Today we will look at a satellite that seems to be far away from us because, as much as other satellites are discussed with interest, this satellite seems to be a bit outcast. Yet this satellite is quite different from other satellites in this solar family with its twin satellites.
In our solar system, Mars is in the fourth place in terms of distance from the sun. The closest and largest satellite to Mars is Phobos. It is located much closer to its own planet than other satellites, and is one of the few light-reflecting objects in the solar system. The satellite was discovered by Asaph Hall, an astronomer from the United States of America, on 18th August 1877. The newly discovered satellite was named after Phobos, the symbol of fear and a son of Greek mythological gods Ares and Aphrodite by English educator Henry George Madan.
The diameter of the satellite is 22.2 km and orbits Mars once in 7 hours and 39 minutes at an average distance of 5,969 km. Phobos is tidally locked in relation to Mars, meaning that the diurnal motion of Phobos is almost equal to its annual motion. The speed of rotation of this satellite is faster than the speed of rotation on the axis of Mars. On average, Phobos rises twice in the Martian day (24 hours and 37 minutes) to the west of any equatorial region of Mars and sets 4 hours and 15 minutes to the east. Phobos has an average orbital speed of 2.13 km per second. The mass of Phobos is so small that its escape velocity is almost negligible compared to other satellites. Phobos' escape velocity is 11.39 mtr per second or 41 km per hour. (Escape Velocity: The lowest velocities which a body must have in order to escape the gravitational attraction of a particular planet, satellite, star or other object.)
There is still some confusion about the origin of Phobos. Carbonated asteroids have a lot of similarities with Phobos. So some say the satellite duo of Mars are actually asteroids that somehow come out of the asteroid belt between Mars and Jupiter and are rotating Mars at very fast speeds. There are also people who support other doctrines. According to different theories, as a result of a cosmic collision on the surface of Mars, a part of Mars has come out and is rotating Mars and has become known as Phobos. Maybe that's why Phobos, instead of being round like other satellites, has become strangely irregular in shape. But too much number of ditches at the surface of Phobos has called the decision into question. In addition to this, it is also true that the presence of Phyllosilicate on the surface of Mars has been found in large quantities in Phobos. The presence of reddish and bluish substances on the surface of Phobos has further complicated the origin of Phobos. Only this issue needs more in-depth observation and research which will unveil the cloud of mystery and reveal the origin of Phobos.
As mentioned earlier, Phobos is an irregular satellite. Phobos's mass is so little that its gravitational force is almost negligible. Whatever the origin of Phobos, the very low gravitational force for a very small mass may has been a hindrance to Phobos' actual spherical retention. This is why this satellite has no atmosphere. This satellite is fairly cool in nature even closer to the sun. The average temperature of its illuminated surface is -4 degree Celsius and the average temperature of its dark surface is further reduced to -112 degree Celsius. The density of Phobos is very low. Its surface is made up of carbon rich metals. Phobos has a three-foot layer of dust on the surface and a large poreous layer beneath that layer of dust which suggests that there may be a large amount of water ice beneath the surface of Phobos.
There are numerous ditches due to cosmic collisions throughout Phobos. These valleys do not exceed 30 mtr in depth, about 100-200 mtr in width and can be up to a few km in length. Phobos's largest crater is called Stickney which is about 9 km in diameter. Scientists have divided the craters of Phobos into a total of 12 categories based on the time of their origin. All of these dents have been formed as a result of collisions with various meteorites. In addition to Stickney, there are a few notable craters viz - Clustril, Drunlo, Flimnap, Grindrig, Gulliver, Limtoc, etc. They have been named after various locations and characters in Jonathan Swift's world-famous novel Gulliver's Travel. Also, some dents have been named after astronomers such as Hall, Opic, Roche, Todd, Wendell, Sharpless, etc.
It is speculated that Phobos may have a faint cover of dust around it. However, it has not been possible to observe that zone in depth. Phobos images, sent by the Mars Global Surveyor, suggest that the satellite is covered by a layer of Regolith with a thickness of 100 mtr. (Regolith: The very thin layer of matter located on the surface of a planet or satellite is called a regolith.) This layer is thought to have originated as a result of a long-running cosmic collision on Phobos. But what is surprising here is that the presence of this level in a satellite where the gravitational force is so weak is a matter for research. In this context, it is very necessary to talk about an incident. It has already been said that the gravitational force of Phobos is very weak. If a meteorite suddenly encounters Phobos during space travel and a cosmic collision occurs, the rocky fragments of Phobos, caused by that collision, are scattered around in space. It is thought that a number of such meteorites, large and small, landed on the West Asian country, Yemen in 1980 at a military camp of the then Soviet Union of Soviet Socialist Republics (USSR). These pieces of meteorite are called the Kaidun Meteorite. However, it is very difficult to prove this, because we do not yet know all the details of the actual physical and chemical composition of the nature of Phobos crust through the very dense dust layer on its surface.
