(redirected from Planet Mars)
Also found in: Dictionary, Thesaurus, Medical.


in astronomy, 4th planet from the sun, with an orbit next in order beyond that of the earth.

Physical Characteristics

Mars has a striking red appearance, and in its most favorable position for viewing, when it is opposite the sun, it is twice as bright as Sirius, the brightest star. Mars has a diameter of 4,200 mi (6,800 km), just over half the diameter of the earth, and its mass is only 11% of the earth's mass. The planet has a very thin atmosphere consisting mainly of carbon dioxide (95%) with some nitrogen, argon, oxygen, and other gases. Mars has an extreme day-to-night temperature range, resulting from its thin atmosphere, from about 80°F; (27°C;) at noon to about −100°F; (−73°C;) at midnight; however, the high daytime temperatures are confined to less than 3 ft (1 m) above the surface.

Surface Features

A network of linelike markings first studied in detail (1877) by G. V. Schiaparelli was referred to by him as canali, the Italian word meaning "channels" or "grooves." Percival Lowell, then a leading authority on Mars, created a long-lasting controversy by accepting these "canals" to be the work of intelligent beings. Under the best viewing conditions, however, these features are seen to be smaller, unconnected features. The greater part of the surface area of Mars appears to be a vast desert, dull red or orange in color. This color may be due to various oxides in the surface composition, particularly those of iron. About one fourth to one third of the surface is composed of darker areas whose nature is still uncertain. Shortly after its perihelion Mars has planetwide dust storms that can obscure all its surface details.

Photographs sent back by the Mariner 4 space probe show the surface of Mars to be pitted with a number of large craters, much like the surface of Earth's moon. In 1971 the Mariner 9 space probe discovered a huge canyon, Valles Marineris. Completely dwarfing the Grand Canyon in Arizona, this canyon stretches for 2,500 mi (4,000 km) and at some places is 125 mi (200 km) across and 2 mi (3 km) deep. Mars also has numerous enormous volcanoes—including Olympus Mons (c.370 mi/600 km in diameter and 16 mi/26 km tall), the largest in the solar system—and lava plains. In 1976 the Viking spacecraft landed on Mars and studied sites at Chryse and Utopia. They recorded a desert environment with a reddish surface and a reddish atmosphere. Experiments analyzed soil samples for evidence of microorganisms or other forms of life; none was found, but a reinterpretation (2010) of the results in light of data collected later suggests that organic compounds may have been present. In 1997, Mars Pathfinder landed on Mars and sent a small rover, Sojourner, to take soil samples and pictures. Among the data returned were more than 16,000 images from the lander and 550 images from the rover, as well as more than 15 chemical analyses of rocks and extensive data on winds and other weather factors. Mars Global Surveyor, which also reached Mars in 1997 and remained operational until 2006, returned images produced by its systematic mapping of the surface. The European Space Agency's Mars Express space probe went into orbit around Mars in late 2003 and sent the Beagle 2 lander to the surface, but contact was not established with the lander. In addition to studying Mars itself, the orbiter has also studied Mars's moons. The American rovers Spirit and Opportunity landed successfully in early 2004 and have explored the Martian landscape (Spirit's last transmission was in 2010). In 2008 NASA's Phoenix lander touched down in the planet's north polar region; it conducted studies for five months. Curiosity, another NASA rover, landed on Mars near its equator in 2012.

Analysis of space probes' data indicates that Mars appears to lack active plate tectonicsplate tectonics,
theory that unifies many of the features and characteristics of continental drift and seafloor spreading into a coherent model and has revolutionized geologists' understanding of continents, ocean basins, mountains, and earth history.
..... Click the link for more information.
 at present; there is no evidence of recent lateral motion of the surface. With no plate motion, hot spots under the crust stay in a fixed position relative to the surface; this, along with the lower surface gravity, may be the explanation for the giant volcanoes. However, there is no evidence of current volcanic activity.

There is evidence of erosion caused by floods and small river systems as well as evidence of ancient lakebeds. The possible identification of rounded pebbles and cobbles on the ground, and sockets and pebbles in some rocks, suggests conglomerates that formed in running water during a warmer past some 2–4 billion years ago, when liquid water was stable and there was water on the surface, possibly even large lakes or an ocean. Rovers have identified minerals and rocks believed to have formed in the presence of liquid water. There is also evidence of flooding that occurred less than several million years ago, most likely as the result of the release of water from aquifers deep underground or the melting of ice. However, a study of ancient Martian impact craters suggests that the atmospheric pressure on early Mars was consistent with a thin atmosphere, and that the warm conditions required for liquid water may have been rare or intermittent. Data received beginning in 2002 from the Mars Odyssey space probe suggests that there is water in sand dunes found in the northern hemisphere, and the Mars Reconnaissance Orbiter, which went into orbit around the planet in 2006, collected radar data that indicates the presence of large subsurface ice deposits in the mid-northern latitudes of Mars. Most of the known water on Mars, however, lies in a frozen layer under the planet's large polar ice caps, which themselves consist of water ice and dry ice (frozen carbon dioxide); the lander Phoenix found and observed frozen water beneath the soil surface in the north polar region in 2008.

Seasonal Changes

Because the axis of rotation is tilted about 25° to the plane of revolution, Mars experiences seasons somewhat similar to those of the earth. One of the most apparent seasonal changes is the growing or shrinking of white areas near the poles known as polar caps. These polar caps, which are are composed of water ice and dry ice (frozen carbon dioxide). During the Martian summer the polar cap in that hemisphere shrinks and the dark regions grow darker; in winter the polar cap grows again and the dark regions become paler. The seasonal portion of the ice cap is dry ice. When the ice cap is seasonally warmed, geyserlike jets of carbon dioxide gas mixed with dust and sand erupt from the ice.

Astronomical Characteristics

The mean distance of Mars from the sun is about 141 million mi (228 million km); its period of revolution is about 687 days, almost twice that of the earth. At those times when the sun, earth, and Mars are aligned (i.e., in opposition) and Mars is at its closest point to the sun (perihelion), its distance from the earth is about 35 million mi (56 million km); this occurs every 15 to 17 years. At oppositions when Mars is at its greatest distance from the sun (aphelion) it is about 63 million mi (101 million km) from the earth. It rotates on its axis with a period of about 24 hr 37 min, a little more than one earth day.

Satellites of Mars

Mars has two natural satellites, discovered by Asaph Hall in 1877. The innermost of these, Phobos, is about 7 mi (11 km) in diameter and orbits the planet with a period far less than Mars's period of rotation (7 hr 39 min), causing it to rise in the west and set in the east. The outer satellite, Deimos, is about 4 mi (6 km) in diameter.


