|
|
| Line 1: |
Line 1: |
| − | {{Copyedited}}{{Paid}}{{Images OK}}{{Submitted}}{{Approved}}
| |
| − | {{Planet Infobox/Mars}}
| |
| | | | |
| − | '''Mars''' is the fourth [[planet]] from the [[Sun]] in our [[solar system]] and is named after the [[Roman mythology|Roman god]] of war. It is also known as the "Red Planet," due to its reddish appearance when seen from the [[Earth]].
| |
| − |
| |
| − | Like the Earth, Mars has a rocky surface and [[polar ice caps]]. Its [[rotational period]] and seasonal cycles are similar to those of the Earth. Of all the planets in the Solar System, it has the highest [[mountain]], [[Olympus Mons]], and the largest canyon, [[Valles Marineris]]. The availability of Mars samples in the form of [[Martian meteorite]]s gives "ground-truth" data to researchers, just as in the case of studying meteorites from the [[Moon]]. In addition, Mars has two [[natural satellite|moon]]s, [[Phobos (moon)|Phobos]] and [[Deimos (moon)|Deimos]], both of which are small and oddly shaped.
| |
| − |
| |
| − | Until the first flyby of Mars by [[Mariner 4]] in 1965, many thought that the planet might have ample liquid water. This belief was based on early observations of Mars, showing periodic variations in light and dark patches, particularly in the polar latitudes, and long dark striations that suggested the presence of irrigation channels of liquid water. Subsequent analyses indicated that the striations were optical illusions.
| |
| − |
| |
| − | Nonetheless, of all the planets in the solar system other than Earth, Mars is thought to be the most likely to harbor liquid [[water]], and perhaps some [[life]] forms. Consequently, popular attention has been drawn to Mars, and probes to this planet continue to be equipped with instruments to attempt to discover microscopic life. In addition, some think that we may be able to make Mars habitable in the future—a concept known as "[[terraforming]]."
| |
| − |
| |
| − | As of late 2006, Mars is host to four orbiting [[spacecraft]]: [[Mars Global Surveyor]], [[Mars Odyssey]], [[Mars Express]], and [[Mars Reconnaissance Orbiter]]. This is more than any planet other than Earth has. It is also home to two [[Mars Exploration Rover]]s, ''[[Spirit rover|Spirit]]'' and ''[[Opportunity rover|Opportunity]]''.
| |
| − |
| |
| − | ==Viewing Mars==
| |
| − |
| |
| − | When seen from Earth with the naked eye, Mars usually appears to have a distinct yellow, orange, or reddish color. Its brightness varies over the course of its orbit, more so than the brightness of any other planet. The apparent magnitude of its brightness can be as high as -2.9, a value surpassed only by [[Venus]], the [[Moon]], and the [[Sun]]. For much of the year, [[Jupiter(planet)|Jupiter]] may appear brighter to the naked eye than Mars.
| |
| − |
| |
| − | During its orbit, the farthest point of Mars from Earth is more than seven times its closest point. When least favorably positioned, it can be lost in the Sun's glare for months at a time. It is most favorably positioned twice every 32 years, alternately at 15- and 17-year intervals, and always between late July and late September. During those times, a wealth of surface detail can be observed through a [[telescope]]. Especially noticeable, even at low magnification, are the [[polar ice cap]]s.<ref>[http://www.shallowsky.com/mars.html "Mars."] Access date: June 15, 2006.</ref>
| |
| − |
| |
| − | Approximately every 780 days, [[opposition (astronomy)|opposition]] occurs, which is about when Mars is nearest to Earth. Given the eccentricities of the orbits, the times of opposition and minimum distance can differ by up to 8.5 days. The minimum distance varies between about 55 and 100 million kilometers, due to the planets' [[ellipse|elliptical]] orbits.<ref>[http://www.spds.nasa.gov/planetary/factsheet/marsfact.html "Mars Fact Sheet"], <i>NASA Planetary Factsheets</i>. Access date: June 13, 2006.</ref>
| |
| − |
| |
| − | On August 27, 2003, at 9:51:13 UT, Mars made its closest approach to Earth in nearly 60,000 years: 55,758,006 kilometers (approximately 35 million miles). 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 <small>B.C.E.</small>]], and the next time will be in 2287. However, this record approach was only very slightly closer than other recent close approaches. For instance, the minimum distance on August 22, 1924 was 0.37284 astronomical units (AU) (compared to 0.37271 AU on August 27, 2003), and the minimum distance on August 24, 2208, will be 0.37278 AU.<ref>[http://www.space.com/spacewatch/mars_10_closest_030822.html "NightSky Friday - Mars and Earth: The Top 10 Close Passes Since 3000 B.C.E."] <i>Space.com</i>. Access date: June 13, 2006.</ref>
| |
| − |
| |
| − | The orbital changes of Earth and Mars are making the approaches nearer: the 2003 record will be bettered 22 times by the year 4000.
| |
| − |
| |
| − | ===Historical observations of Mars===
| |
| − | [[Image:Karte Mars Schiaparelli MKL1888.png|left|thumb|250px|Map of Mars by Giovanni Schiaparelli]]
| |
| − |
| |
| − | The history of observations of Mars is marked by the [[opposition (astronomy)|oppositions]] of Mars, when the planet is closest to Earth and hence is most easily visible, which occur every couple of years. Even more notable are the [[perihelic opposition]]s of Mars, which occur approximately every 16 years and are distinguished because Mars is close to [[apsis|perihelion]], making it even closer to Earth.
| |
| − |
| |
| − | By the nineteenth century, the resolution of telescopes reached a level sufficient for surface features to be identified. A perihelic opposition of Mars occurred on September 5, 1877. In that year, [[Italy|Italian]] astronomer [[Giovanni Schiaparelli]] used a 22-centimeter [[telescope]] in [[Milan]] to help produce the first detailed map of Mars. These maps notably contained features he called ''canali'', which were later shown to be an [[optical illusion]]. These ''canali'' were supposedly long straight lines on the surface of Mars to which he gave names of famous rivers on Earth. His term was popularly mistranslated as “canals.”
