SOLAR SYSTEM FAMILY-FACTS ABOUT MARS, THE RED PLANET

The gradual rise of modern civilizations meant frequent territorial conflicts, as mighty conquistadors tried to bring the whole wide world under their control. It can be assumed that during those times man felt a desperate need for a god of war or conflicts, whom they could worship and in His name continue their plunder. Thus, a red star like object(Planet Mars), which our early ancestors saw as blood, soon became a god associated with war, conflict, pillage and the long cherished masculinity.

 A Bit of Mythology- According to the Roman Mythology, Mars, the son of their supreme god Jupiter and goddess Juno, was the god of intense rage, passion, destruction and war. He was also the father of Romulus and Remus, the twin mythical founders of the Roman Empire, and occupied a significant place in the hearts of the Roman people. It is also good to note that in the month of March(the word originates from the Latin word, Martius) celebrations like military processions and demonstrations were arranged in the honour of Mars.

                                       In Greek Mythology, the red planet was personified as ''Aris'' or ''Ares'', the counterpart of Mars. But unlike the Roman god, who brought lasting peace after a long and violent war, Ares was completely different. The Greek god was a bit unpopular among the people as He only brought devastation and carnage. Apart from the Greeks and the Romans, historical evidence suggests that other cultures also worshipped this red planet as a deity related to war, famine, plunder and conflicts. The Babylonians knew Mars as ''Nergal''(a great hero & a king of conflicts), the Egyptians called it ''The Red One'', the Chinese, Koreans, Japanese referred to it as a ''fiery star'' and finally the ancient Indians knew Him as ''Mangala''(a god of war, and the son of the Earth Goddess).

Basic Facts- Mars is the fourth and the last officially recognized terrestrial planet of our solar system. This celestial body is quite smaller compared to Earth and appears reddish due to the presence of a compound called iron oxide, which is basically rust. Mars has also got two irregularly shaped natural satellites-Deimos and Phobos. The planet is visible as a bright reddish or orangish dot in the night sky, sometimes just after sundown or at dead night. The red planet, as it is often called, becomes visibly distinct with increasing brightness as it reaches the period of opposition i.e., an orbital configuration when its separation from our planet becomes the least. 

The left side image is of  Mars under clear conditions, while the right side picture has been taken a global dust storm/Image Credits:NASA Hubble, CC BY 2.0, via Wikimedia Commons

Planetary Characteristics:

• Rotational & Orbital Characteristics- Mars completes its orbit around the Sun once in every 687 Earth days, and is situated at an average distance of 230 million km, in an elliptical orbit with an orbital eccentricity of 0.09. At aphelion, this separation becomes equal to 249.2 million km and at perihelion it is 206.7 million km. The length of a Martian day(or Sol) is slightly longer than Earth, and is equal to 24 hours, 37 minutes and 22.7 seconds. The red planet also shares a number of similarities with Earth, like having a fairly good orbital velocity of 24.007 km/s or 86,430 km/s, and an axial tilt of 25.19° with the orbital plane. This axial tilt is responsible for the formation of Martian seasons, and seasonal variation in the volume of ice caps similar to its counterpart on Earth. The Martian seasons are longer in duration when compared to Earth, as the red planet is situated much farther from the Sun. 

• Internal Structure- Since Mars is a terrestrial planet, its internal structure is quite similar to Earth. The interior is divided into a dense metallic core composed of iron, nickel and sulfur, a silicate mantle and a crust that varies in thickness from 50-125 km at maximum. The silicate mantle(thought to be dormant at present) is responsible for the formation of tectonic and volcanic features. The planet is however seismically active with frequent marsquakes and a total of 174 low magnitude quakes have been detected by the seismometer on board the Insight Lander. Mars has an equatorial radius of 3,390 km, and is nearly half in size compared to Earth, which has an equatorial radius of 6,378 km. The elements that make up Mars' crust are compounds of iron, magnesium, calcium, aluminum, potassium and the average density is around 3.9 g/cc compared to 5.51 g/cc of Earth.

