The Palnet Mars2

7/31/2019 The Palnet Mars2

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Chapter 1
http://en.wikipedia.org/wiki/File:Martian_Methane_Map.jpg


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Mars

Animation that rolls Mars around to show all the major features of the Martian

topography.

Mars is the fourth planet from the Sun in the Solar System. Named after the Roman god

of war, Mars, it is often described as the "Red Planet" as the iron oxide prevalent on its

surface gives it a reddish appearance.Mars is a terrestrial planet with a

thin atmosphere, having surface features reminiscent both of the impact craters of

the Moon and the volcanoes, valleys, deserts, and polar ice caps of Earth.

The rotational period and seasonal cycles of Mars are likewise similar to those of Earth,as is the tilt that produces the seasons. Mars is the site of Olympus Mons, the highest

known mountain within the Solar System, and of Valles Marineris, the largest canyon.

The smooth Borealis basin in the northern hemisphere covers 40% of the planet and

may be a giant impact feature.

Until the first successful flyby of Mars occurred in 1965, byMariner 4, many speculated

about the presence of liquid water on the planet's surface. This was based on observed

periodic variations in light and dark patches, particularly in the polar latitudes, which

appeared to be seas and continents; long, dark striations were interpreted by some asirrigation channels for liquid water. These straight line features were later explained

asoptical illusions, though geological evidence gathered by unmanned missions suggest

that Mars once had large-scale water coverage on its surface.In 2005, radar data

revealed the presence of large quantities of water ice at the poles, and at mid-

latitudes. The Mars roverSpiritsampled chemical compounds containing water
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molecules in March 2007. ThePhoenixlander directly sampled water ice in shallow

Martian soil on July 31, 2008.

Mars has two moons, Phobos and Deimos, which are small and irregularly shaped.

These may be captured asteroids, similar to 5261 Eureka, aMartian trojan asteroid.

Mars is currently host to three functional orbiting spacecraft:Mars Odyssey,Mars

Express, and theMars Reconnaissance Orbiter, and one on the surface, the Mars

Exploration RoverOpportunity. Defunct spacecraft on the surface include MER-A Spirit,

and several other inert landers and rovers, both successful and unsuccessful such as

the Phoenixlander, which completed its mission in 2008. Observations byNASA's now-

defunctMars Global Surveyorshow evidence that parts of the southern polar ice cap

have been receding. Observations by the Mars Reconnaissance Orbiterhave revealed

possible flowing water during the warmest months on Mars.

Mars can easily be seen from Earth with the naked eye. Its apparent magnitude reaches

3.0 a brightness surpassed only by Jupiter, Venus, the Moon, and the Sun. Optical

ground based telescopes are typically limited to resolving features about 300 km (186

miles) across when Earth and Mars are closest, because of Earth's atmosphere.

Mars

Global view of Mars as seen by theViking 1orbiter in 1980, showing theValles

Marineris(center)

Designations
http://en.wikipedia.org/wiki/Phoenix_(spacecraft)http://en.wikipedia.org/wiki/Phoenix_(spacecraft)http://en.wikipedia.org/wiki/Phoenix_(spacecraft)http://en.wikipedia.org/wiki/Moons_of_Marshttp://en.wikipedia.org/wiki/Phobos_(moon)http://en.wikipedia.org/wiki/Deimos_(moon)http://en.wikipedia.org/wiki/Asteroidhttp://en.wikipedia.org/wiki/5261_Eurekahttp://en.wikipedia.org/wiki/List_of_Mars_trojan_asteroidshttp://en.wikipedia.org/wiki/Spacecrafthttp://en.wikipedia.org/wiki/Mars_Odysseyhttp://en.wikipedia.org/wiki/Mars_Odysseyhttp://en.wikipedia.org/wiki/Mars_Odysseyhttp://en.wikipedia.org/wiki/Mars_Expresshttp://en.wikipedia.org/wiki/Mars_Expresshttp://en.wikipedia.org/wiki/Mars_Expresshttp://en.wikipedia.org/wiki/Mars_Expresshttp://en.wikipedia.org/wiki/Mars_Reconnaissance_Orbiterhttp://en.wikipedia.org/wiki/Mars_Reconnaissance_Orbiterhttp://en.wikipedia.org/wiki/Mars_Reconnaissance_Orbiterhttp://en.wikipedia.org/wiki/Mars_Exploration_Roverhttp://en.wikipedia.org/wiki/Mars_Exploration_Roverhttp://en.wikipedia.org/wiki/Opportunity_roverhttp://en.wikipedia.org/wiki/Opportunity_roverhttp://en.wikipedia.org/wiki/Opportunity_roverhttp://en.wikipedia.org/wiki/NASAhttp://en.wikipedia.org/wiki/Mars_Global_Surveyorhttp://en.wikipedia.org/wiki/Mars_Global_Surveyorhttp://en.wikipedia.org/wiki/Mars_Global_Surveyorhttp://en.wikipedia.org/wiki/Apparent_magnitudehttp://en.wikipedia.org/wiki/Jupiterhttp://en.wikipedia.org/wiki/Venushttp://en.wikipedia.org/wiki/Viking_1http://en.wikipedia.org/wiki/Viking_1http://en.wikipedia.org/wiki/Viking_1http://en.wikipedia.org/wiki/Valles_Marinerishttp://en.wikipedia.org/wiki/Valles_Marinerishttp://en.wikipedia.org/wiki/Valles_Marinerishttp://en.wikipedia.org/wiki/Valles_Marinerishttp://en.wikipedia.org/wiki/File:Mars_Valles_Marineris_EDIT.jpghttp://en.wikipedia.org/wiki/File:Mars_symbol.svghttp://en.wikipedia.org/wiki/File:Mars_Valles_Marineris_EDIT.jpghttp://en.wikipedia.org/wiki/File:Mars_symbol.svghttp://en.wikipedia.org/wiki/Valles_Marinerishttp://en.wikipedia.org/wiki/Valles_Marinerishttp://en.wikipedia.org/wiki/Viking_1http://en.wikipedia.org/wiki/Venushttp://en.wikipedia.org/wiki/Jupiterhttp://en.wikipedia.org/wiki/Apparent_magnitudehttp://en.wikipedia.org/wiki/Mars_Global_Surveyorhttp://en.wikipedia.org/wiki/NASAhttp://en.wikipedia.org/wiki/Opportunity_roverhttp://en.wikipedia.org/wiki/Mars_Exploration_Roverhttp://en.wikipedia.org/wiki/Mars_Exploration_Roverhttp://en.wikipedia.org/wiki/Mars_Reconnaissance_Orbiterhttp://en.wikipedia.org/wiki/Mars_Expresshttp://en.wikipedia.org/wiki/Mars_Expresshttp://en.wikipedia.org/wiki/Mars_Odysseyhttp://en.wikipedia.org/wiki/Spacecrafthttp://en.wikipedia.org/wiki/List_of_Mars_trojan_asteroidshttp://en.wikipedia.org/wiki/5261_Eurekahttp://en.wikipedia.org/wiki/Asteroidhttp://en.wikipedia.org/wiki/Deimos_(moon)http://en.wikipedia.org/wiki/Phobos_(moon)http://en.wikipedia.org/wiki/Moons_of_Marshttp://en.wikipedia.org/wiki/Phoenix_(spacecraft)


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Orbital characteristicsAphelion 249,209,300 km

