury's magnetic field, compared with that of Earth, is weak, but strong enough to deflect the solar wind. Which of the following early telescope observations convinced Galileo that the Copernican heliocentric model provided a better explanation for the Solar System than did the Greek geocentric model? Moons seen to be orbiting another planet, Jupiter, rather than Earth The internal structure of Mercury is a dense iron core taking up almost half of the volume of the planet and a rocky mantle surrounding the core. Which of the following are NOT seen on Jupiter's satellite Io? impact craters The greenhouse effect, which heats a planet's surface above the predicted equilibrium surface temperature for the planet without an atmosphere, is far less effective on Mars than on Earth. Why is this? The Martian atmosphere is very thin and traps less infrared radiation from the surface. Recent calculations show that the Tunguska explosion in Siberia in 1908, which had an explosive power of several hundred kilotons of TNT, was probably caused by a small stony asteroid about 80 m across disintegrating explosively in the atmosphere before hitting the ground. What is the most likely cause of the smooth and relatively crater-free surfaces of lunar maria?

lava flows relatively late in the geological history of the Moon What is the mass of Saturn compared to the mass of Jupiter? about 1/3 the mass of Jupiter Which of the following has apparently had the least influence on the evolution of the surface and geology of Mars? an internal magnetic field Why does no major planet orbit the Sun at the location of the asteroid belt? Jupiter's gravitational pull stirred up the planetesimals, preventing them from coalescing into a single large object. Which of the following chemicals is the least abundant in the atmosphere of Jupiter? CO2—carbon dioxide How many of the large Galilean satellites are in synchronous rotation around Jupiter (always turning the same face toward Jupiter)? all 4 A major feature of the atmosphere of Mars is occasional strong winds and dust storms. The structure of Callisto, the outer Galilean satellite of Jupiter, is thought to be a thick ice crust and a slushy mantle of ice and water over a core of rock. The fact that there are several distinct and different types of meteorites (stony, stony-iron, and iron) is probably indicative of fragmentation of asteroids that had become differentiated in a similar fashion to Earth (with the heavier iron sinking to the center).

The oblateness of Jupiter, which is a measure of the amount by which its equatorial diameter exceeds its polar diameter and is a consequence of its fluid structure and rapid rotation, is 6.5%. Showers of shooting stars or meteors are seen at regular times each year on Earth because Earth passes through a cloud of remnant dust and rock fragments from an old comet that is circling the Sun in the comet's old orbit. It has been known that Jupiter has moons since Galileo turned his telescope to the sky in 1610. The name 1987 FD refers to the fourth asteroid to be discovered during the second half of March, 1987. The moons of Uranus orbit the planet in the same plane as the rings. There is no evidence of plate tectonics (continental drift) on Mercury. The most likely explanation is that the planet cooled too rapidly and the mantle became too rigid. The surface temperature of Venus has been found by radio observations and by remote exploration by American and Soviet spacecraft to be approximately 730 K.

The Tharsis rise on Mars, a region that is higher than the surrounding plain by about 5 km (over 16,000 ft), was caused by an upwelling magma plume in Mars's interior, which has raised this whole region. What characteristic of Jupiter's moon Io makes it different from any other known satellite in the Solar System? It is volcanically active. A chunk of rock and metal 10 km in diameter orbiting the Sun would be called an asteroid. The overall interior structure of Jupiter and Saturn is expected to be four-layered—a rocky inner core, a liquid outer core of “ices,” a mantle of liquid hydrogen and helium, and an extensive gaseous atmosphere. We have seen that our best Earth-bound views of Mercury and Venus occur when these planets are at their greatest elongations. Where is Mars when we have our best Earth-bound view of it? opposition Which of the following statements is NOT true of the Moon? It has extensive lava floodplains over most of its surface, near side and far side. Craters on Mercury appear to have been produced by impacts from objects early in the planet's history.

The most ambitious mission so far to study the asteroids is a soft unmanned landing to gather materials and return them to Earth. The spacecraft Clementine observed the Moon in 1994 and provided evidence for ice near the South Pole. How was this information gathered? Reflections of ultraviolet, visible, and infrared from the lunar surface were analyzed. The eruptive plumes observed on Io are thought to most closely resemble geysers, where material is shot upward by the pressure of gas produced below the surface. Which of the following objects in the solar system rotates quickest around its own axis? Jupiter Each of the following statements about the similarities of Mercury and our Moon is true, except one. Which comparison is not valid? Both have large, circular, and relatively flat basins or maria on parts of their surfaces. Compared to earthquakes, moonquakes are much weaker and less frequent, occurring mostly when the Moon is at perigee. Computer simulations of the formation of the Solar System show that the material in the vicinity of the asteroid belt did not form into a much larger planet because Jupiter's gravitational pull flung most of the material in this region out of the Solar System and prevented coalescence of the rest.

