Composition on mars
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Composition of Mars: A Comprehensive Overview
Chemical Composition of Mars
Mars' chemical composition has been extensively studied through various models and data from spacecraft and meteorites. The cosmochemical model by Ganapathy and Anders (1974) 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 iron-rich, with a composition similar to garnet wehrlite, and the core contains about 3.5% sulfur .
Elemental Composition of the Martian Crust
The Martian crust has been analyzed through data from orbiting spacecraft and Martian meteorites. The crust is primarily composed of tholeiitic basalts formed by extensive partial melting, with minimal weathering observed . Siliceous or calc-alkaline rocks, which are common on Earth, are rare on Mars. This suggests that the Martian crust has a unique geological history, distinct from Earth's .
Oxygen Isotope Model and Bulk Composition
The oxygen isotopic composition of Mars, derived from SNC meteorites, indicates that Mars is composed of approximately 85% H-chondritic, 11% CV-chondritic, and 4% CI-chondritic material . The bulk composition of Mars includes a silicate mantle and crust making up about 80% of the planet, with the remaining 20% being a metal-sulfide core containing about 10.6% sulfur . This model also suggests that alkalis and halogens were likely lost from the Martian mantle through hydrothermal leaching or vaporization during accretion .
Surface Composition and Mineralogy
Mars' surface composition has been studied using data from the Mars Global Surveyor's Thermal Emission Spectrometer (TES). The surface is divided into two main compositions: a basaltic composition dominated by plagioclase feldspar and clinopyroxene, and an andesitic composition dominated by plagioclase feldspar and volcanic glass . These compositions are distributed along the planetary dichotomy, with basaltic compositions on older surfaces and more silicic compositions in the younger northern plains .
Atmospheric Composition
The Martian atmosphere has a similar isotopic composition of carbon and oxygen to Earth, but is enriched in nitrogen-15 by about 75% . This enrichment suggests an initial abundance of nitrogen equivalent to a partial pressure of at least 2 millibars, and an initial abundance of oxygen equivalent to an atmospheric pressure of at least 2 bars .
Geophysical Constraints on Composition
Geophysical observations and mineral physics modeling provide additional constraints on Mars' composition. The Fe content in the Martian mantle is estimated to be between 9.9 and 11.9 mol%, with Al content less than 1.5 mol% . The core is estimated to contain between 10.6 and 14.9 wt% sulfur . These findings suggest that Mars has a higher Fe/Si ratio compared to CI chondrites, indicating a unique compositional structure .
Conclusion
The composition of Mars is a complex interplay of various elements and minerals, shaped by its unique geological history and formation processes. From its iron-rich mantle and sulfur-containing core to its basaltic and andesitic surface compositions, Mars presents a distinct planetary profile. Understanding these compositions not only provides insights into Mars' past but also helps in drawing comparisons with other terrestrial planets.
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