1.665 861AU

Perihelion 206,669,000 km

1.381 497 AU

Semi-major axis 227,939,100 km

1.523 679 AU

Eccentricity 0.093 315

Orbital period 686.971 days

1.8808Julian years

668.5991sols

Synodic period 779.96 days

2.135 Julian years

Average orbital speed 24.077 km/s

Mean anomaly 19.3564

Inclination 1.850 toecliptic

5.65 toSun'sequator

1.67 toinvariable plane

Longitude of ascending node 49.562

Argument of perihelion 286.537

Satellites 2

Physical characteristics

Equatorialradius 3,396.2 0.1 km
http://en.wikipedia.org/wiki/Osculating_orbithttp://en.wikipedia.org/wiki/Osculating_orbithttp://en.wikipedia.org/wiki/Apsishttp://en.wikipedia.org/wiki/Apsishttp://en.wikipedia.org/wiki/Astronomical_unithttp://en.wikipedia.org/wiki/Astronomical_unithttp://en.wikipedia.org/wiki/Astronomical_unithttp://en.wikipedia.org/wiki/Apsishttp://en.wikipedia.org/wiki/Apsishttp://en.wikipedia.org/wiki/Semi-major_axishttp://en.wikipedia.org/wiki/Orbital_eccentricityhttp://en.wikipedia.org/wiki/Orbital_eccentricityhttp://en.wikipedia.org/wiki/Orbital_periodhttp://en.wikipedia.org/wiki/Orbital_periodhttp://en.wikipedia.org/wiki/Julian_year_(astronomy)http://en.wikipedia.org/wiki/Julian_year_(astronomy)http://en.wikipedia.org/wiki/Julian_year_(astronomy)http://en.wikipedia.org/wiki/Timekeeping_on_Marshttp://en.wikipedia.org/wiki/Timekeeping_on_Marshttp://en.wikipedia.org/wiki/Timekeeping_on_Marshttp://en.wikipedia.org/wiki/Orbital_periodhttp://en.wikipedia.org/wiki/Orbital_periodhttp://en.wikipedia.org/wiki/Orbital_speedhttp://en.wikipedia.org/wiki/Mean_anomalyhttp://en.wikipedia.org/wiki/Mean_anomalyhttp://en.wikipedia.org/wiki/Inclinationhttp://en.wikipedia.org/wiki/Ecliptichttp://en.wikipedia.org/wiki/Ecliptichttp://en.wikipedia.org/wiki/Ecliptichttp://en.wikipedia.org/wiki/Sunhttp://en.wikipedia.org/wiki/Sunhttp://en.wikipedia.org/wiki/Sunhttp://en.wikipedia.org/wiki/Equatorhttp://en.wikipedia.org/wiki/Equatorhttp://en.wikipedia.org/wiki/Equatorhttp://en.wikipedia.org/wiki/Invariable_planehttp://en.wikipedia.org/wiki/Invariable_planehttp://en.wikipedia.org/wiki/Invariable_planehttp://en.wikipedia.org/wiki/Longitude_of_the_ascending_nodehttp://en.wikipedia.org/wiki/Argument_of_periapsishttp://en.wikipedia.org/wiki/Argument_of_periapsishttp://en.wikipedia.org/wiki/Natural_satellitehttp://en.wikipedia.org/wiki/Equatorhttp://en.wikipedia.org/wiki/Equatorhttp://en.wikipedia.org/wiki/Equatorhttp://en.wikipedia.org/wiki/Natural_satellitehttp://en.wikipedia.org/wiki/Argument_of_periapsishttp://en.wikipedia.org/wiki/Longitude_of_the_ascending_nodehttp://en.wikipedia.org/wiki/Invariable_planehttp://en.wikipedia.org/wiki/Equatorhttp://en.wikipedia.org/wiki/Sunhttp://en.wikipedia.org/wiki/Ecliptichttp://en.wikipedia.org/wiki/Inclinationhttp://en.wikipedia.org/wiki/Mean_anomalyhttp://en.wikipedia.org/wiki/Orbital_speedhttp://en.wikipedia.org/wiki/Orbital_periodhttp://en.wikipedia.org/wiki/Timekeeping_on_Marshttp://en.wikipedia.org/wiki/Julian_year_(astronomy)http://en.wikipedia.org/wiki/Orbital_periodhttp://en.wikipedia.org/wiki/Orbital_eccentricityhttp://en.wikipedia.org/wiki/Semi-major_axishttp://en.wikipedia.org/wiki/Apsishttp://en.wikipedia.org/wiki/Astronomical_unithttp://en.wikipedia.org/wiki/Apsishttp://en.wikipedia.org/wiki/Osculating_orbit


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87 C63 C 20 C

Apparent magnitude +1.6 to 3.0

Angular diameter 3.525.1"

Atmosphere

Surfacepressure 0.636 (0.40.87)kPa

./Composition (mole fractions)

95.32%carbon dioxide

2.7%nitrogen

1.6%argon

0.13%oxygen0.08%carbon monoxide

210ppmwatervapor

100 ppmnitric oxide

15 ppm molecular hydrogen

2.5 ppmneon

850ppbHDO

300ppbkrypton

130 ppbformaldehyde

80 ppbxenon

18 ppbhydrogen peroxide10 ppbmethane

Physical characteristics

Size comparison of Earth and Mars.
http://en.wikipedia.org/wiki/Apparent_magnitudehttp://en.wikipedia.org/wiki/Angular_diameterhttp://en.wikipedia.org/wiki/Angular_diameterhttp://en.wikipedia.org/wiki/Atmospheric_pressurehttp://en.wikipedia.org/wiki/Atmospheric_pressurehttp://en.wikipedia.org/wiki/Atmospheric_pressurehttp://en.wikipedia.org/wiki/Pascal_(unit)http://en.wikipedia.org/wiki/Pascal_(unit)http://en.wikipedia.org/wiki/Pascal_(unit)http://en.wikipedia.org/wiki/Mole_fractionhttp://en.wikipedia.org/wiki/Mole_fractionhttp://en.wikipedia.org/wiki/Mole_fractionhttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Argonhttp://en.wikipedia.org/wiki/Argonhttp://en.wikipedia.org/wiki/Argonhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Carbon_monoxidehttp://en.wikipedia.org/wiki/Carbon_monoxidehttp://en.wikipedia.org/wiki/Carbon_monoxidehttp://en.wikipedia.org/wiki/Parts_per_millionhttp://en.wikipedia.org/wiki/Parts_per_millionhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Nitric_oxidehttp://en.wikipedia.org/wiki/Nitric_oxidehttp://en.wikipedia.org/wiki/Nitric_oxidehttp://en.wikipedia.org/wiki/Neonhttp://en.wikipedia.org/wiki/Neonhttp://en.wikipedia.org/wiki/Neonhttp://en.wikipedia.org/wiki/Parts-per_notationhttp://en.wikipedia.org/wiki/Parts-per_notationhttp://en.wikipedia.org/wiki/Heavy_waterhttp://en.wikipedia.org/wiki/Heavy_waterhttp://en.wikipedia.org/wiki/Heavy_waterhttp://en.wikipedia.org/wiki/Ppbhttp://en.wikipedia.org/wiki/Ppbhttp://en.wikipedia.org/wiki/Kryptonhttp://en.wikipedia.org/wiki/Kryptonhttp://en.wikipedia.org/wiki/Kryptonhttp://en.wikipedia.org/wiki/Formaldehydehttp://en.wikipedia.org/wiki/Formaldehydehttp://en.wikipedia.org/wiki/Formaldehydehttp://en.wikipedia.org/wiki/Xenonhttp://en.wikipedia.org/wiki/Xenonhttp://en.wikipedia.org/wiki/Xenonhttp://en.wikipedia.org/wiki/Hydrogen_peroxidehttp://en.wikipedia.org/wiki/Hydrogen_peroxidehttp://en.wikipedia.org/wiki/Hydrogen_peroxidehttp://en.wikipedia.org/wiki/Methanehttp://en.wikipedia.org/wiki/Methanehttp://en.wikipedia.org/wiki/Methanehttp://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/File:Mars_Earth_Comparison.pnghttp://en.wikipedia.org/wiki/File:Mars_Earth_Comparison.pnghttp://en.wikipedia.org/wiki/File:Mars_Earth_Comparison.pnghttp://en.wikipedia.org/wiki/File:Mars_Earth_Comparison.pnghttp://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/Methanehttp://en.wikipedia.org/wiki/Hydrogen_peroxidehttp://en.wikipedia.org/wiki/Xenonhttp://en.wikipedia.org/wiki/Formaldehydehttp://en.wikipedia.org/wiki/Kryptonhttp://en.wikipedia.org/wiki/Ppbhttp://en.wikipedia.org/wiki/Heavy_waterhttp://en.wikipedia.org/wiki/Parts-per_notationhttp://en.wikipedia.org/wiki/Neonhttp://en.wikipedia.org/wiki/Nitric_oxidehttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Parts_per_millionhttp://en.wikipedia.org/wiki/Carbon_monoxidehttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Argonhttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Mole_fractionhttp://en.wikipedia.org/wiki/Pascal_(unit)http://en.wikipedia.org/wiki/Atmospheric_pressurehttp://en.wikipedia.org/wiki/Angular_diameterhttp://en.wikipedia.org/wiki/Apparent_magnitude


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Geological history

Mars is a terrestrial planet that consists of minerals

containing silicon and oxygen, metals, and other elements that typically make up rock.

The surface of Mars is primarily composed of tholeiitic basalt,although parts are

more silica-rich than typical basalt and may be similar to andesiticrocks on Earth or

silica glass. Regions of low albedo show concentrations of plagioclase feldspar, with

northern low albedo regions displaying higher than normal concentrations of sheet

silicates and high-silicon glass. Parts of the southern highlands include detectable

amounts of high-calciumpyroxenes. Localized concentrations

of hematite and olivine have also been found. Much of the surface is deeply covered by

finely grainediron(III) oxide dust.

Like Earth, this planet has undergone differentiation, resulting in a dense, metallic core

region overlaid by less dense materials. Current models of the planet's interior imply a

core region about 1794 65 km in radius, consisting primarily of iron and nickel with

about 1617% sulfur. Thisiron sulfide core is partially fluid, and has twice the

concentration of the lighter elements than exist at Earth's core. The core is surrounded

by a silicate mantle that formed many of the tectonic and volcanic features on the

planet, but now appears to be dormant. Besides silicon and oxygen, the most abundant

elements in the martian crust are iron, magnesium, aluminum, calcium, and potassium.

The average thickness of the planet's crust is about 50 km, with a maximum thicknessof 125 km. Earth's crust, averaging 40 km, is only one third as thick as Mars crust,

relative to the sizes of the two planets.

Although Mars has no evidence of a current structured global magnetic

field,observations show that parts of the planet's crust have been magnetized, and that

alternating polarity reversals of its dipole field have occurred in the past.

This paleomagnetism of magnetically susceptible minerals has properties that are very

similar to the alternating bands found on the ocean floors of Earth. One theory,

published in 1999 and re-examined in October 2005 (with the help of theMars GlobalSurveyor), is that these bands demonstrate plate tectonics on Mars four billion years

ago, before the planetarydynamo ceased to function and the planet's magnetic field

faded away.

