Mars equatorial mesospheric clouds: Global occurrence and physical properties from Mars Global Surveyor Thermal Emission Spectrometer and Mars Orbiter Camera limb observations
Mars equatorial mesospheric clouds: Global occurrence and physical properties from Mars Global Surveyor Thermal Emission Spectrometer and Mars Orbiter Camera limb observations
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DOI：
10.1029/2006je002805
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发表时间：
2007-04-19
影响因子：
4.8
通讯作者：
Smith, Michael D.
中科院分区：
文献类型：
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作者：
Clancy, R. Todd;Wolff, Michael J.;Smith, Michael D.
[ 1]我们报告了在火星向阳面（当地时间1300 - 1400）大气中出现的一种新型云，表现为高海拔（60 - 80公里），垂直离散的气溶胶散射层。火星全球勘测者（MGS）从热发射光谱仪（TES）可见光通道进行的临边观测表明，在远日点北方夏季的开始和结束时出现了峰值频率（L-S = 30度和150度），它们被限制在赤道附近（15 ° S - 15 ° N）纬度和两个经度范围（40 ° E - 2 ° W和50 ° W - 120 ° W）。来自MGS火星轨道器相机（MOC）的边缘图像表明，这些火星赤道中层（MEM）云在20 - 50公里尺度上存在显著的水平变化。根据投影临边高度的分布，MEM云在70 - 75公里高度上显示出峰值光学深度，这对于低压形成区（类似于1 μ bar）来说是相当大的（最低点τ（维斯）为0.01级）。平均TES临边红外光谱（5 - 40 μ m）和对应于MEM发生的太阳波段辐射廓线表明，在0 - 25公里高度处有尘埃气溶胶（r（eff）= 1.5 - 2.0 μ m，τ（维斯）类似于0.4），被水冰云覆盖（r（eff）= 1.5 - 2.0 μ m，τ（维斯）与0.2相似）。在MEM云层高度缺乏可探测的红外辐射，排除了水与CO2冰的区别，但表明
[ 1] We report the occurrence of a new type of cloud in the Mars dayside (1300 1400 Local Time) atmosphere, apparent as high-altitude ( 60 to 80 km), vertically discrete aerosol scattering layers. Mars Global Surveyor (MGS) limb observations from the Thermal Emission Spectrometer (TES) visible channel indicate peak frequencies at the beginning and end of the aphelion northern summer season (L-S = 30 degrees and 150 degrees), where they are confined to equatorial (15 degrees S - 15 degrees N) latitudes and two longitude ranges (40 degrees E - 2 degrees W and 50 degrees W - 120 degrees W). Limb images from the MGS Mars Orbiter Camera (MOC) indicate significant horizontal variations in these Mars equatorial mesospheric (MEM) clouds on 20 - 50 km scales. On the basis of the distribution of projected limb heights, MEM clouds exhibit peak optical depths over 70 - 75 km altitudes, that are substantial ( nadir tau(vis) of order 0.01) for the low-pressure region of formation ( similar to 1 mu bar). Averaged TES limb infrared spectral ( 5 - 40 mu m) and solarband radiance profiles corresponding to MEM occurrence indicate dust aerosols (r(eff) = 1.5 - 2.0 mu m, tau(vis) similar to 0.4) at 0 - 25 km altitudes, capped by water ice clouds (r(eff) = 1.5 - 2.0 mu m, tau(vis) similar to 0.2) at 20 - 45 km altitudes. The lack of detectable infrared radiances at MEM cloud heights precludes distinction of water versus CO2 ice, but indicates