Television observations from Surveyor 3
Television observations from Surveyor 3
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DOI：
10.1029/jb073i012p03989
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发表时间：
1968-06
影响因子：
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通讯作者：
E. Shoemaker;R. Batson;H. Holt;E. Morris;J. Rennilson;E. Whitaker
中科院分区：
文献类型：
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作者：
E. Shoemaker;R. Batson;H. Holt;E. Morris;J. Rennilson;E. Whitaker
登月后，“勘测者3号”上的电视摄像机共拍摄了6315张照片。这些照片提供了许多关于月球着陆点位置的新信息，月球表面的详细地形和地质特征，以及在日食和太阳部分直接照射期间从月球上看到的地球的外观。“勘测者3号”降落在一个直径略大于200米的柔和陨石坑上，这个陨石坑有一个较低的圆形边缘，深度约为15米。宇宙飞船位于陨石坑的东壁，大约在陨石坑中心和边缘峰顶之间。宇宙飞船向西倾斜14.7°±1.0°。着陆点的地平面坐标为南纬2.94°，西经23.34°，相对于航图情报中心的地平面控制。着陆点的小形态元素包括小陨石坑、线状山脊和沟槽以及碎片。这些陨石坑和碎片在形状分布和大小分布上都与勘测者1号着陆点观测到的陨石坑和碎片相似。“勘测者1号”和“勘测者3号”照片中的大多数陨石坑都被推断为撞击形成的。它们的大小-频率分布与流星体的重复轰击所产生的分布相对应，这种轰击时间足够长，陨石坑的数量已经达到稳定状态或达到平衡。在“勘测者3号”着陆点观测到的一些陨石坑被推断为二次撞击的起源，有些可能是由于下沉或碎片进入地下的裂缝或裂缝而形成的。据推测，着陆点的碎片主要是由产生大多数陨石坑的重复轰击过程产生的。从观察到的表面碎片的大小分布推断出碎片的体积尺寸-频率分布，类似于流星体反复轰击相干岩石所产生的分布，其质量-频率分布类似于从观测到的流星和在地球上回收的陨石中发现的分布。在“勘测者3号”现场，在直径分别为13米和15米的两个陨石坑周围，观察到两个明显的块状碎片散落区域。13米高的陨石坑有一个尖锐的凸起边缘，15米高的陨石坑有一个更柔和的圆形边缘。与凹陷陨石坑相关的石块的平均圆度是与凸起陨石坑相关的石块的两倍，而且它们埋得更深。每块碎片的大小-频率分布函数类似于坚硬岩石（如亚利桑那州的陨石坑）中撞击产生的碎片的大小-频率分布。“勘测者3号”着陆点表面的大部分碎片显然是低凝聚力碎片物质层的一部分，沿着“勘测者3号”着陆点的陨石坑壁的上部至少有1米厚，在陨石坑中心附近可能更厚。来自“勘测者3号”照片的证据表明，这层碎片或风化层受到下坡蠕变或大块运动的影响。蠕变可能是由地震震动引起的，主要是由于近距离和远距离的撞击事件，可能部分是由于月球内部的地震活动。“勘测者3号”对月球表面产生的扰动，与“勘测者1号”产生的扰动一样，暴露出了深度为几厘米或更浅的物质，这些物质比月球表面的物质颜色更深。细粒碎片碎片的反照率在只有几分之一毫米的深度可能比光学观察到的表面低20%到30%。所有突出在表面一般水平面上的粗碎片的反照率都高于表面的细颗粒基质。这些一般的光度关系可以解释，如果假设在月球浅层的粒子表面倾向于被一种深色物质所覆盖；这种假想物质的术语是“月球清漆”。在石块和粗糙碎片的突出表面上，月球清漆被导致圆角的过程擦洗掉。月球表面暴露的细颗粒表面也受到类似的影响，但是，由于它们与表面下的颗粒混合得相对较快，所以这个过程是不完整的，因此，暴露在月球表面的细颗粒物质的反照率比块状物和其他大碎片要低。月球清漆对微粒的覆盖显然发生在表面之下。在勘测者3号航天器脚垫2附近未受干扰的月球表面部分，估计正常亮度因子（正常反照率）为8.5%。被表面采样器扰动的月球表面区域的正常亮度因子估计为6.6%，被表面采样器放置在脚垫2上的细粒物质的正常亮度因子估计为7.6%。所有这些估计的误差可能高达25%，因为从相机反射镜散射的光需要校正的不确定性。通过颜色重建方法对颜色差异的初步研究显示，在各种粗块、表面的细粒度矩阵或受表面采样器干扰的细粒度材料之间，没有可确定的颜色差异。“勘测者3号”拍摄的地球日食照片显示，地球周围的折射光晕中有一个明亮的区域，这与太阳的位置有关，在地球上大部分没有云的地区出现了一系列明亮的珠子。云层倾向于掩盖太阳的折射光线，其中大部分光线穿过大气层的下部。这些珠子出现在地球光学轮廓的洼地中。对折射光颜色的初步还原表明，靠近太阳位置的最亮区域的相关色温接近4800°K。光的色温往往较低，因为它遵循更大的大气吸收路径。对勘测者3号拍摄的部分被照亮的地球照片的初步分析显示，地球上的颜色与水星号和双子座号宇航员在轨道上记录的颜色相似。
A total of 6315 pictures were taken by the television camera on Surveyor 3 after the lunar landing. These pictures have provided much new information about the location of the landing site on the moon, the detailed topographic and geologic characteristics of the lunar surface, and the appearance of the earth as seen from the moon, both during eclipse of the sun and during partial direct illumination by the sun. Surveyor 3 landed in a subdued crater slightly more than 200 meters in diameter, which has a low rounded rim and is about 15 meters deep. The spacecraft is situated on the east wall of the crater, about half way between the center of the crater and the rim crest. The spacecraft is inclined 14.7° ± 1.0° toward the west. The selenographic coordinates of the landing site are 2.94°S latitude, 23.34°W longitude, relative to selenodetic control adopted by the Aeronautical Chart and Information Center. Small morphologic elements of the landing site include small craters, linear ridges and troughs, and fragmental debris. The craters and fragmental debris resemble those observed at the Surveyor 1 landing site, both in distribution of shape and in distribution of size. Most of the craters in Surveyor 1 and 3 pictures are inferred to be of impact origin. Their size-frequency distribution corresponds to the distribution that would be produced by repetitive bombardment by meteoroids, a bombardment sufficiently prolonged that the crater population has reached a steady state or has come to equilibrium. Some of the craters observed at the Surveyor 3 landing site are inferred to be of secondary impact origin, and some probably have been formed either by subsidence or by drainage of fragmental debris into cracks or fissures in the subsurface. Fragmental debris at the landing site is inferred to have been derived primarily by the same process of repetitive bombardment that produced the majority of craters. The inferred volumetric size-frequency distribution of fragments, derived from the observed size distribution of fragments on the surface, is similar to the distribution that would be produced by repetitive bombardment