Today we have reached Titania, the largest satellite of Uranus which is the penultimate planet of our solar system. This satellite is not only the largest satellite of Uranus but also the eighth largest of the hundreds of satellites in the solar system.
The
satellite was discovered by Sir William Herschel, an eminent astronomer, on
11th January 1787. On the same day, he also discovered Oberon, the second
largest satellite of Uranus. The newly discovered satellite was named after the
Queen of Fairies 'Titania' in 'A Midsummer Night's Dream', a play written by the
famous playwright William Shakespeare in 1595. Titania is an ancient Greek word
meaning daughter of Titan. However, this satellite has another name. In 1851,
another astronomer, William Lassell, named the satellite Uranus-III for its
distance from Uranus. In this regard one thing is important to
mention here, at the time of mid-nineteenth century all the satellites of far
distant planets could not been discovered. For this reason Titania had regarded
as Uranus-III instead of Uranus-XVII
With
a diameter of 1,578 km, the satellite is located at an average distance of
4,36,000 km from Uranus. Currently, Titania is ranked 17th in terms of distance
from Uranus by 16 small and large satellites. The satellite orbits Uranus once
every 7.8 earth-days, with an average orbital velocity of 3.64 km per second.
Like
the other satellites in the solar system, Titania is also tidally locked to its
planet Uranus, meaning that a part of Titania is always bound to Uranus. Uranus
orbits the Sun once every 84 earth-years, and Titania orbits Uranus at the
equatorial plane, so that one of Titania's poles is either illuminated for 42
consecutive earth-years or dark for 42 earth-years. Titania
is located entirely in the Magnetosphere of Uranus. (Magnetosphere: The
region created in space by the ionized stellar wind of a star facing the
magnetic field of a nearest astronomical body.) The escape velocity of
this satellite is 0.773 km per second or 2,782.8 km per hour. (Escape velocity:
The minimum speed which is required to reach space beyond the
gravitational force of an astronomical object.)
The
density of Titania is much higher than that of Saturn's satellites. It is also
understood that Titania is made up of almost equal amounts of water-ice and
other elements. Other elements here include rock and carbon along with heavy
organic compounds. The presence of Carbon dioxide has been found on the surface
of it. The cause of it is not yet known. However, it is speculated that Carbon
dioxide may be produced here under the influence of ultraviolet rays from the
sun or strong charged particles from the magnetosphere of Uranus with the
compound present in Titania. Some scientists propose that a geological event in
Titania in the past has released the trapped Carbon dioxide from the water-ice,
which has led to the presence of this chemical in Titania.
There
are two theories about the origin of Titania. According to the first theory,
the dust and gas that formed around Uranus after its formation was identified
as a Sub-Nebula from which Titania has been originated. According to the second
theory, the satellite is thought to have originated from a piece of Uranus
caused by a cosmic collision of an object with Uranus. However, satellites
derived from sub-nebulae have very little ice but subsequent activities may
result in the formation of water ice. However, it has not been possible to
resolve any of these doctrines correctly.
The
core at the centre of Titania is equal to 58% of the total mass of the
satellite and 66% of the total diameter. It is a rocky region and is surrounded
by a mantle of water-ice about which our perception is not so clear. If the
mantle of this ice is composed of an anti-freezing agent such as ammonia, there
may be a 50 km deep sea at the core-mantle boundary below the subsurface of
Titania. The average temperature of that sea may be -83.150 Celsius.
After the formation of satellite, its surface cools rapidly, but radioactive
radiation from the central core generates a tremendous amount of heat. The
effect of these two opposite conditions is to cause a great deal of stress on
the surface of Titania. Its effect lasted at least 20 crore years, and this is
why so many canyons have formed on the surface of Titania. However, our knowledge
of the history of the geological evolution of Titania is extremely limited.
The
surface color of Titania is light red. The topography of Titania is influenced
by two forces. Firstly, the energy used to form the crater created by cosmic
collisions and secondly, the energy generated from below the surface.
Scientists have divided Titania's topography into three categories: crater,
canyon and rupes (Rupes: One type of steep terrain.) The largest
canyon in Titania is the 'Gertrude' Canyon with a diameter of 326 km. Some of the
other notable dents of this satellite are Ursula, Jessica, Mopsa, Marina,
Adriana, Katherine etc. Here each name is named after the female characters in
various plays written by Shakespeare. All of Titania's craters
have a flat surface with a central peak except Jessica dent where a pit is
present at its center. The network of faults is spread all over the surface of
Titania, resulting in a large numbers of gorge getting appeared. The largest
canyon in Titania is the 'Messina Chasma', which stretches 1,492 km from the
equator to the South Pole. There is also a type of geological structure called 'Graben' which is about 21 km long. Notable among the rupes is the 'Rousillion' Rupes near the Ursula Canyon with a diameter of 402 km.
Although
Carbon dioxide was found in the climate of Titania, but no Nitrogen or Methane
have been found, perhaps because of Titania’s weak gravitational force which could
not hold such a light chemical. The rotation of the carbon cycle is clearly
observed in this satellite.
Till
date, only once we have been able to explore the world of Titania by
spacecraft. On 24th January 1986, the Voyager-II spacecraft made its flyby
3,65,200 km from Titania. (Flyby: According to the
terminology of astronomy, the incident of observation by an observer spacecraft
at the shortest distance on a star, planet or satellite.) Then
Voyager-II sent some high-quality images of Titania to Earth. All of those
images covered 40 percent of Titania. There was sunlight at the South Pole
during the expedition so this part was well seen. The North Pole was shrouded
in darkness so Voyager's powerful camera was unable to study that region.
To
date, no definite future space mission to Titania has been announced by any
space research institute around the world. Earlier, several Titania expeditions
were announced, but for various reasons, all of them were later cancelled.
However, the US space agency is currently planning to build an orbiter,
centered on Uranus and its satellite system. (Orbiter: A spacecraft that
collects information for a certain period of time while orbiting a specific
cosmic object without landing anywhere and is destroyed at the end of the
period.) Though the plan of this orbiter is now in its initial state only.
There
has been only one expedition to Titania, so in that sense we don't know much
about Titania. In order to know and understand the unknown information of all
these satellites in more depth, we have to organize missions by sending more
and more spacecraft, centered on the satellite. Who knows, some source of our
future existence may be deeply rooted in the sea of unknown information of
Titania, we have to bring that undisclosed information to light, unveil the
possible way to save our own existence in the future.
