Mars is the fourth planet in increasing order of distance from the Sun and the second in increasing order of size and mass. Its distance from the Sun is between 1.381 and 1.666 AU (206.6 to 249.2 million kilometers), with an orbital period of 669.58 Martian days (686.71 days or 1.88 Earth years).
It is a terrestrial planet, like Mercury, Venus, and Earth, about 10X less massive than Earth but 10X more massive than the Moon. Its topography presents analogies as well with the Moon, through its craters and its impact basins, as with the Earth, with formations of tectonic and climatic origin such as volcanoes, rifts, valleys, mesas. , dune fields and polar ice caps. The highest volcano in the Solar System, Olympus Mons (which is a shield volcano), and the largest canyon, Valles Marineris, are found on Mars.
Mars, red planet!
Mars has today lost almost all of its internal geological activity, and only minor events would still occur episodically on its surface, such as landslides, probably CO2 geysers in the polar regions, perhaps earthquakes. , even rare volcanic eruptions in the form of small lava flows.
The period of rotation of Mars is of the same order as that of the Earth and its obliquity gives it a cycle of seasons similar to the one we know; these seasons are however marked by an orbital eccentricity five and a half times higher than that of the Earth, hence a noticeably more pronounced seasonal asymmetry between the two hemispheres.
Mars can be observed with the naked eye, with a much lower brightness than that of Venus but which can, during close oppositions, exceed the maximum brightness of Jupiter, reaching an apparent magnitude of -2.914, while its diameter apparent range varies from 25.1 to 3.5 arc seconds depending on whether its distance from Earth varies from 55.7 to 401.3 million kilometers. Mars has always been visually characterized by its red color, due to the abundance of amorphous hematite – iron (III) oxide – on its surface. This is what made it associated with war since Antiquity, hence its name in the West after the god Mars of war in Roman mythology, assimilated to the god Ares in Greek mythology. In French, Mars is often nicknamed “the red planet” because of this particular color.
Before Mariner 4 flew over Mars in 1965, it was believed that there was liquid water on the surface and that life forms similar to those existing on Earth could have developed there, a very fruitful theme in science fiction. Seasonal variations in albedo on the planet’s surface were attributed to vegetation, while rectilinear formations seen in astronomical glasses and telescopes of the time were interpreted, notably by American amateur astronomer Percival Lowell, as irrigation canals crossing desert expanses with water from the polar caps. All these speculations were swept away by space probes which studied Mars: as early as 1965, Mariner 4 made it possible to discover a planet devoid of a global magnetic field, with a cratered surface reminiscent of the Moon, and a thin atmosphere.
Since then, Mars has been the subject of more ambitious exploration programs than for any other object in the Solar System: of all the stars that we know, it is indeed the one that presents the environment having the most similarities to that of of our planet. This intensive exploration has given us a much better understanding of Martian geological history, revealing in particular the existence of a remote epoch – the Noachian – where surface conditions must have been quite similar to those on Earth at the same time, with the presence of large amounts of liquid water; the Phoenix probe thus discovered in the summer of 2008 water ice at a shallow depth in the soil of Vastitas Borealis (a flat and very extensive region of the planet Mars within which the north polar cap is located).
Mars has two small natural satellites, Phobos and Deimos.
Size: 6779 km in diameter
Mass: 639e21 kg (6.39 × 1020 tons)
Distance to the Sun: from 207 million km (Perihelion) to 250 million km (Aphelia)
Distance to Earth: 56 to 400 million km
Feature: most studied planet after Earth
Observation: visible to the naked eye, red color
1 Martian day: A little more than a terrestrial day (24h 39 mn)
1 Martian year: 687 Earth days
Active ground robots: Curiosity (M.S.L), Perseverance (March 2020)
Can we see Mars with the naked eye?
Even though it has a less visible glow than Venus, it is quite possible to observe Mars with the naked eye. It has been a long time since the men who trod our planet before us have contemplated it. When you observe it, you can even notice its red color.
|3389.5 ± 0.2 km|
(2106.1 ± 0.1 mi)
|3396.2 ± 0.1 km|
(2110.3 ± 0.1 mi; 0.533 Earths)
|3376.2 ± 0.1 km|
(2097.9 ± 0.1 mi; 0.531 Earths)
(55907000 sq mi; 0.284 Earths)
(0.1421 lb/cu in)
(12.2072 ft/s2; 0.3794 g)
Moment of inertia factor
(18100 km/h; 11250 mph)
Sidereal rotation period
24h 37m 22.7s
Equatorial rotation velocity
(868.22 km/h; 539.49 mph)
|25.19° to its orbital plane|
North pole right ascension
21h 10m 44s
North pole declination
Mars lost its magnetosphere 4 billion years ago, so the solar wind could be in direct contact with the ionosphere, which resulted in a decrease in the density of the atmosphere by stripping the atoms of the outer layer. Compared to Earth, the atmosphere on Mars is quite thin. The atmospheric pressure on the surface ranges from 30 Pa at Olympus Mons to more than 1,155 Pa in the Hellas Planitia, with a mean surface pressure of 600 Pa.
