Martian atmosphere composition
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Composition of the Martian Atmosphere
Major Components: Carbon Dioxide Dominance
The Martian atmosphere is predominantly composed of carbon dioxide (CO2), which constitutes about 96% of the atmospheric volume. This was confirmed by multiple missions, including the Viking 1 and the Curiosity rover's Sample Analysis at Mars (SAM) instrument1 4 5. The high concentration of CO2 is a critical factor in the planet's climate and surface conditions.
Trace Gases: Nitrogen, Argon, and Oxygen
In addition to CO2, the Martian atmosphere contains trace amounts of nitrogen (N2), argon (Ar), and oxygen (O2). The volume mixing ratios relative to CO2 for these gases are approximately 0.06 for N2, 0.015 for Ar, and 0.003 for O2 at an altitude near 135 kilometers1. The presence of these gases has been consistently observed by various instruments, including the Viking 1 mission and the Curiosity rover1 4 5.
Isotopic Composition: Insights from Meteorites and Rovers
The isotopic composition of the Martian atmosphere provides valuable insights into its history and evolution. Measurements from the Curiosity rover indicate that the isotopic ratios of carbon and oxygen in CO2 are similar to those found on Earth, suggesting a common origin or similar processes affecting both planets2 4 5. Additionally, Mars shows an enrichment in 15N relative to Earth by about 75%, which is attributed to atmospheric escape processes2.
Noble Gases: Argon, Krypton, and Xenon
Noble gases such as argon (Ar), krypton (Kr), and xenon (Xe) are also present in the Martian atmosphere. The ratio of argon-36 to argon-40 has been measured to be around 1 to 2750 ± 500, indicating a slightly more massive atmosphere in the past3. The isotopic composition of these noble gases, particularly the ratios of 40Ar/36Ar and 129Xe/132Xe, provides further evidence of atmospheric loss and the planet's geophysical processes7.
Atmospheric Pressure and Temperature
The atmospheric pressure on Mars varies with altitude and location. At the Viking 1 landing site, the pressure was measured to be 7.3 millibars with an air temperature of 241K1. The average temperature in the upper atmosphere, between 140 and 200 kilometers, is about 180 ± 20K1.
Evolution and Stability
The Martian atmosphere has undergone significant changes over geological time. Photochemical reactions in the exosphere produce fast atoms of oxygen, carbon, and nitrogen, contributing to the escape of these elements and influencing the atmospheric composition10. The current atmospheric reservoirs of CO2 and H2O were largely established after the early atmospheric loss, approximately 4 billion years ago4 5.
Conclusion
The Martian atmosphere is a complex system dominated by CO2, with trace amounts of N2, Ar, and O2. Isotopic and noble gas measurements provide critical insights into the planet's atmospheric history and evolution. Understanding these components and their interactions is essential for unraveling the mysteries of Mars' past and its potential for supporting life.
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Composition and Structure of the Martian Atmosphere: Preliminary Results from Viking 1
The upper atmosphere of Mars is mainly composed of CO2 with trace quantities of N2, Ar, O, O2, and CO, with molecular oxygen being a major component of the ionosphere.
Highly CitedIsotopic Composition of the Martian Atmosphere
The isotopic composition of Mars' atmosphere is similar to Earth's, with nitrogen and oxygen levels similar to Earth's, but with a higher 15N enrichment due to escape.
Highly CitedComposition of the Atmosphere at the Surface of Mars: Detection of Argon-36 and Preliminary Analysis
Mars had a slightly more massive atmosphere in the past, but less total outgassing has occurred than on Earth, with argon-36 to argon-40 ratio of 1 to 2750 500.
Highly CitedIsotope Ratios of H, C, and O in CO2 and H2O of the Martian Atmosphere
The Curiosity rover's SAM instrument confirms that Mars' atmospheric reservoirs of CO2 and H2O were largely established 4 billion years ago, but atmospheric loss or surface interaction may still be ongoing.
Highly CitedAbundance and Isotopic Composition of Gases in the Martian Atmosphere from the Curiosity Rover
The Curiosity rover's SAM instrument confirms the origin of martian meteorites and suggests that the current atmospheric reservoirs of CO2 and H2O were largely established after early atmospheric loss 4 billion years ago.
Highly CitedComposition of the Martian atmosphere
Viking spacecraft data on Mars' atmosphere is insufficient for accurate conclusions, and returning a gas sample for laboratory analysis is preferable to in situ measurements.
Martian Volatiles: Isotopic Composition, Origin, and Evolution
Martian volatiles show isotopic fractionation in noble gases and nitrogen, suggesting partial loss of the planetary atmosphere early in history.
Highly CitedStability of the Martian Atmosphere
The stability of the Martian atmosphere is influenced by changes in atmospheric water and mixing, with carbon monoxide and molecular oxygen abundances varying in response to these changes.
Highly CitedBehavior of Carbon Dioxide and Other Volatiles on Mars
The polar caps of Mars consist almost entirely of frozen CO2, with occasional thin coatings of water ice.
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