of coherent rocks by meteoroids with a mass-frequency distribution like that found from observed meteors and recovered meteorites on earth. Two prominent strewn fields of blocky debris were observed around two craters, 13 and 15 meters across, at the Surveyor 3 site. The 13-meter crater has a sharp raised rim, and the 15-meter crater has a more subdued rounded rim. The blocks associated with the subdued crater have twice as high a mean roundness as the blocks associated with the raised-rim crater, and they are much more deeply buried. The size-frequency distribution function for the fragments in each of the strewn fields of blocks resembles the size-frequency distribution for fragments ejected by impacts in strong rock, such as Meteor Crater, Arizona. Most of the fragments at the surface of the Surveyor 3 landing site are evidently part of a layer of fragmental material of low cohesion that is at least 1 meter thick along the upper parts of the wall of the crater in which Surveyor 3 landed and may be much thicker near the center of the crater. The evidence from the Surveyor 3 pictures suggests that this layer of debris, or regolith, is subject to downslope creep or mass movement. Creep is probably caused by seismic shaking, due mainly to near and far impact events and perhaps due partly to internal lunar seismicity. Disturbances of the lunar surface produced by Surveyor 3, like those produced by Surveyor 1, exposed material at depths of a few centimeters or less that was darker than the material at the surface. The albedo of the fine-grained fragmental debris is probably 20 to 30% lower at depths of only a fraction of a millimeter than it is at the optically observed surface. All coarse fragments protruding above the general level of the surface have a higher albedo than the fine-grained matrix of the surface. These general photometric relationships can be explained if it is assumed that the surfaces of the particles in the shallow lunar subsurface tend to become coated with a dark substance; the term proposed for this hypothetical substance is ‘lunar varnish’ On the protruding surface of blocks and coarse fragments the lunar varnish is scrubbed off by the processes that cause rounding. The exposed surfaces of fine particles on the lunar surface are similarly affected, but, because they are mixed relatively rapidly with particles just beneath the surface, the process is incomplete and the fine-grained material exposed at the lunar surface, therefore, has a lower albedo than blocks and other large fragments. Coating of particles by lunar varnish evidently takes place just beneath the surface. The estimated normal luminance factor (normal albedo) of an undisturbed part of the lunar surface next to footpad 2 of the Surveyor 3 spacecraft is 8.5%. An area of the lunar surface disturbed by the surface sampler has an estimated normal luminance factor of 6.6%, and fine-grained material placed on footpad 2 by the surface sampler has an estimated normal luminance factor of 7.6%. The errors in all these estimates may be as high as 25% because of uncertainties of correction required for light scattered from the camera mirror. Preliminary search for color differences, by color reconstitution methods, revealed no determinable differences in color among various coarse blocks, the fine-grained matrix of the surface, or fine-grained material disturbed by the surface sampler. Surveyor 3 pictures of the eclipse of the sun by the earth revealed a bright region in the refraction halo surrounding the earth, which was correlated with the position of the sun, and a series of bright beads that occurred over regions of the earth largely clear of clouds. Clouds tend to occult the refracted rays of the sun, most of which pass through the lower part of the atmosphere at the limb; the beads occurred in the depressions in the optical silhouette of the earth. Preliminary reduction of the color of the refracted light showed that the brightest region, near the position of the sun, exhibited a correlated color temperature close to 4800°K. The color temperature tended to be lower for light that followed paths of greater atmospheric absorption. Preliminary analysis of Surveyor 3 pictures of the partly illuminated earth revealed colors similar to the colors recorded from orbit by the Mercury and Gemini astronauts.