Mars is the fourth planet in our solar system and the second smallest after Mercury. Named after the ancient Roman god of war. Its nickname "Red Planet" comes from the reddish hue of the surface, which is due to the predominance of iron oxide. Every few years, when Mars is in opposition to Earth, it is most visible in the night sky. For this reason, people have observed the planet for many millennia, and its appearance in the sky has played a large role in the mythology and astrological systems of many cultures. In the modern era, it has become a treasure trove of scientific discoveries that have expanded our understanding of the solar system and its history.
Size, orbit and mass of Mars
The radius of the fourth planet from the Sun is about 3396 km at the equator and 3376 km in the polar regions, which corresponds to 53% of the Earth's radius. And although it is about half as much, the mass of Mars is 6.4185 x 10²³ kg, or 15.1% of the mass of our planet. The inclination of the axis is similar to that of the earth and is equal to 25.19° to the plane of the orbit. This means that the fourth planet from the Sun is also experiencing a change of seasons.
At its furthest distance from the Sun, Marsorbits at a distance of 1.666 AU. e., or 249.2 million km. At perihelion, when it is closest to our star, it is 1.3814 AU away from it. e., or 206.7 million km. The red planet takes 686.971 Earth days, which is equivalent to 1.88 Earth years, to complete an orbit around the Sun. In Martian days, which on Earth are one day and 40 minutes, a year is 668.5991 days.
Soil composition
With an average density of 3.93 g/cm³, this characteristic of Mars makes it less dense than Earth. Its volume is about 15% of the volume of our planet, and its mass is 11%. Red Mars is the result of the presence of iron oxide on the surface, better known as rust. The presence of other minerals in the dust provides other shades - gold, brown, green, etc.
This terrestrial planet is rich in minerals containing silicon and oxygen, metals and other substances that are usually found in rocky planets. The soil is slightly alkaline and contains magnesium, sodium, potassium and chlorine. Experiments done on soil samples also show that its pH is 7.7.
Although liquid water cannot exist on the surface of Mars due to its thin atmosphere, large concentrations of ice are concentrated within the polar caps. In addition, from the pole to 60° latitude, the permafrost belt extends. This means that water exists under most of the surface as a mixture of its solid and liquid states. Radar data and soil samples confirmed the presence of underground reservoirsalso in mid-latitudes.
Internal structure
The 4.5 billion year old planet Mars consists of a dense metallic core surrounded by a silicon mantle. The core is composed of iron sulfide and contains twice as many light elements as the Earth's core. The average thickness of the crust is about 50 km, the maximum is 125 km. If we take into account the size of the planets, then the earth's crust, the average thickness of which is 40 km, is 3 times thinner than the Martian one.
Modern models of its internal structure suggest that the size of the core in a radius of 1700-1850 km, and it consists mainly of iron and nickel with approximately 16-17% sulfur. Due to its smaller size and mass, gravity on the surface of Mars is only 37.6% of Earth's. The gravitational acceleration here is 3.711 m/s², compared to 9.8 m/s² on our planet.
Surface characteristics
Red Mars is dusty and dry from above, and geologically it closely resembles Earth. It has plains and mountain ranges, and even the largest sand dunes in the solar system. Here is also the highest mountain - the shield volcano Olympus, and the longest and deepest canyon - the Marinera Valley.
Impact craters are typical elements of the landscape that dot the planet Mars. Their age is estimated in billions of years. Due to the slow rate of erosion, they are well preserved. The largest of them is the Hellas Valley. The circumference of the crater is about 2300 km, and its depth reaches 9 km.
On the surface of Mars alsoravines and channels can be distinguished, and many scientists believe that water once flowed through them. Comparing them with similar formations on Earth, it can be assumed that they are at least partially formed by water erosion. These channels are quite large - 100 km wide and 2 thousand km long.
Mars satellites
Mars has two small moons, Phobos and Deimos. They were discovered in 1877 by astronomer Asaph Hall and are named after mythical characters. According to the tradition of taking names from classical mythology, Phobos and Deimos are the sons of Ares, the Greek god of war, who was the prototype of the Roman Mars. The first of them personifies fear, and the second - confusion and horror.