| |
| − |
| |
| − | Influenced by the observations, the orientalist [[Percival Lowell]] founded an [[Lowell Observatory|observatory]] that had 12- and 18-inch telescopes. The observatory was used for the exploration of Mars during the last good opportunity in 1894 and the following less favorable oppositions. He published several books on Mars and life on Mars that greatly influenced the public mind. The ''canali'' were also observed by other astronomers, such as Perrotin and Thollon in [[Nice]], using one of the largest telescopes of that time.
| |
| − |
| |
| − | The seasonal changes (consisting of the diminishing of the polar caps and the dark areas formed during the Martian summer) in combination with the canals led to speculation about life on Mars, and it was a long-held belief that Mars contained vast seas and vegetation. The telescope never reached the resolution required to give proof to any speculations. However, as bigger telescopes were used, fewer long, straight ''canali'' were observed. During an observation in 1909 by Flammarion with a 33-inch telescope, irregular patterns were observed, but no ''canali'' were seen.<ref>Zahnle, K. (2001). "Decline and Fall of the Martian empire." <i>Nature</i> 412.</ref>
| |
| − |
| |
| − | Even in the 1960s, articles were published on Martian biology, putting aside explanations other than life for the seasonal changes on Mars. Detailed scenarios for the metabolism and chemical cycles for a functional ecosystem were published.<ref>Salisbury, F. B. (1962). "Martian Biology." <i>Science</i> 136.</ref>
| |
| − |
| |
| − | It was not until [[spacecraft]] visited the planet during [[NASA]]'s [[Mariner program|Mariner missions]] in the 1960s that these myths were dispelled. The results of the Viking life detection experiments started an intermission in which the hypothesis of a dead Mars, hostile to life, was generally accepted.
| |
| − |
| |
| − | Some maps of Mars were made using the data from these missions, but it wasn't until the [[Mars Global Surveyor]] mission, launched in 1996 (and operational as of 2006), that complete, extremely detailed maps were obtained.<ref>These maps are now available online at [http://www.google.com/mars/ Google Mars].</ref>
| |
| − |
| |
| − | ==Mars in early human culture==
| |
| − | [[Image:Mars symbol.svg|30px|left]]
| |
| − |
| |
| − | In Roman mythology, Mars was the god of war and patron of warriors. The symbol for Mars is a circle with a small arrow pointing out from behind it, which is a stylized representation of a shield and spear used by the Roman god. This symbol is also used in biology to denote the male sex.<ref>[http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=167 "Planet Symbols."] <i>NASA Solar System Exploration</i>. Access date: June 13, 2006.</ref>
| |
| − |
| |
| − | In [[Babylonian Empire|Babylonian]] astronomy, the planet was named after ''[[Nergal]]'', their [[deity]] of fire, war, and destruction, most likely due to the planet's reddish appearance.<ref>[http://www.uapress.arizona.edu/onlinebks/mars/chap01.htm "Motions of Mars."] <i>The Planet Mars: A History of Observation and Discovery</i>. Access date: June 13, 2006.</ref> When the [[Ancient Greece|Greeks]] equated Nergal with their god of war, Ares, they named the planet ''Areos aster'', or "star of Ares." Then, following the [[Interpretatio graeca|identification]] of Ares and Mars, it was translated into Latin as ''stella Martis'', or "star of Mars," or simply ''Mars''. The Greeks also called the planet ''Pyroeis'', meaning "fiery."
| |
| − |
| |
| − | In [[Hindu mythology]], Mars is known as ''Mangala''. It is also called ''Angaraka'' in [[Sanskrit]]. He is the god of war and is [[celibate]]. He is the owner of the [[Aries (astrology)|Aries]] and [[Scorpio]] signs, and a teacher of the occult sciences. The planet was known by the ancient Egyptians as "Horus the Red." The [[Hebrews]] named it ''Ma'adim'', or "the one who blushes." This is where one of the largest [[canyons]] on Mars, the [[Ma'adim Vallis]], gets its name. It is known as ''al-Mirrikh'' in both Arabic and Persian, and ''Merih'' in Turkish. The etymology of ''al-Mirrikh'' is unknown. Ancient Persians named it ''Bahram'', the [[Zoroastrianism|Zoroastrian]] god of faith. Ancient Turks called it ''Sakit''. The [[China|Chinese]], [[Japan]]ese, [[Korea|Korean]], and [[Vietnam]]ese cultures refer to the planet as ''fire star'', a naming based on the ancient Chinese philosophical group of [[Five elements (Chinese philosophy)|Five Elements]].
| |
| − |
| |
| − | ==Physical characteristics==
| |
| − |
| |
| − | The red/orange appearance of Mars' surface is caused by [[iron(III) oxide]] (rust).<ref name=rust>Peplow, M. (2004). [http://www.nature.com/news/2004/040503/full/040503-6.html;jsessionid=2E40E6D0BDA9D25A3BAF1DFC53F9FA40 "How Mars got its rust."] <i>Nature</i>. Access date: April 18, 2006.</ref> Mars has half the [[radius]] of the Earth and only one-tenth the [[mass]]. It is less dense, and its surface area is only slightly less than the total area of Earth's dry land.<ref name="nssdc">Williams, D. R. (2004). [http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html "Mars Fact Sheet."] Access date: June 24, 2006.</ref> While Mars is larger and more massive than [[Mercury (planet)|Mercury]], Mercury has higher density and therefore has slightly stronger gravity at its surface.
| |
| − |
| |
| − | [[Image:Terrestrial_planet_size_comparisons.jpg|thumb|left|360px|Size comparison of terrestrial planets (''left to right''): [[Mercury (planet)|Mercury]], [[Venus]], [[Earth]], and Mars]]
| |
| − | <br clear=left />
| |
| − |
| |
| − | ===Geology===
| |
| − |
| |
| − | 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 a portion of the Martian surface might be more silica-rich than typical basalt, perhaps similar to [[andesitic]] stones on Earth, though these observations may also be explained by silica glass. Much of the surface is deeply covered by [[iron(III) oxide]] dust as fine as talcum powder.<ref>NASA Mars Page: [http://erc.arc.nasa.gov/MarsVolc/basalt.htm "Volcanology of Mars."] Accessed in 2006.</ref>
| |
| − |
| |
| − | [[Image:nasa_mars_opportunity_rock_water_150_eng_02mar04.jpg|150px|thumb|right|Photo of microscopic rock forms indicating past signs of water, taken by the rover ''Opportunity''.]]