See J. K. Beatty and A. Chaikin, ed., The New Solar System (3d ed. 1991); F. W. Taylor, The Scientific Exploration of Mars (2010); W. J. Clancey, Working On Mars: Voyages of Scientific Discovery with the Mars Exploration Rovers (2012).


in Roman religion and mythology, god of war. In early Roman times he was a god of agriculture, but in later religion (when he was identified with the Greek AresAres
, in Greek religion and mythology, Olympian god of war. He is usually said to be the son of Zeus and Hera; but in some legends he and Eris, his twin sister, were born when Hera touched a flower.
..... Click the link for more information.
) he was primarily associated with war. Mars was the father of Romulus, the founder of the Roman nation, and, next to Jupiter, he enjoyed the highest position in Roman religion. The Salii, his priests, honored him by dancing in full armor in the Campus Martius, the site of his altar. Chariot races and the sacrifice of animals were primary features of the festivals held in his honor in March (named for him) and October. Mars was represented as an armed warrior. His attributes include the spear and shield, and the wolf and woodpecker were sacred to him. He was frequently associated with Bellona, the Roman goddess of war.


(marz) The fourth planet in the Solar System in outward succession from the Sun. It orbits the Sun every 686.98 days at a distance that varies between 1.38 and 1.67 AU. Its reddish 6795-km-diameter disk is most favorably placed for observation during oppositions that coincide with the time when it is near its perihelion (see Mars, oppositions). Mars rotates in 24h 37m 22.67s. A single rotation is called a sol. The planet's axis is tilted by 25.19° to its orbital plane. The rotation rate and axial tilt help to make the Red Planet the most earthlike of all the other planets, even though it has only 28% of the Earth's surface area and less than 38% of its gravity. Mars has two small natural satellites: Phobos and Deimos. Orbital and physical characteristics are given in Table 1, backmatter.

Telescopes reveal an orange-red surface with indistinct darker markings, once thought to be seas and named maria. White polar caps expand and contract with the Martian seasons. When it became apparent that the maria also varied in intensity and shape with the seasons, it was suggested that they were areas of lichenlike vegetation that flourished when water became available from the poles during each Martian spring. Canals, charted by some observers, were postulated as an artificial planet-wide water distribution network. Observations by Mariner spacecraft showed that the canals were a myth and revealed the maria as areas of darker bedrock on which the Martian winds deposit varying amounts of lighter-colored dust, so changing their appearance. North of the Martian equator, lowlands of volcanic origin predominate and impact craters are relatively few. In the southern hemisphere, heavily cratered highlands overlying a thick but weak crust form the chief terrain. Hellas Planitia, a deep impact basin in the southern hemisphere, is the largest such feature so far known in the Solar System, while Olympus Mons, in the northern hemisphere, is the Solar System's largest volcano. For details of Martian topography see Mars, polar caps; Mars, surface features; Mars, volcanoes.

The Martian atmosphere has a surface pressure of about 7 millibars, or 0.007 times the average pressure at the Earth's surface, and extends to include an ionosphere at altitudes between 100 and 300 km. Daytime surface temperatures rarely climb above 0 °C (273 K) except during summer in the southern hemisphere, when they can rise to 20 °C (293 K). Most areas experience minimum temperatures as low as –140 °C (133 K) before sunrise each morning. NASA's Mars Global Surveyor, launched in 1996, confirmed that Mars' weather is driven by convection currents in the atmosphere that cause warm gases to rise from the summer hemisphere and descend upon the winter hemisphere.

Tests by the Viking spacecraft, which landed in 1976, show an atmosphere comprising mainly carbon dioxide (95%), with nitrogen (2.7%), argon (1.6%), oxygen (0.15%), a variable trace of water vapor, and traces of carbon monoxide, krypton, and xenon. The water vapor sometimes freezes to form clouds of ice crystals, especially above high topographic features such as the volcanoes, or condenses as fog in low-lying areas, such as Hellas Planitia and the Valles Marineris. The rich variety of clouds systems – leewaves, cirrus, orographically produced clouds – are a major part of the planet's meteorology. More extensive surface obscurations occur during dust storms, which can engulf the entire planet. Such events happened in 1971 at the beginning of the Mariner 9 mission and in 1977 during the Viking mission. These global phenomena, which can occur both just before and just after perihelion when summer occurs in the southern hemisphere, will distribute material to altitudes of more than 40 km and last for several months. However, global storms do not seem to appear every Martian year.

Mars has no radiation belts and only a weak magnetic field, at most 0.2% as strong as the Earth's; this suggests that it lacks a molten nickel-iron core and may have no iron core at all. The surface rocks, however, appear to be rich in iron, resembling the minerals hematite and magnetite and lending the planet its red coloration. NASA's Mars Pathfinder mission of 1997 also discovered that Martian dust contains magnetic composite particles. See also Viking probes.

Enlarge picture
An illustration of the Roman god Mars in his chariot from the 1494 edition of Astrolabum Planum. Reproduced by permission of Fortean Picture Library.


(religion, spiritualism, and occult)

Mars, named after the Roman god of war, is one of Earth’s closest neighbors, the next planet from the Sun after the Earth. Because Mars is farther from the Sun than the Earth, it can appear anywhere on the ecliptic, rather than staying close to the Sun, as Mercury and Venus appear to stay when viewed from the Earth. When Mars is at its closest point to the Earth, it is a mere 35 million miles from away and appears as bright as Sirius—the brightest star in the sky. At its farthest point from Earth, the eccentric orbit of Mars may place it approximately 250 million miles away. Mars’s orbital period is 686.98 days which is somewhat less than 2 terrestrial years.

In 1726, Jonathan Swift wrote in Gulliver’s Travels of the discovery of two Martian moons. This occurred 150 years before Asaph Hall actually discovered the two moons that were named Deimos (terror) and Phobos (fear) after Mars’s sons. This seems appropriate since Mars is often associated with impulsive or precipitous actions. In traditional astrology, Mars rules over the signs of Aries and Scorpio and is exalted (a place of special import) in the sign of Capricorn. In Hellenistic astrology, it is considered to be of a nocturnal sect, that is, it operates at its best in charts of night births.

In the Mesopotamian astral religion, Mars was associated with Nergal, the god of the underworld. Nergal was also the god of the noonday Sun and said to spread plagues, pestilence, forest fires, fevers, and wars. Robert Powell thinks the Babylonians connected the planet’s eccentric movements along the ecliptic—often said to reach 6° of south latitude—with the gods’ negative associations. Mars was thus known as “he who is constantly wandering about,” “the angry fire god,” or “the god of war.” According to Nick Campion, Mars’s malefic qualities were thought to be heightened when it was bright (and therefore closest to the earth), diminished when it was faint, and when at its reddest could signify prosperity but also epidemics. The Babylonian legend of Irra speaks of the gods’ attempt to overthrow Marduk, the patron god of the Babylonians. In it, Irra lures the god of good (Marduk) into the underworld and seizes the reigns of power on Earth. As the new ruler of humans, the god perverts their minds and gets them to war against each other so that he may attain his goal to destroy and annihilate Earth. When Marduk returns from the underworld, he finds his worshippers slain and his cities in ruins. In his book History of the Planets, Powell said:

The poem ends with an exhortation to mankind to appease the evil god by allotting a place in their cult to his service, so that he may spare them from another catastrophe like the one described. The subject matter of the legend as well as its treatment implies that, in his quality as a planet, the patron god was unable to protect the community of his worshippers during his periods of absences from the nocturnal sky.