During the Solar System's formation, Mars was created as the result of a stochastic

process of run-away accretion out of the protoplanetary disk that orbited the Sun. Mars
http://en.wikipedia.org/wiki/Terrestrial_planethttp://en.wikipedia.org/wiki/Siliconhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Rock_(geology)http://en.wikipedia.org/wiki/Tholeiitic_magma_serieshttp://en.wikipedia.org/wiki/Basalthttp://en.wikipedia.org/wiki/Silicahttp://en.wikipedia.org/wiki/Andesitichttp://en.wikipedia.org/wiki/Albedohttp://en.wikipedia.org/wiki/Plagioclase_feldsparhttp://en.wikipedia.org/wiki/Pyroxeneshttp://en.wikipedia.org/wiki/Hematitehttp://en.wikipedia.org/wiki/Olivinehttp://en.wikipedia.org/wiki/Iron(III)_oxidehttp://en.wikipedia.org/wiki/Planetary_differentiationhttp://en.wikipedia.org/wiki/Ironhttp://en.wikipedia.org/wiki/Nickelhttp://en.wikipedia.org/wiki/Sulfurhttp://en.wikipedia.org/wiki/Iron(II)_sulfidehttp://en.wikipedia.org/wiki/Mantle_(geology)http://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Paleomagnetismhttp://en.wikipedia.org/wiki/Magnetic_stripinghttp://en.wikipedia.org/wiki/Mars_Global_Surveyorhttp://en.wikipedia.org/wiki/Mars_Global_Surveyorhttp://en.wikipedia.org/wiki/Mars_Global_Surveyorhttp://en.wikipedia.org/wiki/Mars_Global_Surveyorhttp://en.wikipedia.org/wiki/Plate_tectonicshttp://en.wikipedia.org/wiki/1000000000_(number)http://en.wikipedia.org/wiki/Dynamo_theoryhttp://en.wikipedia.org/wiki/Formation_and_evolution_of_the_Solar_Systemhttp://en.wikipedia.org/wiki/Stochastic_processhttp://en.wikipedia.org/wiki/Stochastic_processhttp://en.wikipedia.org/wiki/Protoplanetary_diskhttp://en.wikipedia.org/wiki/Protoplanetary_diskhttp://en.wikipedia.org/wiki/Stochastic_processhttp://en.wikipedia.org/wiki/Stochastic_processhttp://en.wikipedia.org/wiki/Formation_and_evolution_of_the_Solar_Systemhttp://en.wikipedia.org/wiki/Dynamo_theoryhttp://en.wikipedia.org/wiki/1000000000_(number)http://en.wikipedia.org/wiki/Plate_tectonicshttp://en.wikipedia.org/wiki/Mars_Global_Surveyorhttp://en.wikipedia.org/wiki/Mars_Global_Surveyorhttp://en.wikipedia.org/wiki/Magnetic_stripinghttp://en.wikipedia.org/wiki/Paleomagnetismhttp://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Mantle_(geology)http://en.wikipedia.org/wiki/Iron(II)_sulfidehttp://en.wikipedia.org/wiki/Sulfurhttp://en.wikipedia.org/wiki/Nickelhttp://en.wikipedia.org/wiki/Ironhttp://en.wikipedia.org/wiki/Planetary_differentiationhttp://en.wikipedia.org/wiki/Iron(III)_oxidehttp://en.wikipedia.org/wiki/Olivinehttp://en.wikipedia.org/wiki/Hematitehttp://en.wikipedia.org/wiki/Pyroxeneshttp://en.wikipedia.org/wiki/Plagioclase_feldsparhttp://en.wikipedia.org/wiki/Albedohttp://en.wikipedia.org/wiki/Andesitichttp://en.wikipedia.org/wiki/Silicahttp://en.wikipedia.org/wiki/Basalthttp://en.wikipedia.org/wiki/Tholeiitic_magma_serieshttp://en.wikipedia.org/wiki/Rock_(geology)http://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Siliconhttp://en.wikipedia.org/wiki/Terrestrial_planet


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has many distinctive chemical features caused by its position in the Solar System.

Elements with comparatively low boiling points such as chlorine, phosphorus and

sulphur are much more common on Mars than Earth; these elements were probably

removed from areas closer to the Sun by the young star's energetic solar wind.

The geological history of Mars can be split into many periods, but the following are the

three primary periods:

Noachian period (named after Noachis Terra): Formation of the oldest extant

surfaces of Mars, 4.5 billion years ago to 3.5 billion years ago. Noachian age

surfaces are scarred by many large impact craters. The Tharsis bulge, a volcanic

upland, is thought to have formed during this period, with extensive flooding by liquid

water late in the period.

Hesperian period (named after Hesperia Planum): 3.5 billion years ago to 2.93.3billion years ago. The Hesperian period is marked by the formation of extensive lava

plains.

Amazonian period (named after Amazonis Planitia): 2.93.3 billion years ago to

present. Amazonian regions have few meteorite impact craters, but are otherwise

quite varied. Olympus Mons formed during this period, along with lava flows

elsewhere on Mars.

Some geological activity is still taking place on Mars. The Athabasca Valles is home to

sheet-like lava flows up to about 200 Mya. Water flows in the grabens calledthe Cerberus Fossae occurred less than 20 Mya, indicating equally recent volcanic

intrusions. On February 19, 2008, images from theMars Reconnaissance

Orbitershowed evidence of an avalanche from a 700 m high cliff.

Soil
http://en.wikipedia.org/wiki/Solar_windhttp://en.wikipedia.org/wiki/Noachis_Terrahttp://en.wikipedia.org/wiki/Tharsishttp://en.wikipedia.org/wiki/Amazonis_Planitiahttp://en.wikipedia.org/wiki/Impact_eventhttp://en.wikipedia.org/wiki/Olympus_Monshttp://en.wikipedia.org/wiki/Athabasca_Valleshttp://en.wikipedia.org/wiki/Mya_(unit)http://en.wikipedia.org/wiki/Cerberus_Fossaehttp://en.wikipedia.org/wiki/Mars_Reconnaissance_Orbiterhttp://en.wikipedia.org/wiki/Mars_Reconnaissance_Orbiterhttp://en.wikipedia.org/wiki/Mars_Reconnaissance_Orbiterhttp://en.wikipedia.org/wiki/Mars_Reconnaissance_Orbiterhttp://en.wikipedia.org/wiki/File:Spirit_Mars_Silica_April_20_2007.jpghttp://en.wikipedia.org/wiki/Mars_Reconnaissance_Orbiterhttp://en.wikipedia.org/wiki/Mars_Reconnaissance_Orbiterhttp://en.wikipedia.org/wiki/Cerberus_Fossaehttp://en.wikipedia.org/wiki/Mya_(unit)http://en.wikipedia.org/wiki/Athabasca_Valleshttp://en.wikipedia.org/wiki/Olympus_Monshttp://en.wikipedia.org/wiki/Impact_eventhttp://en.wikipedia.org/wiki/Amazonis_Planitiahttp://en.wikipedia.org/wiki/Tharsishttp://en.wikipedia.org/wiki/Noachis_Terrahttp://en.wikipedia.org/wiki/Solar_wind


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Rover exposes silica-rich dust

ThePhoenixlander returned data showing Martian soil to be slightly alkaline and

containing elements such as magnesium, sodium, potassium andchloride. These

nutrients are found in gardens on Earth, and are necessary for growth of

plants.[44]Experiments performed by the Lander showed that the Martian soil has

a basic pH of 8.3, and may contain traces of the salt perchlorate.

Streaks are common across Mars and new ones appear frequently on steep slopes of

craters, troughs, and valleys. The streaks are dark at first and get lighter with age.

Sometimes the streaks start in a tiny area which then spreads out for hundreds of

metres. They have also been seen to follow the edges of boulders and other obstacles

in their path. The commonly accepted theories include that they are dark underlyinglayers of soil revealed after avalanches of bright dust or dust devils. Several

explanations have been put forward, some of which involve water or even the growth of

organisms.

Hydrology

Microscopic photo taken byOpportunityshowing a gray hematite concretion, indicative

of the past presence of liquid water

Liquid water cannot exist on the surface of Mars due to low atmospheric pressure,

except at the lowest elevations for short periods. The two polar ice caps appear to be

made largely of water. The volume of water ice in the south polar ice cap, if melted,
http://en.wikipedia.org/wiki/Phoenix_(spacecraft)http://en.wikipedia.org/wiki/Phoenix_(spacecraft)http://en.wikipedia.org/wiki/Phoenix_(spacecraft)http://en.wikipedia.org/wiki/Magnesiumhttp://en.wikipedia.org/wiki/Sodiumhttp://en.wikipedia.org/wiki/Potassiumhttp://en.wikipedia.org/wiki/Chloridehttp://en.wikipedia.org/wiki/Mars#cite_note-bbc080627-44http://en.wikipedia.org/wiki/Mars#cite_note-bbc080627-44http://en.wikipedia.org/wiki/Mars#cite_note-bbc080627-44http://en.wikipedia.org/wiki/Base_(chemistry)http://en.wikipedia.org/wiki/PHhttp://en.wikipedia.org/wiki/Salt_(chemistry)http://en.wikipedia.org/wiki/Perchloratehttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Opportunity_roverhttp://en.wikipedia.org/wiki/Opportunity_roverhttp://en.wikipedia.org/wiki/Hematitehttp://en.wikipedia.org/wiki/Concretionhttp://en.wikipedia.org/wiki/File:Nasa_mars_opportunity_rock_water_150_eng_02mar04.jpghttp://en.wikipedia.org/wiki/File:Nasa_mars_opportunity_rock_water_150_eng_02mar04.jpghttp://en.wikipedia.org/wiki/File:Spirit_Mars_Silica_April_20_2007.jpghttp://en.wikipedia.org/wiki/File:Nasa_mars_opportunity_rock_water_150_eng_02mar04.jpghttp://en.wikipedia.org/wiki/File:Nasa_mars_opportunity_rock_water_150_eng_02mar04.jpghttp://en.wikipedia.org/wiki/File:Spirit_Mars_Silica_April_20_2007.jpghttp://en.wikipedia.org/wiki/File:Nasa_mars_opportunity_rock_water_150_eng_02mar04.jpghttp://en.wikipedia.org/wiki/File:Nasa_mars_opportunity_rock_water_150_eng_02mar04.jpghttp://en.wikipedia.org/wiki/File:Spirit_Mars_Silica_April_20_2007.jpghttp://en.wikipedia.org/wiki/Concretionhttp://en.wikipedia.org/wiki/Hematitehttp://en.wikipedia.org/wiki/Opportunity_roverhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Perchloratehttp://en.wikipedia.org/wiki/Salt_(chemistry)http://en.wikipedia.org/wiki/PHhttp://en.wikipedia.org/wiki/Base_(chemistry)http://en.wikipedia.org/wiki/Mars#cite_note-bbc080627-44http://en.wikipedia.org/wiki/Chloridehttp://en.wikipedia.org/wiki/Potassiumhttp://en.wikipedia.org/wiki/Sodiumhttp://en.wikipedia.org/wiki/Magnesiumhttp://en.wikipedia.org/wiki/Phoenix_(spacecraft)


