Mars photographed by Viking Orbiters
|Name of discoverer||Known to ancients|
|Name origin||Roman god of war|
|Order from primary||4|
|Semi-major axis||227,920,000 km|
|Titius-Bode prediction||1.6 AU|
|Sidereal year||686.980 da|
|Synodic year||779.94 da|
|Avg. orbital speed||24.077 km/s|
|Inclination||1.850° to the ecliptic|
|Sidereal day||24.6229 h|
|Solar day||24.6597 h|
|Rotational speed||465.11 m/s|
|Mass||6.4185 * 1023 kg|
|Mean radius||3389.5 km|
|Equatorial radius||3396.2 km|
|Polar radius||3376.2 km|
|Surface gravity||3.71 m/s²|
|Escape speed||5.03 km/s|
|Surface area||144,800,000 km²|
|Minimum temperature||140 K|
|Mean temperature||218 K|
|Maximum temperature||300 K|
|Number of moons||2|
|Magnetic dipole moment at present||2.1 * 1018 N-m/T|
|Magnetic dipole moment at creation||1.51 * 1023 N-m/T|
|Decay time||535 a|
|Half life||370.83 a|
- 1 Ancient knowledge and naming
- 2 Orbital characteristics
- 3 Rotational characteristics
- 4 Physical characteristics
- 5 Life on Mars
- 6 Problem for uniformitarian theories
- 7 Young Mars Creation model.
- 8 Mars in popular culture
- 9 Observation and exploration
- 10 Satellites
- 11 References
- 12 Related Links
Ancient knowledge and naming
Mars has the Roman name of the classical god of war. This name in turn derives from the Greek name Ares for this god. (The traditional symbol of Mars is his shield and spear.) The ancient Egyptians simply called Mars Her Descher, or "the red one." The Hindus call Mars Mangala, one of the Navagraha. The Maya people also tracked Mars regularly.
Mars is in a highly elliptical orbit around the Sun and maintains an average distance slightly more than 1.5 AU. The synodic period of Mars is roughly 26 months. This fact makes Mars a particularly difficult object to explore, because opportunities to launch a rocket probe to Mars occur so far apart in time.
Mars' sidereal and solar days are only slightly longer than the days of earth. This fact has led long-term Mars mission planners to adopt a permanent system for keeping time "local" to Mars. The first mission to use this "Mars solar clock" was Viking 1 in 1976.
Mars is half the size of Earth and has about 11% of earth's mass. The large proportion of iron in Mars' clay-like topsoil gives Mars its distinctive color.
The weather on Mars is seasonal, on account of Mars's axial inclination. Yet because Mars's orbit is so eccentric, "summer" and "winter" on the northern and southern hemispheres can vary greatly. Temperatures vary from 140 K to 300 K, with an average temperature of 210 K. (The freezing point of water is 273.15 K.)
Mars' atmosphere is quite thin and has an average pressure of 6.36 mb or 0.636% of that of earth. Its chief components are 95.32% carbon dioxide, 2.7% nitrogen, 1.6% argon, 0.13% oxygen, and 0.08% carbon monoxide. In addition it has trace amounts of water (210 ppm), nitrogen oxide (100 ppm), neon (2.5 ppm), hydrogen-deuterium oxide (HDO) (0.85 ppm), krypton (0.3 ppm), and xenon (0.08 ppm). Winds on Mars vary in speed from 2-7 m/s in summer to 5-10 m/s in fall, though the Project Viking landers have recorded winds varying from 17-30 m/s during dust storms that have swept past the landing sites.
Recent warming trends on Mars, including an apparent partial melt of the polar ice caps, have led at least one scientist to question the widely circulating theories of global warming on earth. Specifically, Habibullo Abdussamatov, head of space research at St. Petersburg's Pulkovo Astronomical Observatory in Russia, asserts that the sun, and not any activity specific to the earth, must be responsible for any warming observed on either planet.
Mars has a very weak magnetic field. Data from various missions has established an upper limit of 2.1 * 1018 N-m/T on the magnetic dipole moment of Mars. According to Russell Humphreys's model of the creation of magnetic fields, Mars probably had a magnetic dipole moment at creation of 1.51 * 1023 N-m/T. Thus Mars's magnetic field has been decaying very rapidly. This tremendous decay, and the presence on Mercury of a magnetic field of significant strength, baffles astronomers who have assumed that magnetic fields form on rapidly moving planets that have conductive and liquid cores that can act as dynamos. In fact, Humphreys asserts that the characteristic that determines which of the terrestrial planets will have a persistent magnetic field is the core radius, and that the cores of all four of these planets have similar conductivities. Mercury and Earth have larger cores than do Mars and Venus. The lengths of the sidereal days on those worlds do not matter.
