Meteorites as free sample-returns: Operation of the UK Desert Fireball Network

帮助解释的空间背景是所有样本分析的基础：无论这些样本是岩石、医学测试还是警察证据，我们都需要知道它们来自哪里才能解释结果。陨石是我们唯一的原行星盘样本；是关于我们自己的太阳系形成的唯一幸存的物理记录(包括对我们的太阳盘做出贡献的各种本地恒星源，以及在其内部发生的化学过程)；唯一记录行星体如何发生分化和核心形成的记录。然而，我们几乎没有对它们来自哪里的限制。在我们得到一些小行星的样本返回任务之前，我们需要的是特定陨石的轨道。不幸的是，在数以万计的陨石中，我们只有四颗陨石的轨道是好的，还有几颗是合理的。这个项目的目的是确定多个陨石的轨道。这些结果可能对陨石研究的每一个领域产生影响，就像对任何其他样本的空间背景的了解对随后对其进行的所有分析一样。流星体在穿过我们的大气层时会产生一个明亮的火球。通过从不同角度拍摄火球，可以非常准确地确定物体的大气轨迹。如果物质以陨石的形式留在地球表面，这使我们能够计算出它在进入大气层之前的轨道，以及它降落在地球表面的位置。在过去的50年里，这种技术被多次使用，都是在北半球的温带地区，但尽管观察到了数百次陨石坠落，但只有4次被发现。成功率很低的原因是，在几平方公里的区域内，当有大量灌木丛时，很难回收一块小岩石。我们的解决方案相当简单。在过去的几十年里，在世界的沙漠中发现了数以万计的陨石。把一个火球网络放在沙漠里，它应该是更容易的样本。我们设计了一个火球天文台，可以在澳大利亚沙漠的恶劣环境中自动运行。根据以前在这一地区的野外工作，寻找古老的风化陨石，我们应该有大约70%的机会找到我们看到的陆地上的陨石。我们的第一笔赠款是在沙漠中建立一个由3个天文台组成的小型网络，并测试技术和概念，从2005年6月开始。两年过去了，火球天文台已经建成，部署在澳大利亚的沙漠中，并成功地与卫星互联网和太阳能相结合。除了功能齐全的自主天文台外，还建立了后勤服务，以维持它们的运行，并支持定期的野外工作。英国现在有一个在澳大利亚沙漠运行的火球摄像机网络。轨道是从22个火球计算出来的--这是第一批从南半球火球确定的轨道。最重要的是：这些火球中至少有一个在地面上产生了陨石。一支探险队将在下一个野外季节找回这个样本--以及在此期间落下的任何其他样本--。我们最初的试验网络已被证明是成功的。我们现在需要支持，让我们将这一成功转化为越来越多的有轨道的陨石，最终为陨石科学家提供最基本的信息：了解它们的样本来自哪里。

A spatial context to aid interpretation is fundamental to all sample analysis: whether those samples are rocks, medical tests, or police evidence, we need to know where they came from to interpret the results. Meteorites are our only samples of a protoplanetary disk; the only surviving physical record of the formation of our own Solar System (including the variety of local stellar sources that contributed to our disk, and the chemical processes that occurred within it); the only record of how differentiation and core formation occurs in planetesimals. And yet we have virtually no constraint on where they come from. Until we get sample-return missions to numbers of asteroids, what we need are orbits for specific meteorites. Unfortunately, out of tens of thousands of meteorites, we have good orbits for only four, and reasonable orbits for a couple more. The aim of this project is to determine orbits for numbers of meteorites. The results potentially have implications for every area of meteorite study, just as a knowledge of spatial context of any other sample has implications for all subsequent analyses of it. Meteoroids produce a bright fireball as they transit our atmosphere. By photographing the fireball from different angles, the atmospheric track of the object can be determined with great accuracy. If material survives to the surface as a meteorite, this allows us to work out what its orbit was before it entered the atmosphere, and also where it landed on the Earth's surface. This technique has been employed a number of times over the last 50 years, all in temperate regions of the northern hemisphere, but although hundreds meteorite falls have been observed, only four were recovered. The poor success rate is down to the difficulty in recovering a small rock in an area of several square kilometres when there is significant undergrowth. Our solution was rather simple. Over the last few decades, tens of thousands of meteorites have been found in the world's deserts. Put a fireball network in a desert and it should be much easier samples. We have designed a fireball observatory that can operate automatically in the harsh environment of the Australian desert. Based on previous fieldwork in this area, looking for old weathered meteorites, we should have about a 70% chance of finding meteorites that we see land. Our first grant, to put a small network of 3 observatories out in the desert, and test both the technology and concept, began June 2005. Two years on, fireball observatories have been built, deployed in the Australian desert, and successfully integrated with satellite internet and solar power. In addition to fully-functioning autonomous observatories, logistics to maintain them in operation, and support regular fieldwork, are in place. The UK now has a fireball camera network operating in the Australian desert. Orbits have been calculated from 22 fireballs - the first orbits to be determined from southern hemisphere fireballs. And most important: at least one of these fireballs has produced a meteorite on the ground. An expedition to recover this sample - and any others that fall in the meantime - will be mounted in the next field season. Our initial trial network has proven a success. We now need the support that will let us translate this success into a growing collection of meteorites with orbits, finally providing meteorite scientists with that most basic information: a knowledge of where their samples come from.