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would be sufficient to cover the entire planetary surface to a depth of 11

meters. A permafrost mantle stretches from the pole to latitudes of about 60.

Large quantities of water ice are thought to be trapped within the thick cryosphere of

Mars. Radar data fromMars Expressand theMars Reconnaissance Orbitershow large

quantities of water ice both at the poles (July 2005) and at mid-latitudes (November

2008). The Phoenix lander directly sampled water ice in shallow Martian soil on July 31,

2008.

Landforms visible on Mars strongly suggest that liquid water has at least at times

existed on the planet's surface. Huge linear swathes of scoured ground, known

as outflow channels, cut across the surface in around 25 places. These are thought to

record erosion which occurred during the catastrophic release of water from subsurface

aquifers, though some of these structures have also been hypothesised to result from

the action of glaciers or lava. The youngest of these channels are thought to have

formed as recently as only a few million years ago. Elsewhere, particularly on the oldest

areas of the martian surface, finer-scale, dendritic networks of valleys are spread across

significant proportions of the landscape. Features of these valleys and their distribution

very strongly imply that they were carved by runoff resulting from rain or snow fall in

early Mars history. Subsurface water flow and groundwater sapping may play important

subsidiary roles in some networks, but precipitation was probably the root cause of the

incision in almost all cases.

Other geological features, such as deltas and alluvial fans preserved in craters, also

argue very strongly for warmer, wetter conditions at some interval or intervals in earlier

Mars history. Such conditions necessarily require the widespread presence of

crater lakes across a large proportion of the surface, for which there is also independent

mineralogical, sedimentological and geomorphological evidence. Some authors have

even gone so far as to argue that at times in the martian past, much of the low northern

plains of the planet were covered with a true ocean hundreds of meters deep, though

this remains controversial.

Further evidence that liquid water once existed on the surface of Mars comes from thedetection of specific minerals such as hematite and goethite, both of which sometimes

form in the presence of water. Some of the evidence believed to indicate ancient water

basins and flows has been negated by higher resolution studies by the Mars

Reconnaissance Orbiter. In 2004, Opportunitydetected the mineral jarosite. This forms
http://en.wikipedia.org/wiki/Permafrosthttp://en.wikipedia.org/wiki/Evolution_of_water_on_Mars_and_Earthhttp://en.wikipedia.org/wiki/Cryospherehttp://en.wikipedia.org/wiki/Mars_Expresshttp://en.wikipedia.org/wiki/Mars_Expresshttp://en.wikipedia.org/wiki/Mars_Expresshttp://en.wikipedia.org/wiki/Mars_Reconnaissance_Orbiterhttp://en.wikipedia.org/wiki/Mars_Reconnaissance_Orbiterhttp://en.wikipedia.org/wiki/Mars_Reconnaissance_Orbiterhttp://en.wikipedia.org/wiki/Geomorphologyhttp://en.wikipedia.org/wiki/Outflow_channelshttp://en.wikipedia.org/wiki/Valley_networks_(Mars)http://en.wikipedia.org/wiki/Surface_runoffhttp://en.wikipedia.org/wiki/Groundwater_sappinghttp://en.wikipedia.org/wiki/River_deltahttp://en.wikipedia.org/wiki/Alluvial_fanshttp://en.wikipedia.org/wiki/Lakeshttp://en.wikipedia.org/wiki/Liquidhttp://en.wikipedia.org/wiki/Hematitehttp://en.wikipedia.org/wiki/Goethitehttp://en.wikipedia.org/wiki/Jarositehttp://en.wikipedia.org/wiki/Jarositehttp://en.wikipedia.org/wiki/Goethitehttp://en.wikipedia.org/wiki/Hematitehttp://en.wikipedia.org/wiki/Liquidhttp://en.wikipedia.org/wiki/Lakeshttp://en.wikipedia.org/wiki/Alluvial_fanshttp://en.wikipedia.org/wiki/River_deltahttp://en.wikipedia.org/wiki/Groundwater_sappinghttp://en.wikipedia.org/wiki/Surface_runoffhttp://en.wikipedia.org/wiki/Valley_networks_(Mars)http://en.wikipedia.org/wiki/Outflow_channelshttp://en.wikipedia.org/wiki/Geomorphologyhttp://en.wikipedia.org/wiki/Mars_Reconnaissance_Orbiterhttp://en.wikipedia.org/wiki/Mars_Expresshttp://en.wikipedia.org/wiki/Cryospherehttp://en.wikipedia.org/wiki/Evolution_of_water_on_Mars_and_Earthhttp://en.wikipedia.org/wiki/Permafrost


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only in the presence of acidic water, which demonstrates that water once existed on

Mars.

Polar caps

Northern ice cap of Mars in 1999

South polar cap in 2000

Mars has two permanent polar ice caps. During a pole's winter, it lies in continuous

darkness, chilling the surface and causing the deposition of 2530% of the atmosphere

into slabs of CO2ice (dry ice). When the poles are again exposed to sunlight, the frozen

CO2 sublimes, creating enormous winds that sweep off the poles as fast as 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

theOpportunityrover in 2004.

The polar caps at both poles consist primarily of water ice. Frozen carbon dioxide

accumulates as a comparatively thin layer about one metre thick on the north cap in the

northern winter only, while the south cap has a permanent dry ice cover about eight

metres thick. The northern polar cap has a diameter of about 1,000 kilometres during
http://en.wikipedia.org/wiki/Deposition_(phase_transition)http://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Dry_icehttp://en.wikipedia.org/wiki/Sublimation_(physics)http://en.wikipedia.org/wiki/Cirrus_cloudhttp://en.wikipedia.org/wiki/Opportunity_roverhttp://en.wikipedia.org/wiki/Opportunity_roverhttp://en.wikipedia.org/wiki/Opportunity_roverhttp://en.wikipedia.org/wiki/File:South_Polar_Cap_of_Mars_during_Martian_South_summer_2000.jpghttp://en.wikipedia.org/wiki/File:Martian_north_polar_cap.jpghttp://en.wikipedia.org/wiki/File:South_Polar_Cap_of_Mars_during_Martian_South_summer_2000.jpghttp://en.wikipedia.org/wiki/File:Martian_north_polar_cap.jpghttp://en.wikipedia.org/wiki/Opportunity_roverhttp://en.wikipedia.org/wiki/Cirrus_cloudhttp://en.wikipedia.org/wiki/Sublimation_(physics)http://en.wikipedia.org/wiki/Dry_icehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Deposition_(phase_transition)


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Mars equator is defined by its rotation, but the location of its Prime Meridian was

specified, as was Earth's (at Greenwich), by choice of an arbitrary point; Mdler and

Beer selected a line in 1830 for their first 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"), was chosen for the

definition of 0.0 longitude to coincide with the original selection.

Since Mars has no oceans and hence no 'sea level', a zero-elevation surface also had

to be selected as a reference level; this is also called the areoidof Mars, analogous to

the terrestrialgeoid. Zero altitude is defined by the height at which there is

610.5 Pa (6.105 mbar) of atmospheric pressure. This pressure corresponds to the triple

point of water, and is about 0.6% of the sea level surface pressure on Earth

(0.006 atm). In practice, today this surface is defined directly from satellite gravity

measurements.

