Mars

Mars is the fourth from the in the and the second-smallest planet. Mars is a with polar ice caps of and . It has the largest in the , and some very large . of because it appears of red

such as the landers are the main tools for the .

Mars is a and made of . The ground there is because of (rust) in the rocks and . is very thin. It is mostly with some and and tiny amounts of other gases including . The 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 and frozen carbon dioxide at the north and south . on the surface now, but signs of run-off on the surface were probably caused by water.

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

Mars has two small , called and .

The origin of Mars' moons is unknown and controversial. One theory is that the moons are captured . However, the moons' near circular orbits and low relative to the Martian are not in agreement with the capture . ejected by a large Borealis-size impact vary. 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.

Lack of magnetic field[ | ]

Mars does not have a global . is similar to the magnetic striping found on Earth's ocean floors. One theory is that these bands suggest on Mars four years ago, before the planetary 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 . Of all the planets in the Solar System, the seasons of Mars are the most Earth-like, due to their similar . 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) 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[ | ]

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 (there's not enough air to hold it in), The two polar ice caps appear to be made largely of frozen water. A 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. and at mid-latitudes. The Mars rover sampled containing water molecules in March 2007. The lander found water ice in shallow Martian soil in July 2008.[18]
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 of 25–30% of the atmosphere into slabs of ice (). When the poles are again exposed to sunlight, the frozen CO2 (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 and dust storms. Clouds of water-ice were photographed by the 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 ). Because there is an , 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 . Mars's atmosphere is too thin to protect Mars from , which is part of the reason why Mars has so many craters.

Meteorite craters[ | ]

After the formation of the planets, all experienced the "". About 60% of the surface of Mars shows a record of impacts from that era. This theory suggests that Mars was struck by a -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 that covers 40% of the planet.

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 to think they came from Mars.

Geography[ | ]

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

Our records of watching and recording Mars start with astronomers in the .

Detailed observations of the location of Mars were made by who developed methods using math to predict the future position of the planet. The ancient 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. and astronomers estimated the size of Mars and its distance from Earth. Similar work was done by astronomers.[28]

In the 16th century, proposed a model for the in which the planets follow circular orbits about the . This 'heliocentric' model was the beginning of modern astronomy. It was revised by , who gave an for Mars which better fit the data from our observations.

The first observations of Mars by was by in 1610. Within a century, astronomers discovered distinct features (changes in brightness) on the planet, including the dark patch and polar . They were able to find the planet's day () and .

Better telescopes developed early in the 19th century allowed permanent Martian 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 mark of water in the Martian atmosphere, and the idea of life on Mars became 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, showed that the thin Martian atmosphere contained extensive ; roughly double the quantity found in Earth's atmosphere. The first standard naming of Mars surface features was set in 1960 by the .

Since the 1960s, multiple robotic and 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 (visible light, infrared and others). The discovery of 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, showing canali features as fine lines

Mars sketched as observed by Lowell sometime before 1914. (South top)

During the 1877 opposition, Italian astronomer 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 (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 , and thought to be made by intelligent beings.

Other astronomers thought they could see the canals too, especially the American astronomer who drew maps of an artificial network of on Mars.[41]

Although these results were widely accepted, they were contested. and English naturalist were against the idea; Wallace was extremely outspoken.

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

Meteorites[ | ]

maintains a catalog of 34 Mars , that is, meteorites which originally came from Mars.[45] These assets are highly valuable since they are the only physical samples available of Mars.

Studies at NASA's 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 ). 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.[46]

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:[46]

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 (does it show fossils of some kind, even if very tiny)?


3. Is there any evidence of biominerals? ( usually caused by living things)


4. Is there any evidence of 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.

The significance of water[ | ]

Liquid water is necessary for life and , 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, and, in the southern hemisphere, branched streams.[50] 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 . Several have gone to Mars to study it. Some have (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 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 from the sun. So far we have only sent unmanned probes.

The most recent probe to the planet is the . It landed on in Gale Crater on Mars on 6 August 2012., , and water molecules.[52]

Popular culture[ | ]

Some famous stories were written about this idea. The writers used the name "" for from Mars. In 1898, wrote The War of the Worlds, a famous about Martians attacking the Earth. broadcast a version of this story in the , and many people thought it was really happening and were very afraid. wrote several novels about adventures on Mars.

1. . Springer Science+Business Media.  978-1-4614-2302-7 – via Google Books.
   


2. :. :. :.
   


3. ↑ Astronomycafe.net. Retrieved on 2012-08-14
   


4. ↑ . Marsrover.nasa.gov (2007-06-12). Retrieved on 2012-08-14.
   


5. ↑ . NASA. Retrieved 2011-10-25.
   


6. ↑ . web.archive.org. 20 April 2009.
   


7. . Volcanology of Mars (Retrieved via the ). Retrieved 2009-05-13.
   


8. . Argonne National Laboratory. Retrieved 2006-07-01.
   


9. ↑ Citron, Robert I.; Genda, Hidenori; Ida, Shigeru (2015-05-15). "Formation of Phobos and Deimos via a giant impact". Icarus. 252: 334–338. :. :. :.
   


10. 
    


11. ". Discover Magazine
    


12. 
    


13. at low atmospheric pressure. In other words, it turns directly into water vapour.
    


14. 
    


15. 
    


16. 
    


17. . European Space Agency.
    


18. . www.nasa.gov.
    


19. ↑ 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.
    


20. 
    


21. 
    


22. 
    


23. :. :.
    


24.  0-87169-214-7.
    


25. . UniverseToday. Retrieved 14 September 2013.
    


26. . Princeton University Press. pp. 34–72.  0-691-01196-6.
    


27. . American lectures on the history of religions. Putnam. p. 46.
    


28. . Oxford University Press. p. 297.  0-19-509539-1.
    


29. . Oxford portraits in science. Oxford University Press. pp. 57–61.  0-19-516173-4.
    


30. . Stanford Encyclopedia of Philosophy. Retrieved 2010-01-09.
    


31. :.
    


32. (2nd ed.). Cambridge University Press. pp. 25–28.  .
    


33. :.
    


34. . The planet Mars: a history of observation and discovery. University of Arizona. Retrieved 2010-01-16.
    


35. . Solar System Astrophysics. 1. Springer. p. 228.  0-387-73154-7.
    


36. . Random House. p. 107.  0-394-50294-9.
    


37. . Cambridge University Press. p. 251.  0-521-81306-9.
    


38. . Oxford University Press US. pp. 67–88.  0-19-517181-0.
    


39. :.  16536152.
    


40. :.
    


41. :. :.
    


42. :.
    


43. . Macmillan. pp. 102–110.
    


44. :.  11449281.
    


45. . NASA. Retrieved February 16, 2010.
    


46. ↑ . Gibson E. K. Jr. et al Mail Code SN2, NASA Johnson Space Center, Houston TX 77058, USA.
    


47. . spaceflightnow.com.
    


48.  0-8165-1257-4
    


49. ↑ Raeburn P. 1998. Uncovering the secrets of the red planet Mars. National Geographic Society. Washington D.C.
    


50. ↑ Moore P. et a 1990. The Atlas of the Solar System. Mitchell Beazley Publishers NY.
    


51. . Space.com. Retrieved 2012-12-31.
    


52. 
    


53. . NASA. Retrieved 2011-10-25.
    


54. . NASA. Retrieved 2011-10-25.
    

Notes