The high-speed winds observed on Jupiter occur mainly at the boundaries between the dark belts and the light zones. If astronauts set up a permanent settlement at Tranquility Base on the Moon, how many times each year would the Sun rise and set as seen by a resident of this base? about once per month The general shape of most asteroids is thought to be irregular. The outer three Galilean moons of Jupiter differ from Io, the innermost such moon, by having surfaces of water ice. What appears to be the “impact history” of cratering on the Moon? an early period of heavy bombardment followed by a decrease in intensity (except for a spike around four billion years ago) and then very light bombardment to the present Perhaps the most interesting material to be found inside rocks that have come to us from outer space is amino acids or proteins. The orbits of comets are randomly oriented in the Solar System and can extend far beyond the orbit of Pluto. Neptune's predominantly blue appearance is caused by the absorption of reflected sunlight at the red end of the spectrum by methane in its atmosphere.

Ganymede, one of the large Galilean satellites of Jupiter, is very different from the Earth, but in which one of the following ways does Ganymede RESEMBLE Earth? Ganymede appears to have had tectonic activity at some time in its past. Which one of the following parts of a comet is not visible to the naked eye? hydrogen envelope A shield volcano is a very broad volcano with gently sloping sides, similar in shape to an ancient Greek shield. Jupiter's strong magnetic field contains many charged particles which have been ejected from Io. Neptune's high cirrus clouds consist of methane ice crystals. The Oort cloud is an approximate spherical distribution of comets centered on the Sun, extending out to about 50,000 AU. Which of the following motions is seen to be characteristic of the four Galilean moons of Jupiter? They each keep the same face toward the planet at all times. A meteor shower occurs when Earth passes through a swarm of dust particles in space. One example of a near-Earth object, or NEO, is the asteroid Eros. What is the approximate orbital period of an object that is moving in a circular orbit around the Sun in the Oort cloud?

10 million years Comet tails are the result of melting and evaporation of ices from the comet's nucleus. Mercury is much closer than Venus to the Sun, and yet it never appears brighter than Venus, even when both are at maximum brightness, because Mercury is small, has a dark surface, and has no reflecting clouds. The outer cores of Jupiter and Saturn are made of “ices,” which are actually in the liquid state. Why are they not solid? The temperature here is too high. The four major moons of Jupiter are collectively named after which early astronomer? Galileo It is believed there were originally far more objects in the asteroid belt than there are now. What happened to the rest of them? The gravitational influence of Jupiter deflected most of them out of the Solar System. The blue-green appearance of Uranus is caused by the atmosphere of methane gas, which preferentially absorbs the red parts of the solar spectrum. The dominant component of the regolith on Mars is probably iron-rich clay. In which of the following planets was a ring system first discovered by the occultation or blocking of light from a distant star, as the planet and rings moved in front of it?

Uranus The composition of Jupiter's clouds is ice crystals of ammonia, ammonium hydrosulfide, and water. The Moon's appearance, when its whole surface is examined, could be described as maria only on the near side, no major maria on the far side. The rings of Saturn are in which plane with respect to the planetary system? the equatorial plane of Saturn The tilt of Uranus's axis was first deduced from observed orbital motions of its moons. For the deduction of this tilt to be correct, it was necessary to assume that the moons were orbiting in the equatorial plane of Uranus. What property is shared by the Earth and Europa, one of Jupiter's large moons? Both have warm oceans of water. Venus appears to be very bright in our skies at certain times because it is relatively close to the Sun, Earth is close to it, and it is covered by very reflective clouds. The rotation rate of the planet Venus was first determined by measuring the Doppler shift in radio waves reflected from the planet's surface. Who was the first person to report seeing the rings of Saturn although he did not realize that they were rings?

Galileo Galilei The interesting feature of Jupiter's rotation is that regions at different latitudes appear to rotate at different rates. Uranus lacks an internal source of heat. One consequence of this is that Uranus lacks dynamic atmospheric activity. The densities of the four Galilean satellites of Jupiter are high (rocky) for the two inner satellites because they formed close to Jupiter, low (rock and ice) for the two outer satellites because they formed farther away from Jupiter. The object whose discovery was prefaced by accurate prediction using the measured deviations of known planets from regular orbits and the application of Newton's laws of mechanics, is Neptune. The low average density of Jupiter (about 1300 kg/m3 compared with that of water, 1000 kg/m3) indicates that this planet is composed mainly of hydrogen, in liquid or gaseous form. Which is the most probable heat source that produced extensive and possibly total melting of the Moon at an early stage in its history? decay of radioactive elements within it and the impact energy of meteoritic bombardment Why do most comets have very elliptical orbits, often extending far out beyond the orbit of Pluto?