| |
| − |
| |
| − | There is 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 form only in the presence of water.<ref>[http://www.jpl.nasa.gov/releases/2004/88.cfm "Mineral in Mars 'Berries' Adds to Water Story."] NASA Press Release. March 18, 2004. Access date: June 13, 2006.</ref>
| |
| − |
| |
| − | Although Mars has no intrinsic magnetic field, observations have revealed that parts of the planet's crust have 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.<ref name=plates>[http://www.nasa.gov/centers/goddard/news/topstory/2005/mgs_plates.html "New Map Provides More Evidence Mars Once Like Earth."] NASA Press Release. October 12, 2005. Access date: March 17, 2006.</ref> It is also possible to explain this "[[paleomagnetism]]" (record of the past magnetic field in certain magnetized minerals) based on shifting of the magnetic poles.
| |
| − |
| |
| − | Current models of the planet's interior infer a core region approximately 1,480 kilometers (km) in radius, consisting primarily of [[iron]] with about 15-17 percent [[sulfur]]. This [[iron sulfide]] core is partially fluid, with twice the concentration of light elements that exist in the 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 inactive. The average thickness of the planet's crust is about 50 km, and it is no thicker than 125 km.<ref>Jacqué, D. (2003). [http://www.anl.gov/Media_Center/News/2003/030926mars.htm "APS X-rays reveal secrets of Mars' core."] <i>Argonne National Laboratory</i>. Access date: July 1, 2006.</ref>
| |
| − |
| |
| − | The geological history of Mars is split into three broad epochs:
| |
| − | *'''Noachian epoch''' (named after [[Noachis Terra]]): From the formation of Mars to between 3,800 and 3,500 million years ago. Noachian age surfaces are scarred by many large impact craters. The [[Tharsis bulge]] is thought to have formed during this period, with extensive flooding by liquid water late in the epoch.
| |
| − | *'''Hesperian epoch''' (named after [[Hesperia Planum]]): From 3,500 million years ago to 1,800 million years ago. The Hesperian epoch is marked by the formation of extensive lava plains.
| |
| − | *'''Amazonian epoch''' (named after [[Amazonis Planitia]]): From 1,800 million years ago to the 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.
| |
| − |
| |
| − | An alternative series of classifications has also been put forward, based on data from an instrument (the OMEGA Visible and Infrared Mineralogical Mapping Spectrometer) on board the [[Mars Express]] orbiter.
| |
| − |
| |
| − | ===Geography of Mars (Areography)===
| |
| − |
| |
| − | [[Image:MarsTopoMap-PIA02031 modest.jpg|thumb|left|250px|Topographic map of Mars. 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.]]
| |
| − | Although better remembered for mapping the [[Moon]] starting in 1830, [[Johann Heinrich Mädler]] and [[Wilhelm Beer]] were the first "aerographers." They started off by establishing once and for all that most of Mars' surface features were permanent, and pinned down Mars' rotation period. In 1840 Mädler combined ten years of observations and drew the first ever map of Mars. 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."<ref>[http://www.uapress.arizona.edu/onlinebks/mars/chap04.htm "The Planet Mars: A History of Observation and Discovery."] Access date: June 13, 2006.</ref>
| |
| − |
| |
| − | Today, features on Mars are named from a number of sources. Large [[albedo]] (visible reflectivity) 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).<ref>[http://www.iomoon.com/olympus.htm "Olympus Mons (Nix Olympica)."] Access date: June 13, 2006.</ref>
| |
| − |
| |
| − | 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. Mädler 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 originally selected line.
| |
| − |
| |
| − | Since Mars has no oceans and hence no 'sea level,' a zero-elevation surface or [[mean gravity surface]] must be selected. The zero altitude is defined by the height at which there is 610.5 pascals (Pa) (6.105 mbar) of atmospheric pressure (approximately 0.6 percent that of Earth's). This pressure corresponds to the [[triple point]] of water.<ref>[http://www.crystalinks.com/mars2.html "Mars."] Access date: June 13, 2006.</ref>
| |
| − |
| |
| − | 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 thus 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]].<ref>[http://www.daviddarling.info/encyclopedia/S/SyrtisMajor.html "Syrtis Major."] <i>Encyclopedia of Astrobiology, Astronomy & Spaceflight</i>. Access date: June 13, 2006.</ref>
| |
| − |
| |
| − | The [[shield volcano|shield]] [[volcano]], Olympus Mons (''Mount Olympus''), with a height of 26,000 meters, is the highest known mountain in the [[solar system]]. It is an extinct volcano in the vast upland region Tharsis, which contains several other large volcanoes. It is over three times the height of Mt. Everest, which stands at 8,848 meters.
| |
| − |
| |
| − | Mars is also scarred by a number of [[impact crater]]s. The largest of these is the [[Hellas Planitia|Hellas impact basin]], covered with light red sand.<ref>[http://www.windows.ucar.edu/tour/link=/mars/interior/Martian_global_geology.html "Mars Global Geography."] Access date: June 13, 2006.</ref> Despite being closer to the asteroid belt, there are far fewer craters on Mars compared with [[Moon|the Moon]], because Mars' atmosphere provides protection against small meteors. Some craters have a morphology that suggests that the ground was wet when the meteor impacted.
| |
| − |
| |
| − | The large canyon [[Valles Marineris]] (Latin for ''Mariner Valleys'', also known as Agathadaemon in the old canal maps) has a length of 4,000 kilometers 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 Tharis area, which caused the crust in the area of Valles Marineris to collapse. Another large canyon is Ma'adim Vallis (Ma'adim is 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.
