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Mars
*** Shopping-Tip: Mars
{{portal}}
:''For the Roman god, see
Mars (mythology). For other uses of this term,
Mars (disambiguation).
{{SpecialCharsNote}}
{{Planet Infobox/Mars}}
'''Mars''' is the fourth
planet from the
Sun in our
solar system. It is named after Mars, the
Roman mythology Roman god of war (
Ares in
Greek mythology). Mars is also known as "The Red Planet" due to the reddish appearance it has when seen from Earth at night. Mars has two
natural satellite moons,
Phobos (moon) Phobos and
Deimos (moon) Deimos, which are small and oddly-shaped, and possibly captured
asteroids. Mars can be seen from
Earth by the naked eye with a brightness of up to -2.9 magnitude, only surpassed by Venus, the Moon and the Sun.
The prefix ''areo-'' refers to Mars in the same way ''geo-'' refers to
Earth—for example, ''areology'' versus ''
geology''. '''Areology''' is also used to refer to the study of Mars as a whole rather than just the geological processes of the planet.
The
astronomical symbol for Mars is ♂, a circle with an arrow pointing northeast. This symbol is a stylized representation of the shield and spear of the god Mars, and in biology it is used as a sign for the
male sex.
The
China Chinese,
Korea Korean,
Japanese and
Vietnamese cultures refer to the planet as �星, or ''fire star'', a naming based on the ancient Chinese mythological cycle of
Five elements (Chinese philosophy) Five Elements.
Name
Mars is named after the
Ancient Rome Roman Mars (mythology) god of war. In
Babylonia Babylonian astronomy, the planet was named after ''
Nergal'', their
deity of fire, war, and destruction, most likely due to the planet's reddish appearance. When the
Ancient Greece Greeks equated Nergal with their god of war,
Ares, they named the planet ἌÏ?εως ἀστἡÏ? (''Areos aster''), or "star of Ares". Then, following the
Interpretatio graeca identification of
Ares and
Mars (mythology) Mars, it was translated into Latin as ''stella Martis'', or "star of Mars", or simply ''Mars''. The Greeks also called the planet Î Ï…Ï?όεις ''Pyroeis'' meaning "fiery". The planet was known by the
Ancient Egypt Egyptians as "Her Deschel" or "the Red One". The
Hebrews named it ''Ma'adim'' (מ×?די×?) - "the one who blushes"; this is where one of the largest
canyons on Mars, the
Ma'adim Vallis, gets it's name.
Physical characteristics
The
red, fiery appearance of Mars is caused by
iron(III) oxide (rust) on its surface. Mars has half the
radius of the
Earth and only one-tenth the
mass, being less dense. But it's
surface area is only slightly less than the total area of Earth's dry land.
Atmosphere
{{main|Atmosphere of Mars}}
Mars'
celestial body atmosphere atmosphere is thin: the
atmospheric pressure on the surface is only 0.7-0.9
pascal kPa, compared to Earth's 101.3 kPa. However, the
scale height of the atmosphere is about 11 km, somewhat higher than Earth's 6 km. The atmosphere on Mars consists of 95%
carbon dioxide, 3%
nitrogen, 1.6%
argon, and contains traces of
oxygen and
water. The atmosphere is quite dusty, giving the Martian sky a
tawny color when seen from the surface; data from the
Mars Exploration Rovers indicates the suspended dust particles are roughly 1.5
micrometres across
[[http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2004Sci...306.1753L&db_key=AST&data_type=HTML&format=&high=439c7b95b425777 Lemmon et al., "Atmospheric Imaging Results from the Mars Exploration Rovers: Spirit and Opportunity"]].
Image:2005-1103mars-full.jpg thumb|left|Mars from Hubble Space Telescope October 28, 2005 with sandstorm visible.
In
March 2004 the
Mars Express Orbiter reported they had found
methane in the Martian atmosphere, with a concentration of about 10
Parts per billion ppb by volume
[[http://www.esa.int/SPECIALS/Mars_Express/SEMZ0B57ESD_0.html "Mars Express confirms methane in the Martian atmosphere"] - March 30, 2004 ESA Press release. URL accessed March 17, 2006.]. The presence of methane on Mars would be very intriguing, since as an unstable
gas it indicates that there must be (or have been within the last few hundred years) a source of the gas on the planet.
volcanism Volcanic activity,
comet impacts, and the existence of life in the form of
microorganisms such as
methanogens are among possible but as yet unproven sources. The methane appears to occur in patches, which suggests that it is being rapidly broken down before it has time to become uniformly distributed in the atmosphere, and so it is presumably also continually being released to the atmosphere. Plans are now being made to look for other companion gases that may suggest which sources are most likely; in the Earth's oceans biological methane production tends to be accompanied by
ethane, while volcanic methane is accompanied by
sulfur dioxide.
