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Mars

(Redirected from Orbit of Mars)
For other uses, see Mars (disambiguation).

Mars is the fourth planet from the Sun in the Solar System and the second-smallest planet. Mars is a terrestrial planet with polar ice caps of frozen water and carbon dioxide.[5][6] It has the largest volcano in the Solar System, and some very large impact craters.[5] Mars is named after the mythological Roman god of war because it appears of red color.

Mars ♂
Mars appears as a red-orange globe with darker blotches and white icecaps visible on both of its poles. If you’re using wiki for school, stop it, -your teacher.
Pictured in natural color in 2007
Designations
Pronunciation/ˈmɑːrz/ ( listen)
AdjectivesMartian
Orbital characteristics
Epoch J2000
Aphelion249200000 km
(154800000 mi; 1.666 AU)
Perihelion206700000 km
(128400000 mi; 1.382 AU)
227939200 km
(141634900 mi; 1.523679 AU)
Eccentricity0.0934
686.971 d
(1.88082 yr; 668.5991 sols)
779.96 d
(2.1354 yr)
24.007 km/s
(86430 km/h; 53700 mph)
Inclination
49.558°
286.502°
Satellites2
Physical characteristics
Mean radius
3389.5 ± 0.2 km 
(2106.1 ± 0.1 mi)
Equatorial radius
3396.2 ± 0.1 km 
(2110.3 ± 0.1 mi; 0.533 Earths)
Polar radius
3376.2 ± 0.1 km 
(2097.9 ± 0.1 mi; 0.531 Earths)
Flattening0.00589±0.00015
144798500 km2[1]
(55907000 sq mi; 0.284 Earths)
Volume1.6318×1011 km3
(0.151 Earths)
Mass6.4171×1023 kg
(0.107 Earths)
Mean density
3.9335 g/cm3
(0.1421 lb/cu in)
3.72076 m/s2[2]
(12.2072 ft/s2; 0.3794 g)
0.3662±0.0017
5.027 km/s
(18100 km/h; 11250 mph)
1.025957 d
24h 37m 22s
Equatorial rotation velocity
Lua error in Module:Convert at line 272: attempt to index local 'cat' (a nil value).
25.19° to its orbital plane
North pole right ascension
317.68143°
21h 10m 44s
North pole declination
52.88650°
Albedo
Surface temp. min mean max
Kelvin 130 K 210 K 308 K
Celsius −143 °C[3] −63 °C 35 °C[4]
Fahrenheit −226 °F[3] −82 °F 95 °F[4]
−2.94 to +1.86
3.5–25.1″
Atmosphere
Surface pressure
0.636 (0.4–0.87) kPa
0.00628 atm
Composition by volume

Space probes such as the Viking program landers are the main tools for the exploration of Mars.

Appearance

Artist's impression of Mars four billion years ago vid

Mars is a terrestrial planet and made of rock. The ground there is red because of iron oxide (rust) in the rocks and dust.[7] The planet's atmosphere is very thin. It is mostly carbon dioxide with some argon and nitrogen and tiny amounts of other gases including oxygen. The temperatures on Mars are colder than on Earth, because it is farther away from the Sun and has less air to keep heat in. There is water ice and frozen carbon dioxide at the north and south poles.[6] Mars does not have any liquid water on the surface now, but signs of run-off on the surface were probably caused by water.

The average thickness of the planet's crust is about 50 km (31 mi), with a maximum thickness of 125 km (78 mi).[8]

Moons

Mars has two small moons, called Phobos and Deimos.

 
The moons of Mars: Phobos and Deimos. Phobos is the larger of the two moons, and is the closest of the two to Mars. Phobos has an average radius of 11 km, while Deimos has an average radius of 6 km.

