Composition of mars
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Composition of Mars: A Comprehensive Overview
Chemical Composition of Mars
The chemical composition of Mars has been extensively studied using various models and data from meteorites and spacecraft. One prominent model, based on the cosmochemical model of Ganapathy and Anders, suggests that Mars' composition can be derived using four index elements: Uranium (U), Iron (Fe), Potassium (K), and Thallium (Tl) or Argon-36 (Ar36). This model estimates that Mars has 28 ppb of U, 62 ppm of K, 26.72% Fe, and 0.14 ppb of Tl . The mantle of Mars is described as an iron-rich garnet wehrlite, with a density of 3.52-3.54 g/cm³, and the core contains about 3.5% sulfur .
Oxygen Isotope Model and Bulk Composition
Another approach to understanding Mars' composition involves the use of oxygen isotopes. This model assumes that Mars is the parent body for the Shergottite-Nakhlite-Chassignite (SNC) meteorites and that its oxygen isotopic composition was determined by the nebular material that accreted to form the planet. The bulk composition derived from this model suggests that silicates (mantle and crust) make up about 80% of Mars, with the mantle containing 17.2% FeO. The core, comprising about 20% of the planet, contains approximately 10.6% sulfur . This model also indicates that alkalis and halogens were likely lost from the Martian mantle through hydrothermal leaching or vaporization during accretion .
Martian Crust Composition
The composition of Mars' crust has been inferred from data collected by orbiting and in situ spacecraft, as well as from Martian meteorites. The crust is predominantly composed of tholeiitic basalts formed by extensive partial melting, with surface rocks showing minimal weathering. Siliceous or calc-alkaline rocks, which are common on Earth, are rare on Mars . This data suggests that Martian meteorites may not be fully representative of the planet's older, more voluminous crust .
Alternative Compositional Models
Recent studies challenge the use of CI chondrite as an analog for Mars' composition. An alternative model, based on Martian meteorites and spacecraft observations, suggests that Mars has a systematic depletion in moderately volatile lithophile elements relative to CI chondrites. This model estimates that the Martian core contains less than 7 wt% sulfur, which is lower than previous estimates . The presence of ringwoodite at the core-mantle boundary may have influenced the partitioning of oxygen and hydrogen into the core .
Surface Composition and Geological History
Mars' surface composition has been studied using data from the Mars Global Surveyor's Thermal Emission Spectrometer (TES). This data identifies two primary surface compositions: a basaltic composition dominated by plagioclase feldspar and clinopyroxene, and an andesitic composition dominated by plagioclase feldspar and volcanic glass. The basaltic composition is found on older surfaces, while the more silicic composition is concentrated in the younger northern plains . Additionally, the surface materials could be composed of fine-grained silicates or coarse-grained silicates coated with finely divided limonite .
Atmospheric Composition
The Martian atmosphere is primarily composed of carbon dioxide (CO2), with trace amounts of nitrogen (N2), argon (Ar), oxygen (O2), and carbon monoxide (CO). The isotopic composition of carbon and oxygen in the Martian atmosphere is similar to that of Earth, but Mars is enriched in nitrogen-15 (15N) relative to Earth by about 75% Bandfield2000Yen2005. This enrichment is likely due to atmospheric escape processes, indicating an initial abundance of nitrogen equivalent to a partial pressure of at least 2 millibars .
Conclusion
The composition of Mars is complex and has been studied through various models and data sources. The planet's mantle is iron-rich, and its core contains significant amounts of sulfur. The crust is primarily composed of tholeiitic basalts, with minimal weathering observed on the surface. Alternative models suggest a depletion in moderately volatile elements, and the atmosphere is dominated by CO2 with trace amounts of other gases. These findings provide valuable insights into the geological history and evolution of Mars.
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