The thin atmosphere cannot hold heat and is the cause of the lower temperatures on Mars. The maximum temperature is roughly 20 degrees Celsius (68 degrees Fahrenheit). Recently, evidence has been discovered suggesting that Mars may be warming in the short term.
[[http://mpfwww.jpl.nasa.gov/mgs/newsroom/20050920a.html Orbiter's Long Life Helps Scientists Track Changes on Mars] - Sept. 20, 2005 NASA Press release. URL accessed March 17, 2006.]
Other aspects of the Martian atmosphere vary significantly. In the winter months when the poles are in continual darkness, the surface gets so cold that as much as 25% of the entire atmosphere condenses out into thick slabs of
Carbon dioxide CO2 ice (dry ice). When the poles are again exposed to sunlight the CO
2 ice
Sublimation (physics) sublimates, creating enormous winds that sweep off the poles as fast as 250 mph (400 km/h). These seasonal actions transport large amounts of dust and water vapor giving rise to Earth-like
frost and large
cirrus clouds. Clouds of water-ice were photographed by the ''
Opportunity rover Opportunity'' rover in 2004.
[[http://marsrovers.jpl.nasa.gov/gallery/press/opportunity/20041213a.html "Mars Rovers Spot Water-Clue Mineral, Frost, Clouds"] - Dec. 13, 2004 NASA Press release. URL accessed March 17, 2006.]
Image:Terrestrial_planet_size_comparisons.jpg thumb|left|250px|Size comparison of terrestrial planets (left to right): Mercury, Venus, Earth, and Mars.
Geology
{{main|Geology of Mars}}
The surface of Mars is thought to be primarily composed of
basalt, based upon the
Martian meteorite collection and orbital observations. There is some evidence that some portion of the Martian surface might be more silica-rich than typical
basalt, perhaps similar to
andesitic rocks on Earth, though these observations may also be explained by silica glass. Much of the surface is deeply covered by dust as fine as talcum powder.
Observations of the
magnetic fields on Mars by the
Mars Global Surveyor spacecraft have revealed that parts of the planet's
Crust (geology) crust has been magnetized. This magnetization has been compared to alternating bands found on the ocean floors of Earth. One theory, published in 1999 and reexamined in October 2005 with the help of the
Mars Global Surveyor, is that these bands are evidence of the past operation of
plate tectonics on Mars.
[[http://www.nasa.gov/centers/goddard/news/topstory/2005/mgs_plates.html "New Map Provides More Evidence Mars Once Like Earth"] - Oct. 12, 2005 Goddard Space Flight Center Press release. URL accessed March 17, 2006.]
Shortly after the landing of the
Mars Exploration Rovers in 2004, it was announced by a large group of scientists that they had conclusive evidence that
liquid water existed at one time on the surface of Mars. Key discoveries leading to this conclusion include the detection of various
minerals such as
hematite and
goethite which usually only form in the presence of water.
Image:nasa_mars_opportunity_rock_water_150_eng_02mar04.jpg Opportunity rover thumb|left|Photo of Microscopic rock forms indicating past signs of water, taken by ''[[Opportunity rover|Opportunity''.html" title="Meaning of Opportunity.html" title="Meaning of thumb|left|Photo of Microscopic rock forms indicating past signs of water, taken by ''[[Opportunity rover|Opportunity">thumb|left|Photo of Microscopic rock forms indicating past signs of water, taken by ''[[Opportunity rover|Opportunity''">Opportunity.html" title="Meaning of thumb|left|Photo of Microscopic rock forms indicating past signs of water, taken by ''[[Opportunity rover|Opportunity">thumb|left|Photo of Microscopic rock forms indicating past signs of water, taken by ''[[Opportunity rover|Opportunity''
Topography
Image:PIA02820.jpg thumb|right|Elevation map of Mars based on Mars Global Surveyor data
Image:Mars.jpg thumb|right|Mars, 2001, with polar ice caps visible.
Image:Mars NPArea-PIA00161 modest.jpg thumb|right|North Polar region with icecap. (Courtesy NASA/JPL-Caltech.)