Thus, the Babylonians recognized the need to tame the dangerous, warlike qualities of life by including the god into the sphere of human affairs. This may be looked at as a psychological metaphor for the pacification of man’s wrathful and destructive side through its integration into the psyche.

In another story, Nergal stormed into the land of the dead, deposed Ereshkigal, the queen of the underworld, and set himself up as ruler. A variation of the story has him having a passionate affair with her and ruling the underworld alongside her. This second version mirrors the story of Hades and Persephone, king and queen of the netherworld in Greek mythology. Both of these stories therefore connect the planet Mars with rulership over the underworld, a role that was given to Pluto (Hades) by modern astrologers since the planet bore the name of the Roman god of the underworld. Until modern times, when astrologers assigned the rulership of the sign Scorpio to the planet Pluto, Mars had ruled both Aries and Scorpio. Aries, the first sign of the Zodiac and marker of the spring equinox (the month of March is named after Mars), connects the planet to initiations, births, pioneering situations, initiative, impulsiveness, precipitous behaviors, uniqueness, aggression, and survival instincts. This rulership appears to connect better with the solar qualities of Mars and appropriately, the Sun is said to be exalted in Aries. Scorpio, appears to connect to the underworld qualities of Mars and its association with death, sexuality, diseases, adulteries, prostitution, losses, banishments, murders, and bloodshed.

The sexual impulse often connected to Mars also has its roots in his Greek heritage. In the classical Olympian Pantheon, Mars was known as Ares, the god of war. He was the son of Zeus and Hera who allegedly lived in Thracia, a region known for its fierce people. As a warrior god, Mars is often contrasted with his sister Athene, goddess of war and wisdom, who fought and vanquished him in a battle between the gods. Unlike Athene, Ares embodied the more unrefined, evil, and brutish aspects of warfare—prompting Zeus to call him “the most hateful of the gods.” Only Aphrodite, the goddess of beauty, could tame the wild Ares through her ability to incite his passions. After one of their illicit affairs—as Aphrodite was married to his brother Hephaestus—Ares was forced by Zeus to endure public humiliation for his adultery. Through Ares’s union with the goddess of love, a child named Harmonia (harmony) was produced. Ares also gave birth to two sons, Deimos and Phobos, who gave their names to Mars’s two moons and were said to pull his war chariot.

In Hindu mythology Ares is called Mangala, a personification of the planet Mars. He is often depicted with a chariot being pulled by eight fire-red horses. According to some authors, Mangala is a form of the cruel side of Shiva. In one Hindu myth, the gods were being terrorized by a demon who could only be slain by a “seven-day-old son of Shiva.” The gods thus created the illusion of a beautifully enticing woman who so moved Shiva sexually, that the great ascetic god ejaculated at the sight of her. His sperm fell into the ocean, which, nourished by the Pleiades (the seven sisters), gave birth to Karttikeya—the god of war who, born out of the necessity, killed the demon.

Although the original Roman Mars may have originated as a vegetation god, he became closely modeled on the Greek god of war. However, among the Romans who valued military prowess, Mars quickly rose to the ranks of most popular deity and patron for all soldiers. He is depicted by the Romans wearing a suit of armor, a plumed helmet, and carrying a shield and spear. In the Roman myths, aside from Mars’s affairs with Venus, he is also linked with a vestal virgin Rhea Silvia, who is buried alive for violating the laws of her sisterhood. From this union are born Mars’s twin sons, Romulus and Remus, who become the founders of Rome. It became the custom in Rome that generals, before heading out to combat (typically in March when campaigns were started), would invoke the god in his sanctuary.

The myths thus explain the planetary gods’ associations with many of the significations listed in The Anthology of Vettius Valens:

The star of Ares signifies violence, wars, rapine, screams, insolence, adulteries, taking away of belongings, losses, banishment, estrangement of parents, captivities, ruination of women, abortion, sexual intercourse, weddings, taking away of good things, lies, situations void of hope, violent thefts, piracy, plunderings, breaches of friends, anger, combat, reproaches, enemies, lawsuits. It introduces violent murders and cuts and bloodshed, attacks of fever, ulcerations, pustules, inflammations, imprisonment, tortures, manliness, perjury, wandering, excelling at villainy, those who gain their ends through fire or iron, handicraftsman, workers in hard materials. It makes leaders and military campaigns and generals, warriors, supremacy, the hunt, the chase, falls from heights or from quadrupeds, weak vision, apoplexy. Of the parts of the body, it is lord of the head, rump, genitals; of the inner parts, it is lord of the blood, spermatic ducts, bile, excretion of feces, the hind-parts, walking backward, falling on one’s back; it also has that which is hard and severe. It is lord of the essence iron and order, clothes because of Aries, and wine and pulse. It is of the nocturnal sect, red with respect to color, pungent with respect to taste.

Robert Schmidt has extracted from all of the planetary significations a primary principle representing the basic nature of each of the planets. He says Mars represents the principle of separation and severance in a birth chart. Thus Mars’s association with impulsiveness or pioneering tendencies are derived from the planet’s desire to separate from others; the same may be said of competitive behaviors as one might find in sports, for example. The severing principle is also fundamental in Mars’s use of sharp cutting objects and why he is perhaps associated with weaponry and armor, which cuts one off from one’s enemy.

Modern astrology, with its emphasis on inner psychological dynamics, focuses more on Mars’s correlation with the impulse to act and react. Psychological astrologers point to the planet’s representation of one’s need to assert, to initiate, to vitalize, to act, to do, to endeavor, to survive. Behaviors characterized as aggressive, self-assertive, enterprising, independent, combative, ambitious, etc., are derived from these basic inner drives. When other factors in the chart point in this direction, these behaviors often make use of Mars-ruled situations or objects such as: new births, enterprises or projects, competitions, accidents, permanent departures and exiles, divorce, mechanical work, fights, operations, sexual acts, etc.

Some of the most conclusive (although not without its detractors) statistical work involving the confirmation of astronomical correlations with human affairs have centered on the planet Mars. In the 1950s French statistician and psychologist Michel Gauquelin began his studies that attempted to demonstrate—under the rules laid down by science—that the planets could be significantly (statistically) correlated with certain professions. While the results showed a statistical correlation between eleven professions and five planets, the statistical effect shown by Mars in the charts of sports champions was by far the greatest. This has been coined the Gauquelin Mars effect in the astrological literature and has yet to be refuted—although many have tried. Gauquelin’s work also showed that the positions of the planets just past culminating and just past rising had the greatest strength in producing the professional patterns demonstrated.


Campion, Nick. Cosmos: A Cultural History of Astrology. London: London Books, 2001.
DeFouw, Hart, and Robert Svoboda. Light on Life. New York: Arkana Penguin Books, 1996.
Gauquelin, Michel. Cosmic Influences on Human Behavior. Santa Fe, NM: Aurora Press, 1994.
Guttman, Ariel, and Kenneth Johnson. Mythic Astrology. St. Paul, MN: Llewellyn Publications, 1998.
Holden, James Herschel. A History of Horoscopic Astrology. Tempe, AZ: American Federation of Astrologers, 1996.
Perry, Glenn. Mapping the Landscape of the Soul. San Rafael, CA: Association of Astrological Psychology, 2001.
Powell, Robert. History of the Planets. San Diego: ACS Publications, 1985.
Schmidt, Robert. Original Source Texts and Auxiliary Materials for the Study of Hellenistic Astrology. Cumberland, MD: Phaser Foundation, 2002.
Wilson, James. A Complete Dictionary of Astrology. London: W. Hughes, 1819. Reprint, New York, S. Weiser, 1969.

