月球水冰探测进展

月球上是否存在水冰是第二次月球探测热潮中的热点问题。 1 994年克莱门汀号 (Clementine)环月探测器搭载的频率为 2 .2 73GHz双基地雷达探测到月球南极一些地区出现同向极化增加等独特的回波特征 ,这些地区正好处于极地永久阴影区 ,表明这些地区可能存在水冰。Arecibo天文台频率为 2 .38GHz的地基雷达对月球极地进行制图 ,也得到类似结论。 1 998年月球勘探者号 (LunarProspec tor)环月探测器搭载的中子探测仪在月球极地永久阴影区探测到高含量的氢信号大多认为是水冰引起的。但雷达探测和中子探测结果均存在多解性。月球表面粗糙度同样可以引起雷达回波呈现出类似水冰的异常特征 ,而中子探测仪测量到的仅仅是氢信号而非水 ,而且月球勘探者号撞击月表之后并没有探测到任何的水蒸气信号。月球极地水冰存在与否、存在形式和存在数量等科学问题的回答需要对月球极地特别是永久阴影区作进一步探索

REVIEW ON EXPLORATION OF WATER ICE ON THE MOON

It is one of the most important scientific topic whether there is water on the Moon. Most scientists think that there is no any form of water on the Moon. However, a bistatic radar experiment measured the magnitude and polarization of the radar echo versus bistatic angle for selected lunar areas during the Clementine mission. Observations of the lunar south pole yield a same-sense polarization enhancement around bistatic angle β=0. The observed enhancement is localized to the permanently shadowed regions. A probable explanation for these differences is the presence of water ice in the permanently shadowed region. The Arecibo 12.6-centimeter wavelength ground-based radar system imaged the polar regions of the moon and gained the similar results. Lunar Prospector’s thermal and epithermal neutron data reveal the enhanced concentrations of hydrogen in permanent shade. It could be due to water molecules. However, we are far from finding the truth. For radar imaging, the roughness of lunar surface can also produce unusual echo. For neutron spectrograph, what we can decide is hydrogen, not water. Furthermore, we are failing to find any water vapor after the impact of Lunar Prospector. Human should do more work for exploration of water ice on the Moon than ever.