An approximate true-color image, taken by Mars Exploration Rover Opportunity, shows

the view of Victoria Crater from Cape Verde. It was captured over a three-week period,

from October 16 November 6, 2006.
http://en.wikipedia.org/wiki/Prime_Meridianhttp://en.wikipedia.org/wiki/Greenwichhttp://en.wikipedia.org/wiki/Mariner_9http://en.wikipedia.org/wiki/Mariner_9http://en.wikipedia.org/wiki/Airy-0http://en.wikipedia.org/wiki/Sinus_Meridianihttp://en.wikipedia.org/wiki/Geoidhttp://en.wikipedia.org/wiki/Pascal_(unit)http://en.wikipedia.org/wiki/Bar_(unit)http://en.wikipedia.org/wiki/Triple_pointhttp://en.wikipedia.org/wiki/Triple_pointhttp://en.wikipedia.org/wiki/Opportunity_roverhttp://en.wikipedia.org/wiki/Victoria_Craterhttp://en.wikipedia.org/wiki/File:Victoria_Crater,_Cape_Verde-Mars.jpghttp://en.wikipedia.org/wiki/File:Victoria_Crater,_Cape_Verde-Mars.jpghttp://en.wikipedia.org/wiki/File:Victoria_Crater,_Cape_Verde-Mars.jpghttp://en.wikipedia.org/wiki/File:Victoria_Crater,_Cape_Verde-Mars.jpghttp://en.wikipedia.org/wiki/Victoria_Craterhttp://en.wikipedia.org/wiki/Opportunity_roverhttp://en.wikipedia.org/wiki/Triple_pointhttp://en.wikipedia.org/wiki/Triple_pointhttp://en.wikipedia.org/wiki/Bar_(unit)http://en.wikipedia.org/wiki/Pascal_(unit)http://en.wikipedia.org/wiki/Geoidhttp://en.wikipedia.org/wiki/Sinus_Meridianihttp://en.wikipedia.org/wiki/Airy-0http://en.wikipedia.org/wiki/Mariner_9http://en.wikipedia.org/wiki/Mariner_9http://en.wikipedia.org/wiki/Greenwichhttp://en.wikipedia.org/wiki/Prime_Meridian


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Chapter 3


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region Tharsis, which contains several other large volcanoes. Olympus Mons is over

three times the height of Mount Everest, which in comparison stands at just over

8.8 km.

The large canyon, Valles Marineris (Latin forMarinerValleys, also known as

Agathadaemon in the old canal maps), has a length of 4,000 km and a depth of up to

7 km. The length of Valles Marineris is equivalent to the length of Europe and extends

across one-fifth the circumference of Mars. By comparison, the Grand Canyon on Earth

is only 446 km long and nearly 2 km deep. Valles Marineris was formed due to the

swelling of the Tharsis area which caused the crust in the area of Valles Marineris to

collapse. Another large canyon is Ma'adim Vallis (Ma'adimis Hebrew for Mars). It is

700 km long and again much bigger than the Grand Canyon with a width of 20 km and a

depth of 2 km in some places. It is possible that Ma'adim Vallis was flooded with liquid

water in the past.

Caves

THEMIS image of probable Mars cave entrances, informally named (A) Dena, (B)

Chloe, (C) Wendy, (D) Annie, (E) Abby (left) and Nikki, and (F) Jeanne.

Images from the Thermal Emission Imaging System (THEMIS) aboard NASA's Mars

Odyssey orbiter have revealed seven possible cave entrances on the flanks of the Arsia

Mons volcano.[98]The caves, named after loved ones of their discoverers, are

collectively known as the "seven sisters." Cave entrances measure from 100 m to

252 m wide and they are believed to be at least 73 m to 96 m deep. Because light does

not reach the floor of most of the caves, it is likely that they extend much deeper than

these lower estimates and widen below the surface. "Dena" is the only exception; its

floor is visible and was measured to be 130 m deep. The interiors of these caverns may

be protected from micrometeoroids, UV radiation, solar flares and high energy particles

that bombard the planet's surface.
http://en.wikipedia.org/wiki/Tharsishttp://en.wikipedia.org/wiki/Mount_Everesthttp://en.wikipedia.org/wiki/Valles_Marinerishttp://en.wikipedia.org/wiki/Mariner_programhttp://en.wikipedia.org/wiki/Mariner_programhttp://en.wikipedia.org/wiki/Grand_Canyonhttp://en.wikipedia.org/wiki/Ma%27adim_Vallishttp://en.wikipedia.org/wiki/Hebrewhttp://en.wikipedia.org/wiki/THEMIShttp://en.wikipedia.org/wiki/Thermal_Emission_Imaging_Systemhttp://en.wikipedia.org/wiki/2001_Mars_Odysseyhttp://en.wikipedia.org/wiki/2001_Mars_Odysseyhttp://en.wikipedia.org/wiki/Cavehttp://en.wikipedia.org/wiki/Arsia_Monshttp://en.wikipedia.org/wiki/Arsia_Monshttp://en.wikipedia.org/wiki/Mars#cite_note-cushing_titus_wynn07-98http://en.wikipedia.org/wiki/Mars#cite_note-cushing_titus_wynn07-98http://en.wikipedia.org/wiki/Mars#cite_note-cushing_titus_wynn07-98http://en.wikipedia.org/wiki/Solar_flarehttp://en.wikipedia.org/wiki/File:Mars_caves_from_NASA_orbiters.jpghttp://en.wikipedia.org/wiki/File:Mars_caves_from_NASA_orbiters.jpghttp://en.wikipedia.org/wiki/File:Mars_caves_from_NASA_orbiters.jpghttp://en.wikipedia.org/wiki/File:Mars_caves_from_NASA_orbiters.jpghttp://en.wikipedia.org/wiki/Solar_flarehttp://en.wikipedia.org/wiki/Mars#cite_note-cushing_titus_wynn07-98http://en.wikipedia.org/wiki/Arsia_Monshttp://en.wikipedia.org/wiki/Arsia_Monshttp://en.wikipedia.org/wiki/Cavehttp://en.wikipedia.org/wiki/2001_Mars_Odysseyhttp://en.wikipedia.org/wiki/2001_Mars_Odysseyhttp://en.wikipedia.org/wiki/Thermal_Emission_Imaging_Systemhttp://en.wikipedia.org/wiki/THEMIShttp://en.wikipedia.org/wiki/Hebrewhttp://en.wikipedia.org/wiki/Ma%27adim_Vallishttp://en.wikipedia.org/wiki/Grand_Canyonhttp://en.wikipedia.org/wiki/Mariner_programhttp://en.wikipedia.org/wiki/Valles_Marinerishttp://en.wikipedia.org/wiki/Mount_Everesthttp://en.wikipedia.org/wiki/Tharsis


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Atmosphere

The tenuous atmosphere of Mars, visible on the horizon in this low-orbit photo

Mars lost its magnetosphere 4 billion years ago, so the solar wind interacts directly with

the Martianionosphere, lowering the atmospheric density by stripping away atoms from

the outer layer. Both Mars Global Surveyor and Mars Express have detected ionised

atmospheric particles trailing off into space behind Mars. Compared to Earth,

the atmosphere of Mars is quite rarefied. Atmospheric pressure on the surface ranges

from a low of 30 Pa(0.030 kPa) on Olympus Mons to over 1,155 Pa (1.155 kPa) in

the Hellas Planitia, with a mean pressure at the surface level of 600 Pa (0.60 kPa).The

surface pressure of Mars at its thickest is equal to the pressure found 35 km above the

Earth's surface. This is 0.6% of the Earth's surface pressure (101.3 kPa). The scale

height of the atmosphere is about 10.8 km, which is higher than Earth's (6 km) because

the surface gravity of Mars is only about 38% of Earth's, an effect offset by both the

lower temperature and 50% higher average molecular weight of the atmosphere of

Mars.
http://en.wikipedia.org/wiki/Magnetospherehttp://en.wikipedia.org/wiki/Solar_windhttp://en.wikipedia.org/wiki/Ionospherehttp://en.wikipedia.org/wiki/Mars_Global_Surveyorhttp://en.wikipedia.org/wiki/Celestial_body_atmospherehttp://en.wikipedia.org/wiki/Atmospheric_pressurehttp://en.wikipedia.org/wiki/Pascal_(unit)http://en.wikipedia.org/wiki/Pascal_(unit)http://en.wikipedia.org/wiki/Olympus_Monshttp://en.wikipedia.org/wiki/Hellas_Planitiahttp://en.wikipedia.org/wiki/Scale_heighthttp://en.wikipedia.org/wiki/Scale_heighthttp://en.wikipedia.org/wiki/File:Mars_atmosphere.jpghttp://en.wikipedia.org/wiki/File:Mars_atmosphere.jpghttp://en.wikipedia.org/wiki/File:Mars_atmosphere.jpghttp://en.wikipedia.org/wiki/File:Mars_atmosphere.jpghttp://en.wikipedia.org/wiki/Scale_heighthttp://en.wikipedia.org/wiki/Scale_heighthttp://en.wikipedia.org/wiki/Hellas_Planitiahttp://en.wikipedia.org/wiki/Olympus_Monshttp://en.wikipedia.org/wiki/Pascal_(unit)http://en.wikipedia.org/wiki/Pascal_(unit)http://en.wikipedia.org/wiki/Atmospheric_pressurehttp://en.wikipedia.org/wiki/Celestial_body_atmospherehttp://en.wikipedia.org/wiki/Mars_Global_Surveyorhttp://en.wikipedia.org/wiki/Ionospherehttp://en.wikipedia.org/wiki/Solar_windhttp://en.wikipedia.org/wiki/Magnetosphere


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The atmosphere of Mars consists of about 95% carbon dioxide, 3% nitrogen,

1.6% argon and contains traces of oxygen and water.[6]The atmosphere is quite dusty,

containing particulates about 1.5 m in diameter which give the Martian sky

a tawny color when seen from the surface.

Methane map

Methane has been detected in the Martian atmosphere with a mole fraction of about

30 ppb; it occurs in extended plumes, and the profiles imply that the methane was

released from discrete regions. In northern midsummer, the principal plume contained

19,000 metric tons of methane, with an estimated source strength of 0.6 kilogram persecond. The profiles suggest that there may be two local source regions, the first

centered near 30 N, 260 W and the second near 0, 310 W. It is estimated that Mars

must produce 270 ton/year of methane.