The dichotomy of Martian topography is striking: northern plains flattened by lava flows contrast with the southern highlands, pitted and cratered by ancient impacts. The surface of Mars as seen from Earth is consequently divided into two kinds of areas, with differing
albedo. The paler plains covered with dust and sand rich in reddish iron oxides were once thought of as Martian 'continents' and given names like
Arabia Terra (''land of Arabia'') or
Amazonis Planitia (''Amazonian plain''). The dark features were thought to be seas, hence their names
Mare Erythraeum,
Mare Sirenum and
Aurorae Sinus. The largest dark feature seen from Earth is
Syrtis Major.
The
shield volcano shield volcano,
Olympus Mons Olympus Mons (''Mount Olympus''), is at 26 km the highest known mountain in the solar system. It is in a vast upland region called
Tharsis, which contains several large volcanos. See
list of mountains on Mars. The Tharsis region of Mars also has the solar system's largest canyon system,
Valles Marineris or the ''
Mariner program Mariner Valley'', which is 4000 km long and 7 km deep. Mars is also scarred by a number of
impact craters. The largest of these is the
Hellas Planitia Hellas impact basin, covered with light red sand. See
list of craters on Mars.
The difference between Mars' highest and lowest points is nearly 31 km (from the top of Olympus Mons at an altitude of 26 km to the bottom of the Hellas impact basin at an altitude of 4 km below the datum). In comparison, the difference between Earth's highest and lowest points (
Mount Everest and the
Mariana Trench) is only 19.7 km. Combined with the planets' different radii, this means Mars is nearly three times "rougher" than Earth.
The
International Astronomical Union's
Working Group for Planetary System Nomenclature is responsible for naming Martian surface features. (
#Nomenclature See below)
'''Zero elevation''': Since Mars has no oceans and hence no 'sea level', a zero-elevation surface or
mean gravity surface must be selected. The
datum for Mars is defined by the fourth-degree and fourth-order spherical harmonic gravity field, with the zero altitude defined by the 610.5 Pa (6.105 mbar) atmospheric pressure surface (approximately 0.6% of Earth's) at a temperature of 273.16 K. This pressure and temperature correspond to the
triple point of water.
'''Zero meridian''': Mars' equator is defined by its rotation, but the location of its
Prime Meridian was specified, as was Earth's, by choice of an arbitrary point which was accepted by later observers. The German astronomers
Wilhelm Beer and
Johann Heinrich Mädler selected a small circular feature as a reference point when they produced the first systematic chart of Mars features in 1830-32. In 1877, their choice was adopted as the prime meridian by the Italian astronomer
Giovanni Schiaparelli when he began work on his notable maps of Mars. After the spacecraft
Mariner 9 provided extensive imagery of Mars in 1972, a small crater (later called
Airy-0), located in the
Sinus Meridiani ('Middle Bay' or 'Meridian Bay') along the line of Beer and Mädler, was chosen by
Merton Davies of the
RAND RAND Corporation to provide a more precise definition of 0.0° longitude when he established a planetographic control point network.
Image:MarsTopoMap-PIA02031 modest.jpg Olympus Mons.html" title="Meaning of thumb thumb|right|250px|Topographic map of Mars, courtesy NASA/JPL-Caltech. Notable features include the Tharsis volcanoes in the west (including [[Olympus Mons), Valles Marineris to the east of Tharsis, and Hellas Basin in the southern hemisphere..html" title="Meaning of right|250px|Topographic map of Mars, courtesy NASA/JPL-Caltech. Notable features include the Tharsis volcanoes in the west (including [[Olympus Mons">thumb|right|250px|Topographic map of Mars, courtesy NASA/JPL-Caltech. Notable features include the Tharsis volcanoes in the west (including [[Olympus Mons), Valles Marineris to the east of Tharsis, and Hellas Basin in the southern hemisphere.">right|250px|Topographic map of Mars, courtesy NASA/JPL-Caltech. Notable features include the Tharsis volcanoes in the west (including [[Olympus Mons">thumb|right|250px|Topographic map of Mars, courtesy NASA/JPL-Caltech. Notable features include the Tharsis volcanoes in the west (including [[Olympus Mons), Valles Marineris to the east of Tharsis, and Hellas Basin in the southern hemisphere.
Moons
{{main|Mars' natural satellites}}
Mars has two tiny natural moons,
Phobos (moon) Phobos and
Deimos (moon) Deimos, which orbit very close to the planet and are thought to be captured
asteroids.
Both satellites were discovered in
1877 by
Asaph Hall, and are named after the characters
Phobos (mythology) Phobos (panic/fear) and
Deimos (mythology) Deimos (terror/dread) who, in
Greek mythology, accompanied their father
Ares, god of war, into battle. Ares was known as Mars to the
Ancient Rome Romans.
