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首页> 外文期刊>Journal of geophysical research. Planets >Stability of Mg‐sulfates at-10°C and the rates of dehydration/rehydration processes under conditions relevant to Mars
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Stability of Mg‐sulfates at-10°C and the rates of dehydration/rehydration processes under conditions relevant to Mars

机译:毫克量的稳定硫酸盐在10°C和利率的脱水/补液过程火星环境相关

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摘要

We report the results of low temperature (-10°C) experiments on the stability fields and phase transition pathways of five hydrous Mg‐sulfates. A low temperature form of MgSO_4·7H_2O (LT‐7w) was found to have a wide stability field that extends to low relative humidity (~13% RH at -10°C). Using information on the timing of phase transitions,we extracted information on the reaction rates of five important dehydration and rehydration processes. We found that the temperature dependencies of rate constants for dehydration processes differ from those of rehydration, which reflect differences in reaction mechanisms. By extrapolating these rate constants versus T correlations into the T range relevant to Mars, we can evaluate the possibility of occurrence of specific processes and the presence of common Mg‐sulfate species present on Mars in different periods and locations. We anticipate in a moderate obliquity period, starkeyite and LH‐MgSO_4·H_2O should be two common Mg‐sulfates at the surface, another polymorph MH‐MgSO_4·H_2O can exist at the locations where hydrothermal processes may have occurred. In polar regions or within the subsurface of other regions, meridianiite (coexisting with water ice, near 100% RH) and LT‐7w (over a large RH range) are the stable phases. During a high obliquity period, meridianiite and LT‐7w should exhibit widespread occurrence. The correlations of reaction rates versus temperature found in this study imply that dehydration and rehydration of hydrous Mg‐sulfates would always be slower than the sublimation and crystallization of water ice, which would be supported by mission observations from Odyssey and by Mars Exploration Rovers.
机译:我们报告的结果低温(-10°C)字段和稳定性实验阶段过渡途径五含水镁的硫酸盐。一种低温MgSO_4 7·h_2o (LT列车7 w)被发现有一个宽的稳定场吗延伸到低相对湿度(~ 13% RH-10°C)。转换,我们提取信息脱水和反应速率的五个重要补液过程。速率常数的温度依赖性脱水过程的不同补液,反映的差异反应机制。常量与T相关性的范围有关火星,我们可以评估的可能性发生的具体过程和硫酸存在共同毫克量的物种上火星在不同的时间和地点。预计适度倾斜,starkeyite和LH MgSO_4·H_2O应该有两个常见毫克高硫酸盐表面在另一个地方变形MH MgSO_4·H_2O可以存在地方水热过程发生。其他地区的地下,meridianiite(冰与水共存,近100% RH)LT列车7 w(在大型RH)范围内是稳定的阶段。meridianiite和LT 7 w应该表现出广泛的发生。发现在这个研究暗示和温度脱水和含水的补液Mg硫酸盐总是低于水冰的升华和结晶。这将是由任务观察从奥德赛火星探测车。

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