Masursky H, Batson R M, McCauley J F, Soderblom L A, Wildey R L, Carr M H, Milton D J, Wilhelms D E, Smith B A, Kirby T B, Robinson J C, Leovy C B, Briggs G A, Duxbury T C, Acton C H, Murray B C, Cutts J A, Sharp R P, Smith S, Leighton R B, Sagan C, Veverka J, Noland M, Lederberg J, Levinthal E, Pollack J B, Moore J T, Hartmann W K, Shipley E N, De Vaucouleurs G, Davies M E
Science. 1972 Jan 21;175(4019):294-305. doi: 10.1126/science.175.4019.294.
At orbit insertion on 14 November 1971 the Martian surface was largely obscured by a dust haze with an extinction optical depth that ranged from near unity in the south polar region to probably greater than 2 over most of the planet. The only features clearly visible were the south polar cap, one dark, spot in Nix Olympica, and three dark spots in the Tharsis region. During the third week the atmosphere began to clear and surface visibility improved, but contrasts remained a fraction of their normal value. Each of the dark spots that apparently protrude through most of the dust-filled atmosphere has a crater or crater complex in its center. The craters are rimless and have featureless floors that, in the crater complexes, are at different levels. The largest crater within the southernmost spot is approximately 100 kilometers wide. The craters apparently were formed by subsidence and resemble terrestrial calderas. The south polar cap has a regular margin, suggsting very flat topography. Two craters outside the cap have frost on their floors; an apparent crater rim within the cap is frost free, indicating preferentia loss of frost from elevated ground. If this is so then the curvilinear streaks, which were frost covered in 1969 and are now clear of frost, may be low-relief ridges. Closeup pictures of Phobos and Deimos show that Phobos is about 25 +/-5 by 21 +/-1 kilometers and Deimos is about 13.5 +/- 2 by 12.0 +/-0.5 kilometers. Both have irregular shapes and are highly cratered, with some craters showing raised rims. The satellites are dark objects with geometric albedos of 0.05.
1971年11月14日进入火星轨道时，火星表面大部分被尘雾遮蔽，消光光学深度在南极地区接近1，而在火星大部分区域可能大于2。唯一清晰可见的特征是南极冰盖、奥林匹斯山的一个暗斑以及塔尔西斯地区的三个暗斑。在第三周，大气开始晴朗，地表能见度提高，但对比度仍只是正常水平的一小部分。每个明显穿透大部分充满尘埃的大气层的暗斑中心都有一个环形山或环形山群。这些环形山没有边缘，底部没有特征，在环形山群中处于不同高度。最南端暗斑内最大的环形山宽约100公里。这些环形山显然是由下沉形成的，类似于地球上的破火山口。南极冰盖边缘规则，表明地形非常平坦。冰盖外的两个环形山底部有霜；冰盖内一个明显的环形山边缘无霜，表明高处地面的霜优先流失。如果是这样，那么1969年被霜覆盖而现在无霜的曲线状条纹可能是低浮雕山脊。火卫一和火卫二的特写照片显示，火卫一约为25±5千米×21±1千米，火卫二约为13.5±2千米×12.0±0.5千米。两者形状不规则，布满环形山，有些环形山边缘隆起。这两颗卫星是暗天体，几何反照率为0.05。