From the surface of Mars, the motions of Phobos and Deimos appear very different from that of our own moon. Speedy Phobos rises in the west, sets in the east, and rises again in just 11 hours, while Deimos, being only just outside synchronous orbit, rises as expected in the east but very slowly. Despite its 30 hour orbit, it takes 2.7 days to set in the west as it slowly falls behind the rotation of Mars, and as long again to rise.
The exploration of Mars
Image:Vikinglander-view.jpg Viking_1 thumb|right|[[Viking 1|Viking Lander 1 site.html" title="Meaning of Viking Lander 1.html" title="Meaning of thumb|right|[[Viking 1|Viking Lander 1">thumb|right|[[Viking 1|Viking Lander 1 site">Viking Lander 1.html" title="Meaning of thumb|right|[[Viking 1|Viking Lander 1">thumb|right|[[Viking 1|Viking Lander 1 site
Dozens of
spacecraft, including
orbiters,
landers, and
rovers, have been sent to Mars by the
Russian Federal Space Agency Soviet Union, the
NASA United States,
ESA Europe, and
JAXA Japan to study the planet's surface, climate, and geography. Roughly two-thirds of all spacecraft destined for Mars have failed in one manner or another before completing or even beginning their missions. Part of this high failure rate can be ascribed to technical problems, but enough have either failed or lost communications for no apparent reason that some researchers half-jokingly speak of an Earth-Mars "
Bermuda Triangle", or a
Mars Curse.
Mars Missions
{{main|Exploration of Mars}}
The first successful fly-by mission to Mars was
NASA's
Mariner 4 launched in
1964. The first successful objects to land on the surface were two
Soviet Union Soviet probes from the
Mars probe program, launched in
1971, but both lost contact within seconds of landing. Then was the
1975 NASA launches of the
Viking program, which consisted of two orbiters, each having a lander. Both landers successfully touched down in 1976 and remained operational for many years.
Following the
1992 failure of NASA's
Mars Observer orbiter, they launched the
Mars Global Surveyor in
1996. This mission was a complete success, having finished its primary mapping mission in early 2001. Only a month after the launch of the Surveyor, NASA launched the
Mars Pathfinder, carrying a robotic exploration vehicle, which landed in the
Ares Vallis on Mars. This mission was another big success, and received much publicity, partially due to the many spectacular images that were sent back to Earth.
Following various failures in the late 90s, in
2001 NASA launched the successful
Mars Odyssey orbiter, which is still in orbit as of March 2006. It notably determined that there are significant deposits of water ice in the upper meter or so of Mars'
regolith within 30° of the north and south pole.
In
2003, the
European Space Agency ESA launched the
Mars Express craft consisting of the
Mars Express Orbiter and the lander
Beagle 2. It was announced in early 2004 that the orbiter detected
methane in the atmosphere, which is a critical factor in determining if there is
life on Mars. Unfortunately attempts to contact the Beagle 2 failed and it was declared lost in early February 2004.
Also in
2003, NASA launched the twin
Mars Exploration Rover Mission Mars Exploration Rovers named ''
Spirit rover Spirit'' (MER-A) and ''
Opportunity rover Opportunity'' (MER-B). Both missions landed successfully in January 2004 and have met or exceeded all their targets. Among the most significant science returns has been the conclusive evidence that liquid water existed at some time in the past at both landing sites.
Dust devils (see picture below) are known to be passing over the Rovers, cleaning their solar panels, and thus extending their lifespan. It should be noted that dust devils were first detected on Mars from the surface by
Mars Pathfinder.
[Metzger S. M., [http://mpfwww.jpl.nasa.gov/science/lpsc98/1915.pdf Dust Devil Vortices at the Ares Vallis MPF Landing Site] (PDF)]
Image:Marsdustdevil2.gif Dust_devil.html" title="Meaning of thumb thumb|center|580px|[[Dust devil on Mars, photographed by the Mars rover ''
Spirit rover Spirit''.html" title="Meaning of center|580px|[[Dust devil">thumb|center|580px|[[Dust devil on Mars, photographed by the Mars rover ''
Spirit rover Spirit''">center|580px|[[Dust devil">thumb|center|580px|[[Dust devil on Mars, photographed by the Mars rover ''
Spirit rover Spirit''
On
August 12 2005 the NASA
Mars Reconnaissance Orbiter probe was launched toward the planet, to conduct a two-year science survey. The purpose of the mission is to do more studies and prepare the upcoming lander missions. It arrived in orbit on
March 10,
2006. The next scheduled mission to Mars is the NASA
Phoenix (spacecraft) Phoenix Mars lander, expected to launch in
2007.