The surface pressure on Mars at its strongest is equal to that of the pressure. which can be found at an altitude of 35 km above the Earth’s surface. The altitude of the Mars atmosphere scale is estimated to be about 10.8 km (6,21 miles), which is higher than Earth (6 km or 3,72 miles) because the surface gravity of Mars is only 38% of Earth’s.
|0.636 (0.4–0.87) kPa|
|Composition by volume|
Climate of Mars
Of all the planets in the Solar System, the seasons of Mars are the most Earth-like, due to the similar tilts of the two planets’ rotational axes. The lengths of the Martian seasons are about twice those of Earth’s because Mars’s greater distance from the Sun leads to the Martian year being about two Earth years long. Martian surface temperatures vary from lows of about −143 °C (−225 °F) at the winter polar caps to highs of up to 35 °C (95 °F) in equatorial summer.
The wide range in temperatures is due to the thin atmosphere which cannot store much solar heat, the low atmospheric pressure, and the low thermal inertia of Martian soil.The planet is 1.52 times as far from the Sun as Earth, resulting in just 43% of the amount of sunlight.
If Mars had an Earth-like orbit, its seasons would be similar to Earth’s because its axial tilt is similar to Earth’s. The comparatively large eccentricity of the Martian orbit has a significant effect. Mars is near perihelion when it is summer in the Southern Hemisphere and winter in the north, and near aphelion when it is winter in the Southern Hemisphere and summer in the north. As a result, the seasons in the Southern Hemisphere are more extreme and the seasons in the northern are milder than would otherwise be the case. The summer temperatures in the south can be warmer than the equivalent summer temperatures in the north by up to 30 °C (54 °F).
Mars has the largest dust storms in the Solar System, reaching speeds of over 160 km/h (100 mph). These can vary from a storm over a small area, to gigantic storms that cover the entire planet. They tend to occur when Mars is closest to the Sun, and have been shown to increase the global temperature.
Orbit and rotation
Mars orbits the Sun in an elliptical orbit with a semi-major axis of 227.94 million kilometers, covering a complete revolution in 1.88 Julian years , 686.98 days . Its orbit is tilted by 1.85 ° with respect to the ecliptic and is eccentric by a factor of 0.093.
Mars is, after Venus , the planet closest to Earth on average; naturally the Martian orbit is external to the Earth’s one, which measures on average about 150 million kilometers from the sun.
Mars’s average distance from the Sun is roughly 230 million km (143 million mi), and its orbital period is 687 (Earth) days. The solar day (or sol) on Mars is only slightly longer than an Earth day: 24 hours, 39 minutes, and 35.244 seconds. A Martian year is equal to 1.8809 Earth years, or 1 year, 320 days, and 18.2 hours.
Comparison between Mars and Earth
The mass of Mars is equal to 0.107 times that of the Earth, and its volume is equal to 0.150 times that of the Earth . The planet’s equatorial diameter is 6787 km (with a polar flattening of about 1%) and its average density is 3.95 times that of water.
The Martian rotation axis is inclined by 25° 11′ and its rotation period around its own axis is 24 h 37 min 25 s: both values are similar to the corresponding terrestrial parameters.
The conquest of Mars
Since the 1960s, around forty probes have been sent to Mars, which is to say the enthusiasm of earthlings for this small planet! This passion for Mars is partly explained by its proximity to Earth and by the fact that it has many similarities with our planet. Many scientists believe that life may have appeared on Mars one day.
The conquest of Mars is more than ever the next great adventure of human civilization. There is no doubt that soon men will set foot on the soil of the Red Planet in order to study its geology on site, and perhaps even to develop new energies there.