The origin of Mars' moons is unknown and controversial. One theory is that the moons are captured asteroids. However, the moons' near circular orbits and low inclination relative to the Martian equator are not in agreement with the capture hypothesis.[9]

Estimates of the mass ejected by a large Borealis-size impact vary. Simulations suggest that a body about 0.02 of Mars mass (~0.002 Earth mass) in size can produce a sizable debris disk in Martian orbit. Much of the material would stay close to Mars.[9] There are several other large impact basins on Mars that could also have ejected enough debris to form the moons.[9]

Physical geography

Lack of magnetic field

Mars does not have a global magnetic field.[10] Despite this, observations show that parts of the planet's crust have been magnetized. This suggests that polarity reversals have occurred in the past. This paleomagnetism is similar to the magnetic striping found on Earth's ocean floors. One theory is that these bands suggest plate tectonic activity on Mars four billion years ago, before the planetary dynamo stopped working and the planet's magnetic field faded.

Rotation

A Martian day is called a sol, and is a little longer than an Earth day. Mars rotates in 24 hours and 37 minutes. It rotates on a tilted axis, just like the Earth does, so it has four different seasons. Of all the planets in the Solar System, the seasons of Mars are the most Earth-like, due to their similar axial tilt. The lengths of the Martian seasons are almost twice those of Earth's, as Mars's greater distance from the Sun leads to the Martian year being almost two Earth years long.

Martian surface temperatures vary from lows of about −143 °C (−225 °F) (at the winter polar caps)[3] to highs of up to 35 °C (95 °F) (in equatorial summer).[4] The wide range in temperatures is due mostly to the thin atmosphere which cannot store much solar heat. The planet is also 1.52 times as far from the Sun as Earth, resulting in just 43% of the amount of sunlight.[11]

Water

 
Microscopic photo taken by Opportunity showing a gray hematite concretion, suggesting the past presence of liquid water

A 2015 report says Martian dark streaks on the surface were affected by water.[12]

Liquid water cannot exist on the surface of Mars due to its low atmospheric pressure (there's not enough air to hold it in),[13] except at the lowest elevations for short periods.[14] The two polar ice caps appear to be made largely of frozen water.[6] The amount of ice in the south polar ice cap, if melted, would be enough to cover the entire planet's surface 11 meters deep.[6] A permafrost mantle stretches from the pole to latitudes of about 60°.[15]

Geological evidence gathered by unmanned missions suggest that Mars once had much liquid water on its surface.[16] In 2005, radar data revealed the presence of large quantities of water ice at the poles,[17] and at mid-latitudes. The Mars rover Spirit sampled chemical compounds containing water molecules in March 2007. The Phoenix lander found water ice in shallow Martian soil in July 2008.[18]Landforms seen on Mars strongly suggest that liquid water at some time existed on the planet's surface. Huge areas of ground have been scraped and eroded.

Polar caps

 
North polar early summer ice cap (1999)
 
South polar midsummer ice cap (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 25–30% of the atmosphere into slabs of CO2 ice (dry ice). When the poles are again exposed to sunlight, the frozen CO2 sublimes (turns to vapor), creating enormous winds that sweep off the poles as fast as 400 km/h. Each season this moves large amounts of dust and water vapor, giving rise to Earth-like frost and large cirrus clouds and dust storms. Clouds of water-ice were photographed by the Opportunity rover in 2004.

The polar caps at both poles consist primarily of water ice.[6]

Atmosphere

Mars has a very thin atmosphere with barely any oxygen (it is mostly carbon dioxide).[19] Because there is an atmosphere, however thin it is, the sky does change colour when the sun rises and sets. The dust in the Martian atmosphere makes Martian sunsets somewhat blue. Mars's atmosphere is too thin to protect Mars from meteors, which is part of the reason why Mars has so many craters.

Meteorite craters

After the formation of the planets, all experienced the "Late Heavy Bombardment". About 60% of the surface of Mars shows a record of impacts from that era.[20] Much of the remaining surface is probably lying over the immense impact basins caused by those events. There is evidence of an enormous impact basin in the northern hemisphere of Mars, spanning 10,600 by 8,500 km (6,600 by 5,300 mi), or roughly four times larger than the largest impact basin previously known.[21] This suggests that Mars was struck by a Pluto-sized body about four billion years ago. The event is thought to be the cause of the difference between the Martian hemispheres. It made the smooth Borealis Basin that covers 40% of the planet.[22][23]

Some meteorites hit Mars with so much force a few pieces of Mars went flying into space – even to Earth! Rocks on Earth are sometimes found which have chemicals that are exactly like the ones in Martian rocks. These rocks also look like they fell really quickly through the atmosphere, so it is reasonable to think they came from Mars.