| |
| − |
| |
| − | [[Image:Mars_Hubble.jpg|thumb|right|Mars in 2001, with polar ice caps visible]]
| |
| − |
| |
| − | ===Atmosphere===
| |
| − |
| |
| − | The [[celestial body atmosphere|atmosphere]] of Mars is relatively thin; the [[atmospheric pressure]] on the surface varies from around 30 Pa (0.03 kPa) on Olympus Mons to over 1,155 Pa (1.155 kPa) in the depths of [[Hellas Planitia]], with a mean surface-level pressure of 600 Pa (0.6 kPa)<ref name="stanhellas">[http://www-star.stanford.edu/projects/mgs/sum/s0403210230.html "Martian Weather Observation."] MGS radio science measured 11.50 mbar at 34.4 degrees S 59.6 degrees E -7152 meters.</ref>, compared to Earth's 101.3 kPa. The equivalent pressure of Mars' atmosphere can be found at a height of 35 km above the Earth's surface. The [[scale height]] of the atmosphere is about 11 km, higher than Earth's 6 km.
| |
| − |
| |
| − | The atmosphere on Mars consists of 95 percent [[carbon dioxide]], 3 percent [[nitrogen]], 1.6 percent [[argon]], and traces of [[oxygen]] and [[water]].<ref name="nssdc"/> The atmosphere is quite dusty, giving the Martian sky a [[tawny]] color when seen from the surface; the particulates responsible are about 1.5 [[1 E-6 m|µm]] across.<ref name=dusty>Lemmon <i>et al.</i>,
| |
| − | [http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2004Sci...306.1753L&db_key=AST&data_type=HTML&format=&high=439c7b95b425777 "Atmospheric Imaging Results from the Mars Exploration Rovers: Spirit and Opportunity."]</ref>
| |
| − |
| |
| − | Several researchers claim to have detected [[methane]] in the Martian atmosphere, at a concentration of about 10 parts per billion (ppb) by volume.<ref name=methane>
| |
| − | [http://www.esa.int/SPECIALS/Mars_Express/SEMZ0B57ESD_0.html "Mars Express confirms methane in the Martian atmosphere."] ESA Press Release. March 30, 2004. Access date: March 17, 2006.</ref>
| |
| − | Methane is an unstable [[gas]] that is broken down by [[ultraviolet]] radiation, typically lasting in the atmosphere for about 340 years,<ref>Baucom, M. (2006). [http://www.americanscientist.org/template/AssetDetail/assetid/49613 "Life on Mars?"] <i>American Scientist</i> 94.</ref> and its possible presence on Mars could indicate that there is (or has been within the last few hundred years) a source of the gas on the planet. Possible sources include [[volcanism|volcanic]] activity, [[comet]] impacts, and [[microorganism]]s such as [[methanogen]]s. It was recently shown that methane could also be produced by a nonbiological process involving water, carbon dioxide, and the [[mineral]] [[olivine]], which is believed to be common on Mars.<ref name=olivine>Oze, C., Sharma, M. (2005). "Have olivine, will gas: Serpentinization and the abiogenic production of methane on Mars." <i>Geophysical Research Letters</i> 32, L10203.</ref>
| |
| − |
| |
| − | In the winter months when the poles are in continuous darkness, the surface gets so cold that as much as 25–30 percent of the entire atmosphere condenses out into thick slabs of [[Carbon dioxide|CO<sub>2</sub>]] ice (dry ice).<ref>Mellon, J. T., W. C. Feldman, and T. H. Prettyman. (2003). [http://adsabs.harvard.edu/abs/2004Icar..169..324M "The presence and stability of ground ice in the southern hemisphere of Mars."] <i>Icarus</i> 169: 324-340.</ref>
| |
| − |
| |
| − | When the poles are again exposed to sunlight, the CO<sub>2</sub> ice [[Sublimation (physics)|sublimes]] (is converted directly to gas), creating enormous winds that sweep off the poles as fast as 400 kilometers per hour (km/h) (250 miles per hour (mph)). These seasonal actions transport large amounts of dust and water vapor, giving rise to Earth-like [[frost]] and large, [[cirrus cloud]]s. Clouds of water-ice were photographed by the ''[[Opportunity rover|Opportunity]]'' rover in 2004.<ref name=clouds>[http://marsrovers.jpl.nasa.gov/gallery/press/opportunity/20041213a.html "Mars Rovers Spot Water-Clue Mineral, Frost, Clouds."] NASA Press Release. Dec. 13, 2004. Access date: March 17, 2006.</ref>
| |
| − |
| |
| − | [[Image:Magneticmap med.jpg|thumb|left|250px|Strength of Mars' magnetic field (red and blue indicate stronger than average areas)]]
| |
| − |
| |
| − | ===Magnetosphere===
| |
| − |
| |
| − | Evidence indicates that in Mars' distant past, it may have had a strong enough [[magnetosphere]] to deflect the [[solar wind]] (from the [[Sun]]). However, about four billion years ago, Mars' planetary [[Dynamo theory|dynamo]] ceased, leaving only remnants of the planetary magnetic field to be frozen into magnetically susceptible minerals. Over time, most of this material was reprocessed through various geological events leaving only sections of the ancient southern highlands with remnant magnetic fields. Because of this, the solar wind interacts directly with the Martian [[ionosphere]] and thus the Martian atmosphere has been slowly stripped off into space, although the exact amount lost remains uncertain. Both [[Mars Global Surveyor]] and [[Mars Express]] have detected ionized atmospheric particles trailing off into space behind Mars.<ref name=swind>[http://science.nasa.gov/headlines/y2001/ast31jan_1.htm "The Solar Wind at Mars."] - Science@NASA. Jan. 31, 2001. Access date: September 8, 2006.</ref><ref name=swind2>Lundin, R., et al. (2004). [http://www.sciencemag.org/cgi/content/abstract/305/5692/1933 "Solar Wind-Induced Atmospheric Erosion at Mars: First Results from ASPERA-3 on Mars Express."] <i>Science</i> 305: 1933-1936.</ref>
| |
| − |
| |
| − | [[Image:2005-1103mars-full.jpg|thumb|right|Mars from Hubble Space Telescope, October 28, 2005, with duststorm visible]]
| |
| − |
| |
| − | ===Climate===
| |
| − |
| |
| − | Of all the planets, Mars' seasons are the most Earth-like, due to the similar tilts of the two planets' rotational axes. However, 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 approximately two Earth years in length. Martian surface temperatures vary from approximately -140 [[Celsius|°C]] to 0 °C<ref>[http://hypertextbook.com/facts/2001/AlbertEydelman.shtml "Temperature on the Surface of Mars."] Access date: November 22, 2006.</ref> Recent evidence has suggested that Mars is subject to short-term regional climate changes.<ref name=warming>[http://mpfwww.jpl.nasa.gov/mgs/newsroom/20050920a.html "Orbiter's Long Life Helps Scientists Track Changes on Mars."] NASA Press Release. Sept. 20, 2005. Access date: March 17, 2006.</ref>
| |
| − |
| |
| − | If Mars had an Earth-like orbit, its seasons would be similar to Earth's because its axial tilt is similar to Earth's. However, the comparatively large eccentricity of the Martian orbit has a significant effect. Mars is near [[Apsis|perihelion]] (closest point to the Sun) when it is summer in the southern hemisphere and winter in the north, and near [[Apsis|aphelion]] (farthest point from the Sun) when it is winter in the southern hemisphere and summer in the north. As a result, the seasons in the southern hemisphere are more extreme and the seasons in the northern are milder than would otherwise be the case.