The implied methane destruction lifetime may be as long as about 4 Earth years and as

short as about 0.6 Earth years. This rapid turnover would indicate an active source of
http://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Argonhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Mars#cite_note-nssdc-6http://en.wikipedia.org/wiki/Mars#cite_note-nssdc-6http://en.wikipedia.org/wiki/Mars#cite_note-nssdc-6http://en.wikipedia.org/wiki/%CE%9Cmhttp://en.wikipedia.org/wiki/Tawny_(color)http://en.wikipedia.org/wiki/Methanehttp://en.wikipedia.org/wiki/Mole_fractionhttp://en.wikipedia.org/wiki/Ppbhttp://en.wikipedia.org/wiki/File:Martian_Methane_Map.jpghttp://en.wikipedia.org/wiki/File:Martian_Methane_Map.jpghttp://en.wikipedia.org/wiki/File:Martian_Methane_Map.jpghttp://en.wikipedia.org/wiki/File:Martian_Methane_Map.jpghttp://en.wikipedia.org/wiki/File:Martian_Methane_Map.jpghttp://en.wikipedia.org/wiki/File:Martian_Methane_Map.jpghttp://en.wikipedia.org/wiki/Ppbhttp://en.wikipedia.org/wiki/Mole_fractionhttp://en.wikipedia.org/wiki/Methanehttp://en.wikipedia.org/wiki/Tawny_(color)http://en.wikipedia.org/wiki/%CE%9Cmhttp://en.wikipedia.org/wiki/Mars#cite_note-nssdc-6http://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Argonhttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Carbon_dioxide


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the gas on the planet. Volcanic activity, cometary impacts, and the presence

of methanogenic microbial life forms are among possible sources. Methane could also

be produced by a non-biological process calledserpentinizationinvolving water, carbon

dioxide, and themineral olivine, which is known to be common on Mars.

Ammonia was also detected on Mars, but with its relatively short lifetime its not clear

what produced it. Ammonia is not stable there and breaks down after a few hours, so

one possible source is volcanic activity. By

Climate

Mars from Hubble Space TelescopeOctober 28, 2005 with dust storm visible.

Of all the planets in the Solar System, the seasons of Mars are the most Earth-like, due

to the similar tilts of the two planets' rotational axes. The lengths of the Martian seasons

are about twice those of Earth's, as Mars greater distance from the Sun leads to the

Martian year being about two Earth years long. Martian surface temperatures vary from

lows of about 87 C(125 F) during the polar winters to highs of up to 5

C (23 F) in summers. The wide range in temperatures is due to the thin atmosphere

which cannot store much solar heat, the low atmospheric pressure, and the low thermal

inertia of Martian soil. The planet is also 1.52 times as far from the sun as Earth,

resulting in just 43% of the amount of sunlight.

If Mars had an Earth-like orbit, its seasons would be similar to Earth's because its axial

tilt is similar to Earth's. The comparatively large eccentricity of the Martian orbit has a

significant effect. Mars is near perihelion when it is summer in the southern hemisphere

and winter in the north, and nearaphelion when it is winter in the southern hemisphere

and summer in the north. As a result, the seasons in the southern hemisphere are more
http://en.wikipedia.org/wiki/Volcanismhttp://en.wikipedia.org/wiki/Comethttp://en.wikipedia.org/wiki/Methanogenhttp://en.wikipedia.org/wiki/Microorganismhttp://en.wikipedia.org/wiki/Serpentinitehttp://en.wikipedia.org/wiki/Serpentinitehttp://en.wikipedia.org/wiki/Serpentinitehttp://en.wikipedia.org/wiki/Mineralhttp://en.wikipedia.org/wiki/Olivinehttp://en.wikipedia.org/wiki/Hubble_Space_Telescopehttp://en.wikipedia.org/wiki/Volumetric_heat_capacityhttp://en.wikipedia.org/wiki/Volumetric_heat_capacityhttp://en.wikipedia.org/wiki/Axial_tilthttp://en.wikipedia.org/wiki/Axial_tilthttp://en.wikipedia.org/wiki/Apsishttp://en.wikipedia.org/wiki/Apsishttp://en.wikipedia.org/wiki/File:2005-1103mars-full.jpghttp://en.wikipedia.org/wiki/File:2005-1103mars-full.jpghttp://en.wikipedia.org/wiki/File:2005-1103mars-full.jpghttp://en.wikipedia.org/wiki/File:2005-1103mars-full.jpghttp://en.wikipedia.org/wiki/Apsishttp://en.wikipedia.org/wiki/Apsishttp://en.wikipedia.org/wiki/Axial_tilthttp://en.wikipedia.org/wiki/Axial_tilthttp://en.wikipedia.org/wiki/Volumetric_heat_capacityhttp://en.wikipedia.org/wiki/Volumetric_heat_capacityhttp://en.wikipedia.org/wiki/Hubble_Space_Telescopehttp://en.wikipedia.org/wiki/Olivinehttp://en.wikipedia.org/wiki/Mineralhttp://en.wikipedia.org/wiki/Serpentinitehttp://en.wikipedia.org/wiki/Microorganismhttp://en.wikipedia.org/wiki/Methanogenhttp://en.wikipedia.org/wiki/Comethttp://en.wikipedia.org/wiki/Volcanism


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Mars has a relatively pronounced orbital eccentricity of about 0.09; of the seven other

planets in the Solar System, only Mercury shows greater eccentricity. It is known that in

the past Mars has had a much more circular orbit than it does currently. At one point

1.35 million Earth years ago, Mars had an eccentricity of roughly 0.002, much less than

that of Earth today. The Mars cycle of eccentricity is 96,000 Earth years compared to

the Earth's cycle of 100,000 years. Mars also has a much longer cycle of eccentricity

with a period of 2.2 million Earth years, and this overshadows the 96,000-year cycle in

the eccentricity graphs. For the last 35,000 years the orbit of Mars has been getting

slightly more eccentric because of the gravitational effects of the other planets. The

closest distance between the Earth and Mars will continue to mildly decrease for the

next 25,000 years.

Images comparing Mars' orbit with Ceres, a dwarf planet in the asteroid belt. The left is

shown from the north ecliptic pole. The right is shown from the ascending node. The

segments of orbits south of the ecliptic are plotted in darker colors. The perihelia (q)

and aphelia (Q) are labelled with the date of nearest passage. The orbit of Mars is red,

Ceres is yellow.
http://en.wikipedia.org/wiki/Orbital_eccentricityhttp://en.wikipedia.org/wiki/Mercury_(planet)http://en.wikipedia.org/wiki/Ceres_(dwarf_planet)http://en.wikipedia.org/wiki/Dwarf_planethttp://en.wikipedia.org/wiki/Asteroid_belthttp://en.wikipedia.org/wiki/Ecliptichttp://en.wikipedia.org/wiki/Perihelionhttp://en.wikipedia.org/wiki/Aphelionhttp://en.wikipedia.org/wiki/File:ThePlanets_Orbits_Ceres_Mars.svghttp://en.wikipedia.org/wiki/File:ThePlanets_Orbits_Ceres_Mars_PolarView.svghttp://en.wikipedia.org/wiki/File:ThePlanets_Orbits_Ceres_Mars.svghttp://en.wikipedia.org/wiki/File:ThePlanets_Orbits_Ceres_Mars_PolarView.svghttp://en.wikipedia.org/wiki/Aphelionhttp://en.wikipedia.org/wiki/Perihelionhttp://en.wikipedia.org/wiki/Ecliptichttp://en.wikipedia.org/wiki/Asteroid_belthttp://en.wikipedia.org/wiki/Dwarf_planethttp://en.wikipedia.org/wiki/Ceres_(dwarf_planet)http://en.wikipedia.org/wiki/Mercury_(planet)http://en.wikipedia.org/wiki/Orbital_eccentricity


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Phobos in color byMars Reconnaissance OrbiterHiRISE, on March 23, 2008

Deimos in color on February 21, 2009 by the same (not to scale)

Mars has two relatively small natural moons, Phobos and Deimos, which orbit close tothe planet. Asteroid capture is a long-favored theory but their origin remains

uncertain. Both satellites were discovered in 1877 by Asaph Hall, and are named after

the characters Phobos (panic/fear) and Deimos(terror/dread) who, in Greek mythology,

accompanied their father Ares, god of war, into battle. Ares was known as Mars to the

Romans.

From the surface of Mars, the motions of Phobos and Deimos appear very different

from that of our own moon. Phobos rises in the west, sets in the east, and rises again in

just 11 hours. Deimos, being only just outside synchronous orbitwhere the orbital

period would match the planet's period of rotationrises as expected in the east but

very slowly. Despite the 30 hour orbit of Deimos, it takes 2.7 days to set in the west as it

slowly falls behind the rotation of Mars, then just as long again to rise.
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Because the orbit of Phobos is below synchronous altitude, the tidal forces from the

planet Mars are gradually lowering its orbit. In about 50 million years it could either

crash into Mars surface or break up into a ring structure around the planet.

The origin of the two moons is not well understood. Their low albedo and carbonaceous

chondrite composition have been regarded as similar to asteroids, supporting the

capture theory. The unstable orbit of Phobos would seem to point towards a relatively

recent capture. But both have circular orbits, very near the equator, which is very

unusual for captured objects and the required capture dynamics are complex. Accretion

early in the history of Mars is also plausible but would not account for a composition

resembling asteroids rather than Mars itself, if that is confirmed.

