火星印象 Visions of Mars

Visions of Mars
火星印象



Robot explorers transform a distant object of wonder into intimate terrain.

大风车带你看真实的世界


长久以来，火星一直吸引着人类的想像力。天空中那颗行动怪异的红色星球，总是古人眼中的不祥或凶暴象徵：希腊人称它阿瑞斯，战争之神；巴比伦人称它为内尔格勒，冥界之神。在古中国纪录中，它叫作荧惑，亦即火之星。即使哥白尼1543年提出太阳而非地球为在地宇宙中心的理论后，火星的古怪天际运动仍是个谜。直到1609年，克卜勒才分析出，所有太阳系行星的轨道皆为椭圆，而太阳正位于椭圆的中心上。

伽利略同年首次以望远镜观察火星。17世纪中叶，望远镜进步到可看到火星上随季节扩大和缩小的极地冰帽，和被认为是一片浅海的暗斑——大三角。义大利天文学家卡西尼藉由准确观测某些特徵，足以让他计算出火星的转动週期。他的结论是，火星上的一天比地球一天多40分钟；误差只有3分钟。虽然邻居金星较近且较大，却覆盖着无法看透的云层；火星表面和地球相似的程度，足以引起人们推测其上有生命的存在。

随着时代而进步的望远镜，渐能克服地球厚重且多变的大气所造成的散焦效应，提供更精细的火星地图；其中明确指出海洋，甚至有依季节变动植被的沼泽，随着冰帽变动而变的情形亦可见。最为精确的火星绘图师之一乔凡尼‧斯基亚帕雷利，率先使用义大利文的canali一字来为连接大量假定为地表水分之间的线状联繫管道命名。这个字可译成「水道」，但「运河」才确实激起一般大众的想像力，尤其是伯西佛‧洛威尔这位住在波士顿的富有上层人士，他在1893年开始认为运河是火星文明的人工产物。洛威尔是业余天文学家，且对此极为热衷，但他并非成癖的怪人。他在亚利桑那州旗竿镇附近的方山上设立自己的天文台，位置约有2000公尺高，以他自己的说法是「远离人间烟尘」；而他为火星所制的绘图，即使是在反对其理论的天文学家眼中，仍优于斯基亚帕雷利的作品。洛威尔倡言，火星是濒死的星球，其上的高智慧生物正试图以运河灌溉系统，将储存在极地冰帽内逐渐减少的水予以分散及保存，以对抗日益严重的干化作用。

此种看法在H.G.威尔斯的经典科幻小说《世界大战》（1898）中被戏剧化。入侵地球的火星人看来丑陋且手法残忍，隔着遥远的太空羡慕地注视着「我们温暖的星球，上面有绿色的植被和灰色的水域」。

接下来半世纪对于火星的想像，主要是把它当成地球的幽暗翻版，将我们关心、忧心及争论的事物皆反映其上。诸如殖民主义、集体主义，及自然资源被产业耗尽等当时令人烦恼的议题，皆在不同的火星乌托邦内得到充分的阐述空间。科幻文学中较小的一条支脉，将火星或多或少地描绘成基督教的来世所在；在1938年C. S.路易斯所着《来自寂静的星球》中，便创造了一个纯真的世界「马腊肯迪拉」……
Visions of Mars
Robot explorers transform a distant object of wonder into intimate terrain.
By John Updike
Photograph by NASA/JPL/Cornell University
Mars has long exerted a pull on the human imagination.The erratically moving red star in the sky was seen as sinister or violent by the ancients: The Greeks identified it with Ares, the god of war; the Babylonians named it after Nergal, god of the underworld. To the ancient Chinese, it was Ying-huo, the fire planet. Even after Copernicus proposed, in 1543, that the sun and not the Earth was the center of the local cosmos, the eccentricity of Mars's celestial motions continued as a puzzle until, in 1609, Johannes Kepler analyzed all the planetary orbits as ellipses, with the sun at one focus.

In that same year Galileo first observed Mars through a telescope. By the mid-17th century, telescopes had improved enough to make visible the seasonally growing and shrinking polar ice caps on Mars, and features such as Syrtis Major, a dark patch thought to be a shallow sea. The Italian astronomer Giovanni Cassini was able to observe certain features accurately enough to calculate the planet's rotation. The Martian day, he concluded, was forty minutes longer than our twenty-four hours; he was only three minutes off. While Venus, a closer and larger planetary neighbor, presented an impenetrable cloud cover, Mars showed a surface enough like Earth's to invite speculation about its habitation by life-forms.

Increasingly refined telescopes, challenged by the blurring effect of our own planet's thick and dynamic atmosphere, made possible ever more detailed maps of Mars, specifying seas and even marshes where seasonal variations in presumed vegetation came and went with the fluctuating ice caps. One of the keenest eyed cartographers of the planet was Giovanni Schiaparelli, who employed the Italian word canali for perceived linear connections between presumed bodies of water. The word could have been translated as "channels," but "canals" caught the imagination of the public and in particular that of Percival Lowell, a rich Boston Brahmin who in 1893 took up the cause of the canals as artifacts of a Martian civilization. As an astronomer, Lowell was an amateur and an enthusiast but not a crank. He built his own observatory on a mesa near Flagstaff, Arizona, more than 7,000 feet high and, in his own words, "far from the smoke of men"; his drawings of Mars were regarded as superior to Schiaparelli's even by astronomers hostile to the Bostonian's theories. Lowell proposed that Mars was a dying planet whose highly intelligent inhabitants were combating the increasing desiccation of their globe with a system of irrigation canals that distributed and conserved the dwindling water stored in the polar caps.