Recent hits

Spacecraft Insight detected seismic waves made by the biggest meteorite impacts ever seen on Mars.[24][25]

Geography

Mars is home to the highest known mountain in the Solar System, Olympus Mons. Olympus Mons is about 17 miles (or 27 kilometers) high. This is more than three times the height of Earth's tallest mountain, Mount Everest. It is also home to Valles Marineris, the third largest rift system (canyon) in the Solar System, 4,000 km long.

Observation of Mars

 
A coloured drawing of Mars made in 1877 by the French astronomer Trouvelot

Our records of watching and recording Mars start with ancient Egyptian astronomers in the 2nd millennium BC.[26][27]

Detailed observations of the location of Mars were made by Babylonian astronomers who developed methods using math to predict the future position of the planet. The ancient Greek philosophers and astronomers developed a model of the solar system with the Earth at the center ('geocentric'), instead of the sun. They used this model to explain the planet's motions.[28] Vedic and Islamic astronomers estimated the size of Mars and its distance from Earth.[29][30] Similar work was done by Chinese astronomers.[31]

In the 16th century, Nicholas Copernicus proposed a model for the Solar System in which the planets follow circular orbits about the Sun. This 'heliocentric' model was the beginning of modern astronomy. It was revised by Johannes Kepler, who gave an elliptical orbit for Mars which better fit the data from our observations.[32][33][34][35]

The first observations of Mars by telescope was by Galileo Galilei in 1610. Within a century, astronomers discovered distinct albedo features (changes in brightness) on the planet, including the dark patch and polar ice caps. They were able to find the planet's day (rotation period) and axial tilt.[36][37]

Better telescopes developed early in the 19th century allowed permanent Martian albedo features to be mapped in detail. The first crude map of Mars was published in 1840, followed by better maps from 1877 onward. Astronomers mistakenly thought they had detected the spectroscopic mark of water in the Martian atmosphere, and the idea of life on Mars became popular among the public.

Yellow clouds on Mars have been observed since the 1870s, which were windblown sand or dust. During the 1920s, the range of Martian surface temperature was measured; it ranged from –85 to 7 oC. The planetary atmosphere was found to be arid with only traces of oxygen and water. In 1947, Gerard Kuiper showed that the thin Martian atmosphere contained extensive carbon dioxide; roughly double the quantity found in Earth's atmosphere. The first standard naming of Mars surface features was set in 1960 by the International Astronomical Union.

Since the 1960s, multiple robotic spacecraft and rovers have been sent to explore Mars from orbit and the surface. The planet has remained under observation by ground and space-based instruments across a broad range of the electromagnetic spectrum (visible light, infrared and others). The discovery of meteorites on Earth that came from Mars has allowed laboratory examination of the chemical conditions on the planet.

Martian 'canals'

 
Map of Mars by Giovanni Schiaparelli, compiled between 1877 and 1886, in Milan,[38][39] showing canali features as fine lines
 
Mars sketched as observed by Lowell sometime before 1914. (South top)

During the 1877 opposition, Italian astronomer Giovanni Schiaparelli in Milan[38][39] used a 22 cm (8.7 in) telescope to help produce the first detailed map of Mars. What caught people's attention was that the maps had features he called canali. These were later shown to be an optical illusion (not real). These canali were supposedly long straight lines on the surface of Mars to which he gave names of famous rivers on Earth. His term canali was popularly mistranslated in English as canals, and thought to be made by intelligent beings.[40][41]

Other astronomers thought they could see the canals too, especially the American astronomer Percival Lowell who drew maps of an artificial network of canals on Mars.[42][43][44][45][46]

Although these results were widely accepted, they were contested.[47] Greek astronomer Eugène M. Antoniadi and English naturalist Alfred Russel Wallace were against the idea; Wallace was extremely outspoken.[48] As bigger and better telescopes were used, fewer long, straight canali were observed. During an observation in 1909 by Flammarion with a 84 cm (33 in) telescope, irregular patterns were observed, but no canali were seen.[49]

Life on Mars

 
Mars by Viking 1 in 1980

Because Mars is the one of the closest planets to Earth in the Solar System, many have wondered if there is any kind of life on Mars. Today we know that the kind of life, if any, would be some simple bacteria-type organism.

