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Of all the planets and satellites outside Earth that are expected to have future human habitation, there is no doubt that Titan is at the very top of the list. Today we will try to know in a little detail about our possible future residence.
Titan
is the second largest satellite of our solar system and it is largest satellite
of saturnine satellite system. Its size is 1.06 times the size of Mercury, 1.5
times the size of the Moon and 40 percent of our Earth. Ganymede, the largest
satellite in the solar system, is only 113 kilometre more in diameter. That is
why Titan is called ‘Planet like Satellite’.
The
satellite was discovered on March 25, 1655 by the Dutch astronomer Christiaan
Huygens. In 1847, the famous astronomer Sir John
Herschel, who was the worthy son of another famous astronomer, Sir
William Herschel, named the newly discovered satellite Titan after the
name of any of the children of Greek God Uranus (Heaven) and Gaea (Earth). Of
all the satellites discovered to date, Titan is probably the only one to have
the solid surface and dense atmosphere, just like earth, together. There are a
lot of similarities between Titan's climate and the early climate of the earth
because the chemical and geological changes, that Titan is going through now,
had passed through the earth crore of years ago.
With
a diameter of 5,149 kilometre, the satellite is located sixth from Saturn in
terms of distance. The average distance from Saturn to Titan is 12,21,870
kilometre. Like Triton, Titan is bound to its planet in synchronous rotation,
meaning that Titan's diurnal motion is approximately equal to its annual
motion. One day on Titan equals 15 days and 22 hours as Earth's time. At about
the same time, Titan orbits Saturn once. Its average orbital speed is 5.57
kilometre per second. Depending on Titan's mass, its escape velocity (Escape Velocity: The minimum velocity that a
moving body must have to escape from the gravitational field of a celestial
body)
is 2.64 kilometre per second or 9,504 kilometre per hour. But the most
surprising thing is that its air pressure is much higher than that of the
earth. Its value is 1.45 air pressure. Titan feels 1.19 times more air pressure
than the Earth, which means that the amount of air pressure felt on Titan is
equal to the pressure felt during swimming at a depth of 50 metre in sea.
Like Earth, Titan's core is rocky and has a range of about 3,400 kilometre. It has a layer of ice on it. Titan was formed with the solar system, but its surface is only 10 crore to 100 crore years old. So it can be said that Titan's surface age is now going through a new and complex process. Both flat and uneven surfaces have been observed here. Evidence of volcanic eruptions has also been found here. The ice layer found on the surface of Titan is very solid in nature. The sign of air flow exists here. The number of craters, created as a result of cosmic collisions, on this surface is quite small and it is estimated that these craters have been filled with different types of hydro-carbon precipitation to form different types of liquid reservoirs.
Few numbers of craters have been found on the surface of Titan as a result of several cosmic collisions. One of which is the 440 kilometre wide Menrva Crater. Apart from this, 60 km wide Sinlap Crater and the 30 kilometre wide Ksa Crater with its distinct peak have been also discovered. Evidence of soil erosion has been found in these ditches. Like Triton, Titan has super-cold volcanoes or Cryo-Volcanoes that emit super-cold ammonia-methane compounds instead of hot lava. In December 2010, the Cassini Spacecraft has discovered a chain of three mountains, ranging in height from 1,000 metre to 1,500 metre. The name of this mountain range is Sotra-Patera, around which traces of frozen lava flow have been observed. Scientists speculate that Sotra-Patera is a Cryo-Volcano.
In 2006, the Cassini spacecraft has discovered a mountain range 150 km long, 30 km wide and 1.5 kilometre high at the South Pole of Titan, with a methane ice cap at the top. Most of Titan's mountain peaks are located in the 'Ridge Belts' of the equatorial region. These mountains are fold mountain ranges like the earth. One of the possible reasons for their formation is Saturn's intense gravitational pull. The highest peak in Titan is 3,337 metre. This mountain range is located in the 'Mithirim Montes' mountain range. Many of Titan's mountains have been named by the International Astronomical Union (IAU).
Titan's sand is not made up of tiny particles of silicate like Earth. Instead, methane precipitation results in the erosion of water ice. Again, many believe that sand has been produced from Tholins, a biochemical produced by photo-chemical reactions in Titan's atmosphere.
A few large black and white spots have been found on the surface of Titan. The most notable white spot is Xandu. It is a white spot with the size of Australia. Xandu is a plateau which is covered by water ice. Among them, dunes, hills, rivers and valleys have been found to exist. Scientists are currently studying the critical boundary between Shangri-La, the dark region, around Xandu. In 1994, the Hubble Space Telescope discovered the Xandu. It is thought that the Tholins, which is being produced in Titan's atmosphere due to the sun's ultraviolet rays, gradually accumulate on the surface of Titan with the rain of methane, and the surface of the planet becomes dark black. However, whether there is any other reason is still a matter of research.
