Mars

Mars
Orange-brown globe with white snow caps
Mars in true color,[a] as captured by the Hope orbiter. The Tharsis Montes can be seen at the center, with Olympus Mons just to the left and Valles Marineris at the right
Designations
AdjectivesMartian
Symbol♂
Orbital characteristics[1]
Epoch J2000
Aphelion249261000 km
(154884000 mi; 1.66621 AU)[2]
Perihelion206650000 km
(128410000 mi; 1.3814 AU)[2]
227939366 km
(141634956 mi; 1.52368055 AU)[3]
Eccentricity0.0934[2]
686.980 d
(1.88085 yr; 668.5991 sols)[2]
779.94 d
(2.1354 yr)[3]
24.07 km/s
(86700 km/h; 53800 mph)[2]
19.412°[2]
Inclination
49.57854°[2]
2022-Jun-21[5]
286.5°[3]
Satellites2 (Phobos and Deimos)
Physical characteristics
Mean radius
3389.5 ± 0.2 km[b][6]
(2106.1 ± 0.1 mi)
Equatorial radius
3396.2 ± 0.1 km[b][6]
(2110.3 ± 0.1 mi; 0.533 Earths)
Polar radius
3376.2 ± 0.1 km[b][6]
(2097.9 ± 0.1 mi; 0.531 Earths)
Flattening0.00589±0.00015[5][6]
1.4437×108 km2[7]
(5.574×107 sq mi; 0.284 Earths)
Volume1.63118×1011 km3[8]
(0.151 Earths)
Mass6.4171×1023 kg[9]
(0.107 Earths)
Mean density
3.9335 g/cm3[8]
(0.1421 lb/cu in)
3.72076 m/s2[10]
(12.2072 ft/s2; 0.3794 g)
0.3644±0.0005[9]
5.027 km/s
(18100 km/h; 11250 mph)[11]
1.02749125 d[12]
24h 39m 36s
1.025957 d
24h 37m 22.7s[8]
Equatorial rotation velocity
241 m/s
(870 km/h; 540 mph)[2]
25.19° to its orbital plane[2]
North pole right ascension
317.68143°[6]
21h 10m 44s
North pole declination
52.88650°[6]
Albedo
Temperature209 K (−64 °C) (blackbody temperature)[14]
Surface temp. min mean max
Celsius −110 °C[15] −60 °C[16] 35 °C[15]
Fahrenheit −166 °F[15] −80 °F[16] 95 °F[15]
Surface absorbed dose rate8.8 μGy/h[17]
Surface equivalent dose rate27 μSv/h[17]
−2.94 to +1.86[18]
−1.5[19]
3.5–25.1″[2]
Atmosphere[2][20]
Surface pressure
0.636 (0.4–0.87) kPa
0.00628 atm
Composition by volume

Mars is the fourth planet from the Sun. The surface of Mars is orange-red because it is covered in iron(III) oxide dust, giving it the nickname "the Red Planet".[21][22] Mars is among the brightest objects in Earth's sky and its high-contrast albedo features have made it a common subject for telescope viewing. It is classified as a terrestrial planet and is the second smallest of the Solar System's planets with a diameter of 6,779 km (4,212 mi). In terms of orbital motion, a Martian solar day (sol) is equal to 24.5 hours and a Martian solar year is equal to 1.88 Earth years (687 Earth days). Mars has two natural satellites that are small and irregular in shape: Phobos and Deimos.

The relatively flat plains in northern parts of Mars strongly contrast with the cratered terrain in southern highlands – this terrain observation is known as the Martian dichotomy. Mars hosts many enormous extinct volcanos (such as Olympus Mons, 21.9 km or 13.6 mi tall) and one of the largest canyons in the Solar System (Valles Marineris, 4,000 km or 2,500 mi long). Geologically, the planet is fairly active with marsquakes trembling underneath the ground, dust devils sweeping across the landscape, and cirrus clouds. Carbon dioxide is substantially present in Mars's polar ice caps and thin atmosphere. During a year, there are large surface temperature swings on the surface between −78.5 °C (−109.3 °F) to 5.7 °C (42.3 °F)[c] similar to Earth's seasons, as both planets have significant axial tilt.

Mars was formed approximately 4.5 billion years ago. During the Noachian period (4.5 to 3.5 billion years ago), Mars's surface was marked by meteor impacts, valley formation, erosion, and the possible presence of water oceans. The Hesperian period (3.5 to 3.3–2.9 billion years ago) was dominated by widespread volcanic activity and flooding that carved immense outflow channels. The Amazonian period, which continues to the present, was marked by the wind as a dominant influence on geological processes. Due to Mars's geological history, the possibility of past or present life on Mars remains of great scientific interest.