| |
| − |
| |
| − | [[Image:Mars NPArea-PIA00161 modest.jpg|left|thumb|Mars' northern ice cap]]
| |
| − |
| |
| − | Mars also has the largest dust storms in the solar system. These can vary in size from a storm covering a small area to gigantic storms that cover the entire planet. They tend to occur when Mars is closest to the Sun, which increases the global temperature.<ref>[http://science.nasa.gov/headlines/y2001/ast16jul_1.htm "Planet Gobbling Dust Storms."] Access date: June 7, 2006.</ref>
| |
| − |
| |
| − | Mars possesses polar caps at both poles, which mainly consist of water ice. Frozen carbon dioxide (dry ice) accumulates as a thin layer (about one meter thick) on the north cap in the northern winter only, while the south cap has a permanent dry ice cover, about eight meters thick.<ref name="darling">Darling, David. [http://www.daviddarling.info/encyclopedia/M/Marspoles.html "Mars, Polar Caps."] <i>Encyclopedia of Astrobiology, Astronomy, and Spaceflight.</i> Access date: January 29, 2007.</ref> The northern polar cap has a diameter of approximately 1,000 kilometers during the northern Mars summer, and contains about 1.6 million kilometers<sup>3</sup> of ice, which, if spread evenly on the cap, would be 2 kilometers thick<ref name="brown">Carr, M. H. (2003). [http://www.planetary.brown.edu/planetary/documents/2757.pdf "Oceans on Mars: An assessment of the observational evidence and possible fate."] <i>Journal of Geophysical Research</i> 108: 5042 (.pdf file). Access date: January 29, 2007.</ref> The [[Planum Australe|southern polar cap]] has a diameter of 350 kilometers, and a thickness of 3 kilometers.<ref name="nasa">Phillips, T. [http://science.nasa.gov/headlines/y2003/07aug_southpole.htm "Mars is Melting."] <i>Science at NASA.</i> Access date: January 29, 2007.</ref> Both polar caps show spiral cuts, which remain unexplained. Both polar caps shrink and re-grow following temperature fluctuations of the Martian seasons.
| |
| − |
| |
| − | ==Orbit and rotation==
| |
| − |
| |
| − | {| align=right width=135 style="margin-right:5px; border: 1px solid #cccccc"
| |
| − | | bgcolor=black |
| |
| − | [[Image:ThePlanets_Orbits_Ceres__Mars_PolarView.svg|150px|Orbit of Mars (red) and Ceres (yellow).]]
| |
| − | [[Image:ThePlanets_Orbits_Ceres__Mars.svg|150px|Orbit of Mars (red) and Ceres (yellow)]]
| |
| − | |}
| |
| − |
| |
| − | Mars has a relatively pronounced orbital eccentricity of about 9 percent. Of the other planets in the solar system, only [[Mercury]] shows greater eccentricity. Mars' average distance from the Sun is roughly 230 million kilometers (1.5 AU) and its orbital period is 687 (Earth) days. The solar day (or sol) on Mars is only slightly longer than an Earth day: 24 hours, 39 minutes, and 35.244 seconds.
| |
| − |
| |
| − | Mars' axial tilt is 25.19 degrees, which is similar to the axial tilt of the Earth. As a result, Mars has seasons like the Earth, though Mars' are about twice as long given its longer year.
| |
| − |
| |
| − | The image to the right shows a comparison between Mars and [[1 Ceres|Ceres]], a dwarf planet in the [[asteroid belt]], as seen from the [[ecliptic]] pole (''upper image'') and from the ascending node (''lower image''). The segments of orbits below the ecliptic are plotted in darker colors. The [[perihelion|perihelia]] (q) and [[aphelion|aphelia]] (Q) are labeled with the date of the nearest passage.
| |
| − |
| |
| − | ==Moons==
| |
| − | [[Image:Phobos deimos diff.jpg|left|thumb|150px|Phobos (top) and Deimos (bottom) are the two moons orbiting Mars]]
| |
| − |
| |
| − | Mars has two tiny natural satellites, Phobos and [[Deimos (moon)|Deimos]], that orbit very close to the planet. These moons may be captured [[asteroid]]s, similar to [[5261 Eureka]], which has been labeled a "[[Trojan asteroid]]" of Mars.<ref>5261 Eureka appears to be an asteroid that has the same orbit as Mars, trailing behind Mars at a nearly fixed distance.</ref> <ref>[http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=31031 "Close inspection for Phobos."] Access date: June 13, 2006.</ref> Phobos and Deimos are believed to have generated a dust ring around Mars, and thus have been highly [[Space weathering|space-weathered]] by repeated impacts of their own dust particles.