—Maria J. Mateus



the planet of the solar system fourth in distance from the sun; astronomical symbol, Ó.

General information. Mars belongs to the terrestrial group of planets; it has comparatively small mass and dimensions and quite high average density. It revolves around the sun in an elliptical orbit at an average distance of 1.524 AU (228 million km). Owing to considerable eccentricity (e = 0.093), this distance varies between 206 million km, at perihelion, and 249 million km, at aphelion. The inclination of the orbit of Mars to the plane of the ecliptic is 1.8°. The planet’s mean orbital velocity is 24.2 km/sec, and the period of revolution around the sun (sidereal period) is 1.881 years (687 days). Mars, the sun, and the earth align in a straight line once every 780 days (synodic period). The time elapsing between successive oppositions of Mars, when the planet as seen from the earth is opposite the sun, is also 780 days. At this time, Mars is particularly suitable for observation. The disk that is visible in the sky has an average diameter of 18” at this time.

Figure 1. Oppositions of Mars. (P) Perihelion of orbit of Mars; favorable oppositions —1971, 1986, 1988.

Mars approaches closest to the earth—a distance of 56 million km—when opposition occurs near the perihelion of the orbit of Mars. At this time, Mars is seen at an angle of 24“-25” and details measuring 60-100 km are visible through a telescope. Such oppositions, which are called most favorable oppositions, occur once every 15 to 17 years in August (the oppositions that occur in July and September are often also called favorable). The last favorable opposition of Mars was in 1971, and future ones, which will be less suitable for observations, will be in 1986 and 1988 (see Figure 1). When opposition occurs near aphelion, Mars is about 100 million km from the earth. Mars appears as a round disk at oppositions and at upper conjunctions with the sun, when it is behind the sun and almost 400 million km from the earth. At other times the sun does not illuminate the entire disk of Mars visible from the earth, and the disk exhibits a partial (or gibbous) phase. Mars exhibits the gibbous phase, like the moon, three or four days before its full phase, at maximum phase angle (the angle between the directions from the planet to the sun and to the earth). This angle is 47°.

The (average) linear diameter of Mars is 6,800 km, that is, slightly more than half (0.53) that of the earth. The polar diameter is 1/190 less than the equatorial radius. This is the magnitude of flattening of the planet’s figure obtained from dynamic calculations based on the motion of the satellites of Mars. Direct measurements of the angular diameters of Mars along and perpendicular to the equator produce a much greater flattening value (1/125), but such measurements are not very reliable. The volume of Mars is 0.15 that of the earth. The mass of Mars is 6.423 × 1023 kg (0.107 that of the earth). The average density of the planet is 3.97 g/cm3. The gravitational acceleration at the planet’s surface is 3.72 m/sec2, or 0.38 that of the earth. The escape velocity (a body thrust at this velocity will overcome the force of gravity and escape the planet) near the surface of Mars is 5.0 km/sec.

The permanent surface details of Mars (the bright and dark spots) make it easy to observe the planet’s rotation about its axis. The period of rotation (the sidereal day) is 24 hr 37 min 22.7 sec in earth units of time (solar). The direction of the northern end of the axis of rotation has the following coordinates (1950.0): right ascension a = 317.32° and declination δ = +52.68° (in the constellation Cygnus, near the border with the constellation Cepheus). The equatorial plane corresponding to this is inclined 25.2° to the orbital plane of Mars, that is, almost as much as the earth’s equatorial plane is inclined to the earth’s orbital plane (ecliptic). For this reason, Mars has changes of seasons and climatic zones (polar, temperate, and tropical) just like the earth. However, the length of each season on Mars is 1.9 times longer than that on the earth.

The values for the rotation period, the mass, the linear diameter, and the dynamic flattening of Mars obtained from observations enable us to make a model of the internal structure of the planet. It is probable that Mars has a small iron core with a density of about 9.5 g/cm3, in which 1-8 percent of the mass of the planet is concentrated; the radius of the core constitutes 15-33 percent of the radius of Mars.

History of the study of Mars. Man has known Mars as a planet since antiquity. During favorable oppositions Mars appears to be the brightest object in the midnight sky (— 2.7 stellar magnitude) and has an orange-red color, which led people to believe it to be an attribute of the god of war (Ares in ancient Greek mythology and Mars in ancient Roman mythology). The laws of planetary motion were established in the early 17th century on the basis of observations of Mars made by Tycho Brahe and J. Kepler. The physical properties of Mars were first studied in the midnth century, when telescopes were built powerful enough to discern individual details on the planet, including the polar caps (C. Huygens saw them in 1656, but they were not identified until later) and the dark “seas” (maria) against the bright background of the “land.” Observation of these details led to the first estimation of the rotation period by G. Cassini (24 hr 40 min).

Intensive investigation of Mars was undertaken in the mid-19th century, particularly after the exceptionally close opposition of Mars of 1877, when G. Schiaparelli, observing the planet, discovered a large number of new markings on its surface, in particular, numerous dark, straight formations that he arbitrarily called “canals.” Opinion was divided on the nature of the canals. Many scientists doubted that they were real and considered them a psychophysiological illusion that resulted when viewing extremely small details on the planet’s disk. However, at the end of the 19th century and beginning of the 20th, P. Lowell ascribed a literal meaning to Schiaparelli’s “canals.” On this basis and as a result of evaluating the physical conditions on the planet, Lowell expressed and persistently propagandized the idea that Mars was populated by intelligent beings. The subsequent study of Mars by astrophysical methods, in which the Soviet scientists G. A. Tikhov, N. P. Barabashov, V. G. Fesenkov, and V. V. Sharonov played an outstanding role, resulted in a clearer idea of the physical conditions on Mars. Photographs of the planet failed to confirm that it had canals.

A new and very fruitful stage in the study of Mars was reached with the beginning of the space age and the launching of space probes toward Mars: the American Mariner series—Mariner 4 (1964), Mariner 6 and Mariner 7 (1969), and Mariner 9 (1971) —and the Soviet Mars series—Mars 2 and Mars 3 (1971). By means of these space probes, the last three of which have become artificial satellites of Mars, the planet was investigated from close range so that the objects of study were not details measuring 60-100 km, as before, but those much smaller than 1 km. The descent capsule of the Soviet Mars 3 probe was the first to soft-land on the planet.