To date, there have been a very few space missions that are centered on Phobos. The spacecrafts, sent by various space research organisations around the world, sent high-quality images of Phobos to earth as part of a series of missions, usually aimed at Mars.
On 5th August 1969, just 16 days after the first successful manned lunar mission, the US space agency (National Aeronautics and Space Administration or NASA) had sent Mariner-7 spacecraft which sent the first image of Phobos to Earth from the orbit of Mars. The Mariner-9 spacecraft then sent several images of Phobos to Earth from December 1971 to February 1972. Subsequently, between February and March in 1977, the Viking-1 spacecraft sent many images of Phobos to earth. Then Russia came forward. Their spacecraft Phobos-2 sent many images of Phobos to Earth in 1989. Meanwhile, NASA sent Mars Global Surveyor (MGS) for Mars. This spacecraft sent many images of Phobos to earth in the first phase in 1997 and in the second as well as last phase in 2003. The next spacecraft, the Mars Express (ME), sent images of Phobos in four phages to earth. The first time was in 2004 and later in 2006, 2010 and lastly in 2019. The first image of Phobos appearing in the night sky from the surface of Mars was sent by Spirit Rover on August 25, 2005. The Mars Reconnaissance Orbiter (MRO) collected images of Phobos in 2006 and 2007. It is informed with pride that on 1st July 2020, the Mars Orbiter Mission or MoM, which is also known as the Mangalyaan, of the Indian Space Research Organization (ISRO), sent high quality images of Phobos to the earth from 4,200 km of Phobos.
In 2011, the Russian space agency launched a space expedition called Phobos-Grunt which aims to conduct life science oriented research. But unfortunately, during the research, the spacecraft was completely destroyed in space and the mission failed.
Since 2013, a team of scientists from NASA and two other world renowned universities have been busy to prepare for next mission to Phobos. Their mission will be called Phobos Surveyor Mission (MSM), which is expected to begin sometime from 2023 to 2033. The PADME Mission and the Merlin Mission are scheduled to begin in 2021 as part of the Discovery Mission. In the first mission, the spacecraft will enter the orbit of Mars and make flyby over Phobos (Flyby: In the term of space science, the event of an observer passing over a planet or satellite with the shortest distance) and send various information to Earth. In the second mission, the Marlin spacecraft will land on the surface of Phobos after orbiting Phobos. In addition, the spacecraft of Pandora Mission will rotate around Phobos. The Japanese Space Research Organisation (Japanese Aerospace Exploration Agency or JEXA) will launch the Martian Moons Exploration (MMX) in 2024. Various space research institutes of the world will take part in this mission. The spacecraft will land on the surface of Phobos and collect soil samples and return to Earth five years later, in 2029.
In
addition, between 2021 and 2030, the Russian space agency (Roscosmos) will
resume their Phobos-Grunt mission, which was failed in 2011. The European Space
Agency (ESA) will launch an expedition in 2024 on Phobos, named Phootprint
Mission.
This Phobos satellite is probably going to be the first destination in the human mission to Mars. It is assumed that many important tasks of future Mars missions can be done from here. Landing on Phobos is less risky and expensive than that on Mars and probably it will be the base camp of future Mars mission. The sand of Phobos will also play an important role in the formation of human settlements on Mars.
In the meantime, the fact is that the future will come when Phobos will no longer be in our solar system. Scientists have found that the distance between Phobos and Mars is decreasing by 2 meter every 100 years, meaning that Phobos is moving closer to Mars by 20 millimeter every year. If this continues, within 3 crore to 5 crore years from today Phobos will come to a certain distance from Mars and will break into pieces. The light particles will form a planetary ring around Mars and the heavier particles will enter the atmosphere of Mars and burn up like a meteorite or fall to the ground of Mars.
So it can be said that the identity of our solar family will change in the near future. New star-system will be formed with the Sun and its family members. Then we have to know and write everything anew. This is called change, this is called science.
DECLARATION: All The Images Have
Been Sourced From Google.