• Surface Geology- The Martian surface appears reddish in colour due to the presence of a compound called iron(III) oxide, a reddish mineral which is the primary source of iron for the steel industry(on Earth of course!). Along with fine particles of this iron oxide, the surface is also covered by a thin layer of soil, composed of magnesium, sodium, potassium and chlorine. Scientists speculate that after the Solar System's formation, each and every planet was subjected to a period of heavy bombardment from countless large asteroids and protoplanetary objects. That's why the Martian surface, like other planetary surfaces, is covered by a vast number of impact basins, some dating back to billions of years into the past while others are fairly recent as measured in geologic time frames. There is evidence of a huge impact basin, the Borealis Basin in the northern hemisphere, and has dimensions spanning by 10,600 km to 8,500 km. But the Borealis Basin, has not yet been officially recognized as an impact basin although theoretical modelling suggests an impact by another celestial body. This impact basin is nearly four times larger than the Moon's South-Pole Aitken Basin, the largest impact crater of our solar system. Mars is also featured with 43,000 impact craters, like the Hellas Planitia Impact Basin(diameter=2300km), and ice filled Korolev Crater(diameter=82km). Other Martian surface features include a number of volcanic features like the Tharsis Montes, Alba Mons, Tholi and Patera, Elysium, Syrtis Major, Arabia Terra, and the largest volcanic mountain found in our Solar System i.e., the Olympus Mons. Olympus Mons(altitude of 21-27km, two and a half times larger than mount Everest) is an ancient shield volcano which suggests that once upon a time volcanic activity played an important role in shaping the red planet. However the planet is currently volcanically silent and the presence of ridges, valleys, canyons(largest one is the Valles Marineris, length of 4000 km and a depth of 7 km) are essentially results of past tectonic activity.

The Korolev Crater/Image Credits: ESA/DLR/FU Berlin, CC BY-SA 3.0

• Surface Temperature- Mars is a cold desert, and is extremely dry with average global surface temperatures being not more than -63℃(210K). The highest recorded daytime temperatures are about 20℃ and sometimes it goes as low as 0℃(273K). The night-time temperature ranges between -172℃(256K) to -107℃(166K).

• A Thin Atmosphere- Mars has got a very thin atmosphere, with surface pressures being only 1% compared to what we experience at Earth's surface. This thin atmosphere is unstable as the gases are slowly escaping into outer space due to the smaller size of the planet and its lesser gravitational pull. However, the red planet did have a thicker atmosphere back in its past but it slowly thinned out when the planet lost its magnetosphere due to the bombardment by other celestial debris. The thin atmosphere is composed of 96% Carbon Dioxide, 1.93% Argon, 1.89% Nitrogen, and traces of Oxygen, Carbon Monoxide, Water Vapour, Nitrogen Oxide, Hydrogen, Krypton and Xenon. The Martian atmosphere also takes a brownish-orange to somewhat pinkish hue due to the presence of suspended fine particles of dust. Although the atmosphere is thin, it is capable of producing global dust storms, dust devils, wind currents, clouds of water vapour and surface weathering due to wind erosion. These phenomena occurs due to the extreme contrast between day and night temperatures, as solar heating of the day side and radiative cooling of the night side induces pressure gradients. The Martian atmosphere also contains an abundance of methane that arises from an active process, which can either be from biogenic(from biological organisms, unconfirmed) sources or chemical reactions that occur between various minerals(also unconfirmed). 

 A Blue Sunset as pictured by the Spirit Rover/Image Credits: NASA's Mars Exploration Rover, Public domain, via Wikimedia Commons, by Spirit Rover

• Magnetic Field & Magnetosphere- At present, Mars does not possess a geomagnetic dipolar field like Earth, but has crustal(surface) magnetization. This crustal magnetization along with certain surface features and a bunch of anomalies suggest that in its past the planet did possess a fairly good magnetic field. Why Mars lost its magnetic field is not clear, but scientists speculate that the planet isn't large enough to keep its geo-dynamo going for billions of years. With the loss of its magnetic field, Mars also lost its magnetosphere and as a result got bombarded by the intense solar radiation and eventually also lost its dense atmosphere.

• Hydrosphere & the Presence of Water- Liquid water doesn't exist under present conditions but surface features suggests the past existence of liquid water just like Earth. However, the polar ice caps do contain water, in the form of ice mixed with solidified carbon dioxide gas. It is estimated that if the polar ice caps are melted then the whole planetary surface might be covered by a few meters of liquid water. The two permanent polar ice caps vary with seasonal variations. During winter, owing to lower temperatures the volume of the ice caps increases with further precipitation of carbon dioxide in the form of dry ice. During summer, the solid carbon dioxide sublimes along with water molecules that form clouds and transport large volumes of water vapour along with dust grains. In situ exploration of the planetary surface by rovers, and landers have revealed hundreds of landform features that point towards the existence of huge quantities of liquid water. Ma'adim Vallis, a 200 km long and 20 km wide canyon with a depth of 2 km, believed to be carved out from the action of flowing water, is a much larger canyon compared to the Grand Canyon on Earth.  