Like
Earth, Titan also has liquids. Flowing
rivers and lakes have been found there. This information first came to us
through the Voyager Mission and was further established by the Hubble Space
Telescope and the Cassini-Higgins Mission. Hydro-Carbons such as
Methane, Ethane, etc. have been found in Titan in reservoirs, rivers and
oceans. The largest river in Titan is the Vid Fumina, a little over 402
kilometre long. The river flows through a canyon about 560 metre deep. It can
be said that this river is the Nile river of Titan. This river falls into the
second largest lake of Titan or the sea like Ligeia Mare. This lake is
three times larger than Lake Michigan in the United States. The lake is 20 to
40 metre deep and is located in the North Pole of Titan. However, it is
estimated that the actual depth of the lake may be up to 200 metre somewhere.
The
largest lake in Titan is Lake Kraken Mare. It is located in the northern
hemisphere of Titan and covers an area of 40,000 square miles. With the depth
of 160 metre, it is greater than the Caspian Sea of the earth. This lake also
has several islands like Lake Ligeia Mare. But the islands on Lake Ligeia Mare
are a little bit of strange kind. They sometimes disappear and reappear. That
is why these islands are called Magic Island. As mentioned earlier, in the
satellite Titan, rivers, seas are made up of hydro-carbon and nitrogen
dissolved in them. Scientists speculate that the Magic Islands are probably not
an island made up of solid rock. Rather, they may be transient bubbles of
hydrogen. However, scientists cannot be sure until they have the knowledge or
evidence of intensive research on this subject.
Titan's atmosphere extends for about a thousand kilometre. This atmosphere is so dense that it is very difficult to observe the surface clearly. Titan's atmosphere contains 96 percent nitrogen and the remaining 3 percent hydrogen, methane, and other substances. The sky from Titan will look like orange color filled with dust, just as the sky from our earth looks like azure blue. Because of this dust, very little amount of light reaches the surface of Titan. The vast distance between Titan and sun along with its dense atmosphere, the amount of sunlight received here is only 1 percent of the amount of sunlight, received on Earth. About 90 percent of this amount of light is absorbed by Titan's atmosphere. As a result, only 0.1 percent of the amount of sunlight reaching the Earth's surface reaches Titan's surface. Titan's average temperature is -179.2 degree Celsius due to the presence of hydrocarbons like methane. Only the presence of the hydrocarbons, greenhouse effect is occurred in Titan. Titan has been able to retain some amount of temperature despite being so far away from the sun. Otherwise, Titan would have become a much cooler satellite. Another reason for the cooling of Titan's atmosphere is the presence of anti greenhouse effect, present in the upper atmosphere. This substance reflects sunlight and sends it back into space.
As mentioned earlier, Titan's gravitational pull is very low. So Titan doesn't get rain the way it does on our planet. Rather, it can be said that methane rains on Titan at the same speed as the snow on Earth. Maybe a rainbow can be seen in the sky of Titan. Evidence has also been found that the time interval between two rains at any place on Titan is hundreds of years. The reason for this is that the distance of Titan from the sun and the elements of the atmosphere have made Titan a very cool satellite. As a result, it takes a long time for liquid methane to evaporate and condense.
Due to the distance from the Earth, it is virtually impossible to see Titan with the naked eye and it is not impossible to observe with the help of a telescope, but it is a very difficult task because Saturn's bright ring obstructs here. So it has been possible to observe Titan in the modern age through the advanced technology of science.
Four times so far people of Earth have been able to see the mysterious world of Titan through the spacecraft. The first such incident occurred on September 2, 1979, when Pioneer-11 flew 3,63,000 kilometre from Titan. Then, on November 12, 1980, Voyager-I flew 6,500 kilometre from Titan. The third expedition to Titan took place on August 25, 1981, when Voyager-II made a flyby at a distance of 6,66,000 kilometre from Titan. Although the campaign was closed for many days after that, the scope and receipt of the latest fourth campaign is still the highest. I will mention that campaign in due course.
Pioneer-11 is the first spacecraft to have the honour of reaching Titan, but in fact the first accurate information about Titan has been presented to us by the two Voyager spacecrafts. Voyager was the first to determine the true diameter of Titan and reported that Titan was the second largest satellite in the solar system after Jupiter's Ganymede. Titan is about 50 percent larger than our Earth's satellite Moon. Titan is called the 'Planet Like Satellite' because of its size. Voyager also accurately determined the density, temperature, and composition of Titan's atmosphere.