Surface features. On the planet’s surface, dark (gray with a light bluish or red-brown tint) spots stand out against a background of vast red-orange areas. On a purely conventional basis, the former are called maria (seas), and the latter, deserts. Photometric observations of Mars at different phase angles produce an albedo of 0.16 in the visible region of the spectrum and 0.26 in the infrared region, which indicate that there is a significant decrease in the reflectivity of the planet’s surface with shorter waves. The reddish soil of the earth’s deserts has similar characteristics. The laws of reflection and of the polarization of reflected light for the deserts on Mars and for powdery limonite (a mineral with a chemical composition of Fe2O3 + n H2O) have much in common. The maria have a lower albedo than the deserts, especially at long wavelengths, and thus their color seems to be a greenish dark blue. But the contrast between the maria and the deserts diminishes to almost nothing for shorter wavelengths in the near-ultraviolet region of the spectrum; to a large extent this is owing to the dispersion of light in the Martian atmosphere.

The most noticeable features on the planet are the two polar caps. These are white spots whose size varies through the course of the Martian year, growing during the cold season and receding (almost vanishing) during the warm season. At the same time, the dark maria on Mars basically preserve their outlines, experiencing only slight short-term changes. These are both seasonal and from opposition to opposition. This makes it possible to draw maps of the surface with an accuracy of detail to P-2°. Such maps are compiled on the basis of drawings and photographs of Mars gathered from international centers.

The names of the bright and dark areas on Mars were primarily suggested by Schiaparelli and the French astronomer E. Antoniadi, both of whom made extensive use of the mythological figures and geographical concepts of antiquity, as well as of some modern terms. Thus, the prime (zero) meridian in the system of coordinates on Mars—the areographic system of coordinates—passes through the Sinus Meridiani. Adjoining the Sinus Meridiani and running along the parallel is the Sinus Sabaeus (ancient name of Arabia), and below it is the bright Deucalionis Regio (in mythology Deucalion was the son of Prometheus and the husband of Pyrrha, after whom the region Pyrrhae Regio has been named). Near the north pole is Utopia. The planet’s most notable dark detail is the Syrtis Major (named by analogy with the gulf near Libya). Far to the south of it are the circular bright regions Hellas and Ausonia (the poetic name of Italy). Further to the east is the dark Mare Cimmerium (the ancient name of the Black Sea).

The flyby of Mars by American Mariner spacecraft, which photographed the planet from distant range and very close range, contributed much data on the planet’s morphology. Many circular mountains, or craters, similar to those on the moon, were discovered. The craters proved to be the dominant landscape formation on Mars, and their numbers do not depend on the distance from the Martian equator or on elevations above mean level. They appear both on deserts and on the maria. There are two types: small bowl-shaped craters (10-15 km in diameter) and large flat-bottomed craters (from 15 km to several hundred km in diameter). The latter appear more worn away than the small ones (or the lunar ones of the same size).

Three types of terrain had been identified in the section of the Martian landscape that had been investigated from close range by 1972: cratered terrain; featureless terrain, that is, without craters (such as Hellas) ; and chaotic terrain (for example, Pyrrhae Regio), where there are few craters but the surface is covered by formations indicating displacements and cave-ins, that is, tectonic movements. There are vast plateaus, which are highly elevated above the planet’s mean level but have no major or sharp irregularities (in particular, mountain ridges). The huge Coprates canyon measures more than 5 km deep, about 500 km long, and approximately 120 km wide. The “gullies” that branch out from it are evidently the result of wind and water erosion. The Nix Olympica area is a vast circular volcanic region whose outer ring, with a diameter of about 500 km, rises 6 km above the surrounding landscape. Mars is geologically active; signs of recent volcanic activity, crustal movements, and glacial and wind erosion have been observed on the planet. Investigation of Mars from close range has not continued long enough to reveal volcanic activity. But around those craters (calderas) whose volcanic origin is authentic there are very few craters of meteoritic origin, which confirms the recent birth of the volcanoes.

The increased accuracy and resolution of radar determinations of distance have made it possible to ascertain the relief of the Martian surface along several parallels near the equator. It has been established that the range of elevations on Mars is considerable, at least 13 km; this is the difference in elevation between the two bright areas Tharsis and Amazonis. The dark area of Syrtis Major is 6 km higher than Amazonis; that is, it is at the mean level. Similar measurements have been made with infrared spectrometers mounted on Mariners 6, 7, and 9. During the flight of the Mariners above various areas of Mars, the spectrometer recorded the intensity of the band of carbon dioxide (CO2) absorption in the Martian atmosphere. Because the intensity of this zone is greater where the surface of the planet underlying the atmosphere is deeper, such measurements have made it possible to ascertain the topographic relief of Mars. The lowest area proved to be Hellas, an enormous circular, bowl-shaped depression about 1,700 km in diameter lying 5.5 km lower than the adjoining Hellespontus; the sloping transition between them has the form of distinct scarps. A similar experiment, conducted from the earth along the longitudes from 240° to 160° (through 0°) in the zone of areographic latitude from —20° to +40°, established the existence of two broad crests extending at an angle to the meridian from north to south and separated by a distance of 180°. The Coprates canyon mentioned above is located in the central part of an enormous fracture that stretches along the parallel for more than 80° of longitude, that is, more than 4,000 km. The largest-scale photographs of Mars reveal a variety of landscape formations, some of which bear a striking resemblance to those on the earth: morainal ridges, sand dunes, and even thermokarst, which forms as a result of thawing permafrost. There is nothing resembling straight canals. However, strongly meandering canals with tributaries, resembling the channels of former rivers, have been found. They are recent formations since they do not show signs of meteoritic or wind erosion.

The microrelief of Mars resembles that of the moon; the finegrained structure of the Martian surface manifests itself in specific polarization characteristics and in the opposition effect, which consists in the fact that the total brightness of Mars increases rapidly by 20-30 percent for phase angles less than 6°. A possible explanation of this effect is that shadows disappear when the surface is viewed in approximately the direction from which the illumination comes.

The surface is very irregular near the southern polar cap of Mars. Here there are numerous craters, which along with other formations become more distinct as the cap recedes. The same factor also explains the extremely irregular outlines of the southern polar cap itself. In mid-winter it reaches maximum size, stretching to latitude —57°; with the arrival of summer, it diminishes. The remnants of the cap are not over the actual pole but at the point with the coordinates (330°, —84°), which is probably related to the higher elevation of this point. The Mountains of Mitchel (275°, —73°) are almost never without snow. Judging by the small number of small craters in the vicinity of the southern polar cap and by the smoothness of certain details, it may be assumed that in the comparatively recent past these areas were subjected to the smoothing action of glaciers. In this area, U-shaped valleys, which are typical of glacial formations, have been discovered. Only twice since the mid-19th century— in 1894 and in 1911—has the southern polar cap vanished completely. The northern polar cap has never been known to vanish completely. Possibly this is because the summer in the northern hemisphere occurs at aphelic opposition—when the heat from the sun is least. Moreover, these periods are the least favorable for observation. As a result of the precession of the axis of rotation of Mars, this situation changes periodically, every several dozen millennia, and in 20,000-30,000 years the southern hemisphere will become colder. The same thing has probably occurred in the past, and it is then that the glacial formations now observed on Mars could have formed.

Atmosphere. The presence of an atmosphere on Mars has been indicated by the darkening of its disk observed at the limb, by the slow fading of stars that are occulted by the planet, and by the obscuring of surface details toward the edge of the disk. A light haze is observed above the limb, as well as high, tenuous dispersed clouds and dust storms. Large areas of the planet cannot be seen during the dust storms, sometimes for long periods. Such a dust storm, which concealed virtually all the details of the Martian surface for two months, occurred soon after the favorable opposition of 1971.

