A Journey To Titan- The Largest Moon Of Saturn

 Before entering into the world of Titan, let’s have a gander through the sixth and second largest planet in the solar system; Saturn which is known for its magnificent ring system. The rings were first observed by the Italian astronomer Galileo Galilei in 1610 but he could only make out blobs on either side of the Saturn through his telescope which he thought were the moons of the planet. In 1656 Dutch astronomer Christiaan Huygens correctly spotted the blobs as the rings around Saturn.

 

 The rings are made up of a series of concentric rings, some of which are brighter than the others and several individual rings named A, B, C, D, E, F and G (named in the order of their discovery) of which the classical rings are A, B and C which have being known since 17^th century.

Fig 1. Rings of Saturn with captions

A and B rings are the brightest that can be seen through a telescope. These rings are separated by the Cassini division, this large gap in the rings is caused by the gravitational pull of Saturn’s moon Mimas. The outer edge of the A ring is due to the gravitational pull of the other two moons: Janus and Epimetheus. As a result of these gravitational pull any particles just outside the A ring will be pulled out of that area. Two narrow gaps are seen within the outer parts of the A ring which are much narrower than the Cassini division: 1) The Encke gap which is due to the gravitational pull of a small moon called Pan that orbits Saturn within the gap.2) The Keeler gap is due to the gravitational pull of a small moon called Daphnis that also orbits Saturn within the gap. B ring is the brightest of all the rings and it is inside the A ring. The C ring is located inside the B ring and it is fainter and harder to see than A and B ring. The dark D ring is the closest one to the Saturn. The E ring is the farthest from Saturn and it is much wider than the other rings. This ring is centered on Saturn’s moon Enceladus. The F ring was discovered by the Pioneer 11 spacecraft in September 1979. F ring is the narrowest and it is located outside the A ring. Inside the F ring is a moon called Prometheus and just outside F ring is another moon called Pandora. G ring is a narrow ring located between F and E rings.

Though Saturn is eminent and most famous for the planetary rings, but the other three giant planets: Jupiter, Uranus and Neptune also have ring systems. The difference is that the rings around Jupiter, Uranus and Neptune are much smaller, darker and fainter than the rings of Saturn. Planets have the colors that they have because of what they are made of and how their surfaces reflect and absorb sunlight. The outer atmosphere of Saturn is mostly composed of hydrogen and helium with traces of ammonia, phosphine, water vapor and hydrocarbon giving it a yellowish-brown color. Saturn has 82 moons with known orbits; 53 of them have names.

Titan, the largest icy moon of Saturn is the only known moon which have a close-knit atmosphere in solar system. Being the second largest natural satellite in the solar system, Titan is only the known body after our mother Earth, which shows eloquent proof of multiple liquid rivers and lakes with the atmosphere made of nitrogen and methane. One interesting fact is that Titan’s mass is composed mainly of water in the form of icy and rocky material which is half the mass of the planet mercury. Titan was a mystery hidden inside the hazy and smoggy atmosphere.

 

   

 

Fig 2: Titan

Instead of water Titan has methane which gets evaporated into clouds causing it to rain liquid methane. It is unique from the other moons in the solar system by the presence of the notable atmosphere which is thicker than any of the terrestrial planets except Venus. In terms of scientific information Titan is a gold mine for scientists. But it is extremely difficult to study the surface because it is entirely covered with clouds of methane. In 1997 Cassini space probe made a seven-year journey to study the entire Saturn system including its rings and the natural satellites, but Cassini didn’t make this journey of its own. Cassini carried a small atmospheric entry probe that landed on Saturn’s moon Titan in 2005 near Adiri region. Huygens which was a part of the Cassini-Huygens mission became the first spacecraft to land on Titan. The probe was named after the Dutch astronomer Christiaan Huygens, the discoverer of Titan in 1655. After entering Titan, Huygens started sending the signals regarding properties of the atmosphere and the nature of the moon’s surface. It was only designed to survive for about 90 minutes on the surface. The probe successfully recorded back 350 images to inquire into a world similar to the planet Earth.

                                             Fig 3: 360 view of Huygens descent to Titan

In order to learn more about the origins of life, American space agency NASA is planning to explore Titan’s atmosphere through a rotorcraft lander mission Dragonfly in 2026 for digging out the possibility of the existence of extraterrestrial habitability at various locations by performing vertical takeoffs and landings. It has eight rotors and fly like a drone. The landing site of Dragonfly is in the equatorial part of the icy moon which is known as Shangri-La that traits sand dunes similar to Namibia, a country in Southern Africa were the dunes rise up to 300 meters which is nearly 600 meters on Titan. The only difference is that in Titan instead of sand the dunes are made up of dark hydrocarbon grain or bits of frozen methane and ethane; that shows some spectacular similarities to our mother planet.  The thick atmosphere, glacial temperature and low gravity of the icy moon pave the way for scientific exploration by helping the rotorcraft landing mission to stay easily over the surface and expected to fly more than 100 miles with lesser energy. The unique feature that distinguishes Titan from any other moons in the solar system is its resemblance to the planet Earth due to 95 percent nitrogen (78 percent in Earth), 5 percent methane (0.00017 percent in Earth) along with other carbon rich components and a surface pressure of 50% higher than our planet.

Fig 4: Dragonfly Spacecraft

As the surface of Titan is rich of diverse organic material it is the perfect environment to study the pre-life chemical interactions that similarly took place on Earth. Titan is one of the most habitable worlds in the solar system. Scientists have calculated that rain on Titan falls at about 3.5 miles per hour. The diameter of Titan raindrops is about 0.37 inches which is 50 percent larger than in Earth.

Will Titan be another Earth…….? Let’s wait for NASA’s new mission: ‘Dragonfly’ to explore the exciting future opportunity and the ambiguity hidden inside this extraordinary and exceptional world of Titan.