Phobos is about 22 km in diameter, and the distance to Mars from it is 9234.42 km at perigee and 9517.58 km at apogee. This is below synchronous altitude and it takes only 7 hours for the satellite to circle the planet. Scientists have calculated that in 10-50 million years, Phobos may fall to the surface of Mars or break up into a ring structure around it.
Deimos has a diameter of about 12 km, and its distance from Mars is 23455.5 km at perigee and 23470.9 km at apogee. The satellite makes a complete revolution in 1.26 days. Mars may have additional satellites that are smaller than 50-100 m in diameter, and there is a ring of dust between Phobos and Deimos.
According to scientists, these satellites were once asteroids, but then they were captured by the planet's gravity. The low albedo and composition of both moons (carbonaceouschondrite), which is similar to the material of asteroids, support this theory, and the unstable orbit of Phobos would seem to suggest a recent capture. However, the orbits of both moons are circular and in the plane of the equator, which is unusual for captured bodies.
Atmosphere and climate
The weather on Mars is due to the presence of a very thin atmosphere, which is 96% carbon dioxide, 1.93% argon and 1.89% nitrogen, as well as traces of oxygen and water. It is very dusty and contains particulate matter as small as 1.5 microns in diameter, which turns the Martian sky a dark yellow when viewed from the surface. Atmospheric pressure varies within 0.4–0.87 kPa. This is equivalent to about 1% of the earth at sea level.
Due to the thin layer of the gaseous shell and the greater distance from the Sun, the surface of Mars warms up much worse than the surface of the Earth. On average, it is -46 ° C. In winter, it drops to -143 ° C at the poles, and in summer at noon at the equator it reaches 35 ° C.
Dust storms are raging on the planet, which turn into small tornadoes. More powerful hurricanes occur when dust rises and is heated by the Sun. The winds intensify, creating storms that are thousands of kilometers long and last several months. They actually hide almost the entire surface area of Mars from view.
Traces of methane and ammonia
Traces of methane were also found in the planet's atmosphere, the concentration of which is 30 parts per billion. It is estimated thatMars should produce 270 tons of methane per year. Once released into the atmosphere, this gas can only exist for a limited period of time (0.6–4 years). Its presence, despite its short lifetime, indicates that an active source must exist.
Suggested options include volcanic activity, comets and the presence of methanogenic microbial life forms below the planet's surface. Methane can be produced by a non-biological process called serpentinization, involving water, carbon dioxide and olivine, which is common on Mars.
Mars Express also detected ammonia, but with a relatively short lifetime. It is not clear what produces it, but volcanic activity has been suggested as a possible source.
Exploring the planet
Trying to find out what Mars is began in the 1960s. In the period from 1960 to 1969, the Soviet Union launched 9 unmanned spacecraft to the Red Planet, but all of them failed to reach the goal. In 1964, NASA began launching Mariner probes. The first were "Mariner-3" and "Mariner-4". The first mission failed during deployment, but the second, launched 3 weeks later, successfully completed the 7.5 month journey.
Mariner 4 took the first close-up images of Mars (showing impact craters) and provided accurate data on atmospheric pressure on the surface and noted the absence of a magnetic field and a radiation belt. NASA continued the program with the launch of another pair of flyby probes Mariner 6 and 7,who reached the planet in 1969
In the 1970s, the USSR and the USA competed to be the first to put an artificial satellite into orbit around Mars. The Soviet M-71 program included three spacecraft - Kosmos-419 (Mars-1971C), Mars-2 and Mars-3. The first heavy probe crashed during launch. Subsequent missions, Mars 2 and Mars 3, were a combination of an orbiter and lander and were the first stations to land extraterrestrially (other than on the Moon).
They were successfully launched in mid-May 1971 and flew from Earth to Mars for seven months. On November 27, the Mars 2 lander crash-landed due to an onboard computer failure and became the first man-made object to reach the surface of the Red Planet. On December 2, Mars-3 made a regular landing, but its transmission was interrupted after 14.5 from the broadcast.
Meanwhile, NASA continued the Mariner program, and in 1971 probes 8 and 9 were launched. Mariner 8 crashed into the Atlantic Ocean during launch. But the second spacecraft not only reached Mars, but also became the first successfully launched into its orbit. While the dust storm lasted on a planetary scale, the satellite managed to take several photographs of Phobos. As the storm subsided, the probe took pictures that provided more detailed evidence that water once flowed on the surface of Mars. A hill called the Snows of Olympus (one of the few objects that remained visible during a planetary dust storm) was also found to be the highest formation in the solar system, leading torenaming it Mount Olympus.