They originally formed outside the orbit of Pluto and were flung into highly elongated orbits by the giant planets. The Moon apparently has a small iron-rich core that was entirely molten in the Moon's history, as shown by magnetic measurements. In order to measure Venus's rotation it was necessary to send a beam of electromagnetic radiation through the cloud layer. This electromagnetic radiation was radio. A small piece of rock orbiting the Sun would be called a meteoroid. By dating the Moon rocks we can determine its age. How long ago did the Moon form? We believe the Moon was formed molten and then cooled. Because the oldest rocks are about 4.3 billion years old, the formation of the Moon must have occurred around 4.5 billion years ago. Mercury's average density and the fact that it has a (weak) magnetic field leads to the conclusion that its central core is probably composed of solid and/or molten iron. Evidence of hot-spot volcanoes caused by hot, rising plumes under the planet's surface is present on Venus and Mars, as well as on Earth. What distinguishes those on Earth from those on the other planets?

Plate tectonics on Earth has moved the hot-spot volcanic site continuously over recent geological time, whereas no such movement has occurred on Venus or Mars. The moons of Mars are irregularly shaped, cratered, and grooved. One effect of the tidal drag of the ocean waters on Earth is to slow down Earth's spin rate. The most geologically active object in the planetary system at the present time is Io, a moon of Jupiter. A comet's tail is always aligned from the comet head in a direction away from the Sun. Planet Saturn: Facts About Saturn’s Rings, Moons & Size Planet Saturn: Facts About Saturn’s Rings, Moons & Size By Charles Q. Choi, Space.com Contributor | November 17, 2014 10:25pm ET MORE Credit: NASA/JPL Saturn is the sixth planet from the sun and the second largest planet in the solar system. Saturn was the Roman name for Cronus, the lord of the Titans in Greek mythology. Saturn is the root of the English word "Saturday." Saturn is the farthest planet from Earth visible to the naked human eye, but it is through a telescope that the planet's most outstanding features can be seen: Saturn's rings.

Although the other gas giants in the solar system — Jupiter, Uranus and Neptune — also have rings, those of Saturn are without a doubt the most extraordinary. Physical characteristics of Saturn Saturn is a gas giant made up mostly of hydrogen and helium . Saturn is big enough to hold more than 760 Earths, and is more massive than any other planet except Jupiter, roughly 95 times Earth's mass. However, Saturn has the lowest density of all the planets, and is the only one less dense than water — if there were a bathtub big enough to hold it, Saturn would float. The yellow and gold bands seen in Saturn's atmosphere are the result of super-fast winds in the upper atmosphere, which can reach up to 1,100 mph (1,800 km/h) around its equator, combined with heat rising from the planet's interior. Saturn spins faster than any other planet except Jupiter, completing a rotation roughly every 10-and-a-half hours. This rapid spinning causes Saturn to bulge at its equator and flatten at its poles — the planet is 8,000 miles (13,000 kilometers) wider at its equator than between the poles.

Saturn's most recent curiosity may be the giant hexagon circling its north pole, with each of its sides nearly 7,500 miles (12,500 km) across — big enough to fit nearly four Earths inside. Thermal images show it reaches some 60 miles (100 km) down into the planet's atmosphere. It remains uncertain what causes it. Other titanic storms appear in Saturn’s atmosphere once every Saturn year (approximately 30 Earth-years), disrupting the temperature and winds of the planet’s skies. Six such storms have been observed on the planet since 1876, but in 2011, NASA’s Cassini spacecraft became the first orbiter to observe one. Like other giant planets, Saturn also has northern and southern lights , caused by particles from the sun. Composition & structure Atmospheric composition (by volume): 96.3 percent molecular hydrogen, 3.25 percent helium, minor amounts of methane, ammonia, hydrogen deuteride, ethane, ammonia ice aerosols, water ice aerosols, ammonia hydrosulfide aerosols Magnetic field: Saturn has a magnetic field about 578 times more powerful than Earth's.

Chemical composition: Saturn seems to have a hot solid inner core of iron and rocky material surrounded by an outer core probably composed of ammonia, methane, and water. Next is a layer of highly compressed, liquid metallic hydrogen, followed by a region of viscous hydrogen and helium. This hydrogen and helium becomes gaseous near the planet's surface and merges with its atmosphere. Internal structure: Saturn seems to have a core between about 10 to 20 times as massive as Earth. Orbit & rotation Average distance from the sun: 885,904,700 miles (1,426,725,400 km). By comparison: 9.53707 times that of Earth. Perihelion (closest approach to sun): 838,519,000 miles (1,349,467,000 km). By comparison: 9.177 times that of Earth. Aphelion (farthest distance from sun): 934,530,000 miles (1,503,983,000 km).