| |
| − |
| |
| − | Both satellites were discovered in 1877 by [[Asaph Hall]] and are named after the Greek mythological characters [[Phobos (mythology)|Phobos]] (panic/fear) and [[Deimos (mythology)|Deimos]] (terror/dread), who accompanied their father Ares, the god of war, into battle. Ares was known as Mars to the Romans.<ref>[http://www.theoi.com/Olympios/AresAttendants.html "Ares attendants: Deimos & Phobos."] Access date: June 13, 2006.</ref>
| |
| − |
| |
| − | From the Martian surface, 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 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 it takes as long again to rise.<ref name="phobos.html">[http://www.nineplanets.org/phobos.html "Phobos."] Access date: June 13, 2006.</ref>
| |
| − |
| |
| − | Because Phobos' orbit is below synchronous altitude, the tidal forces are lowering its orbit. It has been predicted that in about 50 million years, it will either crash into Mars' surface or break up into a ring structure around the planet.<ref name="phobos.html"/>
| |
| − |
| |
| − | Famous literary author [[Jonathan Swift]] made reference to these moons of Mars approximately 150 years before their actual discovery by Asaph Hall, detailing reasonably accurate descriptions of their orbits in the nineteenth chapter of his novel ''Gulliver's Travels''.
| |
| − |
| |
| − | ==Life==
| |
| − |
| |
| − | Some evidence suggests that the planet was once significantly more habitable than it is today, but it is still an open question whether living [[organism]]s ever existed there.
| |
| − | The [[Viking program|Viking probes]] of the mid-1970s carried experiments designed to detect microorganisms in Martian soil at their respective landing sites. They gave some apparently positive results that were later disputed by many scientists, resulting in a continuing fight.
| |
| − |
| |
| − | At the [[Johnson Space Center|Johnson space center lab]], organic compounds have been found in the [[meteorite]] [[ALH84001]], which is supposed to have come from Mars. They concluded that these were deposited by primitive life forms extant on Mars before the meteorite was blasted into space by a meteor strike and sent on a 15 million-year-voyage to Earth. Small quantities of [[methane]], and [[formaldehyde]] are both claimed to be hints for life, as these particles would quickly break down in the Martian atmosphere.<ref>Krasnopolsky, V.A., J.-P Maillard, T. C. Owen. (2004). "Detection of methane in the Martian atmosphere: Evidence for life?" <i>Icarus</i> 172: 537-547.</ref><ref name=form>[http://www.nature.com/news/2005/050221/full/050221-15.html "Formaldehyde claim inflames martian debate."] Nature.com. February 25, 2005. Access date: March 3, 2006.</ref> It is possible that these compounds may be replenished by volcanic or geological means, such as [[serpentinization]].<ref>Oze, C. and M. Sharma. (2005). "Have olivine, will gas: Serpentinization and the abiogenic production of methane on Mars." <i>Geophysical Research Letters</i> 32: L10203.</ref>
| |
| − |
| |
| − | In general, Mars shows some promise in terms of [[planetary habitability|habitablity]] but also several handicaps. It is half of an [[astronomical unit]] beyond the Sun's [[habitable zone]] and water is thus frozen on its surface, although liquid water flows in the past suggest the planet's potential. Its lack of a magnetosphere and extremely thin atmosphere are a greater challenge: the planet has little [[heat transfer]] across its surface, poor insulation against bombardment and the [[solar wind]], and insufficient atmospheric pressure to keep water in liquid form—instead, it sublimates to a gaseous state. Mars is also nearly, or perhaps totally, geologically dead. The end of volcanic activity has stopped the recycling of chemicals and minerals between the surface and interior of the planet.
| |
| − |
| |
| − | ==Exploration==
| |
| − | [[Image:Vikinglander-view.jpg|thumb|right|Viking Lander 1 site]]
| |
| − |
| |
| − | Dozens of [[spacecraft]]—including [[orbiter]]s, [[lander]]s, and [[rover]]s—have been sent to Mars by the former [[Russian Federal Space Agency|Soviet Union]], the [[NASA|United States]], [[ESA|Europe]], and [[JAXA|Japan]] to study the planet's surface, climate, and geology.
| |
| − |
| |
| − | Roughly two-thirds of all spacecraft destined for Mars have failed in one manner or other 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]], or even a reference made to a "Great Galactic Ghoul" that feeds on Martian spacecraft.<ref>[http://www.thespacereview.com/article/232/1 "Is the Great Galactic Ghoul losing his appetite?"] Access date: June 13, 2006.</ref>
| |
| − |
| |
| − | ===Past missions===
| |
| − |
| |
| − | 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, [[Mars 2]] and [[Mars 3]], from the [[Mars probe program]] launched in 1971, but both lost contact within seconds of landing. Then came 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 6 and 3 years, for Viking 1 and Viking 2 respectively. The Viking landers also relayed the first color pictures of Mars.<ref>[http://burro.astr.cwru.edu/stu/20th_far_mars.html "Other Mars Missions."] Access date: June 13, 2006.</ref> They also mapped the surface of Mars so well that the images are still sometimes used. The Soviet probes [[Phobos program|Phobos 1 and 2]] were also sent to Mars in 1988 to study Mars and its two moons. Unfortunately, Phobos 1 lost contact on the way to Mars, and Phobos 2, while successfully photographing Mars and Phobos, failed just before it was set to release two landers onto Phobos' surface.
