Antarctic Search for Meteorites

南极寻找陨石

• 批准号: 9615276
• 负责人: Ralph Harvey
• 金额: $ 26.04万
• 依托单位: Case Western Reserve University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-08-01 至 2001-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9615276&HistoricalAwards=false
• 关键词: Antarctic; Search; Meteorites

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.

该奖项支持97/98、98/99和99/2000南极洲夏季野外季节南极陨石搜索计划(ANSMET)的继续。自1976年以来，ANSMET已经从横跨北极山脉的地点发现了7800多个陨石样本。在接下来的三年里，将在已知含有陨石的地区进行系统搜索，并将进行侦察工作，以发现新的陨石聚集区。1997-1998年野外季节期间，将在Pecora Escapment-LaPaz冰原地区进行工作，那里仍有几个小冰场未被搜索，早先的侦察发现了相当多的冰原。在1998-1999年的田间季节，沃尔科特南部？将访问该地区，那里已经发现了1500多块陨石，还有更多的陨石留在那里。在1999-00年度的野外季节期间，将访问Dominion Range-Grosvenor Mountain-Scott Glacier地区的几个冰场，以前的勘察和不完整的系统搜索有望在那里找到大量的陨石。南极洲是世界上首屈一指的陨石猎场，原因有两个。虽然陨石在全球范围内以随机的方式坠落，但如果背景物质是普通的，陆地沉积物的累积速度很低，那么找到陨石的可能性就会增加。因此，东南极冰盖为陨石回收提供了理想的背景。这使得陨石的回收不会偏向于看起来与地球岩石最不同的类型(这在其他大陆是一个问题)，也不会偏向更大的尺寸。但另一个因素可能同样重要。随着东南极冰盖向大陆边缘流动，它的前进有时会被高山或冰表面下的障碍物所阻碍。在这些地区，古老的深冰被推到表面，可能会变得停滞不前，很少有流出，持续缓慢的流入。当这些地方暴露在强风中时，会产生大规模的通货紧缩，清除大量的冰，防止积雪，同时在地表留下滞后的陨石沉积。这些地区表现出流入、流出和通货紧缩之间的平衡，所有这些都与南极近代历史上的环境变化密切相关。在相当长的一段时间内，可能会形成大量集中的陨石，高达每平方米1颗。陨石的陆地暴露年龄表明，其中一些冰面非常古老。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的和具有成本效益的。南极陨石的持续回收具有重要意义，原因有几个。自阿波罗计划以来，这些样本一直是新的非微观地外物质的唯一可靠来源，并将继续下去，直到未来的行星样本返回任务发展(目前没有计划发射)。这些样本提供了关于我们太阳系的小行星、行星和其他天体组成的基本“地面真相”。对这些物质的研究从根本上改变了我们对太阳系的理解，极大地扩展了我们对45.56亿年前太阳系诞生的星云中存在的物质和条件的了解。ANSMET陨石提供了从太阳系形成以来没有改变的原始体到复杂的微型行星的小行星样本，在这些行星上，发生了传统的和外来的地质活动。ANSMET的其他样本证明，与传统观点相反，一些陨石实际上代表着从月球和火星送来的行星物质。ANSMET陨石甚至通过研究只有在不同的恒星环境中进化出来的同位素异常颗粒，促进了陨石可以用于天文学的发现。