By comparison: 9.886 times that of Earth. Saturn's moons Saturn has at least 62 moons . Since the planet was named after Cronus, lord of the Titans in Greek mythology, most of Saturn's moons are named after other Titans, their descendants, as well as after giants from Gallic, Inuit and Norse myths. Saturn's largest moon, Titan , is slightly larger than Mercury, and is the second-largest moon in the solar system behind Jupiter's moon Ganymede. ( Earth's moon is the fifth largest.) Titan is veiled under a very thick, nitrogen-rich atmosphere that might be like what Earth's was long ago, before life. While the Earth's atmosphere extends only about 37 miles (60 km) into space, Titan's reaches nearly 10 times as far. The atmosphere contains a number of hydrocarbons, chemicals that primarily make up fossil fuels on Earth. Methane rain falls from the sky and moves through the moon’s icy crust . A recent study detected propylene , a chemical used to make plastics, in the planet’s atmosphere. These moons can possess bizarre features.

Pan and Atlas are shaped like flying saucers, Iapetus has one side as bright as snow and one side as dark as coal. Enceladus shows evidence of "ice volcanism," spewing out water and other chemicals from the 101 geysers spotted at the moon’s southern pole. A number of these satellites, such as Prometheus and Pandora, are shepherd moons , interacting with ring material to keep rings in their orbits. Though scientists have identified many moons, the chaotic system has other small moons constantly being created and destroyed . Cassini: Mission to Saturn: Images News & Features News & Features The latest stories from Saturn. Explore a historical archive dating back to the earliest days of the mission. Saturn's Rings: Composition, Characteristics & Creation Saturn's Rings: Composition, Characteristics & Creation By Nola Taylor Redd, Space.com Contributor | October 16, 2013 05:54pm ET MORE This rare space wallpaper taken on July 19, by NASA's Cassini spacecraft shows Saturn's rings and our planet Earth and its moon in the same frame.

Credit: NASA/JPL-Caltech/Space Science Institute Saturn, the sixth planet from the sun, is one of the most easily identified targets for astronomers, largely due to its large and distinct ring system. The rings of Saturn have fascinated stargazers for centuries, ever since telescopes were first pointed toward the sky. When Galileo Galilei first observed Saturn in 1610, he thought that the rings were enormous moons, one positioned on each side of the planet. Over several years of observations, he noted that the rings changed shape and even disappeared , as they changed their inclination with respect to Earth. We now know that Galileo was observing a "ring plane crossing." Saturn's equator is tilted relative to its orbit around the sun by 27 degrees – similar to Earth's 23-degree tilt. As Saturn circles the sun, first one hemisphere and then the other is tilted sunward. The tilt causes seasons, just as it does on Earth, and when Saturn reaches equinox, its equator and ring plane are directly in line with the sun. Sunlight hits the rings edge-on, and the fine line of the rings is difficult to detect.

The rings are wide — 170,000 miles across (273,600 km) — but only about 30 feet (10 meters) thick. In 1655, astronomer Christaan Huygens suggested that the strange bodies were solid, inclined rings, and in 1660 another astronomer suggested that the rings were made up of small satellites, an insight that wasn't confirmed for nearly 200 years. In modern times, Pioneer 11 passed through the Saturn ring plane in 1979. In the 1980s, Voyager 1 and Voyager 2 glimpsed the planet's ring system. In 2004, NASA's Cassini-Huygens mission became the first to enter orbit around Saturn, taking detailed observations not only of the planet but of its ring system. Details of Saturn's icy rings are visible in this sweeping view from Cassini of the planet's glorious ring system. The total span, from A ring to F ring, covers approximately 40,800 miles (65,700 km) and was photographed at Nov. 26, 2008.

Credit: NASA/JPL/Space Science Institute Composition and structure Saturn's rings are made up of billions of particles ranging from grains of sand to mountain-size chunks. Composed predominantly of water-ice, the rings also draw in rocky meteoroids as they travel through space. Though Saturn appears surrounded by a single, solid ring when viewed by an amateur astronomer, several divisions exist. The rings are named alphabetically in the order of discovery. Thus the main rings are, from farthest from the planet to closest, A, B and C. A gap 2,920 miles wide (4,700 kilometers), known as the Cassini Division, separates the A and B rings. Other, fainter rings have been discovered as telescope technology has improved. Voyager 1 detected the innermost D ring in 1980. The F ring lies just outside of the A ring, while the G and E ring lay even farther out. The rings themselves contain a number of gaps and structures . Some are created by Saturn's many small moons, while others continue to puzzle to astronomers.

Saturn is not the only planet in the solar system to have rings — Jupiter , Uranus and Neptune also contain faint ring systems — but with its satellites spanning three-quarters of the Earth-moon distance (175,000 miles or 282,000 km), it is by far the largest and most visible. Formation theories Several hypotheses exist as to the how Saturn's rings were formed. Some scientists think that passing comets or asteroids were snagged by the planet's gravity and broken up before reaching it. Another possibility is that the rings were once large moons that spiraled into the planet. Saturn has at least 62 moons . Only one ( Titan ) is large; the rest are small bodies. Only 13 of the moons are larger than 30 miles (50 km). The gravity of these moons affects the structure of Saturn's rings, but also offer insight into possible formation methods. If the icy outer layers were stripped away, leaving the core to crash into Saturn, the result would be rings dominated by nearly pure water-ice.