A third possibility is the involvement of a third body or some kind of impact

disruption. More recent lines of evidence for Phobos having a highly porous interior and

suggesting a composition containing mainly phyllosilicates and other minerals known

from Mars, point toward an origin of Phobos from material ejected by an impact on Mars

that reaccreted in Martian orbit, similar to the prevailing theory for the origin of Earth's

moon. While the VNIRspectra of the moons of Mars resemble those of outer belt

asteroids, the thermal infrared spectra of Phobos are reported to be inconsistent

with chondritesof any class.

Search for life

Viking Lander 2 site May 1979
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Viking Lander 1 site February 1978.

The current understanding of planetary habitabilitythe ability of a world to develop and

sustain lifefavors planets that have liquid water on their surface. This most often

requires that the orbit of a planet lie within the habitable zone, which for the Sun

currently extends from just beyond Venus to about the semi-major axis of Mars. During

perihelion Mars dips inside this region, but the planet's thin (low-pressure) atmosphere

prevents liquid water from existing over large regions for extended periods. The past

flow of liquid water demonstrates the planet's potential for habitability. Some recent

evidence has suggested that any water on the Martian surface may have been too salty

and acidic to support regular terrestrial life.

The lack of a magnetosphere and extremely thin atmosphere of Mars are a challenge:

the planet has little heat transfer across its surface, poor insulation against

bombardment of the solar wind and insufficient atmospheric pressure to retain water in

a liquid form (water instead sublimates to a gaseous state). Mars is also nearly, or

perhaps totally, geologically dead; the end of volcanic activity has apparently stopped

the recycling of chemicals and minerals between the surface and interior of the planet.

Evidence suggests that the planet was once significantly more habitable than it is today,

but whether living organisms ever existed there remains unknown. The Viking probes of

the mid-1970s carried experiments designed to detect microorganisms in Martian soil at

their respective landing sites and had positive results, including a temporary increase ofCO2 production on exposure to water and nutrients. This sign of life was later disputed

by some scientists, resulting in a continuing debate, with NASA scientist Gilbert

Levin asserting that Viking may have found life. A re-analysis of the Viking data, in light

of modern knowledge of extremophile forms of life, has suggested that the Viking tests

were not sophisticated enough to detect these forms of life. The tests could even have
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killed a (hypothetical) life form. Tests conducted by the Phoenix Mars lander have

shown that the soil has a very alkaline pH and it contains magnesium, sodium,

potassium and chloride. The soil nutrients may be able to support life but life would still

have to be shielded from the intense ultraviolet light.

At the Johnson Space Center lab, some fascinating shapes have been found in

the meteorite ALH84001, which is thought to have originated from Mars. Some

scientists propose that these geometric shapes could be fossilized microbes extant on

Mars before the meteorite was blasted into space by a meteor strike and sent on a 15

million-year voyage to Earth. An exclusively inorganic origin for the shapes has also

been proposed.

Small quantities of methane and formaldehyde recently detected by Mars orbiters are

both claimed to be hints for life, as these chemical compounds would quickly break

down in the Martian atmosphere. It is remotely possible that these compounds may

instead be replenished by volcanic or geological means such as serpentinization.

Exploration missions

Western rim of Endeavour Crater

In addition to observation from Earth, some of the latest Mars information comes from

four active probes on or in orbit around Mars as of 2012: 2001 Mars Odyssey, Mars

Express, Mars Reconnaissance Orbiter, and Opportunity rover. The public can request

photos of Mars' surface at 25 cm a pixel with the HiWish program, which uses a 50 cm

diameter telescope in Mars orbit.In the past, dozens of spacecraft, including orbiters, landers, and rovers, have been

sent to Mars by the Soviet Union, the United States, Europe, andJapan to study the

planet's surface, climate, and geology. As of 2008, the price of transporting material

from the surface of Earth to the surface of Mars was approximately US$309,000

per kilogram.
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Current missions

The NASA Mars Odyssey orbiter entered Mars orbit in 2001. Odyssey's Gamma Ray

Spectrometer detected significant amounts of hydrogen in the upper metre or so

of regolith on Mars. This hydrogen is thought to be contained in large deposits of water

ice.

The Mars Express mission of the European Space Agency (ESA) reached Mars in

2003. It carried the Beagle 2 lander, which failed during descent and was declared lost

in February, 2004. In early 2004 the Planetary Fourier Spectrometer team announced

the orbiter had detected methane in the Martian atmosphere. ESA announced in June

2006 the discovery of aurorae on Mars.

In January 2004, the NASA twin Mars Exploration Rovers namedSpirit(MER-A)

andOpportunity(MER-B) landed on the surface of Mars. Both have met or exceeded all

their targets. Among the most significant scientific returns has been conclusive evidence

that liquid water existed at some time in the past at both landing sites. Martian dust

devils and windstorms have occasionally cleaned both rovers' solar panels, and thus

increased their lifespan. Spirit Rover (MER-A) was active until 2010, when it stopped

sending data.

On March 10, 2006, the NASA Mars Reconnaissance Orbiter (MRO) probe arrived in

orbit to conduct a two-year science survey. The orbiter began mapping the Martian

terrain and weather to find suitable landing sites for upcoming lander missions. The

MRO snapped the first image of a series of active avalanches near the planet's north

pole, scientists said March 3, 2008.

The Mars Science Laboratory, named Curiosity, launched on November 26, 2011, and

is expected to reach Mars in August 2012. It is larger and more advanced than the Mars

Exploration Rovers, with a movement rate of 90 m/h. Experiments include a laser

chemical sampler that can deduce the make-up of rocks at a distance of 13 m.

Past missions

Attempted Martian missions

Decade

1960s 13
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1970s 11

1980s 2

1990s 8

2000s 8

2010s 2

Mars 3 lander on a 1972 Soviet stamp.

The first successful fly-by of Mars was on July 1415, 1965, by NASA's Mariner 4. On

November 14, 1971 Mariner 9 became the first space probe to orbit another planet

when it entered into orbit around Mars. The first to contact the surface were

two Soviet probes:Mars 2 lander on November 27 and Mars 3 lander on December 2,

1971 Mars 2 failed during descent and Mars 3 seconds after landing. Mars 6 failed

during descent but did return some atmospheric data in 1974. The 1975 NASA

launches of the Viking program consisted of two orbiters, each having a lander; both

landers successfully touched down in 1976. Viking 1remained operational for six

years, Viking 2 for three. The Viking landers relayed the first color panoramas of

Mars and the orbiters mapped the surface so well that the images remain in use.

The Soviet probes Phobos 1 and 2 were sent to Mars in 1988 to study Mars and its two

moons, but with a focus on Phobos. Phobos 1 lost contact on the way to Mars. Phobos

2, while successfully photographing Mars and Phobos, failed before it was set to

release two landers to the surface of Phobos.

Roughly two-thirds of all spacecraft destined for Mars have failed without completing

their missions, and it has a reputation as difficult space exploration target. Failures since
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Viking include Phobos 1 & 2 (1988), Mars Observer (1990), Mars 96 (1996), Mars

Climate Orbiter (1999), Mars Polar Lander with Deep Space

2 (1999), Nozomi (2003), Beagle 2 (2003), and Fobos-Grunt withYinghuo-1 (2011).

Mars Pathfinder rover on Mars, 1997

View from thePhoenixlander, 2008

Following the 1992 failure of the Mars Observer orbiter, the NASA Mars Global

Surveyor achieved Mars orbit in 1997. This mission was a complete success, having

finished its primary mapping mission in early 2001. Contact was lost with the probe in

November 2006 during its third extended program, spending exactly 10 operationalyears in space. The NASA Mars Pathfinder, carrying a robotic exploration

vehicle Sojourner, landed in the Ares Vallis on Mars in the summer of 1997, returning

many images.

The NASA Phoenix Mars lander arrived on the north polar region of Mars on May 25,

2008. Its robotic arm was used to dig into the Martian soil and the presence of water ice

was confirmed on June 20. The mission concluded on November 10, 2008 after contact

was lost.

Rosetta came within 250 km of Mars during its 2007 flyby.Dawn flew by Mars inFebruary 2009 for a gravity assist on its way to investigate Vesta and then Ceres.

Future missions

In 2008, NASA announced MAVEN, a robotic mission in 2013 to provide information

about the atmosphere of Mars. In 2016, the Russian and ESA plan to send rover and

static lander to Mars. In 2018 the ESA plans to launch its first Rover to Mars;
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the ExoMars rover will be capable of drilling 2 m into the soil in search of organic

molecules.

NASA requested innovative proposals for a new Mars mission by May 10, 2012. One

existing proposal is NASA Discovery program's InSight, which would place a

geophysical lander on Mars to study its deep interior, and understand the processes

that shaped the rocky planets of the inner solar system.

The Finnish-Russian MetNet concept would use multiple small vehicles on Mars to

establish a widespread observation network to investigate the planet's atmospheric

structure, physics and meteorology.[166][167]MetNet was considered for a piggyback

launch on Phobos-Grunt.[168]

A Russian mission concept is Mars-Grunt, a Mars surface sample return

mission. Another proposal is the ESA-NASA three-launch architecture for Mars samplereturn, which uses a rover to cache small samples, a Mars ascent stage to send it into

orbit, and an orbiter to rendezvous with it above Mars and take it to Earth. Solar-electric

propulsion could allow a one launch sample return instead of three. Another sample

return concept was Mars Scout Program's SCIM, which would involve a probe grazing

the upper atmosphere to scoop up dust and air for Earth return.