According to spectral observations, the Martian atmosphere contains from 50 to almost 100 percent carbon dioxide (CO2) and traces of water vapor and carbon monoxide (CO). It follows theoretically that the atmosphere has 0.5-5 percent nitrogen (N2) and approximately the same amount of argon (Ar). At altitudes of more than 1,000 km, the Martian atmosphere consists primarily of extremely rarefied atomic hydrogen (about 104 atoms per cm3). No oxygen (02) has been found on Mars by spectroscopic means, and it has only been possible to establish an upper limit for it: 0.3 percent in relation to CO2. Mars has an ionosphere of several layers. The greatest electron density Nee = 1.5 × 104 cm-3 in the ionosphere is at an altitude of about 130 km. Photometric observations of Mars have led to exaggerated values for the thickness of the planet’s atmosphere because the dispersion of the light of the aerosol components of the Martian atmosphere (approximately five times greater than the dispersion of the gas component) in such analyses was erroneously ascribed to gas. Spectral observations of the molecular zones of CO2 in the infrared region and the weakening of radio signals from Mariners 4, 6, and 7 while occulted by Mars let to a value for total surface pressure equal to 6.5 ± 2.0 millibars (mb), which is 160 times less than the pressure on the earth’s surface. Spectral observations made from the probe Mars 3 gave a similar result. In the low-lying areas (for example, Amazonis) the pressure rises to 12 mb, while in elevated areas it drops to 1-2 mb.

The amount of water vapor in the Martian atmosphere corresponds to 10-60 μm of precipitated water.

Temperature. Measurements of the thermal radiation emitted by Mars in the microwave (1 mm-21 cm) region of the spectrum give an average surface temperature of 220° ± 10°K at an average distance from the sun. At perihelion it is 10 percent higher, and at aphelion it is 10 percent lower. The solar constant on Mars is 59 mW/cm2. The infrared radiometric method enables us to measure the surface temperature of Mars at various points: at the equator just after noon the temperature reaches 300°K and at sunset drops rapidly to 220°K. During the night it drops by 50°K more, so that before sunrise it is 174°K (-100°C). At latitude 45° the corresponding temperatures are 282°, 200°, and 160°K. At the polar caps the temperature rises to just 150°K (that is, about — 125°C). The dark areas are considerably warmer than the bright areas.

The atmosphere of Mars is much colder. The temperature of the atmosphere near the equator has been calculated from radio observations by Mariner 6 when it passed behind Mars. The temperature at the base of the atmosphere measured 250°K, while that at the surface itself measured 274° ± 5°K. The temperature of the night atmosphere at a point with latitude + 36°, as measured by Mariner 7, was 205°K, while nearer to the pole, at latitude +79°, it was 164°K. It was autumn in the northern hemisphere at this time. In the lower atmosphere in the space of 20-25 km the density and pressure decrease by a factor of 10 with altitude, while the temperature drops from 210°K to 150°K. After this the temperature drops more slowly and reaches a minimum of 110°K at an altitude of 50 km; then it rises slowly to 300-350°K at an altitude of about 200 km and remains so until altitudes of more than 1,000 km. The considerably higher temperature of the Martian surface than the temperature of the adjacent layer of the atmosphere causes a strong convection in the lower atmosphere during daytime. Horizontal movements in the Martian atmosphere, to judge by the displacement of clouds, occur at velocities up to 10-15 m/sec. Theoretically, velocities up to 30-40 m/sec can exist, and if we consider the macrorelief, local winds may reach velocities of 100-120 m/sec. Even with the low density, the atmosphere is naturally capable of lifting both small and large dust particles; it can move particles 5-10 jam in diameter distances up to 6,000 km, and particles 75 jam in diameter distances of 50 km.

The variations in the temperature of the atmosphere and surface of Mars, which have been determined at different latitudes in different seasons, agree with long-observed seasonal variations in the details of the planet’s surface. In the spring, the polar caps begin to recede, and a dark band of “thaw” appears around each cap. The maria, which were very dim and gray, show increased contrast, spreading slowly from the poles to the equator. At the same time, there are seasonal changes in the outlines of the maria. By the end of the summer, the blue-green hues of the maria are replaced by red-brown hues. This picture long gave grounds for believing that the polar caps, consisting of ice and snow, were melting and supplying moisture to more distant areas of the planet, which “blossomed” and became very noticeable. The low temperatures in the atmosphere and on the surface of Mars cast doubt on such an interpretation. Above all, this refers to the very nature of the polar caps; at a temperature of — 125°C even CO2 should be in a solid state. Such a low temperature at an altitude of 30 km and the even lower temperatures at greater altitudes also require condensation of atmospheric CO2. The polar caps cannot consist of anything but CO2, and the white clouds frequently observed on Mars also consist of it. At the same time, spectral observations indicate small admixtures of ordinary ice (H2O) in addition to the “dry ice” of CO2 in the caps. It is probable that the last remnants of the southern polar cap, which do not disappear in the course of the summer while vast areas covered with a thin layer of solid CO2 evaporate rapidly in early summer, also consist of ordinary ice. All the same, there is very little water on Mars, unless it is in the form of permafrost, which may exist in other areas besides the circum-polar regions. In these latter areas permafrost consisting of CO2 is quite possible. Random tectonic processes accompanied by liberation of heat may break up the permafrost locally, and then rivers, signs of which are present on Mars (as mentioned above), appear. But movements of dust in the planet’s atmosphere and on the surface play the principal role in the rapid changes on Mars.

Experimental investigations. The flights of the Mariner and Mars probes make it possible to conduct experimental investigations of the geomorphology, geology, and evolution of the surface and atmosphere of Mars. The results obtained permit us to conjecture that the large craters observed on Mars are considerably younger than the lunar craters. At the same time, however, they have been worn away more, apparently the result of weathering processes.

Life. The previously popular belief that Mars is populated by living, and even intelligent, beings is not supported by temperature and spectroscopic observations. No matter how great the adaptability of living organisms to environmental conditions may be, the fact that no signs of oxygen have been found in the Martian atmosphere makes the hypothesis of the existence of higher forms of life on Mars unlikely. But lower forms of life, in particular anaerobic forms, may exist. Because the surface of Mars is quite well irradiated by ultraviolet rays, the synthesis of organic molecules, from which living cells are constructed, is entirely possible. Many terrestrial microorganisms placed during laboratory experiments in conditions resembling those on the surface of Mars have continued to exist and reproduce.

Satellites. Mars has two satellites: Phobos and Deimos. They move near the equatorial plane and very close to the planet, at distances of 9,370 km and 23,520 km. Their periods of revolution are 7 hr 40 min and 30 hr 21 min, respectively. Thus, Phobos moves around the planet more rapidly than it rotates on its axis. Both satellites are very small. As visible from the earth, Phobos has a stellar magnitude of 11.6, and Deimos, of 12.8. Their true dimensions were established in 1971 by direct photographs taken by Mariner 9. Phobos has an irregular shape resembling a potato and measures 26 km long and 21 km wide. Its surface is pocked with craters (100 times more dense than the surface of Mars); the largest measures more than 6 km in diameter. Deimos is less pitted; its diameter reaches 13 km. The two satellites have the smallest albedo in the solar system: ≤0.06.