In 1973, the Soviet Union sent four more probes: the 4th and 5th Mars orbiters, as well as the Mars-6 and 7 orbital and descent probes. All interplanetary stations except Mars- 7”, transmitted data, and the Mars-5 expedition was the most successful. Before the depressurization of the transmitter housing, the station managed to transmit 60 images.
By 1975, NASA launched Viking 1 and 2, which consisted of two orbiters and two landers. The mission to Mars was aimed at searching for traces of life and observing its meteorological, seismic and magnetic characteristics. The results of biological experiments aboard the reentry Vikings were inconclusive, but a reanalysis of the data published in 2012 suggested signs of microbial life on the planet.
Orbiters have provided additional data confirming that water once existed on Mars - large floods have formed deep canyons thousands of kilometers long. In addition, patches of branching streams in the southern hemisphere suggest that precipitation once fell here.
Resumption of flights
The fourth planet from the sun was not explored until the 1990s, when NASA sent the Mars Pathfinder mission, which consisted of a spacecraft that landed a station with the moving Sojourner probe. The device landed on Mars on July 4, 1987 and became proof of the viability of the technologies that will be used in further expeditions, suchlike airbag landing and automatic obstacle avoidance.
The next mission to Mars is the MGS mapping satellite, it reached the planet on September 12, 1997, and began operation in March 1999. During one full Martian year, from low altitude, almost in polar orbit, it studied the entire surface and atmosphere and sent more planetary data than all previous missions combined.
November 5, 2006 MGS lost contact with Earth and NASA recovery efforts ended on January 28, 2007
In 2001, the Mars Odyssey Orbiter was sent to find out what Mars is. Its goal was to search for evidence of the existence of water and volcanic activity on the planet using spectrometers and thermal imagers. In 2002, it was announced that the probe had detected a large amount of hydrogen, evidence of huge deposits of ice in the top three meters of soil within 60° of the South Pole.
On June 2, 2003, the European Space Agency (ESA) launched Mars Express, a spacecraft consisting of a satellite and the Beagle 2 lander. It went into orbit on December 25, 2003, and the probe entered the planet's atmosphere on the same day. Before the ESA lost contact with the lander, the Mars Express Orbiter confirmed the presence of ice and carbon dioxide at the south pole.
In 2003, NASA began exploring the planet under the MER program. It used two rovers Spirit and Opportunity. The mission to Mars had the task of exploring variousrock and soil in order to find evidence of the presence of water here.
12.08.05 the Mars Reconnaissance Orbiter (MRO) was launched and reached the orbit of the planet on 10.03.06. On board the device are scientific instruments designed to detect water, ice and minerals on and below the surface. In addition, MRO will support future generations of space probes by monitoring Mars weather and surface conditions daily, searching for future landing sites, and testing a new telecommunications system that will speed up communication with Earth.
August 6, 2012, NASA's Mars Science Laboratory MSL and the Curiosity rover landed in Gale Crater. With their help, many discoveries have been made regarding local atmospheric and surface conditions, and organic particles have also been detected.
On November 18, 2013, in another attempt to find out what Mars is, the MAVEN satellite was launched, the purpose of which is to study the atmosphere and relay signals from robotic rovers.
Research continues
The fourth planet from the Sun is the most studied planet in the solar system after Earth. Currently, Opportunity and Curiosity stations operate on its surface, and 5 spacecraft operate in orbit - Mars Odyssey, Mars Express, MRO, MOM and Maven.
These probes have captured incredibly detailed images of the Red Planet. They helped discover that there was once water there, and confirmed that Mars and Earth are very similar - they have polar caps, seasons, an atmosphere andthe presence of water. They also showed that organic life could exist today and most likely existed before.
Humanity's obsession with Mars continues unabated, and our efforts to study its surface and unravel its history are far from over. In the coming decades, we will probably continue to send rovers there and send a man there for the first time. And over time, given the availability of the necessary resources, the fourth planet from the Sun will someday become habitable.