Future mission ideas include new polar probes, Martian aircraft, or a network of small

stations. Longterm areas of study may include Martian lava tubes, resource utilization,

and electronic charge carriers in rocks. Micromissions are another possibility, such as

piggybacking a wok-sized spacecraft on an Ariane 5 launch and using a lunar gravity

assist to get to Mars.

Manned mission goals

The ESA hopes to land humans on Mars between 2030 and 2035. This will be preceded

by successively larger probes, starting with the launch of the ExoMars probe and a joint

NASAESA Mars sample return mission.

Manned exploration by the United States was identified as a long-term goal in the Vision

for Space Exploration announced in 2004 by then US President George W. Bush. TheplannedOrionspacecraft would be used to send a human expedition to Earth's moon by

2020 as a stepping stone to a Mars expedition. On September 28, 2007, NASA

administrator Michael D. Griffin stated that NASA aims to put a man on Mars by 2037.

Mars Direct, a low-cost human mission proposed by Robert Zubrin, founder of the Mars

Society, would use heavy-lift Saturn V class rockets, such as the SpaceX Falcon X, or,
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the Ares V, to skip orbital construction, LEO rendezvous, and lunar fuel depots. A

modified proposal, called "Mars to Stay", involves not returning the first immigrant

explorers immediately, if ever (see Colonization of Mars).

Astronomy on Mars

Phobos transits the Sun, as seen by Mars RoverOpportunityon March 10, 2004

With the existence of various orbiters, landers, and rovers, it is now possible to

study astronomy from the Martian skies. While Mars moon Phobos appears about one

third the angular diameter of the full Moon as it appears from Earth, Deimos appears

more or less star-like, and appears only slightly brighter than Venus does from Earth.There are various phenomena, well-known on Earth, that have been observed on Mars,

such as meteors and auroras. A transit of the Earth as seen from Mars will occur on

November 10, 2084. There are also transits of Mercury and transits of Venus, and the

moons Phobos and Deimos are of sufficiently small angular diameter that their partial

"eclipses" of the Sun are best considered transits (see Transit of Deimos from Mars).
http://en.wikipedia.org/wiki/Ares_Vhttp://en.wikipedia.org/wiki/Mars_to_Stayhttp://en.wikipedia.org/wiki/Colonization_of_Marshttp://en.wikipedia.org/wiki/Astronomical_transithttp://en.wikipedia.org/wiki/Sunhttp://en.wikipedia.org/wiki/MER-Bhttp://en.wikipedia.org/wiki/MER-Bhttp://en.wikipedia.org/wiki/MER-Bhttp://en.wikipedia.org/wiki/Astronomyhttp://en.wikipedia.org/wiki/Angular_diameterhttp://en.wikipedia.org/wiki/Meteorhttp://en.wikipedia.org/wiki/Aurorashttp://en.wikipedia.org/wiki/Transit_of_Earth_from_Marshttp://en.wikipedia.org/wiki/Transit_of_Mercury_from_Marshttp://en.wikipedia.org/wiki/Transit_of_Venus_from_Marshttp://en.wikipedia.org/wiki/Angular_diameterhttp://en.wikipedia.org/wiki/Transit_of_Deimos_from_Marshttp://en.wikipedia.org/wiki/File:15-ml-06-phobos2-A067R1.jpghttp://en.wikipedia.org/wiki/File:15-ml-06-phobos2-A067R1.jpghttp://en.wikipedia.org/wiki/File:15-ml-06-phobos2-A067R1.jpghttp://en.wikipedia.org/wiki/File:15-ml-06-phobos2-A067R1.jpghttp://en.wikipedia.org/wiki/Transit_of_Deimos_from_Marshttp://en.wikipedia.org/wiki/Angular_diameterhttp://en.wikipedia.org/wiki/Transit_of_Venus_from_Marshttp://en.wikipedia.org/wiki/Transit_of_Mercury_from_Marshttp://en.wikipedia.org/wiki/Transit_of_Earth_from_Marshttp://en.wikipedia.org/wiki/Aurorashttp://en.wikipedia.org/wiki/Meteorhttp://en.wikipedia.org/wiki/Angular_diameterhttp://en.wikipedia.org/wiki/Astronomyhttp://en.wikipedia.org/wiki/MER-Bhttp://en.wikipedia.org/wiki/Sunhttp://en.wikipedia.org/wiki/Astronomical_transithttp://en.wikipedia.org/wiki/Colonization_of_Marshttp://en.wikipedia.org/wiki/Mars_to_Stayhttp://en.wikipedia.org/wiki/Ares_V


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Chapter 6


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Viewing

Animation of the apparent retrograde motion of Mars in 2003 as seen from Earth

Because the orbit of Mars is eccentric its apparent magnitude at opposition from the

Sun can range from 3.0 to 1.4. The minimum brightness is magnitude +1.6 when the

planet is in conjunction with the Sun.[7]Mars usually appears a distinct yellow, orange,
http://en.wikipedia.org/wiki/Apparent_magnitudehttp://en.wikipedia.org/wiki/Mars#cite_note-MallamaSky-7http://en.wikipedia.org/wiki/Mars#cite_note-MallamaSky-7http://en.wikipedia.org/wiki/Mars#cite_note-MallamaSky-7http://en.wikipedia.org/wiki/File:Apparent_retrograde_motion_of_Mars_in_2003.gifhttp://en.wikipedia.org/wiki/File:Apparent_retrograde_motion_of_Mars_in_2003.gifhttp://en.wikipedia.org/wiki/File:Apparent_retrograde_motion_of_Mars_in_2003.gifhttp://en.wikipedia.org/wiki/File:Apparent_retrograde_motion_of_Mars_in_2003.gifhttp://en.wikipedia.org/wiki/Mars#cite_note-MallamaSky-7http://en.wikipedia.org/wiki/Apparent_magnitude


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or reddish color; the actual color of Mars is closer to butterscotch, and the redness seen

is just dust in the planet's atmosphere; considering this NASA's Spirit rover has taken

pictures of a greenish-brown, mud-colored landscape with blue-grey rocks and patches

of light red colored sand. When farthest away from the Earth, it is more than seven

times as far from the latter as when it is closest. When least favorably positioned, it can

be lost in the Sun's glare for months at a time. At its most favorable timesat 15- or 17-

year intervals, and always between late July and late SeptemberMars shows a wealth

of surface detail to a telescope. Especially noticeable, even at low magnification, are

the polar ice caps.

As Mars approaches opposition it begins a period of retrograde motion, which means it

will appear to move backwards in a looping motion with respect to the background stars.

The duration of this retrograde motion lasts for about 72 days, and Mars reaches its

peak luminosity in the middle of this motion.

Closest approaches

Relative

The point Mars geocentric longitude is 180 different from the Sun's is known

as opposition, which is near the time of closest approach to the Earth. The time of

opposition can occur as much as 8 days away from the closest approach. The

distance at close approach varies between about 54 [188]and about 103 million km due

to the planets' elliptical orbits, which causes comparable variation in angular size. The

last Mars opposition occurred on March 3, 2012 at a distance of about

100 million km.[190]The average time between the successive oppositions of Mars,

its synodic period, is 780 days but the number of days between the dates of successive

oppositions can range from 764 to 812.

As Mars approaches opposition it begins a period of retrograde motion, which makes it

appear to move backwards in a looping motion relative to the background stars. The

duration of this retrograde motion is about 72 days.

Absolute, around the present time
http://en.wikipedia.org/wiki/Butterscotchhttp://en.wikipedia.org/wiki/NASAhttp://en.wikipedia.org/wiki/Telescopehttp://en.wikipedia.org/wiki/Polar_ice_caphttp://en.wikipedia.org/wiki/Apparent_retrograde_motionhttp://en.wikipedia.org/wiki/Opposition_(planets)http://en.wikipedia.org/wiki/Mars#cite_note-Laskar2003-189http://en.wikipedia.org/wiki/Mars#cite_note-Laskar2003-189http://en.wikipedia.org/wiki/Ellipsehttp://en.wikipedia.org/wiki/Angular_sizehttp://en.wikipedia.org/wiki/Mars#cite_note-sheehan970202-191http://en.wikipedia.org/wiki/Mars#cite_note-sheehan970202-191http://en.wikipedia.org/wiki/Mars#cite_note-sheehan970202-191http://en.wikipedia.org/wiki/Synodic_periodhttp://en.wikipedia.org/wiki/Apparent_retrograde_motionhttp://en.wikipedia.org/wiki/Apparent_retrograde_motionhttp://en.wikipedia.org/wiki/Synodic_periodhttp://en.wikipedia.org/wiki/Mars#cite_note-sheehan970202-191http://en.wikipedia.org/wiki/Angular_sizehttp://en.wikipedia.org/wiki/Ellipsehttp://en.wikipedia.org/wiki/Mars#cite_note-Laskar2003-189http://en.wikipedia.org/wiki/Opposition_(planets)http://en.wikipedia.org/wiki/Apparent_retrograde_motionhttp://en.wikipedia.org/wiki/Polar_ice_caphttp://en.wikipedia.org/wiki/Telescopehttp://en.wikipedia.org/wiki/NASAhttp://en.wikipedia.org/wiki/Butterscotch


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Mars oppositions from 20032018, viewed from above the ecliptic with the Earth

centered

Mars made its closest approach to Earth and maximum apparent brightness in nearly

60,000 years, 55,758,006 km (0.372719 AU),magnitude 2.88, on 27 August 2003 at

9:51:13 UT. This occurred when Mars wa

The Palnet Mars2

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