Vaucouleurs, G de. Fizika planety Mars. Moscow, 1956. (Translated from French.)
Moroz, V. I. Fizika planet. Moscow, 1967.
Novoe o Marse i Venere. Moscow, 1968. (Collection of articles translated from English.)




the name of Soviet unmanned space probes launched toward the planet Mars beginning in 1962.

Mars 1 was launched on Nov. 1, 1962, weighed 893.5 kg, was 3.3 m long, and had a body diameter of 1.1 m. Mars 1 had two sealed compartments: an orbital compartment with the primary on-board equipment for the flight to Mars and a planetary compartment carrying scientific instruments designed for the study of Mars on a close fly-by. The goals of the flight were to study open space, to test the radio link at interplanetary distances, and to photograph Mars. The final stage of the booster rocket carrying the probe was inserted into earth parking orbit and accomplished the launch and necessary velocity increment for the flight to Mars.

The active astroorientation system had earth, stellar, and solar orientation sensors and a system of servomechanisms with control nozzles operating on compressed gas, as well as gyroscopic instruments and logic modules. Solar orientation was maintained during most of the flight to provide illumination for the solar batteries. The probe was equipped with a liquid-propellant engine and a control system to provide for anticipated course corrections. On-board radio equipment operating at frequencies of 186, 936, 3750, and 6000 megahertz measured flight parameters, received commands from earth, and transmitted telemetry data during communication sessions. A temperature-control system maintained a stable temperature of 15°-30°C. During the flight 61 communication sessions were conducted from Mars 1 and more than 3,000 radio commands were transmitted to the probe. In addition to radio aids, a telescope 2.6 m in diameter at the Crimean Astrophysical Observatory was used for trajectory measurements.

The flight of Mars 1 provided new data on the physical properties of space between the orbits of the earth and Mars (at a distance of 1.0-1.24 astronomical units [AU] from the sun), the intensity of cosmic radiation, the magnetic field intensities of the earth and interplanetary space, the flow of ionized gas from the sun, and the distribution of meteoric matter (the probe passed through two meteor showers). The last session was conducted on Mar. 21, 1963, when the probe was 106 million km from the earth. A malfunction of the attitude control system disrupted the aiming of the antenna toward the earth and prevented further radio communication. The approach to Mars took place on June 19, 1963 (about 197,000 km from Mars), after which Mars 1 entered a heliocentric orbit with a perihelion of about 148 million km and an aphelion of about 250 million km.

Mars 2 and Mars 3 were launched on May 19 and 28, 1971, and made a joint flight and simultaneous studies of Mars. Trans-Mars injection was accomplished from earth parking orbit by the final stages of the booster vehicles. Their design and equipment load differed significantly from those of Mars. 1. Mars 2 (and Mars 3) weighed 4,650 kg. They were similar in design and had an orbital module and a descent vehicle. The main units in the orbital module were the instrumentation section, a group of tanks for the propulsion system, a vernier engine with automatic units, a solar battery, antenna-feeder devices, and radiators of the temperature-control system. The descent vehicle was an unmanned Mars probe equipped with systems and devices that effected separation of the vehicle from the orbital station, transfer to an approach trajectory, braking, descent through the atmosphere, and a soft landing on the surface of Mars. The unmanned Mars probe was equipped with a parachute instrumentation container, an aerodynamic braking cone, and a connecting frame on which a jet engine was mounted. The descent vehicle was sterilized before the flight. The probes carried a number of systems designed to support the flight. In contrast to Mars 1, the control systems of Mars 2 and 3 contained a gyrostabilized platform, an on-board digital computer, and a self-contained space navigation system. In addition to solar orientation, simultaneous orientation toward the sun, the star Canopus, and the earth was used at sufficiently great distances from earth (about 30 million km).

The on-board radio system for communication with earth operated in the decimeter and centimeter bands, and communication of the descent vehicle with the orbital module of the station took place in the meter band.

Two solar batteries and a buffer storage battery served as the power source. A self-contained chemical battery was installed in the descent vehicle. The temperature-control system was active, with circulation of the gas that filled the instrument section. The descent vehicle had shield-vacuum heat insulation, a radiation heater with a regulated surface, and an electric heater. The propulsion system was restartable.

The orbital module contained scientific equipment designed for measurements in interplanetary space and for studying the vicinity of Mars and the planet itself from planetary orbit. The equipment included a ferroprobe magnetometer, an infrared radiometer designed to make a map of temperature distribution on the surface of Mars, an infrared photometer for studying the surface relief according to the change in the amount of carbon dioxide, an optical instrument for determining the water vapor content by the spectral method, a photometer operating in the visible region and designed to investigate the reflectivity of the surface and atmosphere, an instrument for determining the radio-frequency brightness temperature of the surface in the 3.4-cm band and for determining its dielectric permeability and the temperature of the surface layer at a depth of up to 30-50 cm, an ultraviolet photometer for determining the density of the upper atmosphere of Mars and the content of atomic oxygen, hydrogen, and argon in the atmosphere, a cosmic-ray counter, a charged-particle energy spectrometer, and an electron and proton energy flowmeter operating from 30 electron volts to 30 kilo electron volts.

Mars 2 and 3 carried two television cameras with different focal lengths for photographing the surface of Mars, and Mars 3 also carried a Stereo unit for conducting the joint Soviet-French experiment designed to study the radio-frequency radiation of the sun at 169 megahertz.

Equipment for measurement of atmospheric temperature and pressure, mass-spectrometric determination of the composition of the atmosphere, measurement of wind velocity, determination of the chemical composition and physical and mechanical properties of the surface layer, and obtaining panorama shots with the television cameras was installed in the descent vehicle.

The flight of the probes to Mars took more than six months; 153 communication sessions were conducted with Mars 2, and 159 with Mars 3. A large body of scientific data was obtained. The “tail” of the earth’s magnetic field was detected at a distance of about 20 million km. With increasing distance from the sun, a decrease in the electron concentration in the interplanetary medium was observed, and the electron temperature was found to be several times lower than near the earth. The flight trajectory of Mars 2 passed at a distance of 1,380 km from the surface of Mars. During the approach to Mars a capsule separated from the probe and carried to the surface of the planet a pennant bearing an image of the State Coat of Arms of the USSR. On Nov. 27, 1971, the propulsion system of Mars 2 was switched on and the station entered Mars orbit with an orbital period of 18 hours. Course corrections of Mars 3 were made on June 8, Nov. 14, and Dec. 2, 1971. The descent vehicle separated on December 2 at 12:14 P.M. Moscow time, at a distance of about 50,000 km from Mars. After 15 min, when the distance between the station and the descent vehicle was not more than 1 km, the descent vehicle moved into an approach trajectory with the planet. The descent vehicle traveled toward Mars for 4.5 hr and at 4:44 P.M. entered the planet’s atmosphere. The descent to the surface in the atmosphere lasted slightly more than 3 min. The descent vehicle landed in the southern hemisphere of Mars, in a region with the coordinates 45° S lat. and 158° W long. A pennant bearing an image of the State Coat of Arms of the USSR was carried by the vehicle. After separation of the descent vehicle, the Mars 3 orbital vehicle moved in a trajectory that passed 1,500 km from the surface of Mars. The braking system effected its transfer into Mars orbit with an orbital period of about 11 days. Transmission of a video signal from the surface of the planet began on December 2 at 4:50:35 P.M. The signal was received by the orbital station’s receivers and was relayed to earth in communication sessions between December 2 and December 5.

