Bishop Janice L, Quinn Richard, Dyar M Darby
SETI Institute, Carl Sagan Center, Mountain View, California, 94043, U.S.A.
Space Science and Astrobiology Division, NASA-Ames Research Center, Moffett Field, California, 94035, U.S.A.
Am Mineral. 2014 Aug;99(8-9):1580-1592. doi: 10.2138/am.2014.4707.
K, Na, Ca, Mg, Fe, Fe, and Al perchlorate salts were studied to provide spectral and thermal data for detecting and characterizing their possible presence on Mars. Spectral and thermal analyses are coordinated with structural analyses to understand how different cations and different hydration levels affect the mineral system. Near-infrared (NIR) spectral features for perchlorates are dominated by HO bands that occur at 0.978-1.01, 1.17-1.19, 1.42-1.48, 1.93-1.99, and 2.40-2.45 μm. Mid-IR spectral features are observed for vibrations of the tetrahedral ion and occur as reflectance peaks at 1105-1130 cm (8.6-9 μm), 760-825 cm (12-13 μm), 630 cm (15.9 μm), 460-495 (20-22 μm), and 130-215 (~50-75 μm). The spectral bands in both regions are sensitive to the type of cation present because the polarizing power is related to the band center for many of the spectral features. Band assignments were confirmed for many of the spectral features due to opposing trends in vibrational energies for the and HO groups connected to different octahedral cations. Differential scanning calorimetry (DSC) data show variable patterns of water loss and thermal decomposition temperatures for perchlorates with different cations, consistent with changes in spectral features measured under varying hydration conditions. Results of the DSC analyses indicate that the bond energies of HO in perchlorates are different for each cation and hydration state. Structural parameters are available for Mg perchlorates (Robertson and Bish 2010) and the changes in structure due to hydration state are consistent with DSC parameters and spectral features. Analyses of changes in the Mg perchlorate structures with HO content inform our understanding of the effects of hydration on other perchlorates, for which the specific structures are less well defined. Spectra of the hydrated Fe and Fe perchlorates changed significantly upon heating to 100 °C or measurement under low-moisture conditions indicating that they are less stable than other perchlorates under dehydrated conditions. The perchlorate abundances observed by Phoenix and MSL are likely too low to be identified from orbit by CRISM, but may be sufficient to be identifiable by a VNIR imager on a future rover.
对高氯酸钾、高氯酸钠、高氯酸钙、高氯酸镁、高氯酸铁（Ⅱ）、高氯酸铁（Ⅲ）和高氯酸铝进行了研究，以提供光谱和热数据，用于探测和表征它们在火星上可能的存在。光谱分析和热分析与结构分析相互配合，以了解不同阳离子和不同水化水平如何影响矿物系统。高氯酸盐的近红外（NIR）光谱特征主要由出现在0.978 - 1.01、1.17 - 1.19、1.42 - 1.48、1.93 - 1.99和2.40 - 2.45μm处的OH带主导。中红外光谱特征是针对四面体离子的振动观测到的，表现为在1105 - 1130 cm⁻¹（8.6 - 9μm）、760 - 825 cm⁻¹（12 - 13μm）、630 cm⁻¹（15.9μm）、460 - 495 cm⁻¹（20 - 22μm）和130 - 215 cm⁻¹（~50 - 75μm）处的反射峰。两个区域的光谱带对存在的阳离子类型敏感，因为对于许多光谱特征而言，极化能力与谱带中心相关。由于与不同八面体阳离子相连的ClO₄⁻和OH基团的振动能量存在相反趋势，许多光谱特征的谱带归属得以确认。差示扫描量热法（DSC）数据显示，不同阳离子的高氯酸盐具有不同的失水模式和热分解温度，这与在不同水化条件下测量的光谱特征变化一致。DSC分析结果表明，高氯酸盐中OH的键能因阳离子和水化状态而异。高氯酸镁的结构参数是已知的（罗伯逊和比什，2010年），并且由于水化状态导致的结构变化与DSC参数和光谱特征一致。对高氯酸镁结构随OH含量变化的分析有助于我们理解水化对其他高氯酸盐的影响，而其他高氯酸盐的具体结构尚不太明确。水合高氯酸铁（Ⅱ）和高氯酸铁（Ⅲ）在加热到100°C或在低湿度条件下测量时，光谱发生了显著变化，这表明它们在脱水条件下比其他高氯酸盐更不稳定。“凤凰号”和“好奇号”火星车观测到的高氯酸盐丰度可能过低，无法通过CRISM从轨道上识别，但可能足以被未来火星车上的可见近红外成像仪识别。