Meteorites

NASA maintains a catalog of 34 Mars meteorites, that is, meteorites which originally came from Mars.[50] These assets are highly valuable since they are the only physical samples available of Mars.

Studies at NASA's Johnson Space Center show that at least three of the meteorites contain possible evidence of past life on Mars, in the form of microscopic structures resembling fossilized bacteria (so-called biomorphs). Although the scientific evidence collected is reliable, and the rocks are correctly described, what made the rocks look like they do is not clear. To date, scientists are still trying to agree if it really is evidence of simple life on Mars.[51]

Over the past few decades, scientists have agreed that when using meteorites from other planets found on Earth (or rocks brought back to Earth), various things are needed to be sure of life. Those things include:[51]

  1. Did the rock comes from the right time and place on the planet for life to exist?
  2. Does the sample contain evidence of bacterial cells (does it show fossils of some kind, even if very tiny)?
  3. Is there any evidence of biominerals? (minerals usually caused by living things)
  4. Is there any evidence of isotopes typical of life?
  5. Are the features part of the meteorite, and not contamination from Earth?

For people to agree on past life in a geologic sample, most or all of these things must be met. This has not happened yet, but investigations are still in progress.[51] Reexaminations of the biomorphs found in the three Martian meteorites are underway.[52]

The significance of water

Liquid water is necessary for life and metabolism, so if water was present on Mars, the chances of life evolving is improved. The Viking orbiters found evidence of possible river valleys in many areas, erosion and, in the southern hemisphere, branched streams.[53][54][55] Since then, rovers and orbiters have also looked closely and eventually proved water was on the surface at one time, and is still found as ice in the polar ice caps and underground.

Today

So far, scientists have not found life on Mars, either living or extinct. Several space probes have gone to Mars to study it. Some have orbited (gone around) the planet, and some have landed on it. There are pictures of the surface of Mars that were sent back to Earth by the probes. Some people are interested in sending astronauts to visit Mars. They could do a better search, but getting astronauts there would be difficult and expensive. The astronauts would be in space for many years, and it could be very dangerous because of radiation from the sun. So far we have only sent unmanned probes.

The most recent probe to the planet is the Mars Science Laboratory. It landed on Aeolis Palus in Gale Crater on Mars on 6 August 2012.[56] It brought with it a mobile explorer called 'Curiosity'. It is the most advanced space probe ever. Curiosity has dug up Martian soil and studied it in its laboratory. It has found sulfur, chlorine, and water molecules.[57]

Popular culture

Main page: Mars in fiction

Some famous stories were written about this idea. The writers used the name "Martians" for intelligent beings from Mars. In 1898, H. G. Wells wrote The War of the Worlds, a famous novel about Martians attacking the Earth.[58] In 1938, Orson Welles broadcast a radio version of this story in the United States, and many people thought it was really happening and were very afraid.[59] Beginning in 1912, Edgar Rice Burroughs wrote several novels about adventures on Mars.

Mars Media

  • PIA17944-MarsCuriosityRover-AfterCrossingDingoGapSanddune-20140209

  • Very high resolution topographic shaded relief map of Mars, based on the Mars Orbiter Laser Altimeter (MOLA) data set from the Mars Global Surveyor spacecraft. The map has a resolution 0.125° (300 dots per inch) and is shown as a

  • Picture of the largest volcano on Mars, Olympus Mons. It is approximately 550 km (340 mi) across.