{{Mars spacecraft}}
Astronomy on Mars
Image:Earth and Moon from Mars PIA04531.jpg Mars Global Surveyor.html" title="Meaning of thumb thumb|right|Earth and Moon from Mars, imaged by [[Mars Global Surveyor on
May 8 2003 13:00
UTC.
South America is visible..html" title="Meaning of right|Earth and Moon from Mars, imaged by [[Mars Global Surveyor">thumb|right|Earth and Moon from Mars, imaged by [[Mars Global Surveyor on
May 8 2003 13:00
UTC.
South America is visible.">right|Earth and Moon from Mars, imaged by [[Mars Global Surveyor">thumb|right|Earth and Moon from Mars, imaged by [[Mars Global Surveyor on
May 8 2003 13:00
UTC.
South America is visible.
{{main|Astronomy on Mars}}
It is now possible, with the existence of various orbiters, landers, and rovers to study
astronomy from the martian skies. In particular, the Earth and the Moon would easily be visible to the
naked eye. Also, one could observe the two
Mars' natural satellites moons of Mars. The moon
Phobos (moon) Phobos appears about one third the
angular diameter that the full
Moon appears from Earth, and when it is full it is bright enough to cast shadows. On the other hand
Deimos (moon) Deimos appears more or less starlike, and appears only slightly brighter than
Venus does from
Earth.
There are also various phenomenon well-known on Earth that have now been observed on Mars, such as
meteors and
Aurora (astronomy) auroras. The first meteor photographed on Mars was on
March 7 2004 by the ''
Spirit (rover) Spirit'' rover. Auroras occur on Mars, but they do not occur at the poles as on Earth, because Mars has no planetwide
magnetic field. Rather, they occur near magnetic anomalies in Mars's
crust (geology) crust, which are remnants from earlier days when Mars did have a magnetic field. They would probably be invisible to the
naked eye, being largely
ultraviolet phenomena.
Colonization of Mars
{{main|Colonization of Mars}}
Plans for crewed interplanetary exploration beyond the Moon have mostly assumed Mars as the first target; serious proposals arguably date from the late 1950's with
Project Orion. Manned Mars exploration by the United States has been explicitly identified as a long-term goal in the
Vision for Space Exploration announced in 2004 by US President
George W. Bush.
Nomenclature
Early nomenclature
Although better remembered for mapping the
Moon starting in 1830,
Johann Heinrich Mädler and
Wilhelm Beer were the first "areographers". They started off by establishing once and for all that most of the surface features were permanent, and pinned down Mars' rotation period. In 1840, Mädler combined ten years of observations and drew the first map of Mars ever made. Rather than giving names to the various markings they mapped, Beer and Mädler simply designated them with letters; Meridian Bay (Sinus Meridiani) was thus feature "a".
Over the next twenty years or so, as instruments improved and the number of observers also increased, various Martian features acquired a hodge-podge of names. To give a couple of examples,
Solis Lacus was known as the "Oculus" (the Eye), and
Syrtis Major was usually known as the "Hourglass Sea" or the "Scorpion". In 1858, it was also dubbed the "Atlantic Canale" by the Jesuit astronomer
Angelo Secchi. Secchi commented that it "seems to play the role of the Atlantic which, on Earth, separates the Old Continent from the New" —this was the first time the fateful ''canale'', which in Italian can mean either "channel" or "canal", had been applied to Mars.
In 1867,
Richard Anthony Proctor drew up a map of Mars based, somewhat crudely, on the Rev.