[ PHOTOS: The Rings and Moons of Saturn ] Editor's Recommendations Saturn's Magnificent Rings Saturn's Magnificent Rings Saturn's Ring System In 1610 Galileo Galilei turned his primitive telescope to the heavens and was astonished to observe a bright star flanked by two dimmer ones. What Galileo had discovered was a strange new world, a planet that was to become one of the wonders of the solar system, and to be named Saturn. Saturn's beauty comes from its magnificent rings that Galileo described as "handles" or large moons on either side of the planet. He said, "I have observed the highest planet [ Saturn ] to be tripled-bodied. This is to say that to my very great amazement Saturn was seen to me to be not a single star, but three together, which almost touch each other". Two years later Galileo was puzzled to discovered the rings had disappeared. What Galileo did not know was that the Earth had passed through Saturn's ring plane and the rings were edge on and could not be resolved with his 20x telescope.

Galileo's discovery of Saturn commenced the scientific process of unraveling the mysteries of Saturn's extensive ring system, but even after 400 years the mysteries have not been all solved. Hubble Space Telescope Image of Saturn's rings edge on. [ more ] In 1655 Christann Huyges proposed that Saturn was surrounded by a solid ring, "a thin, flat ring, nowhere touching, and inclined to the ecliptic." As time went on, more and more observations were made and theories proposed. It took until the mid 1800s before the notion that the ring was made out of small particles rather than being solid became the prominent theory. In 1979 Pioneer 11 became the first spacecraft to fly past Saturn and take pictures of the planet and rings. Although the pictures are of low resolution by today's standards, they were better than any previous photos taken through telescopes. In 1980 and 1981 Voyager 1 and Voyager 2 flew past the planet and took numerous high-resolution images of Saturn and its rings. The next major milestone will be in 2004 when the Cassini spacecraft arrives at Saturn.

Cassini will be the first spacecraft to go into orbit about the planet. Here it will operate studying Saturn, its moons, rings and environment for the next four years. Ring Structure Saturn's ring system is divided up into 7 major divisions with alphabetic designators in the order of discovery. From the innermost ring to the outermost ring the designators are D, C, B, A, F, G and E. Each major division is further subdivided into thousands of individual ringlets. The F and G rings are very thin and difficult to see while the A, B, and C rings are broad and quite visible. Between the A and B rings is a gap called the Cassini division named after Giovanni Cassini who discovered the Gap in 1676. Between the A and F rings lies the Keeler (Encke) gap. Saturn's braided F-Ring. [ more ] Much of the elaborate structure of the rings is due to gravitational effects of nearby satellites. This phenomenon is demonstrated by the relationship between the F-ring and two small moons Prometheus and Pandora that shepherd the ring material. The F-ring shows a complex structure made up of two narrow, braided, bright rings along which "knots" are visible.

Scientists speculate that the knots may be clumps of ring material, or mini moons. In the mid 1980s Dr. Jeff Cuzzi noticed a wavy pattern in the ring material on both sides of the Encke gap. It was suggested that an unseen asteroid-sized moon in the gap caused the disturbance. Dr. Mark Showalter further analyzed the disturbance and used this "moonlet wake" pattern that resembled a motorboat wake, to determine the position and mass of the unseen body. The amplitude of the waves, he said suggested the mass of the unobserved object and the wavelength of the ripples revealed the moon's possible position. Using this mathematical model, Dr. Showalter was able to predict which Voyager images the moon would be in. In 1990 Dr. Showalter's work paid off and Pan was discovered within the Encke gap. Resonance Waves. [ more ] Resonance Structures - Gaps and Spiral Waves Many of Saturn's ring structures appear to be the results of resonance with outer satellites. Several of the gaps or gap edges are located at positions of resonance.

The outer edge of the A-ring seems to be shaped like a six lobed petal and is at a 7:6 resonance with Janus . At this resonance, ring materials circle Saturn 7 times while Janus orbits 6 times. The boundry between the outer edge of the B-ring and the Cassini divison is at a 2:1 resonance with Mimas . The Encke gap is at a 5:3 resonance with Mimas. In addition to the gaps, resonance manifests itself in other ways. One prominent structure within the A-Ring is a 5:3 resonance with Saturn's moon Mimas. This Voyager 2, close encounter image of Saturn's A-Ring, shows two wave patterns formed from the Mimas resonance perturbations. On the left is an outward propagating spiral density wave formed by particles that are bunched together in a spiral pattern. On the right is an inward propagating spiral bending wave that is made up of vertical oscillations of the ring material. The distance between these two waves is about 400 kilometers. Formation of Ring Spokes.