  • Valles Marineris, taken by the Viking 1 probe

  • Edge-on view of Mars atmosphere by Viking 1 probe

  • Mars without (on left) and with a global dust storm in July 2001 (on right), as seen by the Hubble Space Telescope

  • Orbit of Mars and other Inner Solar System planets

References

  1. ↑ Grego, Peter (2012). Mars and how to observe it. Springer Science+Business Media. ISBN 978-1-4614-2302-7. Retrieved 2019-04-26 – via Google Books.
  2. ↑ Hirt, C.; Claessens, S. J.; Kuhn, M.; Featherstone, W. E. (July 2012). "Kilometer-resolution gravity field of Mars: MGM2011". Planetary and Space Science. 67 (1): 147–154. Bibcode:2012P&SS...67..147H. doi:10.1016/j.pss.2012.02.006. hdl:20.500.11937/32270.
  3. ↑ 3.0 3.1 3.2 What is the typical temperature on Mars? Archived 2016-12-01 at the Wayback Machine Astronomycafe.net. Retrieved on 2012-08-14
  4. ↑ 4.0 4.1 4.2 Mars Exploration Rover Mission: Spotlight Archived 2013-11-02 at the Wayback Machine. Marsrover.nasa.gov (2007-06-12). Retrieved on 2012-08-14.
  5. ↑ 5.0 5.1 "Mars: Extreme Planet". NASA. Archived from the original on 2011-10-26. Retrieved 2011-10-25.
  6. ↑ 6.0 6.1 6.2 6.3 6.4 "NASA Jet Propulsion Laboratory - News". Jet Propulsion Laboratory. 20 April 2009. Archived from the original on 2009-04-20.
  7. ↑ "NASA Mars Page". Volcanology of Mars (Retrieved via the Internet Archive). Archived from the original on 2008-01-06. Retrieved 2009-05-13.
  8. ↑ Dave Jacqué (2003-09-26) (in English). APS X-rays reveal secrets of Mars' core. Argonne National Laboratory. http://www.anl.gov/Media_Center/News/2003/030926mars.htm. Retrieved 2006-07-01. 
  9. ↑ 9.0 9.1 9.2 Citron, Robert I.; Genda, Hidenori; Ida, Shigeru (2015-05-15). "Formation of Phobos and Deimos via a giant impact". Icarus. 252: 334–338. arXiv:1503.05623. Bibcode:2015Icar..252..334C. doi:10.1016/j.icarus.2015.02.011. S2CID 17089080.
  10. ↑ "Amos, Jonathan. BBC News Science & Environment". BBC News. 15 June 2020. https://www.bbc.co.uk/news/science-environment-53057055. Retrieved 2020-06-16. 
  11. ↑ Kluger, Jeffrey 1992. "Mars, in Earth's Image Archived 2012-04-27 at the Wayback Machine". Discover Magazine
  12. ↑ Amos, Jonathan 2015. Martian salt streaks 'painted by liquid water'. BBC News Science & Environment. [1] Archived 2016-11-25 at the Wayback Machine
  13. ↑ The reason is that water sublimates at low atmospheric pressure. In other words, it turns directly into water vapour.
  14. ↑ Heldmann, Jennifer L. et al 2005. Formation of Martian gullies by the action of liquid water flowing under current Martian environmental conditions. Journal of Geophysical Research 110 (E5). PDF: [2] Archived 2008-10-01 at the Wayback Machine
  15. ↑ Kostama V.-P. et al 2006. Recent high-latitude icy mantle in the northern plains of Mars: Characteristics and ages of emplacement. Geophysical Research Letters 33 (11): L11201. [3] Archived 2013-11-04 at the Wayback Machine
  16. ↑ NASA 2006. NASA images suggest water still flows in brief spurts on Mars. [4] Archived 2011-08-07 at the Wayback Machine
  17. ↑ esa. "Water ice in crater at Martian north pole". European Space Agency. Archived from the original on 2013-01-02. Retrieved 2013-01-11.
  18. ↑ "NASA - NASA Spacecraft confirms Martian water, mission extended". www.nasa.gov. Archived from the original on 2008-11-29. Retrieved 2019-02-11.