William Rutter Dawes' earlier drawings of 1865, then the best ones available. Proctor explained his system of nomenclature by saying, "I have applied to the different features the names of those observers who have studied the physical peculiarities presented by Mars." Here are some of his names, paired with those later proposed by
Giovanni Schiaparelli Schiaparelli:
* Kaiser Sea =
Syrtis Major
* Lockyer Land =
Hellas Planitia
* Main Sea =
Lacus Moeris
* Herschel II Strait =
Sinus Sabaeus
* Dawes Continent =
Aeria and Arabia
* De La Rue Ocean =
Mare Erythraeum
* Lockyer Sea =
Solis Lacus
* Dawes Sea =
Tithonius Lacus
* Madler Continent =
Chryse Planitia,
Ophir (disambiguation) Ophir,
Tharsis
* Maraldi Sea =
Maria Sirenum and
Cimmerium
* Secchi Continent =
Memnonia
* Hooke Sea =
Mare Tyrrhenum
* Cassini Land =
Ausonia
* Herschel I Continent =
Zephyria,
Aeolis,
Aethiopis
* Hind Land =
Libya
Proctor's nomenclature has often been criticized, mainly because so many of his names honored English astronomers, but also because he used many names more than once. In particular,
William Rutter Dawes Dawes appeared no fewer than ''six'' times (Dawes Ocean, Dawes Continent, Dawes Sea, Dawes Strait, Dawes Isle, and Dawes Forked Bay). Even so, Proctor's names are not without charm, and for all their shortcomings they were a foundation on which later astronomers would improve.
Modern nomenclature
Today, features on Mars derive from a number of sources. Large
albedo features retain many of the older names, but are often updated to reflect new knowledge of the nature of the features. For example 'Nix Olympica' (the snows of Olympus) has become ''
Olympus Mons'' (Mount Olympus).
Large Martian craters are named after important scientists and science fiction writers; smaller ones are named after towns and villages on Earth.
Orbital Characteristics
Mars has a fairly high
eccentricity compared to other
planets in the solar system, and has an average distance from the
Sun of roughly 230 million
kilometers km (1.5
Astronomical Unit AU). It's
orbital period is 687 (Earth)
days, but the
sol solar day (or ''sol'') on Mars is only slightly more than an Earth day: 24 hours, 39 minutes, and 35.244 seconds. See
Timekeeping on Mars.
Close Approaches to Earth
Approximately every 780 days
Opposition (astronomy) opposition occurs, which is when Mars is nearest to
Earth. This minimum distance varies between about 55 and 100 million
kilometers km due to the planets'
ellipse elliptical orbits.
On
August 27,
2003, at 9:51:13 UT, Mars made its closest approach to Earth in nearly 60,000 years: 55,758,006 km (approximately 35 million miles) without
Light-time correction. This occurred when Mars was one day from
Astronomical opposition opposition and about three days from its
perihelion, making Mars particularly easy to see from Earth. The last time it came so close is estimated to have been on
September 12,
Middle Paleolithic 57,617 BC. Detailed analysis of the solar system's gravitational landscape forecasts an even closer approach in 2287. However, to keep this in perspective, this record approach was only an imperceptibly small distance closer than other recent close approaches. For instance, the minimum distance on
August 22 1924 was 0.37284
astronomical unit AU, compared to 0.37271 AU on
August 27 2003, and the minimum distance on
August 24 2208 will be 0.37278 AU.
Observing Mars
{{See also|Aspects of Mars}}
To a naked-eye observer, Mars usually shows a distinct yellow, orange or reddish colour, and varies in brightness more than any other planet as seen from Earth over the course of its orbit, due to the fact that when furthest away from the Earth it is more than seven times as far from the latter as when it is closest (and can be lost in the Sun's glare for months at a time when least favourably positioned). At its most favourable times — which occur twice every 32 years, alternately at 15 and 17-year intervals, and always between late July and late September — Mars shows a wealth of surface detail to a
telescope. Especially noticeable, even at low magnification, are the
polar ice caps.
Transits and occultations
Image:MarsSunsetCut.jpg thumb|right|400px|Photograph of a Martian sunset taken by Spirit at Gusev crater, May 19th, 2005.
A
transit of Earth from Mars transit of the Earth as seen from Mars will occur on
November 10,
2084. At that time the Sun, the Earth and Mars will be exactly in a line. There are also
transit of Mercury from Mars transits of Mercury and
transit of Venus from Mars transits of Venus, and the moon
Deimos (moon) Deimos is of sufficiently small
angular diameter that its partial "eclipses" of the Sun are best considered transits (see
Transit of Deimos from Mars).
The only occultation of Mars by
Venus to be observed was that of October 3, 1590, seen by M. Möstlin at
Heidelberg.
Life on Mars
{{main|Life on Mars}}
Some evidence suggests that the planet once was significantly more habitable than today, but the question on whether living
organisms ever actually existed there is an open one.
The
Viking program Viking probes of the mid-1970s carried experiments designed to detect microorganisms in Martian soil at their respective landing sites, and had some positive results, later denied by many scientists, resulting in
Viking biological experiments ongoing controversy. Also, present biologic activity is one of the explanations that have been suggested for the presence of traces of
methane within the
Atmosphere of Mars Martian atmosphere, but other explanations not involving life are generally considered more likely.