| |
| − |
| |
| − | ===Current missions===
| |
| − |
| |
| − | Following the 1992 failure of [[Mars Observer]] orbiter, NASA 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.<ref>[http://www.cnn.com/TECH/9706/pathfinder/surveyor/ "Mars Global Surveyor."] CNN - Destination Mars. Access date: June 13, 2006.</ref>
| |
| − |
| |
| − | [[Image:Mars-odyssey-sm.jpg|left|thumb|200px|Artist's concept of the 2001 Mars Odyssey]]
| |
| − |
| |
| − | In 2001 NASA launched the successful [[Mars Odyssey]] orbiter, which is still in orbit as of August 2006. Odyssey's Gamma Ray Spectrometer detected significant amounts of elemental hydrogen in the upper meter or so of Mars' [[regolith]]. This hydrogen is thought to be contained in large deposits of water ice.<ref>[http://www.space.com/missionlaunches/odyssey_update_030314.html "Odyssey Spacecraft Generates New Mars Mysteries"], Space.com. Access date: June 13, 2006.</ref>
| |
| − |
| |
| − | In 2003 the [[European Space Agency]] (ESA) launched the [[Mars Express]] craft consisting of the [[Mars Express Orbiter]] and the lander [[Beagle 2]]. Beagle 2 apparently failed during descent and was declared lost in early February 2004.<ref>[http://www.space.com/missionlaunches/beagle_update_040126.html "Europe's Beagle 2 Mars Probe Stays Ominously Silent."] Space.com. Access date: June 13, 2006.</ref> In early 2004, the Planetary Fourier Spectrometer team announced it had detected methane in the Martian atmosphere. ESA announced in June 2006 the discovery of [[Aurora (astronomy)|aurorae]] on Mars.<ref>[http://www.esa.int/SPECIALS/Mars_Express/SEMLQ71DU8E_0.html "Mars Express discovers aurorae on Mars."] ESA Mars Express. Access date: November 2, 2006.</ref>
| |
| − |
| |
| − | Also in 2003, NASA launched the twin [[Mars Exploration Rover Mission|Mars Exploration Rover]]s 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#Martian dust devils|Martian dust devils]] and windstorms have occasionally cleaned both rovers' solar panels, and thus increased their lifespan.<ref>[http://marsrovers.jpl.nasa.gov/science/ "Mars Exploration Rovers – Science."] NASA MER Website. Access date: June 13, 2006.</ref>
| |
| − |
| |
| − | 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 map the Martian terrain and find suitable landing sites for the upcoming lander missions. It arrived in orbit on March 10, 2006.
| |
| − |
| |
| − | ===Astronomical observations from Mars===
| |
| − | [[Image:Earth and Moon from Mars PIA04531.jpg|thumb|right|Earth and Moon from Mars, imaged by Mars Global Surveyor; South America is visible]]
| |
| − |
| |
| − | Given the various orbiters, landers, and rovers, it is now possible to study [[astronomy]] from the Martian skies. In particular, the Earth and the Moon would be easily visible to the [[naked eye]] from Mars. Also, one could observe the two [[Mars' natural satellites|moons of Mars]]. The 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 appears more or less star-like, and appears only slightly brighter than Venus does from Earth.<ref>[http://www.planetary.org/explore/topics/mars/deimos.html "Deimos."] <i>Planetary Societies's Explore the Cosmos</i>. Access date: June 13, 2006.</ref>
| |
| − |
| |
| − | There are also various phenomena well-known on Earth that have now been observed on Mars, including [[meteor]]s and [[Aurora (phenomenon)|auroras]]. The first meteor photographed on Mars was on March 7, 2004, by the rover ''[[Spirit (rover)|Spirit]]''. Auroras occur on Mars, but they do not occur at the poles as on Earth, because Mars has no planet-wide magnetic field. Rather, they occur near magnetic anomalies in Mars' [[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.<ref>[http://www.nature.com/nature/journal/v435/n7043/abs/nature03603.html "Discovery of an aurora on Mars."] <i>Nature</i>. Access date: June 13, 2006.</ref>
| |
| − |
| |
| − | A transit of the Earth as seen from Mars will occur on November 10, 2084. At that time, the Sun, Earth and Mars will be exactly collinear. There are also transits of Mercury and transits of Venus, and the moon Deimos is of sufficiently small angular diameter that its partial "eclipses" of the Sun are best considered transits.
| |
| − |
| |
| − | [[Image:MarsSunsetCut.jpg|thumb|right|400px|Photograph of a Martian sunset taken by Spirit at Gusev crater, May 19, 2005]]
| |
| − |
| |
| − | The only [[occultation]] of Mars by Venus observed was that of October 3, 1590, seen by M. Möstlin at [[Heidelberg]].<ref>Breyer, S. (1979). "Mutual Occultation of Planets." <i>Sky and Telescope</i> 57 (3): 220.</ref>
| |
| − |
| |
| − | ===Future plans===
| |
| − |
| |
| − | Future plans for unmanned Mars exploration include the sending of the [[Phoenix (spacecraft)|Phoenix Lander]] in 2007,<ref>[http://mars.jpl.nasa.gov/mro/science/ "MRO: Science"], NASA's MRO website. Access date: June 13, 2006.</ref> followed by the [[Mars Science Laboratory]] in 2009, the [[Phobos-Grunt]] sample-return mission, to return samples of the Martian moon Phobos. Other missions have been proposed but not yet confirmed.
| |
| − |
| |
| − | 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 President [[George W. Bush]].<ref>[http://www.space.com/news/bush_plan_faq_040115.html#whenmars "When do we get to Mars?"] Space.com FAQ: Bush's New Space Vision. Access date: June 13, 2006.</ref>
| |
| − |
| |
| − | The European Space Agency hopes to land the first humans on Mars between 2030 and 2035. This will be preceded by successively larger probes, starting with the launch of the [[ExoMars]] probe in 2013,<ref>[http://www.esa.int/esaMI/Aurora/SEM1NVZKQAD_0.html#whenmars "ExoMars"], Homepage of Aurora Project at ESA. Access date: June 20, 2006.</ref><ref>[http://news.bbc.co.uk/2/hi/science/nature/6133712.stm "European Mars launch pushed back."] Access date: November 10, 2006.</ref> followed by the 'Mars Sample Return Mission.' Likewise, astronauts will be sent to the Moon between 2020 and 2025 in preparation for this mission.
| |
| − |
| |
| − | == 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 such as [[Giovanni Schiaparelli]] and [[Percival Lowell]], 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'', in which Martians seek to escape their dying planet by invading Earth. Of considerable note is the release of a radio broadcast of ''The War of the Worlds'' on October 30, 1938. It was broadcast as a news release, and many people mistook it for the truth. Also influential was Ray Bradbury's ''The Martian Chronicles'', in which human explorers find a dying Martian civilization, as well as [[Burroughs (Author)|Burroughs']] ''Barsoom series'' and a number of [[Robert A. Heinlein]] stories prior to the mid-sixties.