This vision, along with Lowell's stern Darwinism, was dramatized by H. G. Wells in one of science fiction's classics, The War of the Worlds (1898). The Earth-invading Martians, though hideous to behold and merciless in action, are allowed a dollop of dispassionate human sympathy. Employing advanced instruments and intelligences honed by "the immediate pressure of necessity," they enviously gaze across space at "our own warmer planet, green with vegetation and grey with water, with a cloudy atmosphere eloquent of fertility, with glimpses through its drifting cloud wisps of broad stretches of populous country and narrow, navy-crowded seas."

In the coming half century of Martian fancy, our neighboring planet served as a shadowy twin onto which earthly concerns, anxieties, and debates were projected. Such burning contemporary issues as colonialism, collectivism, and industrial depletion of natural resources found ample room for exposition in various Martian utopias. A minor vein of science fiction showed Mars as the site, more or less, of a Christian afterlife; C. S. Lewis's Out of the Silent Planet (1938) invented an unfallen world, Malacandra. Edgar Rice Burroughs's wildly popular series of Martian romances presented the dying planet as a rugged, racially diverse frontier where, in the words of its Earthling superhero John Carter, life is "a hard and pitiless struggle for existence." Following Burroughs, pulp science fiction, brushing aside possible anatomical differences, frequently mated Earthlings and Martians, the Martian usually the maiden in the match, and the male a virile Aryan aggressor from our own tough planet. The etiolated, brown-skinned, yellow-eyed Martians of Ray Bradbury's poetic and despairing The Martian Chronicles (1950) vanish under the coarse despoilment that human invasion has brought.

But all the fanciful Martian megafauna—Wells's leathery amalgams of tentacles and hugely evolved heads; American journalist Garrett Serviss's 15-foot-tall quasi red men; Burroughs's 10-foot, 4-armed, olive-skinned Tharks; Lewis's beaver-like hrossa and technically skilled pfifltriggi; and the "polar bear-sized creatures" that Carl Sagan imagined to be possibly roaming the brutally cold Martian surface—were swept into oblivion by the flyby photographs taken by Mariner 4 on July 14, 1965, from 6,000 miles away. The portion of Mars caught on an early digital camera showed no canals, no cities, no water, and no erosion or weathering. Mars more resembled the moon than the Earth. The pristine craters suggested that surface conditions had not changed in more than three billion years. The dying planet had been long dead.
Two more Mariner flybys, both launched in 1969, sent back 57 images that, in the words of the NASA release, "revealed Mars to be heavily cratered, bleak, cold, dry, nearly airless and generally hostile to any Earth-style life-forms." But Mariner 9, an orbiter launched in 1971, dispatched, over 146 days, 7,000 photographs of surprisingly varied and violent topography: volcanoes, of which the greatest, Olympus Mons, is 13 miles high, and a system of canyons, Valles Marineris, that on Earth would stretch from New York City to Los Angeles. Great arroyos and tear-shaped islands testified to massive floods in the Martian past, presumably of water, the sine qua non of life as Earth knows it. In 1976 the two Viking landers safely arrived on the Martian surface; the ingenious chemical experiments aboard yielded, on the question of life on Mars, ambiguous results whose conclusions are still being debated into the 21st century.

In the meantime, our geographical and geological intimacy with Mars grows. The triumphant deployment of the little Sojourner rover in 1997 was followed in 2004 by the even more spectacular success of two more durable rovers, Spirit and Opportunity. In four years of solar-powered travels on the red planet, the twin robots have relayed unprecedentedly detailed images, including many clearly of sedimentary rocks, suggesting the existence of ancient seas. The stark, russet-tinged photographs plant the viewer right on the surface; the ladderlike tracks of Spirit and Opportunity snake and gouge their way across rocks and dust that for eons have rested scarcely disturbed under salmon pink skies and a pearlescent sun. In this tranquil desolation, the irruption of our live curiosity and systematic purpose feels heroic.

Now the Phoenix mission, with its surpassingly intricate arm, scoop, imagers, and analyzers, takes us inches below the surface of dust, sand, and ice in Mars's north polar region. Spoonfuls of another planet's substance, their chemical ingredients volatilized, sorted, and identified, become indexes to cosmic history. Meanwhile, the Mars Reconnaissance Orbiter, the newest of three operational spacecraft circling the planet, feeds computers at the University of Arizona with astoundingly vivid and precise photographs of surface features. Some of these false-color images appear totally abstract, yet they yield to knowledgeable eyes riches of scientific information.

The dead planet is not so dead after all: Avalanches and dust storms are caught on camera, and at the poles a seasonal sublimation of dry ice produces erosion and movement. Dunes shift; dust devils trace dark scribbles on the delicate surface. Whether or not evidence of microbial or lichenous life emerges amid this far-off flux, Mars has become an ever nearer neighbor, a province of human knowledge. Dim and fanciful visions of the twinkling fire planet have led to panoramic close-ups beautiful beyond imagining.













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