Martian meteorites
{{main|Mars meteorite}}
A handful of objects are known that are surely
meteorites and may be
Martian meteorite of Martian origin. Two of them may show signs of ancient bacterial activity. On
August 6,
1996 NASA announced that analysis of the
ALH 84001 meteorite, thought to have come from Mars, shows some features that may be
fossils of single-celled organisms, although this idea is controversial. In fact recent research indicates that the rock, since its creation several billion years ago, has never been exposed to temperatures for extended periods of time that would allow for liquid water.
In March 2004, it was suggested that the unique
Kaidun meteorite landed on March 12, 1980 in
Yemen, may have originated on the Martian moon of
Phobos (moon) Phobos.
On
April 14,
2004, NASA revealed that a rock known as "Bounce", studied by the Mars Exploration Rover ''Opportunity'', was similar in composition to the meteorite EETA79001-B, discovered in
Antarctica in 1979. The rock may have been ejected from the same crater as the meteorite, or from another crater in the same area of the Martian surface.
Canals
{{main|Martian canals}}
The belief that there may be life on Mars was popularized in the 19th century, mainly due to the announcement of
Martian canals from the observations by
Percival Lowell and
Giovanni Schiaparelli. Schiaparelli called these observed features ''canali'', meaning ''channels'' in Italian. This was popularly mistranslated as 'canals', and the myth of the
Martian canals began. They were apparently artificial linear features on the surface that were asserted to be canals, and together with the seasonal changes in the brightness of some areas, they were thought to be linked with vegetation growth. This gave rise to
Mars in fiction many stories concerning Martians. The linear features are now known to be mostly non-existent or, in some cases, dry ancient watercourses. The color changes have been ascribed to dust storms.
The Mars flag
Image:Flag of Mars.svg thumb|right|The official Mars Society tricolor
In early 2000, a proposed Mars flag flew aboard the
space shuttle Space Shuttle Discovery Discovery. Designed by
NASA engineer and
Flashline Mars Arctic Research Station task force leader
Pascal Lee and carried aboard by
astronaut John Mace Grunsfeld, the flag consists of three vertical bars (red, green, and blue), symbolizing the transformation of Mars from a barren planet (red) to one bearing sustainable life (green), and finally to a fully
terraforming terraformed planet with open bodies of water (blue). This design was suggested by the
Kim Stanley Robinson science fiction sci-fi trilogy
Mars trilogy ''Red Mars, Green Mars'', and ''Blue Mars''. While other designs have been proposed, the republican tricolor has been adopted by the
Mars Society as its own official banner. In a statement released after the launch of the mission, the Society said that the flag "has now been honored by a vessel of the leading spacefaring nation on Earth," and added that "(i)t is fitting that this action occurred when it did: at the dawning of a new millennium."
[[http://archives.cnn.com/2000/TECH/space/01/07/mars.flag/ "Official 'Mars flag' unfurls in space"] - January 7, 2000 CNN news article.]
Mars in fiction
{{main|Mars in fiction}}
The depiction of Mars in fiction has been stimulated by its dramatic red color and by early scientific speculations that its surface conditions might be capable of supporting life.
Until the arrival of planetary probes, the traditional view of Mars derived from the astronomers
Percival Lowell and
Giovanni Schiaparelli, whose observation of supposedly linear features on the planet created the myth of canals on Mars. For many years, the standard notion of the planet was a drying, cooling, dying world with ancient civilizations constructing irrigation works. Thus originated a large number of science fiction scenarios, the best known of which is
H. G. Wells' ''
The War of the Worlds (novel) The War of the Worlds'', in which Martians seek to escape their dying planet by invading Earth. In the movie ''
Mars Attacks!'' the Martians also invade Earth.
After the
Mariner program Mariner and
Viking program Viking spacecraft had returned pictures of Mars as it really is, an apparently lifeless and canal-less world, these ideas about Mars had to be abandoned and a vogue for accurate, realist depictions of human colonies on Mars developed, the best known of which may be
Kim Stanley Robinson's
Mars trilogy ''Mars'' trilogy. However, pseudo-scientific speculations about the
Face on Mars and other enigmatic landmarks spotted by space probes have meant that ancient civilizations continue to be a popular theme in science fiction, especially in film.
Another popular theme, particularly among American writers, is the Martian colony that fights for independence from Earth. This is a major plot element in the novels of
Greg Bear and
Kim Stanley Robinson, as well as the movie ''
Total Recall (film) Total Recall'' (based on a short story by
Philip K. Dick) and the television series ''
Babylon 5''. Many video games also use this element, such as ''
Red Faction''. Mars was also the setting for the popular 'Doom' video game franchise.