There is a dichotomy on the surface of Mars; the northern hemisphere consists of low-lying volcanic plains, with the southern hemisphere consists of ancient, heavily-cratered highland plains. Mars also has two volcanic regions: Tharsis and Elysium. Within the Tharsis region is the largest volcano in the solar system, Olympus Mons. Olympus Mons is approximately 500 km across and is about the same size as the state of Arizona. Its peak is 24 km above the surrounding plains and it is surrounded by a vertical scarp 6 km high. A large canyon system, Valles Marineris, is located along the Martian equator east of the Tharsis region. Valles Marineris is 2-6km deep and 200-600km wide and approximately 4,500 km long (approximately the distance from San Francisco to Boston). The eastern part of Valles Marineris appears to have a tectonic origin, but the western part is characterized by features such as teardrop islands and longitudinal grooves, indicating it may have been formed by catastrophic flooding in the past. Such flooding may be possible under current climate conditions. Run-off channels in the cratered highland indicate a thicker atmosphere or warmer climate in the past that would have allowed water to be stable on the surface.
Recent satellite imagery has shown that Mars has a 3 kilometre deep ice cap around its polar regions. The northern polar region is surrounded by dune fields. During the Martian winter, a layer of carbon dioxide condenses at the poles and sublimates in the summer, leaving the water-ice and dust polar caps exposed. The ratio of dust to water-ice contained in the polar caps remains unknown.
Persistent rumors tell of a "face on Mars," allegedly located in the Cydonia Mensae region at coordinates 40.9°N and 9.45°W. This alleged "face" is located in the midst of several pyramids and other mountains. Prevailing opinion at NASA is that the "face" is a trick of the eye due to the unusual lighting conditions.
Water on Mars
Mars cannot have liquid water on its surface. The thin atmosphere does not permit this, even during high summer on Mars. Yet the Mars Global Surveyor mission in June 2000 took photographs of gully-like formations on several precipices and crater walls on Mars. These formations tend to occur between 30° and 70° north and south latitude. Mission analysts further suggest that these formations are relatively fresh and estimate that liquid water might be found less than 500 meters beneath the surface.
More recently, NASA's latest mission, the Phoenix lander, has discovered what appears to be water ice very near the surface near Mars' north pole. Furthermore, analysis of a cubic meter of soil at this site reveals that the soil is far more alkaline than expected, and has tolerable levels of salt and low levels of calcium. Investigators have even suggested that the soil might support the growth of an Earth vegetable, like asparagus.
Life on Mars
The possibility that extraterrestrial life exists, or has existed, on Mars has been the subject of persistent scientific speculation for decades. The earliest speculation concerned a possible civilization on Mars, this after Percival Lowell theorized that the straight lines that several astronomers had seen on Mars were in fact artificial constructs, and specifically canals. Lovell popularized his theory as early as 1906, and for a long time the suspicion of a non-human civilization native to Mars would find repeated expression in novels and dramatic presentations. Only with the first successful explorations of Mars would the scientific community, and the public, abandon that theory.
Current speculation concerns the possible finding of microbes. These would be extremophiles, or microbes that survive and even grow in environments lethal to other forms of life. Direct attempts to find such life began in 1976 with the Viking 1 and Viking 2 landers. To date no positive sign of life on Mars has been found. The Viking landers found evidence of unexplained chemical activity, but no clear evidence of microbes. Whether the Viking landers would have been able to detect extremophiles, a concept unknown to the Viking mission planners, is unclear.
The astrobiologists involved with Project Viking suspect that Mars might be an inherently inhospitable environment for life. Ultraviolet light from the sun shines unchecked on Mars, on account of Mars' thin atmosphere and weak magnetic field. The soil of Mars is also very dry, and the soil has a high proportion of oxidizing agents.
Problem for uniformitarian theories
The most formidable current problem that Mars poses for uniformitarians today is that its magnetic field is weak and inconsequential, while a planet (Mercury) of little more than half its weight does have a significant magnetic field. According to current theory, planets derive their magnetic fields by dynamo action. This requires fast rotation and liquid cores. Mars and Earth have comparable sidereal days, but Earth's magnetic field is strong enough to protect Earth from the solar wind, while that of Mars is not. Mercury has a far longer sidereal day than Mars has, and yet Mercury has a significant magnetic field while Mars has none.
Young Mars Creation model.
Discoveries by the Mars Excursion Rover Opportunity have led to a Young Mars Creation model of Martian geology. These discoveries combine with data from the rest of Mars to indicate a massive Martian catastrophe.
Since Opportunity landed in the Meridiani Planum region of Mars it has sent back findings showing that the area was once underwater and that the water was very acidic. This high concentration of sulfuric acid militates against this being a habitable sea. The entire Meridiani Planum region has much evidence of catastrophic flooding, including a clear inlet channel to the southeast and a splash zone in the north.
Mars contains the largest of three major geologic features in the Solar System. The largest impact basin, the largest volcanoes and the largest canyon are all found on Mars and in a clear relationship to each other. This relationship provides the key to understanding Martian geology.
These relationships indicate a major geologic catastrophe on Mars resulting in massive volcanic activity. The dating of this event from craters places it at about the time of the Great Flood on Earth. This volcanic activity would have increased Mars’s atmospheric pressure to allow liquid water to flow on the surface and thus allow the flooding of the Meridiani Planum region.