[ more ] Ring Spokes One of the curious discoveries made by the Voyager spacecraft was the presence of dark radial features up to 20,000 kilometers long that move in curious patterns on the B ring. These features commonly known as spokes had scientists perplexed because they seemed to defy gravity. Spokes are thought to be microscopic dust particles that have levitated away from the ring plane. They appear on both sides, near the densest part of the B ring. They rotate at the same rate as Saturn's magnetic field indicating they are affected by electromagnetic forces. They form about 104,000 kilometers from Saturn's center and extend out to the Cassini division. They are shapped somewhat like an hour glass with the narrow centers located near the synchronous orbit radius. Perhaps they are formed by meteorites that punch through the rings, by tiny moonlets as they plunge through the rings, or dust particles that have taken on a charge and levitated off the larger ring bodies. Ring Formation and Composition Saturn's rings span a great distance with the inner D ring approximately 6,700 kilometers from Saturn's cloud tops to the fringes of the E ring, 480,000 kilometers out.

Surprisingly, most of the rings are only a few tens of meters thick with a total mass equivalent to a medium sized moon. The rings are made out of particles ranging from microscopic dust to barnyard sized boulders with perhaps a few kilometer-sized objects as well. Near-infrared observations from Earth have shown that the rings are composed mostly of ice crystals with some impurities. Scientists once thought that the rings were formed at the same time, as the planets when they coalescing out of swirling clouds of interstellar gas 4.8 billion years ago. Under this model, remnants of material within the Roche limit could not condense and would become rings. However, in recent years this idea seems to be flawed. The rings appear to be young, perhaps only hundreds of millions of years old. One of the clues to this theory is that the rings are bright. As Saturn travels though space, the rings accumulate dust particles that have been darkened from solar radiation. If the rings were old, they should appear dark. Another theory suggests that perhaps a comet few too close to Saturn and tidal forces broke it into pieces similar to comet Shoemaker-Levy/9 .

Perhaps one of Saturn's moons was struck by an asteroid smashing it into the bits and pieces that form the rings. Hopefully the Cassini spacecraft can answer some of these questions. Ring Photo Gallery In Saturn's Shadow With giant Saturn hanging in the blackness and sheltering Cassini from the sun's blinding glare, the spacecraft viewed the rings as never before, revealing previously unknown faint rings and even glimpsing its home world. This marvelous panoramic view was created by combining a total of 165 images taken by the Cassini wide-angle camera over nearly three hours on Sept. 15, 2006. The full mosaic consists of three rows of nine wide-angle camera footprints; only a portion of the full mosaic is shown here. Color in the view was created by digitally compositing ultraviolet, infrared and clear filter images and was then adjusted to resemble natural color. The mosaic images were acquired as the spacecraft drifted in the darkness of Saturn's shadow for about 12 hours, allowing a multitude of unique observations of the microscopic particles that compose Saturn's faint rings. Ring structures containing these tiny particles brighten substantially at high phase angles: i.e., viewing angles where the sun is almost directly behind the objects being imaged.

During this period of observation Cassini detected two new faint rings: one coincident with the shared orbit of the moons Janus and Epimetheus, and another coincident with Pallene's orbit. The narrowly confined G ring is easily seen here, outside the bright main rings. Encircling the entire system is the much more extended E ring. The icy plumes of Enceladus, whose eruptions supply the E ring particles, betray the moon's position in the E ring's left-side edge. Interior to the G ring and above the brighter main rings is the pale dot of Earth. Cassini views its point of origin from over a billion kilometers (and close to a billion miles) away in the icy depths of the outer solar system. Small grains are pushed about by sunlight and electromagnetic forces. Hence, their distribution tells much about the local space environment. (Courtesy NASA/JPL/Space Science Institute) Panoramic Rings Saturn's most prominent feature, its dazzling ring system, takes center stage in this stunning natural color mosaic which reveals the color and diversity present in this wonder of the solar system. Gaps, gravitational resonances and wave patterns are all present, and the delicate color variations across the system are clearly visible.

This mosaic of six images covers a distance of approximately 62,000 kilometers along the ring plane, from a radius of 74,565 kilometers to 136,780 kilometers (46,333 to 84,991 miles) from the planet's center. This view is from Cassini's vantage point beneath the ring plane. The rings are tilted away from Cassini at an angle of about 4 degrees. (Courtesy NASA/JPL/Space Science Institute) Cat's Eye Rings and Peek-a-boo Shadows Astronomers have long known that Saturn's rings reflect sunlight most strongly when Earth is located directly between Saturn and the sun. Flat, shiny surfaces (like a mirror or a pond) can appear particularly bright when light reflects off them in a certain direction. Scientists call this "specular reflection," from the Latin word for mirror. However, even rough surfaces, like those of Earth's moon or Saturn's rings, can appear bright when the source of light is directly behind the observer's head, no matter what the orientation of the surface is.