• Natural Satellites- Mars has two irregularly shaped natural satellites called Phobos(diameter=22 km) and Deimos(diameter=12 km). Both of their origins are debatable and some scientists speculate that they are captured asteroids, while others believe they formed together with their parent planet. 

The Martian surface as pictured by the Viking 2 lander/Image Credits: NASA, Public domain, via Wikimedia Commons 

Life & Biological Considerations: There's a possibility that under intensive in-situ explorations Mars might give us some evidence in favour of the existence of extra-terrestrial microbial life. This assumption comes from the fact that Earth and Mars were quite similar when our Sun was young and these two planets were just born. Scientists estimate that nearly four billion years ago, these planets had a thick atmosphere, large open bodies of liquid water and both of them had nearly equal chances to witness the birth of life forms. But because of certain reasons and owing to their difference in size, atmospheric pressure, chemical composition, Mars' geological evolution diverged from Earth and the red planet became a cold, and dry desert whereas Earth got its surface covered with myriad species of flora and fauna. As mentioned earlier, Mars indeed possessed bodies of liquid water, and the red planet must have had a chance to witness the development of a different biology. Considering this fact, Mars is thus an excellent place where we can look for extra-terrestrial life, alive or fossilized. The search for Martian life began with the Viking Missions whose primary objective was to look for signs of biogenic processes through certain experiments. Though the Viking data temporarily showed signs of Martian life, it has not been accepted and the possible bio-signatures have been explained in terms of non-biogenic chemical reactions. Other experiments for detecting extra-terrestrial life have been conducted by the Mars Science Laboratory, Curiosity Rover, Spirit Rover, Opportunity Rover, and the Phoenix Lander. But in spite of so many in situ explorations, no form of past or present life have been detected on the Martian surface. Abundance of methane, presence of formaldehyde, sudden spike of carbon dioxide levels on exposing Martian soil to air and water cannot convince scientists about the existence of Martian life.  

The Red Planet/Image credits: NASA/JPL-Caltech/MSSS, Public domain, via Wikimedia Commons

Observations & Explorations-

• Observations: Because of a phenomenon called opposition which occurs every 26 months, Mars comes closest towards Earth, and the red planet becomes distinct. The ancient philosophers had a habit of observing the night sky, and this bright red star-like object never failed to grasp their attention. In the fourth century BCE, Aristotle was the first to notice that Mars disappeared(occultation) behind the Moon. Tycho Brahe measured the diurnal parallax of Mars, to determine its distance from Earth. However, the first telescopic observations were done by none other than the famous Italian astronomer Galileo Galilei in 1610, and was later followed by Giovanni Domenico Cassini, who measured the parallax using a telescope for the first time, and Christian Huygens, who provided the first maps of the red planet with its surface features. With the increase of telescopic resolutions towards the 19th century astronomers Giovanni Schiaparelli and Percival Lowell observed surface features that appeared as canals dug out by some advanced Martian civilizations. The idea for the existence of an extraterrestrial civilization was further magnified from the observation of seasonal changes in the Martian ice caps. And, this misconception prevailed even during the mid 20th century till the advent of space explorations. 

• Explorations: It is quite difficult to reach Mars and as a result out of 50 missions only 26(i.e 53%) have reached their destination, safe and sound. Attempts to reach the red planet began in the early 1960s by the United States of America and the Soviet Union, later to be followed by the European Nations, China, Japan, Russia and India. But each and every country who tried to reach Mars, except India, and the recently launched Chinese spacecraft have been greeted with a bunch of failures. And because of so many unsuccessful missions, Mars has acquired a title-''The Cursed Planet'', and has been occasionally labeled as a planet who prefers to eat orbiters, probes, landers and probably humans for breakfast. The list of the past and ongoing missions are as follows:

1. The Soviet Union attempted to reach the red planet with their Mars Program, followed by the Zond Program. A number of orbiters coupled with landers and probes were launched since the 1960s, with none of them being able to fully succeed due to partial or complete space-craft failure. Mars-2, launched on 19th May, 1971, was the first partially successful mission from the Soviet Union. The Mars 2 orbiter couldn't gather much data due to a global dust storm that covered the whole of Mars during that time. The Mars 2 lander however, failed to land successfully and after crashing over the Martian surface became the first manmade object to impact the red planet. The successor to Mars-2, Mars-3, launched on 28th may, 1971 remained in Martian orbit for 8 months and the lander successfully performed a soft landing. Although the lander was operational for only about 20 seconds before communication failure, it became the first manmade object to softly land on the Martian surface. Other missions under the Mars Program were not successful and the Zond Program failed miserably.
2. The United Nations' attempt to reach the red planet started with the Mariner Program from 1964, and like the soviet Union was too greeted with failure. The first Mars mission under the Mariner Program, Mariner-3 failed miserably. It's successor i.e., Mariner-4 became the first successful spacecraft to fly by the planet and return a few images. These were again followed by subsequent Mariner missions up to 1971. Mariner-9 became the first successful artificial satellite of our red planet.
3. The Mariner program was then followed by the Viking Program. Two space-crafts, namely the Viking-1 launched on 20th August and Viking-2 launched on 9th September of 1975, comprising of orbiters and landers enriched the scientists with a huge amount of data including geologic features suggesting past existence of liquid water, observation of magnetic field, seismic activity, atmosphere, the two natural satellites viz., Phobos and Deimos and of course to detect possible signatures of biological life. 
4. The next mission, the Mars Observer, launched during 1992 failed as communications with the spacecraft was lost before its entry into the Martian orbit. So NASA developed another mission, Mars Global Surveyor, launched on 7th November, 1996. This orbiter that remained operational until 2006, was entrusted with the primary task of providing a detailed map of the entire planet, and to look for potential sites for future lander and roving missions. The next mission, the Mars Pathfinder Mission, launched in 4th December, 1996 became one of the most successful Mars mission. The pathfinder mission landed a base station and a roving probe, the Sojourner on the Martian soil. Apart from sending back thousands of high resolution images, the lander and the rover also carried out rock samples analysis, meteorological analysis, and gathered further evidence for the past existence of liquid water.
5. Apart from the Sojourner rover, the Spirit Rover, launched on 10th June 2003 and the Opportunity Rover, launched on 16th July, 2003 under the Mars Exploration Rover Mission provided a load of scientific data. The Opportunity Rover has traveled a distance of 45 kilometers on the Martian soil and remained operational for 14 years, exceeding its calculated lifetime by many orders of magnitude. 
6. The spacecrafts launched by NASA that are operational include the Mars Odyssey-an orbiter launched in 2001, the Mars Reconnaissance Orbiter launched in 2005, the most successful and ever glorious Curiosity Rover launched in November 2011, Maven Orbiter launched in 2013, Insight Lander launched in 2018. Other spacecrafts include the Mars Express launched in 2003 by the ESA, Mars Orbiter Mission launched in 2013 by ISRO(India), ExoMars Trace Gas Orbiter a collaboration between the European Union and Russia, launched in 2016.
7. There are also a bunch of upcoming missions to be sent by NASA, United Arab Emirates and China.  

Very Distant Future- The near future of Mars might become quite bright, as NASA, RosCosmos and the ESA have already started drawing up plans for a future manned mission to the red planet and its eventual colonization in the far future. But there are a certain limitations like extremely cold temperatures, decreased air pressures, lack of atmosphere, no protection from intense radiation, higher levels of dust, lesser gravity and finally the effect of a long journey on the human body. As Mars is a hostile planet and also a distant world, a lot of things needs to be considered before attempting a manned mission, of which the greatest concern is the distance and its isolating effect on the astronauts, as it takes more than 6 months to reach the red planet. And if astronauts get stranded because of spacecraft failure, then there would be virtually no way for them to communicate with their families. In addition to manned missions and space colonization, terraforming of the red planet has also been suggested, which is still a profitable topic for some good science fiction novels and movies. 

                                             However, the very far future is packed with adrenaline. Mars' moon, Phobos is slowly falling towards its planet because of tidal deceleration caused due to the mutual action of gravitational forces. And, it has been predicted based on simulations that within 50 million years from now, Phobos would disintegrate and give its primary a thin ring. On the other hand, Mars' second moon Deimos would fly away. Apart from this, within a span of 5-7 billion years from now, our Sun would evolve into a red giant. During this process, the former would surely gobble up Mercury and Venus, convert Earth into a charred rock and Mars would receive a similar amount of solar flux which our Earth receives at present. In the mean time, the Andromeda Galaxy and the Milky Way Galaxy would merge into a single one, and as a result there's also a faint chance that our solar system might pass through a period of total chaos.  

Earth & Mars on a side by side comparison/Image Credits: Earth: NASA/Apollo 17 crewMars: ESA/MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA, Public domain, via Wikimedia Commons

Some Quick Facts!

References:

1. https://en.wikipedia.org/wiki/Mars

2. https://www.nationalgeographic.com/science/space/solar-system/mars/

3. https://nssdc.gsfc.nasa.gov/planetary/planets/marspage.html

4. Zeilik, Michael. Gregory, Stephen A. Introductory Astronomy And Astrophysics.