See also
*
Areography
*
Astrobiology
*
Astronomy on Mars
*
Colonization of Mars
*
Darian calendar
*
Face on Mars Face on Mars photo article
*
Timekeeping on Mars
*
Exploration of Mars
*
List of artificial objects on Mars
*
List of craters on Mars
*
List of mountains on Mars
*
Extraterrestrial life
*
Terraforming
*
Mars Direct
*
Planets in astrology#Mars Mars in astrology
References
* William Sheehan, [http://www.uapress.arizona.edu/onlinebks/mars/contents.htm ''The Planet Mars: A History of Observation and Discovery''], The University of Arizona Press, Tucson, 1996
* Vladimir A. Krasnopolsky, Jean-Pierre Maillard, Tobias C. Owen, ''[http://www.google.ca/url?sa=U&start=1&q=http://www.cosis.net/abstracts/EGU04/06169/EGU04-A-06169.pdf&e=912 Detection of methane in the Martian atmosphere: evidence for life?]'',
Icarus (journal) Icarus, 172 (2), 537-547.
External links
{{commons|Mars}}
{{wikinewscat|Mars}}
-
NASA's Mars fact sheet
-
Google Mars Interactive image of Mars
-
Marsgeo.com Mars Rover photos, videos & surface geolgy
-
Nine Planets Mars page
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MarsNews.com - News and info site
-
Mars, the Red Planet - both the science and the lore
-
Introduction to Martian topography, with Hubble Space Telescope photos
-
FU Berlin: HRSC (camera) experiment at Mars Express (eng. & ger.; press releases and high resolution images)
-
Technical Notes about Time on Mars
-
On Mars: Exploration of the Red Planet 1958-1978 from the NASA History Office.
-
A Trip Into Space Photos and descriptions of Mars
-
Martian Law - a CATO white paper
-
Computer Simulation of a flyby through Mariner Valley
-
Mars Unearthed - Comparisons of terrains between Earth and Mars
-
3D VRML Mars globe
-
Enterprise Mission: Richard C. Hoagland's Homepage
-
Ralph Aeschliman's Online Atlas of Mars
-
Planets - Mars A kid's guide to Mars.
-
Is there Global Warming on Mars?
-
Mars Express: The Libya Montes Valley
Water on Mars
-
Highly visible ice lake found on Mars - BBC
* Dr.
Tony Phillips: [http://science.nasa.gov/headlines/y2000/ast29jun_1m.htm "Making a Splash on Mars"], ''Science@
NASA'' article,
June 29,
2000. Phillips describes the Martian "gullies" and explains the conditions under which liquid water can exist on the surface of Mars.
-
BBC News story on subsurface ice deposits on Mars
-
BBC News update on Mars Express' findings of polar water ice and water-eroded features on the surface
-
Mars Rover Scientists Wring Water Story from Rocks This image taken by Mars Rover ''Opportunity'' shows microscopic rock forms indicating past signs of water. Courtesy: NASA
-
BBC News Mars pictures reveal frozen sea
Mars exploration
-
The Political Economy of Very Large Space Projects (Journal Of Evolution and Technology)
-
exploreMarsnow Interactive Mars base simulation. Winner of 2003 Webby Award for Science.
-
NASA Mars Exploration Rover Home Page
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Be on Mars Anaglyphs from the Mars Rovers (3D)
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Martian Travel Guide Student's project for Catch a Star
{{Mars Footer}}
{{Footer_SolarSystem}}
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pam:Mars
:''This article is about the block cipher. For MARS (Molecular Adsorbents Recirculation System), see
liver dialysis. For the album by Gackt, see
MARS (album). For pMARS, see
Core War.
In
cryptography, '''MARS''' is a
block cipher which was
IBM's submission to the
Advanced Encryption Standard process (AES). MARS was selected as a finalist. The design team included
Don Coppersmith who had been involved in the creation of the previous
Data Encryption Standard (DES) twenty years earlier.
MARS has a 128-bit
block size (cryptography) block size and a variable
key size of between 128 and 448 bits (in 32-bit increments). Unlike most block ciphers, MARS has a heterogeneous structure: several rounds of a cryptographic core are "jacketed" by unkeyed mixing rounds.
External links
-
IBM's page on MARS
-
SCAN's entry on MARS
-
John Savard's description of MARS
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