This latter phenomenon is known as the "opposition effect." Spectacular examples include the eyes of a cat, which seem to glow brightly when they are illuminated by a flashlight, or highway signs and reflectors that "light up" when they are caught in a car's headlights. On Aug. 16, 2006, as the Cassini orbiter flew directly between the sun and Saturn, its Visual and Infrared Mapping Spectrometer captured a sequence of images that vividly show this opposition brightening. Combined here into a mosaic, the images show -- from left to right -- a small, bright spot moving from the outermost B ring across the Cassini Division and all the way across the A ring. In each image, this spot is centered on the point in the rings directly opposite the sun. Theoretical models for the opposition effect suggest that it can be explained by light being scattered several times within the surfaces of individual, transparent, icy ring particles on scales of about 40 micrometers, or 1/500th of an inch. Similar effects are seen in laboratory studies of bright, finely-textured material such as snow or sugar crystals.

In this mosaic, blue colors highlight the icy rings (2.35 microns), green represents sunlight reflected by the clouds of Saturn (2.86 microns) and red depicts thermal emission from the planet's interior (5.02 microns). The rings were observed while they were in front of the planet, producing a complex interplay of sunlight reflected from the rings and the shadows cast by the rings on the cloud tops of Saturn. The yellow-green sunlit clouds of Saturn are seen in the upper right corner of the mosaic beyond the outer edge of the A ring, and also through the 4,000-kilometer-wide (2,400 mile) Cassini Division in the left third of the mosaic. (Yellow indicates a mixture of reflected sunlight and thermal emission.) The shadowed regions of the planet, on the other hand, appear deep red because only thermal emission produced deep inside Saturn itself is visible. At exact opposition, the shadows of the rings are hidden behind the rings themselves, but away from this point shadows can be seen peeking out from behind the edges of the A and B rings into the Cassini Division, as well as beyond the outer edge of the A ring.

If one looks closely, one can even trace the A ring's shadow behind the partly transparent A ring, as a faint purple band. Within this band, a thin blue-green line crossing obliquely behind the A ring is caused by sunlight passing through the narrow Encke Gap in the outer A ring. (Courtesy NASA/JPL/University of Arizona) Ringscape In Color Nine days before it entered orbit, Cassini spacecraft captured this exquisite natural color view of Saturn's rings. The images that make up this composition were obtained from Cassini's vantage point beneath the ring plane with the narrow angle camera on June 21, 2004, at a distance of 6.4 million kilometers (4 million miles) from Saturn. The image scale is 38 kilometers (23 miles) per pixel. The brightest part of the rings, curving from the upper right to the lower left in the image, is the B ring. Many bands throughout the B ring have a pronounced sandy color. Other color variations across the rings can be seen. Color variations in Saturn's rings have previously been seen in Voyager and Hubble Space Telescope images.

Cassini's images show that color variations in the rings are more pronounced in this viewing geometry than they are when seen from Earth. Saturn's rings are made primarily of water ice. Since pure water ice is white, it is believed that different colors in the rings reflect different amounts of contamination by other materials such as rock or carbon compounds. In conjunction with information from other Cassini instruments, Cassini images will help scientists determine the composition of different parts of Saturn's ring system. (Courtesy NASA/JPL/Space Science Institute) Saturn's Faint Inner D-Ring The D-ring of Saturn is very tenuous and has an extremely small optical depth. This picture was taken 1 hour and 48 minutes before Voyager 2's closest approach to Saturn on August 25, ???? from a distance of 195,400 kilometers. At this resolution, many ringlets and gaps are present in the image. Ringlets of Saturn's B-Ring This pseudo-colored image of the outer edge of Saturn's B-ring shows the ring structure broked up into numerous ringlets. The narrowest features are about 15 kilometers wide with the overall image about 6,000 kilometers wide.

Variations in brightness are due to a combination of differences in ring particle number density and light scattering properties. The B-ring is the most opaque of Saturn's rings. The Cassini division is located at the upper left. Close Encounter with Saturn's A-Ring This high-resolution image shows the outer edge of Saturn's A ring. The many sharp linear features parallel to the ring edge are most probably locations where ring particles are in resonance with one of the several small nearby satellites. Such regions with nearby satellites are likely characterized by more intense particle collisions and a greater density of small "chips." The entire outer band of the A-ring has different scattering properties and therefore different particle characteristics than the main body of the rings to the upper left. The resolution of this image is about 4 kilometers (2.5 miles). Saturn's F-Ring Voyager 2 obtained this picture of Saturn's F-ring on August 26, 1981 just before the spacecraft crossed the planet's ring plane. This edge-on view, taken from a range of 103,000 kilometers (64,000 miles), shows nearly 25` of the F-ring, with at least four distinct components visible.