This shows that, like Earth, Mars has evidence that it is only a few thousands of years old and not 4.6 billion years old.
Mars in popular culture
Mars has figured prominently in science fiction in the Western world for more than a century.
The War of the Worlds
The first novel speculating on a civilization on Mars was The War of the Worlds by H. G. Wells, in 1897. Wells' Martians had a military strength that human civilization could not match, but ultimately perished after contracting various infectious diseases caused by microbes native to Earth to which the Martians effectively had no defense.
In 1938, actor/director Orson Welles and his Mercury Theater produced a radio drama based on this novel. Welles updated the novel to his own period but otherwise remained faithful to the source material. The broadcast created such a panic in the United States that Welles was compelled to order a broadcast disclaimer in mid-show and, at the end of the show, personally assure his listeners that no such thing as an extraterrestrial invasion had taken place.
Other speculations on civilizations
Author Edgar Rice Burroughs published several novels speculating on an elaborate civilization on Mars to which humans traveled, but which was not bent on invading the earth. Author C. S. Lewis, in his novel Out of the Silent Planet, envisioned Mars as the home of three races of non-fallen beings that were instructed to regard the earth as off-limits on account of man's fallen nature.
With the abandonment of the Lowell canal theory, science fiction authors and dramatists envisioned Mars as home to a human colony, such as the situation in the television series Terrahawks. But at least one motion-picture producer saw Mars as a place that very ancient astronauts had once visited. These astronauts, according to this scenario, left behind some advanced equipment that a human rebel was subsequently able to use to give Mars a breathable atmosphere and thus facilitate the Martian colony's liberation from the civilization of earth, which in the story had become venal and tyrannical.
Speculation on microbes
Authors John B. Olson and Randall S. Ingermanson have recently speculated (Oxygen and The Fifth Man) about the finding of microbes on Mars, and the implications that such a discovery would hold for the Christian faith and the possible "back-contamination" of the earth when the crew that found the microbes returned to earth.
Observation and exploration
Observation of Mars has been ongoing since the ancients noted its existence and its movements. The invention of the telescope provoked the first serious study of Mars as a celestial object, and not a prophetic sign. Yet not all of this observation led to proper inferences. Percival Lowell's canal theory would lead to more than half a century of vain speculation on extraterrestrial civilization before the first successful exploratory missions would return evidence forcing the abandonment of that theory.
Mars has been the subject of more attempts to explore it, and more failures, than any other planet. Of approximately 37 separate missions to Mars, only 13 have had any success. The planetary scientists of the Union of Soviet Socialist Republics, so successful in exploring Venus, experienced ten mission failures before achieving their first success, seven years after the United States achieved success with its Mariner 4 mission. That Soviet mission, Mars 3 in 1971, succeeded in placing a lander on Mars, but the lander's system transmitted for only 20 seconds before failing.
In 1975, Project Viking achieved the most notable success by placing two orbiters and two landers on Mars. Neither nation would attempt any further missions to Mars until 1988, when the Soviets lost one craft en route and lost contact with the other (Phobos 2 seconds after its rendezvous with Mars's inner moon Phobos. Nor was the United States' program immune to failure; its Mars Observer vessel was lost prior to arrival after some propulsion systems failed.
In 1996 the Mars Global Surveyor enjoyed the most success to date, returning more images than all previous missions combined. In that same year, the United States landed the first mobile explorer, or "rover," called the Mars Pathfinder.
The United States would, unfortunately, lose the next two successive craft that it sent to Mars. But its Mars Odyssey would arrive intact in 2001 and send back the first high-resolution images. Two years later the European Space Agency would successfully place its Mars Express orbiter in the Martian system; sadly, its associated landing craft would crash-land. The Mars Express orbiter continues in orbit around Mars.
The most successful missions to date have been the Mars Excursion Rover missions. Two of these sophisticated mobile robots, named Spirit and Opportunity, launched in 2003 and arrived safely on Mars about six months later, on opposite sides of the planet. They have been running for four years now, at least fifteen times longer than they were warranted to run. The Opportunity rover has been taking pictures of the Victoria Crater, and Spirit has been photographing the Esperanza formation which contains "vesicular" basalt (characterized by multiple cavities representing dissolved gas escaping from solution during a volcanic eruption).
On May 26, 2008, NASA placed a polar lander on Mars for the first time: the Phoenix lander. As of June 28, 2008, the Phoenix lander is functioning well and has already discovered water ice where it landed. Contrary to prior understandings, the Phoenix lander has found an alkaline soil that might be suitable for growing Earth vegetables.
At least one non-governmental group, calling itself the Mars Society, has been actively studying technologies appropriate to send a crew of from four to six astronauts to Mars for a roughly two-year stay.
Mars has two moons: Phobos and Deimos (which respectively mean "Fear and "Panic" in Greek). Russian scientists in the 1950s posited that Phobos might be hollow, but these claims were discredited in the late 1960s.
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