Antarctic Search for Meteorites

摘要该奖项支持南极陨石搜索（ANSMET）在1997 /98、98/99和99/2000年南极夏季野外季节的继续进行。自1976年以来，ANSMET已经从横越南极山脉沿线的地点回收了7800多块陨石标本。在接下来的三年里，将在已知的含有陨石的地区进行系统的搜索，并进行侦察工作，以发现新的集中。在1997- 1998年的野外季节，将在皮科拉悬崖-拉帕兹冰原地区进行工作，那里的几个小冰原仍未被搜查，早先的侦察发现了大量的冰原。在1998-99年的田间季节，南部沃尔科特？该地区将被访问，在那里已经发现了1500多颗陨石，还有更多的陨石仍然存在。在1999- 2000年的野外季节，将访问多明尼安山脉-格罗夫纳山脉-斯科特冰川地区的几个冰原，在那里以前的侦察和不完整的系统搜索承诺了重要的陨石回收。南极洲是世界上最好的陨石狩猎场有两个原因。虽然陨石在全球范围内以随机的方式坠落，但如果背景物质是平原的，并且陆地沉积物的积累速度较低，找到陨石的可能性就会增加。因此，南极东部冰盖为陨石回收提供了理想的背景。这使得回收的陨石不会偏向于看起来与地球岩石最不同的类型（这是其他大陆的一个问题），也不会偏向于更大的尺寸。但另一个因素可能同样重要。当东南极冰盖向大陆边缘流动时，它的前进偶尔会被山脉或冰表面以下的障碍物阻挡。在这些地区，古老的深冰被推到表面，并可能变得停滞不前，流出很少，流入持续缓慢。当这些地方暴露在强烈的垂直风下时，会产生大规模的通货紧缩，大量的冰被带走，阻止了积雪的积累，同时在地表留下了陨石的滞后沉积物。这些地区呈现出流入、流出和收缩之间的平衡，所有这些都与南极近代史上的环境变化密切相关。在相当长的一段时间内，大量的陨石可以形成，每平方米高达1颗。陨石在陆地上的暴露年龄表明，其中一些冰表面非常古老。到目前为止，南极洲是地球上寻找陨石的最佳地点，ANSMET计划已被证明是可靠且经济有效的。由于几个原因，南极陨石的持续回收是重要的。自阿波罗计划以来，这些样本一直是新的、非微观的地外物质的唯一可靠来源，并且将继续如此，直到未来的行星样本返回任务发展起来（目前没有计划发射）。这些样本提供了关于我们太阳系中小行星、行星和其他天体组成的基本“基础真相”。对这些物质的研究从根本上改变了我们对太阳系的认识，极大地扩展了我们对星云中存在的物质和条件的认识，我们的太阳系就是在45.56亿年前诞生的。ANSMET陨石提供了小行星的样本，从太阳系形成以来未曾改变的原始天体到复杂的微型行星，在这些行星上既有传统的地质活动，也有奇特的地质活动。ANSMET的其他样本证明，与传统观点相反，一些陨石实际上代表了从月球和火星传递给我们的行星物质。ANSMET陨石甚至促进了一项发现，即陨石可以用于天文学，通过研究同位素异常颗粒，这些颗粒只能在不同的恒星环境中进化。

OPP 9615276 Harvey Abstract This award supports continuation of the Antarctic Search for Meteorites (ANSMET) for the 97/98, 98/99, and 99/2000 austral summer field seasons in Antarctica. Since 1976, ANSMET has recovered more than 7800 meteorite specimens from locations along the Transantarctic Mountains. Over the next three years, systematic searches will be conducted in regions known to contain meteorites and reconnaissance work will be conducted to discover new concentrations. During the 1997-98 field season work will be done in the Pecora Escarpment-LaPaz Icefields region, where several small ice fields remain unsearched and earlier reconnaissance located significant concentrations. During the 1998-99 field season the southern Walcott N?v? region will be visited, where more than 1500 meteorites have already been recovered and many more remain. During the 1999-00 field season several ice fields in the Dominion Range- Grosvenor Mountains- Scott Glacier region will be visited, where previous reconnaissance and incomplete systematic searching promise significant meteorite recoveries. Antarctica is the world's premier meteorite hunting-ground for two reasons. Although meteorites fall in a random fashion all over the globe, the likelihood of finding a meteorite is enhanced if the background material is plain and the accumulation rate of terrestrial sediment is low. Consequently the East Antarctic Ice Sheet, provides an ideal background for meteorite recovery. This allows the recovery of meteorites without bias toward types that look most different from earth rocks (a problem on the other continents) and without bias toward larger sizes. But another factor may be equally important. As the East Antarctic Ice Sheet flows toward the margins of the continent, it's progress is occasionally blocked by mountains or obstructions below the surface of the ice. In these areas, old deep ice is pushed to the surface and can become stagnant, with very little outf low and consistent, slow inflow. When such places are exposed to strong katabatic winds, massive deflation results, removing large volumes of ice and preventing accumulation of snow while leaving a lag deposit of meteorites on the surface. These areas exhibit a balance between inflow, outflow and deflation, all of which are intimately tied to environmental change during recent Antarctic history. Over significant stretches of time large concentrations of meteorites can develop, as high as 1 per square meter. Terrestrial exposure ages of meteorites suggest that some of these ice surfaces are very old. Antarctica is by far the best place on Earth to search for meteorites, and the ANSMET program has proven to be reliable and cost effective. Continued recovery of Antarctic meteorites is important for several reasons. These samples have been the only reliable source of new, non-microscopic extraterrestrial material since the Apollo project, and will continue to be until future planetary sample-return missions develop (none are currently scheduled for launch). These samples provide essential "ground- truth" about the composition of asteroids, planets and other bodies of our solar system. Studies of these materials have fundamentally changed our understanding of the solar system, greatly extending our knowledge of the materials and conditions present in the nebula from which our solar system was born 4.556 billion years ago. ANSMET meteorites provide samples of asteroids ranging from primitive bodies unchanged since the formation of the solar system to complex, miniature planets, where both traditional and exotic geological activity has taken place. Other ANSMET samples proved, against the conventional wisdom, that some meteorites actually represent planetary materials, delivered to us from the Moon and Mars. ANSMET meteorites have even promoted the discovery that meteorites can be used to do astronomy, through the study of isotopically anomalous grains that could only have evolved in a different stellar environment.