Perhaps one day, when the technological challenges have been met, man will be able to settle permanently on the red planet and will be able to continue his thirst for knowledge by exploring other worlds …
Before the Mariner program and the launch of the Mariner 4 probe in 1964 (United States), many believed that there could be an intelligent civilization on Mars! But the probe quickly demonstrated through its photos that we were dealing with a nearly dead planet …
In addition to the many craters it revealed, the Mariner 4 probe also shed light on the absence of a Martian magnetic field. After centuries of speculation about the possibility of any life on Mars, the Mariner 4 probe put an end to all hypothesis, except that some believe that microbial life is possible.
Little known to the public due to the date of its flight over Mars (July 1969, at the very moment when man was taking his first steps on the Moon!), This probe took 75 photos that it sent to Earth to a speed of 2 kb / s.
Sent almost at the same time as Mariner 6, this television camera-equipped probe (like Mariner 6) sent Earth 126 photos of the surface of Mars.
After the failure of several other probes, Mariner 9 became, in 1971, the first spacecraft to orbit a planet other than Earth. The technology on board Mariner 9 made it possible to send images to Earth at a resolution never before achieved. Mariner 9 discovered the largest known volcano in the Solar System, Mount Olympus, as well as the gigantic Valles Marineris canyon named after the spacecraft’s success.
The fact that Mariner 9 was put into orbit around Mars has made it possible to study its geography at length and precisely.
Since the end of its mission in 1972, Mariner 9 still revolves around Mars and is moving inexorably closer to it. The probe is expected to enter the Martian atmosphere and disintegrate in 2022!
Mars 2 and 3
The first human-made object to touch the ground of another planet, Mars 2 (USSR) had a lander that crashed on the surface of Mars due to a failure of the descent system. But before crashing, Mars 2 collected an enormous amount of data during its Martian orbit.
Mars 3 is a carbon copy of Mars 2, which landed successfully, but broke down seconds after landing.
Mars 2 and 3 reached the planet Mars in late 1971.
Arrived in 1974 in Martian orbit, Mars 5 is an orbiter which made it possible to recover a few dozen photographs of the planet and to discover the presence of an ozone belt at an altitude of about 30 km. The probe stopped emitting after just a few days, possibly due to impacts from micrometeorites.
Viking 1 and 2
The Viking program is one of the most ambitious projects carried out by NASA. Its main objective, in the continuation of the Mariner program, was to detect the presence of life on Mars. Both probes were equipped with landers, and the mission was a real success.
The result of the Viking program has made it possible to build a gigantic database on the planet Mars. The two probes were sent in 1975, by a Titan rocket. They continued to send data to Earth for several years, until 1982.
The Viking program has given mankind a global view of Mars in an unprecedented resolution of 150 to 300 meters. In addition to impressive pictures of the Martian surface and its geological formation, the probes gave images of the two satellites of Mars, Phobos and Deimos.
The Viking program is the first to take samples from Martian soil. Landers sent us 1,400 images of the planet’s surface. Viking 1 was the first man-made device to send us images from the surface of Mars. After the study of Mars, its orbit was changed to fly over Phobos, one of the two satellites of the red planet.
It was Viking 2 that was tasked with flying over Deimos and allowed us to send us incredible images of this satellite.
Viking 1’s mission lasted 6 years (it ended due to a software update that cut off communications with Earth forever), while Viking 2’s mission lasted 3.5 years (battery faulty).
The results of the analyzes of the two probes will not have detected the presence of any living organism on Mars.
The two Viking probes 1 and 2 are still in orbit around Mars today. They are expected to crash into the Red Planet around 2025!
Mars Global Surveyor
In 1996, NASA sent the MGS mission to Mars, the goal of which was to collect ever more information on the red planet: mapping the surface, studying the atmosphere and the internal structure of the planet. The mission also revealed the possibility of the existence of liquid water on its surface.
Mars Global Surveyor became the first probe to take pictures of other man-made devices orbiting the planet. Among them: Mars Odyssey (NASA) and Mars Express (ESA).
The mission, initially planned to last two years, will have lasted a total of 10 years. It ended in 2006, and was for the time the longest and most successful mission in the history of Martian exploration, providing man with an incredible body of knowledge.
In 1997, twenty years after the Viking program, NASA successfully landed a spacecraft, using a new airbag-based landing technique. The lander deployed a rover, named Sojourner, on Martian soil to analyze the surface of the Red Planet. Mars Pathfinder is the fourth spacecraft to hit Martian soil.
One of NASA’s goals with this project was to successfully send a lander while drastically reducing the cost of the mission, which cost five times less than the Viking program twenty years earlier!