  19. ↑ "NASA's Mars Exploration Program". NASA’s Mars Exploration Program. Archived from the original on 2021-04-23. Retrieved 2021-12-04.
  20. ↑ Barlow N.G. 1988. Conditions on early Mars: constraints from the cratering record. MEVTV Workshop on Early tectonic and volcanic evolution of Mars. LPI Technical Report 89-04 (Easton, Maryland: Lunar and Planetary Institute) p15.
  21. ↑ Sample, Ian 28 June 2008. Cataclysmic impact created north-south divide on Mars. London: Science @ guardian.co.uk. [5] Archived 2017-02-14 at the Wayback Machine
  22. ↑ Minkel J.R. June 2008. Giant asteroid flattened half of Mars, studies suggest. Scientific American. [6] Archived 2016-03-16 at the Wayback Machine
  23. ↑ Chang, Kenneth June 26, 2008. Huge meteor strike explains Mars's shape, reports say. New York Times. [7] Archived 2017-07-01 at the Wayback Machine
  24. ↑ Posiolova L.V. et al. Science 378, 412–417 (2022).
  25. ↑ Kim D. et al. Science 378, 417–421 (2022).
  26. ↑ Novaković, B. (2008). "Senenmut: an ancient Egyptian astronomer". Publications of the Astronomical Observatory of Belgrade. 85: 19–23. arXiv:0801.1331. Bibcode:2008POBeo..85...19N.
  27. ↑ Clagett, Marshall (1989). Ancient Egyptian science: calendars, clocks, and astronomy. Vol. 2. Diane. pp. 162–163. ISBN 0-87169-214-7.
  28. ↑ "Geocentric model". UniverseToday. Archived from the original on 9 September 2013. Retrieved 14 September 2013.
  29. ↑ Swerdlow, Noel M. (1998). "Periodicity and Variability of Synodic Phenomenon". The Babylonian theory of the planets. Princeton University Press. pp. 34–72. ISBN 0-691-01196-6. Retrieved 2017-08-31.
  30. ↑ Valery, Franz; Cumont, Marie (1912). Astrology and religion among the Greeks and Romans. American lectures on the history of religions. Putnam. p. 46. ISBN 9780790542737. Retrieved 2017-08-31.
  31. ↑ Evans, James (1998). The history & practice of ancient astronomy. Oxford University Press. p. 297. ISBN 0-19-509539-1. Archived from the original on 2020-08-03. Retrieved 2017-08-31.
  32. ↑ Gingerich, Owen; MacLachlan, James H. (2005). Nicolaus Copernicus: making the Earth a planet. Oxford portraits in science. Oxford University Press. pp. 57–61. ISBN 0-19-516173-4. Retrieved 2017-08-31.
  33. ↑ Zalta, Edward N., ed. (2005). "Nicolaus Copernicus". Stanford Encyclopedia of Philosophy. Archived from the original on 2016-12-11. Retrieved 2010-01-09.
  34. ↑ Breyer, Stephen (1979). "Mutual occultation of planets". Sky and Telescope. 57 (3): 220. Bibcode:1979S&T....57..220A.
  35. ↑ Longair, M.S. (2003). Theoretical concepts in physics: an alternative view of theoretical reasoning in physics (2nd ed.). Cambridge University Press. pp. 25–28. ISBN 0-521-52878-X. Retrieved 2017-08-31.
  36. ↑ Moore, P. (1984). "The mapping of Mars". Journal of the British Astronomical Association. 94 (2): 45–54. Bibcode:1984JBAA...94...45M.
  37. ↑ Sheehan, William (1996). "Chapter 2: pioneers". The planet Mars: a history of observation and discovery. University of Arizona. Archived from the original on 2012-04-26. Retrieved 2010-01-16.
  38. ↑ 38.0 38.1
    1. REDIRECT Template:Blockquote
    .
  39. ↑ 39.0 39.1 Dave Snyder. "An Observational History of Mars". Archived from the original on January 6, 2009. Retrieved March 10, 2009.
