Tuesday, January 21. 2020WHY ARE SCIENTISTS INTERESTED IN TITAN?
One of Saturn’s satellites, Titan, is the only moon in the Solar System to have a substantial atmosphere. It is covered in thick clouds, and scientists believe conditions beneath these clouds may be similar to those on Earth billions of years ago. Although temperatures on the planet are believed to be well below freezing level, some scientists believe that internal heating may allow areas of liquid water to exist on the moon's surface. Some believe that primitive life may even exist on the moon. The European Space Agency's Huygens probe has been designed to parachute down through Titan's atmosphere in order to investigate the moon at first hand (right). An orange haze surrounding Titan kept its surface a mystery for Earth's scientists until the arrival of the Cassini mission in 2004. Titan’s atmosphere extends about 370 miles high (about 600 kilometers), which makes it a lot higher than Earth's atmosphere. Because the atmosphere is so high, Titan was thought to be the largest moon in the solar system for a long time. It wasn't until 1980 that Voyager was close enough to discover it was actually smaller than Ganymede. Titan’s atmosphere is active and complex, and it is mainly composed of nitrogen (95 percent) and methane (5 percent). Titan also has a presence of organic molecules that contain carbon and hydrogen, and that often include oxygen and other elements similar to what is found in Earth's atmosphere and that are essential for life. There is an unsolved mystery surrounding Titan's atmosphere: Because methane is broken down by sunlight, scientists believe there is another source that replenishes what is lost. One potential source of methane is volcanic activity, but this has yet to be confirmed. Titan's atmosphere may escape to space in a similar way that Earth’s atmosphere does. The Cassini spacecraft has detected polar winds that draw methane and nitrogen (charged with interactions with light) out along Saturn's magnetic field and out of the atmosphere. A similar process is believed to happen on Earth with our own magnetic field. "At Saturn's largest moon, Titan, Cassini and Huygens showed us one of the most Earth-like worlds we've ever encountered, with weather, climate and geology that provide new ways to understand our home planet. Picture Credit : Google Tuesday, January 21. 2020HOW DO RINGS FORM?
Nobody knows for sure how planets get their rings. In the 19th century, the French mathematician Edouard Roche suggested that if any large object, such as a moon or comet, got too close to a planet, it could be torn apart by the planet’s tidal force. The object would be pulled one way by its orbit and another by the planet’s gravity. Once it reached the “Roche limit”, it would break apart into tiny fragments. One theory that astronomers have come up with is that the rings are actually bits and pieces of an old moon, or moons that used to orbit Saturn. In this theory, the old moon was ripped apart somehow. Saturn’s moons mostly have icy outer coats and layers. If the ice layers were stripped away, and the rest of the moon crashed in Saturn, rings could be able to form. It could have been ripped apart by Saturn’s gravity and gravity from other moons. The pushing and pulling may have caused dust and pieces of the old moon to scatter and orbit around the planet, creating a ring. Another theory says that the rings may have been formed as debris, dust, comets, and asteroids passed near Saturn. As these materials passed, Saturn’s immense gravity may have pulled them towards it and trapped them in an orbit around the planet. Similar to the moon theory, the trapped comets and asteroids may have been broken apart by forces of gravity exerted by Saturn and other debris. The debris also, most likely, runs into each other and breaks into even smaller pieces. Over time, the fragments of rock and debris flattened and shaped into the rings we see now. Some astronomers think that the much of the material that composes the rings actually came from the time when Saturn first formed. As Saturn formed, not all the surrounding dust, material, or gas went into Saturn’s final form. Therefore, Saturn may not have used the material to create its body, but its gravity kept the leftover and unused dust and debris in its orbit, creating its rings. In recent studies, a group of mathematicians believe that the rings were formed by a chain of collisions created between particles moving. These mathematicians think that large particles ran into each other at slow rates, and these crashing particles caused smaller particles to run into each other at much higher speeds. The debris in Saturn’s rings could have been smaller remnants of larger events in Saturn’s past, which explains why the debris in Saturn’s rings varies in size. Picture Credit : Google Tuesday, January 21. 2020WHAT ARE SHEPHERD MOONS?
Two of Saturn’s moons - Pandora and Prometheus — are known as shepherd moons. They orbit either side of the narrow F rings, and have earned their name because their gravitational pull prevents the particles in this ring from straying out into space. Saturn, which is the second largest planet in our solar system, is known to have multiple rings and satellites. In 1979, Pioneer 11 discovered the F Ring, located 3,000 kilometres (1900 miles) beyond the outer edge of the A Ring. The F Ring is very active, with features changing on a timescale of hours. The F Ring is also very narrow with a width of only a few hundred kilometres, and has two shepherd satellites called Prometheus and Pandora, which orbit inside and outside the ring, respectively. Although the Voyager and Cassini spacecraft later made detailed observations of the F Ring and its shepherd satellites, their origin has not been clarified. According to the latest satellite formation theory, Saturn used to have ancient rings containing many more particles than they do today, and satellites formed from spreading and accretion of these particles. During the final stage of satellite formation, multiple small satellites tend to form near the outer edge of the ring. On the other hand, observations by Cassini indicate that the small satellites orbiting near the outer edge of the main ring system have a dense core. In their simulations using in part computer systems at the National Astronomical Observatory of Japan, Hyodo and Ohtsuki revealed that the F Ring and its shepherd satellites formed as these small satellites with a dense core collided and partially disintegrated. In other words, the system of the F Ring and its shepherd satellites is a natural outcome of the formation process of Saturn’s ring-satellite system. This new finding is expected to help elucidate the formation of satellite systems both within and outside our solar system. For example, the above formation mechanism can also be applied to the rings and shepherd satellites of Uranus, which are similar to those of Saturn. Picture Credit : Google |
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