For more than eight months the probes carried out a comprehensive program of investigations of Mars from satellite orbits. In this period the Mars 2 probe made 362 orbits, and Mars 3, 20 orbits. The studies of the properties of the Martian surface and atmosphere according to the character of the radiation in the visible, infrared, and ultraviolet bands of the spectrum and in the radio-frequency band made possible determination of the temperature of the surface layer and establishment of its dependence on latitude and time of day. Thermal anomalies were found on the surface; the thermal conductivity, thermal inertia, dielectric constant, and reflectivity of the soil were evaluated; and the temperature of the north polar cap (below — 110°C) was measured. Altitude profiles of the surface based on flight paths were obtained from data on the absorption of infrared radiation by carbon dioxide. The water vapor content was determined in various regions of the planet; it was found to be approximately 5,000 times lower than in the earth’s atmosphere. Measurements of scattered ultraviolet radiation provided information on the structure (extent, composition, and temperature) of the Martian atmosphere. The pressure and temperature on the surface of the planet were determined by the radiosonde method. Data on the altitude of dust clouds (up to 10 km) and the size of dust particles (a large content of small particles about 1 micron in size was observed) were obtained through measurements of the change in atmospheric transparency. The photographs made it possible to determine the optical flattening of the planet, to construct relief profiles based on the image of the limb, to obtain color images of Mars, to detect atmospheric luminosity 200 km beyond the terminator and the change in color near the terminator, and to trace the laminar structure of the Martian atmosphere.

In 1973, Mars 4 (July 21), Mars 5 (July 25), Mars 6 (August 5), and Mars 7 (August 9) were launched for comprehensive study of Mars from a fly-by trajectory, from Mars orbit, and on the planet itself. To this end there are plans for the establishment of an artificial Mars satellite and the landing of a descent vehicle on the surface of the planet. The purposes of the flight are the determination of the physical characteristics of the soil and the properties of surface rocks and experimental verification of the possibility of obtaining television images.




in the mythology of the ancient Romans and other Italic peoples, the god of war.

Protection of the tribal warriors was ascribed to Mars, and this was reflected in the numerous holidays in his honor, which in Rome were held in March and October. At the same time Mars preserved characteristics of a more ancient agricultural divinity, and remnants of magic agricultural rites were unquestionably present in the cult of Mars. Mars was considered the father of Romulus and Remus, the founders of Rome. March, the first month of the ancient Roman calendar, carried the name of Mars. Mars was equated with the ancient Greek god Ares.


The planet fourth in distance from the sun; it is visible to the naked eye as a bright red star, except for short periods when it is near its conjunction with the sun; its diameter is about 4150 miles (6700 kilometers).


the Roman god of war, the father of Romulus and Remus


1. the fourth planet from the sun, having a reddish-orange surface with numerous dark patches and two white polar caps. It has a thin atmosphere, mainly carbon dioxide, and low surface temperatures. Spacecraft encounters have revealed a history of volcanic activity and running surface water. The planet has two tiny satellites, Phobos and Deimos. Mean distance from sun: 228 million km; period of revolution around sun: 686.98 days; period of axial rotation: 24.6225 hours; diameter and mass: 53.2 and 10.7 per cent that of earth respectively
2. the alchemical name for iron


A legendary tragic failure, the archetypal Hacker Dream Gone Wrong. Mars was the code name for a family of PDP-10 compatible computers built by Systems Concepts (now, The SC Group): the multi-processor SC-30M, the small uniprocessor SC-25M, and the never-built superprocessor SC-40M. These machines were marvels of engineering design; although not much slower than the unique Foonly F-1, they were physically smaller and consumed less power than the much slower DEC KS10 or Foonly F-2, F-3, or F-4 machines. They were also completely compatible with the DEC KL10, and ran all KL10 binaries (including the operating system) with no modifications at about 2--3 times faster than a KL10.

When DEC cancelled the Jupiter project in 1983, Systems Concepts should have made a bundle selling their machine into shops with a lot of software investment in PDP-10s, and in fact their spring 1984 announcement generated a great deal of excitement in the PDP-10 world. TOPS-10 was running on the Mars by the summer of 1984, and TOPS-20 by early fall.

Unfortunately, the hackers running Systems Concepts were much better at designing machines than at mass producing or selling them; the company allowed itself to be sidetracked by a bout of perfectionism into continually improving the design, and lost credibility as delivery dates continued to slip. They also overpriced the product ridiculously; they believed they were competing with the KL10 and VAX 8600 and failed to reckon with the likes of Sun Microsystems and other hungry startups building workstations with power comparable to the KL10 at a fraction of the price.

By the time SC shipped the first SC-30M to Stanford in late 1985, most customers had already made the traumatic decision to abandon the PDP-10, usually for VMS or Unix boxes. Most of the Mars computers built ended up being purchased by CompuServe.

This tale and the related saga of Foonly hold a lesson for hackers: if you want to play in the Real World, you need to learn Real World moves.
References in periodicals archive ?
With action planet Mars travelling forward on Tuesday, you'll make progress with discussions and matters of importance around travel and qualifications.
The ` 450- crore Mars Orbiter Mission is India's first interplanetary mission to planet Mars with an orbiter craft designed to orbit Mars in an elliptical orbit.
If you don't stand for something you'll fall for anything, it's time to do what you want, and as the planet Mars highlights home affairs, close ones can expect major changes from here on in.
I have a hard time with the fact that we are on the verge of reaching the planet Mars, but we are incapable of developing effective vaccines against malaria, schistosomiasis or tuberculosis
THE largest known volcano is Olympus Mons - on the planet Mars - three times the height of Mount Everest.
1976: The US spacecraft Viking II landed on the planet Mars after a journey lasting six days short of one year.
The exploration of the planet Mars is celebrated by Chaikin, a public relations advisor to NASA and author of several books on the space program.
First we have Clegg who, in leading a party on 12 per cent which has never been in office, announces to his faithful friends on Planet Mars that the party in power is now "finished", in what could be his David Steel moment.
The discovery of bacteria living three kilometres down in a South African gold mine has sparked new speculation about the possibility of life below the surface of the planet Mars.
The Mars Robotics Lab, which will give young visitors the opportunity to design and program their own robots in order to complete a remote exploration mission to the planet Mars.
A Ball Aerospace-built camera is returning the highest- resolution images of planet Mars from the largest telescopic instrument ever sent beyond Earth's orbit.
Maybe they find it uncomfortable as it is occurring on the planet Mars.