  40. ↑ Milone, Eugene F.; Wilson, William J.F. (2008). Background science and the inner Solar System. Solar System Astrophysics. Vol. 1. Springer. p. 228. ISBN 978-0-387-73154-4. Retrieved 2017-08-31.
  41. ↑ Sagan, Carl (1980). Cosmos. Random House. p. 107. ISBN 0-394-50294-9. Retrieved 2017-08-31.
  42. ↑ Lang, Kenneth R. (2003). The Cambridge guide to the Solar System. Cambridge University Press. p. 251. ISBN 0-521-81306-9. Retrieved 2017-08-31.
  43. ↑ Basalla, George (2006). "Percival Lowell: Champion of Canals". Civilized life in the Universe: scientists on intelligent extraterrestrials. Oxford University Press US. pp. 67–88. ISBN 0-19-517181-0. Archived from the original on 2020-08-03. Retrieved 2017-08-31.
  44. ↑ Maria, K.; Lane, D. (2005). "Geographers of Mars". Isis. 96 (4): 477–506. doi:10.1086/498590. PMID 16536152. S2CID 33079760.
  45. ↑ Perrotin, M. (1886). "Observations des canaux de Mars". Bulletin Astronomique, Serie I (in French). 3: 324–329. Bibcode:1886BuAsI...3..324P. doi:10.3406/bastr.1886.9920. S2CID 128159166.{{cite journal}}: CS1 maint: unrecognized language (link)
  46. ↑ Slipher, E. C. (1921). "Photographing the planets with especial reference to Mars". Publications of the Astronomical Society of the Pacific. 33 (193): 127–139. Bibcode:1921PASP...33..127S. doi:10.1086/123058. S2CID 121667367.
  47. ↑ Antoniadi, E.M. (1913). "Considerations on the physical appearance of the planet Mars". Popular Astronomy. 21: 416–424. Bibcode:1913PA.....21..416A.
  48. ↑ Wallace, Alfred Russel (1907). Is Mars habitable?: a critical examination of Professor Percival Lowell's book "Mars and its canals," with an alternative explanation. Macmillan. pp. 102–110. ISBN 9781465560148. Retrieved 2017-08-31.
  49. ↑ Zahnle, K. (2001). "Decline and fall of the Martian empire". Nature. 412 (6843): 209–213. doi:10.1038/35084148. PMID 11449281. S2CID 22725986.
  50. ↑ "Mars Meteorites". NASA. Archived from the original on April 10, 2012. Retrieved February 16, 2010.
  51. ↑ 51.0 51.1 51.2 Evidence for ancient Martian life Archived 2020-01-24 at the Wayback Machine. Gibson E. K. Jr. et al Mail Code SN2, NASA Johnson Space Center, Houston TX 77058, USA.
  52. ↑ "Spaceflight Now - Breaking News - Three Martian meteorites triple evidence for Mars life". spaceflightnow.com. Archived from the original on 2018-12-26. Retrieved 2019-02-11.
  53. ↑ Strom R.G., Steven K. Croft, and Nadine G. Barlow 1992. The Martian impact cratering record.University of Arizona Press. ISBN 0-8165-1257-4
  54. ↑ Raeburn P. 1998. Uncovering the secrets of the red planet Mars. National Geographic Society. Washington D.C.
  55. ↑ Moore P. et a 1990. The Atlas of the Solar System. Mitchell Beazley Publishers NY.
  56. ↑ Wall, Mike (2012-08-06). "Touchdown! Huge NASA rover lands on Mars". Space.com. Archived from the original on 2020-03-23. Retrieved 2012-12-31.
  57. ↑ Mars Science Laboratory. NASA 2012. http://www.nasa.gov/mission_pages/msl/news/msl20121203.html Archived 2013-01-02 at the Wayback Machine
  58. ↑ "Pop Culture Mars: Literature". NASA. Archived from the original on 2011-10-27. Retrieved 2011-10-25.
  59. ↑ "Pop Culture Mars: Film & Radio". NASA. Archived from the original on 2011-10-27. Retrieved 2011-10-25.

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