The rover, tasked with analyzing the chemical properties of the soil, will send more than 500 photos of the Martian surface. The lander will send more than 16,500 photos to Earth.
Sojourner’s mission, initially scheduled to last 7 days, will operate for more than two months. The Pathfinder mission will have revealed that water once flowed on the surface of Mars, that its atmosphere was once denser, and that the climate was hot and humid, just like on Earth.
The Sojourner rover was the first robot to move on the surface of the Red Planet.
2001 March Odyssey
2001 Mars Odyssey is a probe placed in orbit around Mars in 2002. One of its mission was to detect the presence of water on Mars. The 2001 Mars Odyssey program is a success, as the orbiter revealed that there is water in the form of ice at both Martian poles. The main mission of the program ends in 2004, but the still operational probe will continue to provide important data on Mars, such as atmospheric and climatic phenomena. 2001 Mars Odyssey will also serve as a transmission relay for other programs such as the Mars Exploration Rovers. The probe will also serve as a guide for Mars Reconnaissance Orbiter.
As of this update (March 30, 2018), 2001 Mars Odyssey is still operating and continues to serve NASA. It is expected that the orbiter will continue to operate until 2025.
The Mars Express program is a project carried out by the European Space Agency (ESA). Launched in 2003, it is the first European program to explore the red planet. The purpose of Mars Express is to collect information about the subsoil of Mars, as well as its surface, atmosphere and ionosphere.
Mars Express was equipped with a lander named Beagle 2 which was to land on Mars in order to search for the presence of life. But the lander never achieved its goal, all contact being lost when it separated from the orbiter.
However, the mission was a great success, as it provided a great deal of information on the structure of Mars, including confirming that liquid water had once flowed over its surface.
As of 2014, Mars Express is still in operation. Its mission was extended until the end of 2016.
Mars Exploration Rover (MER)
Launched in 2003 by NASA, the Mars Exploration Rovers mission had one main objective: to study the geology of Mars and the traces of water that once flowed on the surface. The mission included two crawlers, Spirit and Opportunity. The landing technique used for the two rovers was the same as for the Pathfinder: the use of air cushions to cushion their fall.
The two rovers began their exploration in 2004. Initially scheduled to last around 100 days, this mission was a success that went far beyond the expectations of NASA engineers. In 2018, the Opportunity robot continues its journey, more than 14 years after its landing on Mars! The last contact took place on June 10, 2018 and NASA announced the end of its mission on February 13, 2019. As for the rover Spirit, it ceased all contact in 2010.
The MER mission is a great success: the two machines analyzed several rocks whose formation resulted from the action of water in the past.
Mars Reconnaissance Orbiter
MRO is a NASA orbiter launched in 2005 by an Atlas-V rocket (Cape Canaveral). It was put into orbit around the Red Planet in March 2006.
MRO’s mission was to map the surface of Mars. To fulfill this mission, MRO is equipped with the HIRISE telescope, allowing a resolution of 30 cm. The orbiter also serves as a communication relay for surface rovers, such as the Curiosity robot.
Since February 2018 MRO has been taken out of its security mode, in order to activate all of its functions.
Phoenix is a lander, the first to land in a polar region of the Red Planet (Vastitas Borealis, at the North Pole). Like most other missions, Phoenix is tasked with finding traces of frozen water on Mars. Arrived in May 2008 on Martian soil, the spacecraft did indeed detect ice water in July 2008, by taking samples.
Phoenix also studied the March clouds as well as the surface wind speed. His mission ended in November 2008.
Mars Science Laboratory (MSL)
On August 5, 2012, NASA teams achieved an unprecedented feat: they managed to gently land the largest and most sophisticated robot! This success is the result of ten years of research and experimentation of all kinds.
By pushing the limits of technology, scientists have won a crazy gamble: to send a full science lab to Mars. The rover named Curiosity will attempt to answer questions that have been bothering researchers for a long time: does or has there been any form of life on the red planet? In other words, are we alone in the universe?
The Curiosity robot is a technological marvel, packed with unique scientific instruments. Powered by a nuclear battery and equipped to constantly communicate with Earth, it is a perfect machine to face the hostility of the Red Planet.
What we are looking for above all on Mars are the three basic elements that allow life to emerge: water, heat and organic compounds. Curiosity must tell us if these elements have already been present on Mars, by analyzing soil and rock.