Since the late 20th century, Mars has been explored by uncrewed spacecraft and rovers, with the first flyby by the Mariner 4 probe in 1965, the first Mars orbiter by the Mars 2 probe in 1971, and the first landing by the Viking 1 probe in 1976. As of 2023, there are at least 11 active probes orbiting Mars or at the Martian surface. Mars is an attractive target for future human exploration missions, though in the 2020s no such mission is planned.


Cite error: There are <ref group=lower-alpha> tags or {{efn}} templates on this page, but the references will not show without a {{reflist|group=lower-alpha}} template or {{notelist}} template (see the help page).

  1. ^ Cite error: The named reference VSOP87 was invoked but never defined (see the help page).
  2. ^ a b c d e f g h i j k l Cite error: The named reference NasaFactSheet was invoked but never defined (see the help page).
  3. ^ a b c Allen CW, Cox AN (2000). Allen's Astrophysical Quantities. Springer Science & Business Media. p. 294. ISBN 978-0-387-95189-8. Archived from the original on 1 March 2024. Retrieved 18 May 2022.
  4. ^ Cite error: The named reference Souami_Souchay_2012 was invoked but never defined (see the help page).
  5. ^ a b "HORIZONS Batch call for 2022 perihelion" (Perihelion occurs when rdot flips from negative to positive). Solar System Dynamics Group, Jet Propulsion Laboratory. Archived from the original on 8 September 2021. Retrieved 7 September 2021.
  6. ^ a b c d e f Cite error: The named reference Seidelmann2007 was invoked but never defined (see the help page).
  7. ^ Grego P (6 June 2012). Mars and How to Observe It. Springer Science+Business Media. p. 3. ISBN 978-1-4614-2302-7 – via Internet Archive.
  8. ^ a b c Cite error: The named reference lodders1998 was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference konopliv2011 was invoked but never defined (see the help page).
  10. ^ Hirt C, Claessens SJ, Kuhn M, et al. (July 2012). "Kilometer-resolution gravity field of Mars: MGM2011" (PDF). 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. Archived from the original on 1 March 2024. Retrieved 25 August 2019.
  11. ^ Jackson AP, Gabriel TS, Asphaug EI (1 March 2018). "Constraints on the pre-impact orbits of Solar system giant impactors". Monthly Notices of the Royal Astronomical Society. 474 (3): 2924–2936. arXiv:1711.05285. doi:10.1093/mnras/stx2901. ISSN 0035-8711. Archived from the original on 23 April 2022. Retrieved 23 April 2022.
  12. ^ Allison M, Schmunk R. "Mars24 Sunclock — Time on Mars". NASA GISS. Archived from the original on 24 January 2017. Retrieved 19 August 2021.
  13. ^ Cite error: The named reference MallamaMars was invoked but never defined (see the help page).
  14. ^ "Atmospheres and Planetary Temperatures". American Chemical Society. 18 July 2013. Archived from the original on 27 January 2023. Retrieved 3 January 2023.
  15. ^ a b c d "Mars Exploration Rover Mission: Spotlight". Marsrover.nasa.gov. 12 June 2007. Archived from the original on 2 November 2013. Retrieved 14 August 2012. Public Domain This article incorporates text from this source, which is in the public domain.
  16. ^ a b Sharp T, Gordon J, Tillman N (31 January 2022). "What is the Temperature of Mars?". Space.com. Archived from the original on 22 April 2020. Retrieved 14 March 2022.
  17. ^ a b Hassler DM, Zeitlin C, Wimmer-Schweingruber RF, et al. (24 January 2014). "Mars' Surface Radiation Environment Measured with the Mars Science Laboratory's Curiosity Rover". Science. 343 (6169). Tables 1 and 2. Bibcode:2014Sci...343D.386H. doi:10.1126/science.1244797. hdl:1874/309142. PMID 24324275. S2CID 33661472.
  18. ^ Cite error: The named reference Mallama_and_Hilton was invoked but never defined (see the help page).
  19. ^ "Encyclopedia - the brightest bodies". IMCCE. Archived from the original on 24 July 2023. Retrieved 29 May 2023.
  20. ^ Cite error: The named reference barlow08 was invoked but never defined (see the help page).
  21. ^ Rees MJ, ed. (October 2012). Universe: The Definitive Visual Guide. New York: Dorling Kindersley. pp. 160–161. ISBN 978-0-7566-9841-6.
  22. ^ Cite error: The named reference nasa_hematite was invoked but never defined (see the help page).