| |
| − |
| |
| − | After the [[Mariner program|Mariner]] and [[Viking program|Viking]] spacecraft had returned images that showed Mars to be an apparently lifeless and canal-less world, these ideas about Mars had to be abandoned. Since then, a vogue for realist depictions of human colonies on Mars developed, the best known of which may be [[Kim Stanley Robinson]]'s ''Mars'' trilogy. Nonetheless, 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'' (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'' and the ''Zone of the Enders'' series. Mars (and its moons) were also the setting for the popular ''Doom'' video-game franchise and the later ''Martian Gothic''.
| |
| − |
| |
| − | == See also ==
| |
| − |
| |
| − | * [[Astrobiology]]
| |
| − | * [[Earth]]
| |
| − | * [[Planet]]
| |
| − | * [[Solar System]]
| |
| − | * [[Sun]]
| |
| − |
| |
| − | ==Footnotes==
| |
| − | <div class="references-small">
| |
| − | <references />
| |
| − | </div>
| |
| − |
| |
| − | == References ==
| |
| − |
| |
| − | * Sheehan, William. ''[http://www.uapress.arizona.edu/onlinebks/mars/contents.htm The Planet Mars: A History of Observation and Discovery.]'' Tuscon, AZ: The University of Arizona Press, 1996. Access date: December 7, 2006.
| |
| − | * [http://www.nineplanets.org/mars.html Nine Planets Mars page.] Access date: December 7, 2006.
| |
| − | * [http://www.space.com/mars/ Space.com: All About Mars.] Access date: December 7, 2006.
| |
| − | * Squyres, Steve. ''Roving Mars: Spirit, Opportunity, and the Exploration of the Red Planet''. New York: Hyperion, 2005. ISBN 1401301495
| |
| − |
| |
| − | ===External links===
| |
| − |
| |
| − | * [http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html NASA's Mars fact sheet]
| |
| − | * [http://www.worldwindcentral.com/wiki/Mars 3D maps of Mars - WorldWind Central]
| |
| − | * [http://www.google.com/mars/ Google Mars] - Interactive image of Mars
| |
| − | * [http://themis.asu.edu/valles_video/ Flight Into Mariner Valley] - NASA/JPL/Arizona State University 3D flythrough of Valles Marineris
| |
| − | * [http://www.marsgeo.com/ Marsgeo.com] - Mars Rover photos, videos & surface geology
| |
| − | * [http://www.student.oulu.fi/~jkorteni/space/mars/surface/ Introduction to Martian topography, with Hubble Space Telescope photos]
| |
| − | * [http://www.geoinf.fu-berlin.de/mex/ FU Berlin: HRSC (camera) experiment at Mars Express] - Press releases and high resolution images
| |
| − | * [http://www.giss.nasa.gov/tools/mars24/help/notes.html Technical Notes about Time on Mars]
| |
| − | * [http://history.nasa.gov/SP-4212/on-mars.html On Mars: Exploration of the Red Planet 1958-1978] from the NASA History Office.
| |
| − | * [http://www.vias.org/spacetrip/mars_globalview.html A Trip Into Space] - Photos and descriptions of Mars
| |
| − | * [http://www.cato.org/pubs/wtpapers/980815paper.html Martian Law - a CATO white paper]
| |
| − | * [http://www.maniacworld.com/mars_mariner_valley.htm Computer Simulation of a flyby through Mariner Valley]
| |
| − | * [http://www.marsunearthed.com/ Mars Unearthed] - Comparisons of terrains between Earth and Mars
| |
| − | * [http://www.ibiblio.org//e-notes/VRML/Globe/Globe.htm 3D VRML Mars globe]
| |
| − | * [http://ralphaeschliman.com/id30.htm Ralph Aeschliman's Online Atlas of Mars]
| |
| − | * [http://www.projectshum.org/Planets/mars.html Planets - Mars] A kid's guide to Mars.
| |
| − | * [http://www.globalicwarming.com/global-warming-mars.html Is there Global Warming on Mars?]
| |
| − | * [http://news.bbc.co.uk/1/hi/sci/tech/4767403.stm BBC: Wheels on Mars]
| |
| − | * [http://www.geody.com/?world=mars Geody Mars] World's search engine that supports [[NASA World Wind]], [[Celestia]], and other applications.
| |
| − | * [http://www.earthsim.tv Earthsim] - Virtual globe including Mars with overlays and documentaries.
| |
| − |
| |
| − | === Water ===
| |
| − | * [http://news.bbc.co.uk/1/hi/sci/tech/4727847.stm 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.
| |
| − | * [http://news.bbc.co.uk/hi/english/sci/tech/newsid_2009000/2009318.stm BBC News story] on subsurface ice deposits on Mars
| |
| − | * [http://news.bbc.co.uk/1/hi/sci/tech/3426539.stm BBC News update] on Mars Express' findings of polar water ice and water-eroded features on the surface
| |
| − | * [http://www.nasa.gov/vision/universe/solarsystem/opportunity_water.html 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
| |
| − | * [http://news.bbc.co.uk/1/hi/sci/tech/4285119.stm BBC News Mars] - pictures reveal frozen sea
| |
| − |
| |
| − | === Exploration ===
| |
| − | * [http://www.transhumanist.com/volume4/space.htm The Political Economy of Very Large Space Projects (Journal Of Evolution and Technology)]
| |
| − | * [http://www.exploremarsnow.org/ exploreMarsnow] - Interactive Mars base simulation. Winner of 2003 Webby Award for Science.
| |
| − | * [http://marsrovers.jpl.nasa.gov/home/index.html NASA Mars Exploration Rover Home Page]
| |
| − | * [http://dualmoments.com/marsrovers/index.html Be on Mars] - Anaglyphs from the Mars Rovers (3D)
| |
| − | * [http://martian.smolyan.info/ Martian Travel Guide] - Student's project for Catch a Star
| |
| − |
| |
| − | [[Category:Physical sciences]]
| |
| − | [[Category:Astronomy]]
| |
| − | [[Category:Solar System]]
| |
| − |
| |
| − | {{credit|87102653}}
| |