Curiosity is a true robotic geologist: he has all the necessary tools to analyze the structure and chemical composition of rock. It is equipped with several cameras, lasers which analyze the rock according to the light emitted, a drill, allowing the two integrated mini laboratories to analyze the samples taken. The first lab x-rays samples to identify minerals, while the second looks for the presence of organic molecules. Scientists are able to determine if life existed thanks to the presence of organic molecules, without needing to find fossils.
It should be understood that researchers are not trying to find a form of life, but only organic compounds, which would already be a major breakthrough for science.
Curiosity is equipped with 15 times more scientific equipment than other robots sent to Mars, and it should play a major role in improving knowledge of the Red Planet. Unlike other rather light robots, Curiosity weighs almost a ton, which is why it couldn’t be landed with airbags, the load being far too heavy and expensive.
The rover’s landing sequence required a multitude of tests and experiments (in a wind tunnel, in an airplane, in a helicopter over the Mojave Desert), to achieve an incredible technological feat.
It was Gale Crater that was chosen as the landing site for Curiosity, after 5 years of debate.
Very soon after arriving on Mars, Curiosity will provide irrefutable proof that rivers once flowed on its surface, thanks to the presence of eroded pebbles inside the rock.
On June 7, 2018, NASA announced that Curiosity had found organic molecules on the surface of Mars using SAM (Sample Analysis at Mars). Although this announcement does not prove that life once existed on Mars, it does highlight the fact that the red planet has the same compounds that made life on Earth emerge, namely methane in the atmosphere and organic molecules.
Arriving in low orbit around Mars on September 21, 2014, this NASA-led mission aims to study the reasons for the disappearance of the Martian atmosphere. This orbiter will also serve as a transmission relay for the rovers currently roaming the surface of Mars.
Mars Orbiter Mission (MOM)
Mangalyaan (“Martian ship” in Indian language) is an orbiter successfully sent around Mars by the Indian space agency. The probe was placed in orbit around the Red Planet on September 24, 2014.
The mission of the probe is to study the escape from the Martian atmosphere, but also to search for traces of water on the surface of the planet.
In addition to the technological prowess, this mission also represents an incredible financial challenge, as it cost only 75 million euros, which is a paltry sum compared to similar NASA projects.
March 2020 – Rover Perseverance
The objective of the Mars 2020 mission is to search for traces of ancient life and collect fragments of Martian rocks in order to bring them back to earth.
The rover was launched on July 30, 2020 and landed on Mars on February 18, 2021 without incident, in the Martian crater Jezero.
On February 22, 2021, NASA presented the world with a spectacular video of the rover’s landing on Mars, in high definition. We became the first humans who could watch a video of such resolution to discover another world. It’s historic!
The March 2020 mission is scheduled to last around ten years. The rover will aim to dig in Martian soil and extract samples there to disseminate them everywhere in its path. Another spacecraft is scheduled to land on the Red Planet to collect these samples and bring them back to Earth for study.
The technology embedded in the rover and its lander is unprecedented: the artificial intelligence was able to decide for itself whether the rover’s landing was done on ground free of obstacles, in order to ensure optimal security.
You can find more information about the rover on its wikipedia page. I also recommend the NASA site. Be sure to check out the video below, which shows Perseverance landing!
Astrology: The planet Mars for Aries and Scorpios
If we had to choose one word and only one to sum up the influence of Mars would be action. This planet conveys the notion of movement, of speed but also of the balance of power between beings. It is this which determines our capacity to manage the events which mark out our existence. Mars can also illustrate the sexual drive, the lover, the power of games in the alcove. The element that echoes it is Fire.
When the contribution of Mars is positive, we are talking about people animated by a certain spontaneity and brilliant by their dynamism, their ability to provoke events.
When the contribution of Mars is negative, one underlines a side milk soup, an aggressive and susceptible character. It is also the expression of obvious violence.
We understand then that Mars is the predominant planet among the Aries, beings known and recognized for their energy, their ability to play the leader of men but also for their angry character and their exacerbated libido! People of the Scorpio sign are also affected, especially when it comes to aggressiveness and dynamism.
Sources: PinterPandai, NASA Science, Space Facts, The Planets
Photo credit: Wikimedia Commons, The European Space Agency
Photo explanations: True color image of Mars taken by the OSIRIS instrument on the ESA Rosetta spacecraft during its February 2007 flyby of the planet. The image was generated using the OSIRIS orange (red), green, and blue filters.
Alternative description: The first true-colour image generated using the OSIRIS orange (red), green and blue colour filters. The image was acquired on 24 February 2007 at 19:28 CET from a distance of about 240 000 km; image resolution is about 5 km/pixel.