Saturn's G-Ring Saturn's G ring was discovered by Voyager 1 in November 1980 and imaged again by Voyger 2 on August 26, 1981 from a range of about 175,000 kilometers. The 8000 kilometer wide G-ring is extreamly tenuous and difficult to see. It is more neutral in color than the E-ring. In this image the A-ring on the right hand side has been washed out due to the long exposure required to bring out the G-ring. Significant image processing was used to isolate the G-ring from the background noise. This included carefully flattening the image intensity across the image plane with low and high pass filtering applied to the G-ring region. The Planets - How Telescopes Work | HowStuffWorks How Telescopes Work Solar system mosaic Photo courtesy NASA You will find views of the planets through a telescope quite satisfying, and they will keep you coming back for more. You can also observe planets from urban areas, where there may be moderate to substantial light pollution.

With a small telescope (2-inch or 60-mm refractor, 4-inch or 100-mm reflector), you can see some details on the surfaces of planets, but a larger telescope (3- to 4-inch or 75- to 100-mm refractor, 6- to 10-inch or 15- to 25-cm reflector) will reveal better detail. Generally, refractors provide crisper images of planets, but lack the light gathering ability of reflectors. Regardless of which type of telescope you use, observing planets requires good seeing conditions -- steady, dry atmosphere with little or no clouds -- and you should cool your telescope to the outside temperature for about 30 minutes before observing. Cooling the telescope reduces air currents inside the tube that could produce fuzzy, blurring images. Venus You won't see any surface detail on Venus because it is covered with clouds. You can find something interesting to look at, though, because Venus has phases just like the moon, and you can easily see these phases with any telescope. Also, Venus is one of the brightest objects in the sky, and you can find it easily.

Usually, Venus can be seen above the horizon before or after sunset; you can see it referred to in newspapers as "the morning star" or "the evening star." Up Next How much does light weigh? Mars Mars is a difficult but challenging target, because of its distance and small size. In my 4-inch (100-mm) rich-field, reflecting telescope, I can see a small red disc with no surface detail. In an 8- to 10-inch (20- to 25-cm) reflector, you could probably see the polar ice caps and some dark surface features ("canals") depending upon the seeing conditions. However, the face of Mars is constantly changing. Using filters may help to enhance the viewing somewhat. This is about the size of the image of Jupiter in my telescope. Photo courtesy of NASA Jupiter Jupiter is one of the prettiest sights in a small telescope. It is the largest planet in our solar system, and you can find it easily. In my 4-inch reflector, I can see Jupiter as a small, bright yellow disc, usually with two brown cloud bands on either side of its equator.

In a larger telescope (8- to 10-inch / 20- to 25-cm reflector), you could see more cloud bands and the Great Red Spot. You can also see the moons of Jupiter (Galilean satellites) -- Io, Europa, Callisto and Ganymede. The moons orbit Jupiter in changing positions each night, and they are interesting to watch over the course of many days. In a large telescope (8- to 10-inch or 20- to 25-cm reflector), you can even watch the shadow of a moon cross the disc of Jupiter! This is about the size of the image of Saturn in my telescope. Photo courtesy of NASA Saturn Saturn is a favorite object for a telescope because of its rings. The rings of Saturn change their angle as seen from Earth as Saturn orbits the sun. So sometimes the rings are highly visible, while other times you cannot see them at all (viewed edge-on). Saturn is a bright object that you can easily find. In my telescope, Saturn appears as a small, bright yellow ball with the rings around it. I cannot see any surface detail, or the gap between the rings called the Cassini division.

These features would probably be visible in a larger telescope. Like Jupiter, Saturn has several moons -- Titan, Iapetus, Phoebe -- that change position. I have a difficult time seeing Saturn's moons in my telescope, although I may be able to see one of them on a good night. However, a larger telescope would probably reveal them much better. Uranus, Neptune and Pluto Because of their great distance from Earth, these planets are difficult to locate, a challenge for any observer. I have never had any luck locating them with my telescope, and I probably would not have seen much more than a tiny disc if I did. In a larger telescope, it is likely that these planets would still only appear as small discs. Asteroid 951 Gaspra Photo courtesy NASA Asteroids Like the outer planets, asteroids are difficult to see in small telescopes. Because they are so small, they appear in a telescope as points of light, like stars . Typically, to locate an asteroid, you find its position from a chart and then look at the field of stars. The asteroid will be a bright object that looks out of place when compared to the chart.

If you look at the same field on successive nights, the asteroid will be the object that moves in the field. Finding these objects takes patience! Some advanced observers will measure the light intensities of asteroids over time, using photometers or CCD/digital cameras attached to the telescopes. You can use the changes in the light intensities to calculate the rate of the asteroid's rotation.

Question: With which planet do you associate Cassini's Division?
Answer: Saturn