Atmosphere of mars
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The atmosphere of Mars is very thin. Their density is approx. 1.2% of the density of the earth's atmosphere. The mean atmospheric pressure at zero level is 6 hPa (0.006 bar ). That is only 0.6% of the mean air pressure on earth with 1013 hPa (1.013 bar) and corresponds roughly to the pressure that prevails in the stratosphere of the earth at an altitude of 32 km.
The extremely low atmospheric pressure is close to the triple point of water . This means that liquid water can only exist on the surface of Mars in lowlands (mainly the northern hemisphere and Hellas Planitia ) and only at high temperatures for a short time for a few hours. At the lowest point of the Martian surface in Hellas Planitia the pressure reaches a maximum of about 12 hPa (0.012 bar). That is well below the Armstrong limit of 63 hPa (0.063 bar), at which water boils at human body temperature , so a person on Mars cannot survive without a pressure suit or a pressure cabin .
In terms of its chemical composition, the Martian atmosphere, like that of Venus , consists mainly of carbon dioxide . In 2003, traces of methane were also detected in the planet's gas envelope, but it has not yet been possible to explain clearly how this gas got into the atmosphere.
Even though the atmosphere of Mars is so thin, the sky of Mars is not black. Because of the high proportion of dust in the atmosphere, the light is strongly scattered. The day sky appears bright and stars cannot be seen. The color of the day sky varies from orange-red to pink and purple to blue near the rising and setting sun.
construction
The Martian atmosphere is structured as follows:
- Lower atmosphere
- Middle atmosphere: This is where the jet stream of Mars is located .
- Upper atmosphere, also called thermosphere: This is where the highest temperatures of the Martian atmosphere prevail, which are caused by solar radiation. Here the gases begin to separate and no longer form the uniform gas mixture that can be found in the lower layers of the atmosphere.
- Exosphere: begins about 200 kilometers above the Martian surface. Here the atmosphere of the planet merges into space. There is no fixed upper limit to the atmosphere, it flows smoothly into space .
composition
carbon dioxide
The main component of the Martian atmosphere is carbon dioxide ( CO 2 ). The greenhouse gas makes up around 95.9% of the planet's air envelope. During winter (the respective hemisphere) the poles of Mars are completely in the dark and the temperatures drop so much that up to 25% of the CO 2 in the atmosphere freezes to dry ice. When the polar caps of Mars are exposed to sunlight again, the CO 2 sublimes again and is released into the atmosphere.
argon
Compared to other atmospheres in the solar system , the Martian atmosphere has a high proportion of the noble gas argon . In contrast to CO 2 , argon does not change its physical state during the winter and the absolute proportion in the atmosphere remains constant.
water
The water content of the Martian atmosphere is subject to large seasonal fluctuations. The sublimation of carbon dioxide during Martian summer exposes traces of water on the surface. A large part of these water ice deposits is blown up by storms and transported into the Martian atmosphere, which can cause cirrus clouds of water ice to form in the atmosphere . These were first verified by the NASA rover Opportunity in 2004.
methane
In 2003, earth-based telescopes and in 2004 the Planetary Fourier Spectrometer (PFS) on the Mars Express spacecraft detected traces of methane (about 0.01 ppm ) and formaldehyde (0.13 ppm). The concentration of methane is subject to seasonal fluctuations with a maximum in summer. Methane remains in the atmosphere of Mars for about 340 years, formaldehyde only 7.5 hours. Methane is broken down by ultraviolet radiation because the thin atmosphere of Mars does not protect against this radiation. In the process, methane oxidizes to water and carbon dioxide.
To explain the amount of methane in the atmosphere, a production of 150 tons per year is sufficient. However, when converting to formaldehyde, 2.5 million tons would have to come from “methane sources”. Active volcanism , cometary impacts or methane-producing microorganisms come into consideration as sources . But it could also be caused by a geothermal reaction, the serpentinization (components involved are water, carbon dioxide and the mineral olivine , which occurs frequently on Mars). Formaldehyde can be produced by cosmic radiation from gases and ice. However, it is doubted that an abiotic process can produce so much methane, as it requires regions with high geological activity.
The methane is not evenly distributed but shows a pattern of slightly increased concentrations. Obviously, the supply of methane is or was temporarily interrupted before it could be evenly distributed in the atmosphere. In the biological production of methane on earth, which is responsible for around 90 to 95% of all methane deposits, ethane is almost always produced as an associated gas. In contrast, sulfur dioxide is released during volcanic formation . The measurement of these gases in the Martian atmosphere could provide some clarification. This could be done through the Mars Science Laboratory .
In 2009 methane eruptions were reported on Mars.
Goro Komatsu from the Gabriele d'Annunzio University in Pescara presented his discovery of geological structures about 1 km in diameter on satellite images of the Chryse Plain , which resemble methane gas producing mud volcanoes on Earth. However, a primary source for the gas has not yet been found.
Potential human use
The atmosphere could be an important resource for manned Mars missions in the future.
For example, the development of a device that can split the carbon dioxide in the atmosphere into elemental carbon and oxygen is conceivable . In this way, the oxygen for the astronauts' breathing air would not have to be laboriously taken from the earth.
history
It has now been proven that the Martian atmosphere has changed significantly in the past. It is even possible that huge oceans of water existed on Mars about 3.5 billion years ago.
Web links
Individual evidence
- ^ German aerospace society: yearbook . 2002 ( books.google.de ). : "The Martian atmosphere has a density of 0.016 kg / m³ (Earth 1.293 kg / m³)"
- ^ Robert M. Haberle, Christopher P. McKay, James Schaeffer, Nathalie A. Cabrol, Edmon A. Grin, Aaron P. Zent, Richard Quinn: On the possibility of liquid water on present-day Mars , Journal of Geophysical Research, Volume 106, No. El0, October 25, 2001, pp. 23,317-323,326.
- ↑ Manfred Lindinger: Surprise find on Mars: Curiosity finds methane. December 16, 2014, accessed September 3, 2018 .
- ^ Mars Exploration Rover Mission: Press Release Images: Opportunity. In: mars.nasa.gov. Retrieved August 14, 2016 .
- ↑ Mars Express confirms methane in the Martian atmosphere. ESA, March 30, 2004, accessed September 18, 2009 .
- ↑ Alexandra Witze: Mars scientists edge closer to solving methane mystery . In: Nature . tape 563 , October 25, 2018, p. 18-19 , doi : 10.1038 / d41586-018-07177-4 ( nature.com [accessed June 10, 2020]).
- ↑ Martin Baucom: Life on Mars? American Scientist, accessed February 26, 2007 .
- ↑ Michael J. Mumma, Geronimo L. Villanueva, Robert E. Novak, Tilak Hewagama, Boncho P. Bonev, Michael A. DiSanti, Avi M. Mandell, Michael D. Smith: Strong Release of Methane on Mars in Northern Summer 2003 . In: Science . tape 323 , no. 5917 , February 20, 2009, p. 1041-1045 , doi : 10.1126 / science.1165243 , PMID 19150811 .
- ↑ Thorsten Dambeck: Solution to methane riddle. In: Spiegel Online. September 24, 2010, accessed October 11, 2010 .
- ↑ mars.nasa.gov: NASA's MAVEN Reveals Most of Mars' Atmosphere Was Lost to Space. Retrieved August 1, 2020 .
- ↑ National Geographic (2010, with reference ddp ): Mars once covered by a huge ocean ( Memento from April 14, 2015 in the Internet Archive )