I will now mention the mission whose success has helped us better understand Titan. The Cassini-Huygens spacecraft is a joint venture between NASA and the European Space Agency (ESA). Here Cassini is an orbiter that collects information from specific planets or satellites from space without landing anywhere and sends it directly to Earth. This part was made by NASA. Huygens is a lander designed for landing on Titan and planned to communicate with Earth via Cassini. Huygens was created by the European Space Agency.
Finally, on October 15, 1997, the Cassini-Huygens spacecraft was launched into space. On July 1, 2004, 81 months after launch, the Cassini-Huygens spacecraft reached Saturn. About two and a half months later, on October 26, 2004, the spacecraft made its first flyby over 1,200 kilometre above the surface of Titan. Two more months later, on December 24, 2004, Huygens Lander detached from the Cassini Orbiter, gradually reducing its distance from Titan as it rotated. Huygens then slowed down further, advancing towards Titan at a speed of 6 kilometre per second. On January 14, 2005, two and a half hours after entering Titan's atmosphere, Huygens Lander successfully touched the surface. Adiri, one of the brightest places on Titan, is the place where Huygens landed and began its work. Titan is still the farthest place, from the earth, where any man-made object has landed. The data collected by Huygens took 72 minutes or more to reach Earth via Cassini. However, if there is Earth and Saturn at the two ends of the Sun, it is not possible to maintain this communication. On June 21, 2010, Titan's distance with Cassini was only 880 kilometre. Cassini then moved to its original and final destination, Saturn. The Voyager and Cassini- Huygens spacecraft must be credited for the information we learn about Titan today.
But there are still some things that make us think deeply. Is it possible to expect life in compatibility with Titan's environment even if it is not like Earth? Are there aliens on the surface of Titan? If there is, it is assumed that life may have originated from the same organic matter as that of the organic matter from which life originated on Earth. Scientists also speculate that if life had originated on Titan, the oceans or lakes of methane would have remained there. There may be a methanogenic life cycle. Those organisms may breathe in hydrogen instead of oxygen, use acetylene instead of glucose as a source of cellular energy, and release methane instead of carbon dioxide. They may drink ethane, methane or some other hydrocarbons instead of water like us, and their bodies may need such low temperatures for metabolism.
Maybe Titan has huge reservoirs of water under the frozen ice. However, one thing is for sure, at present this satellite is not suitable for human habitation. There are many reasons for this. First of all, Titan's climate is terribly cold because of lack of light and heat due to huge distance between sun and Titan. Secondly, there is no water in the environment here. Thirdly, there is no oxygen. Fourthly, there is very little carbon dioxide. For all these reasons, the cells and life cycles that exist on Earth are not currently possible to form on Titan.
But beyond human habitation, Titan has many more unresolved issues. So NASA is starting the Titan mission again. In 2026, 29 years after the Cassini-Huygens expedition, they have a plan to launch Dragonfly Mission to Titan. The 450 kilogram weight spacecraft will land on Titan in December 2034. The mission will use drones which look like helicopters called Rotor-craft. This vehicle will use Radioisotope Thermo-electric Generator or RTG as the source of energy. The vehicle will land at Shangri-La in the equatorial region of Titan. Its landing site is about 800 kilometre from Higgins' landing site. In this two-and-a-half-year expedition after landing, the rotor-craft will cover a distance of 175 kilometre and reach its final destination at the Selk Crater with a diameter of 90 kilometre. Many more secrets of Titan will definitely be revealed in this mission; new acquaintance with Titan will be made.
Regarding the future
of Titan, scientists say that, the current state of Titan will change in
future. About 500 crore years from now, when the Sun will turn into the Red
Giant Star, (To know more information about Star,
see 'The Brief Story of Stellar Life'. The link of the article is mentioned bellow:
https://spacejagat.blogspot.com/2020/06/the-brief-story-of-stellar-life.html) Titan's surface temperature will rise drastically. Ice will melt into water, liquid methane will turn into gas, and the scattering of ultraviolet rays from the sun will decrease. Then Titan will create a habitable environment like ours on Earth and will last for crore of years. One of the surprising information has come before us. Every year, Titan is moving 11 centimetre away from its planet Saturn.
In the future, Titan may become a full-fledged planet instead of a satellite; Triton will become a ring of Neptune. Mercury, Venus, Earth and Mars will not exist; the sun will swallow every inner planet one by one. Various changes will be seen in different parts of the solar system. If the human race will ensure its settlement in a safe place outside the earth during that time, then perhaps the people present at that time will be able to witness this natural phenomenon.
