SATURN
The atmosphere is primarily composed of hydrogen with small amounts of helium and methane. Saturn is the only planet less dense than water (about 30%). Saturn’s hazy yellow hue is marked by broad atmospheric banding similar to, but fainter than that found on Jupiter.
The wind blows at a high speed on Saturn, near the equator; it reaches velocities of 500 m a second (1100 miles an hour). The wind blows mostly in an Easterly direction. The strongest winds are found near the equator and velocity falls off uniformly at higher latitudes. At latitudes greater than 35 degrees, winds alternate East and West as latitude increases.
Saturn’s ring system makes the planet one of the most beautiful objects in the solar system. The rings are split into a number of different parts which include the bright A and B rings and a fainter C ring. Space probes have shown that the main rings are really made up of a large number of narrow ringlets. The origin of the rings is obscure. It is thought that the rings may have been formed from larger moons that were shattered by impacts of comets and meteoroids. Radial, spoke-like features in the broad B-ring were also found by the Voyagers. The features are believed to be composed of fine, dust-size particles. The spokes were observed to form and dissipate in the time-lapse images taken by the Voyagers.’
In one of nature’s most dramatic examples of “now you see them, now you don’t,” NASA’s Hubble Space Telescope captured Saturn on 22nd May, 1995, as the planet’s magnificent ring system turned edge-on. This ring-plane crossing occurs approximately every 15 years when the Earth passes through Saturn’s ring plane.
The rings do not disappear completely because the edge of the rings reflects sunlight. The dark band across the middle of Saturn is the shadow of the rings cast on the planet (the Sun is almost 3 degrees above the ring plane.) The bright stripe directly above the ring shadow is caused by sunlight reflected off the rings onto Saturn’s atmosphere.
An image, taken by the Hubble Space Telescope, shows a rare storm that appears as a white arrowhead shaped feature near the planet’s equator. The storm is generated by an upwelling of warmer air, similar to a terrestrial thunderhead. The Hubble images are sharp enough to reveal that Saturn prevailing winds shape a dark ‘wedge’ that eats into the Western (left) side of the bright central cloud. The planet’s strongest Eastward winds, clocked at 1600 km (1000 miles) per hour based on Voyager spacecraft images taken in 1980-81, are at the latitude of the wedge. The storm’s white clouds are ammonia ice crystals that form when an upward flow of warmer gases shoves its way through Saturn’s frigid cloud tops.
The top image shows the first image ever taken of bright auroras a Saturn’s Northern and Southern poles as seen in far ultraviolet light by the Hubble Space Telescope. Hubble resolves a luminous, circular band centered on the North Pole, where an enormous auroral curtain rises as far as 2000 km (1200 miles) above the cloud tops.
For comparison, the bottom image is a visible-light colour composite of Saturn as seen by Hubble on 1st December, 1994 evidences that unlike the ultraviolet image, Saturn’s familiar atmospheric belts and zones are clearly seen. The lower cloud deck is not visible at UV wavelengths because sunlight is reflected from higher in the atmosphere.
Saturn has at least 62 Moons, 53 of which have formal names. Titan, the largest comprises more than 90% of the mass in orbit around Saturn, including the rings. Saturn’s second largest Moon, Rhea, may have a tenuous ring system of its own, along with a tenuous atmosphere. Many of the other Moons are very small as 34 are less than 10 km in diameter and another 14 less than 50 km. Traditionally, most of Saturn’s Moons have been named after Titans of Greek mythology. Titan is the only satellite in the Solar System with a major atmosphere in which a complex organic chemistry occurs. It is the only satellite with hydrocarbon lakes.
Saturn’s Moon Enceladus has often been regarded as a potential base for microbial life. Evidence of this life includes the satellite’s salt-rich particles having a ‘ocean-like’ composition that indicates most of Enceladus’s expelled ice comes from the evaporation of liquid salt water.
On 1st July, 2004, the Cassini Huygens space probe performed the SOI (Saturn Orbit Insertion) maneuver and entered into orbit around Saturn. Before the SOI, Cassini had already studied the system extensively, to June 2004; it had conducted a close flyby of Phoebe, sending back high-resolution images and data.
Cassini’s flyby of Saturn’s largest Moon, Titan, has captured radar images of large lakes and their coastline’s with numerous islands and mountains. The orbiter completed two Titan flybys before releasing the Huygens probe on 25th December, 2004. Huygens descended onto the surface of Titan on 14th January, 2005, sending a flood of data during the atmospheric descent and after the landing. Cassini has since conducted multiple flybys of Titan and other icy satellites.
Since early 2005, scientists have been tracking lightning on Saturn. The power of the lightning is approximately 1000 times that of lightning on Earth.
In 2006, NASA reported that Cassini had found evidence of liquid water reservoirs that erupt in geysers on Saturn’s moon Enceladus. Images shown jets of icy particles being emitted into orbit around Saturn from vents in the Moon’s South polar region. According to Andrew Ingersoll, California Institute of Technology, “Other Moons in the Solar System have liquid water oceans covered by kilometers of icy crust. What’s different here is that pockets of liquid water may be no more than tens of meters below the surface.” In May, 2011, NASA scientists at an Enceladus Focus Group Conference reported that Enceladus “is emerging as the most habitable spot beyond Earth in the solar System for life as we know it”.
Cassini photographs have led to other significant discoveries. They have revealed a previously undiscovered planetary ring, outside the brighter main rings of Saturn and inside the G and E rings. The source of this ring is believed to be the crashing of a meteoroid off two of the Moons of Saturn. In July 2006, Cassini images provided evidence of hydrocarbon lakes near Titan’s North Pole, the presence of which were confirmed in January 2007. In March 2007, additional images near Titan’s North pole revealed hydrocarbon ‘seas’, the largest of which is almost the size of the Caspian Sea. In October 2006, the probe detected an 8000 km diameter cyclone like storm with an eye wall at Saturn’s South pole.
From 2004 to 2nd November, 2009, the probe discovered and confirmed 8 new satellites. Its primary mission ended in 2008 when the spacecraft had completed 74 orbits around the planet. The probe’s mission was extended to September, 2010 and then extended again to 2017, to study a full period of Saturn’s seasons.
A lot of probe of the Saturn is yet to completed, nothing certain can so far be said about the Saturn, but a mystery is being revealed. What earlier sounded impossible is on the verge of solution last.
“It is difficult to say what is impossible for the dream of yesterday is the hope of today and reality of tomorrow.”—Robert Goddard.
