3D numerical modeling of high-velocity impacts: cratering rates on Venus, interaction between the ejecta and atmosphere, obliquity of the K-T impact.

高速撞击的 3D 数值模拟：金星上的陨石坑速率、喷射物与大气之间的相互作用、K-T 撞击的倾斜度。

• 批准号: PP/D001986/1
• 负责人: Joanna Morgan
• 金额: $ 1.5万
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2006
• 资助国家: 英国
• 起止时间: 2006 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=PP%2FD001986%2F1
• 关键词: 3D; numerical; modeling; velocity; impacts

We are applying for funds to bring a Russian Scientist (Natalia Artemieva) to help us learn more about meteorite impacts. She has written a computer modelling programme (called SOVA) that can accurately model what happens to a meteorite as it travels through an atmosphere, what happens when it hits the surface of a planet or moon, and then how material (gas, melted rocks and solid particles) is ejected away from the site of impact and through the atmosphere. Artemieva's computer programming skills complement Morgan, Collins and Bland's expertise in impacts. The main reasons for the visits are to: 1) Determine the cratering rate on Venus Throughout the history of our solar system, meteorites have regularly collided with our planets and moons. We know approximately how often this happens, for example a 10-km diameter meteorite will hit Earth about once every 100 million years. We can use the density of impact craters to tell us how old planetary surfaces are, and when we do this we find that Venus's surface is only about 600 million years old (i.e. much younger than the Moon or Mars), suggesting a planet-wide volcanic event on Venus at this time. However these calculations are only approximate because, until now, no one has determined the affect of Venus's very dense atmosphere on meteor entry. Artemieva and Bland will use SOVA to correctly model the entry of meteorites through the Venusian atmosphere, obtain a properly constrained cratering rate for Venus, and calculate the age of Venus's surface. 2) Model the interaction between the ejecta and atmosphere When we look at middle- to large-sized craters on Earth they are surrounded by material that has been ejected from the crater in rapid, turbulent flows. These ejecta deposits are similar to so-called 'pyroclastic flows' around volcanoes and some craters on Mars. The former are known to cause climate change, and the latter are thought to be possible only if there is ice beneath the surface of Mars. Previous models of ejecta travelling from an impact site have treated the ejected material in a simplistic manner. Collins and Artemieva will use SOVA to properly simulate the interaction between ejecta and atmosphere, and the deposition of this material around the impact site. They will use their model to test: whether meteorite impacts can cause climate cooling (as happens with pyroclastic flows), and whether there is ice beneath the Martian surface. 3) Determine the angle of the K-T impact 65 Ma Meteorites can be more environmentally damaging if they hit a planet at a low angle to the surface because then they can release a larger volume of gasses from the near-surface rocks. A low angle might therefore explain why the impact 65 million years ago at Chicxulub in Mexico was so devastating and caused a mass extinction including that of the dinosaurs. Morgan has collected samples of the ejecta from around the world, and determined the size of particles at each site. Morgan and Artemieva will use SOVA to model how particles are ejected from an impact site for different impact angles. They will then compare the observed and modelled data to determine the angle at which this meteorite hit Earth. From this we will be able to calculate better the volumes of climatically active gasses released into the atmosphere by this impact.

我们正在申请资金，邀请一位俄罗斯科学家(Natalia Artemieva)来帮助我们更多地了解陨石撞击。她编写了一个名为SOVA的计算机模拟程序，可以准确地模拟陨石在穿过大气层时会发生什么，当它撞击行星或月球表面时会发生什么，然后物质(气体、熔岩和固体颗粒)是如何从撞击地点喷出并穿过大气层的。Artemieva的计算机编程技能与Morgan、Collins和Bland在Impact方面的专业知识相辅相成。这次访问的主要原因是：1)确定金星上的陨石坑速度在我们太阳系的整个历史上，陨石经常与我们的行星和卫星相撞。我们大约知道这种情况发生的频率，例如，直径10公里的陨石大约每1亿年撞击地球一次。我们可以使用撞击坑的密度来告诉我们行星表面的年龄，当我们这样做时，我们发现金星表面只有大约6亿年的历史(即比月球或火星年轻得多)，这表明此时金星上发生了一次全行星范围的火山事件。然而，这些计算只是近似值，因为到目前为止，还没有人确定金星非常稠密的大气层对流星进入的影响。Artemieva和Bland将使用SOVA来正确模拟陨石通过金星大气的进入，获得适当约束的金星陨石率，并计算金星表面的年龄。2)建立喷出物与大气相互作用的模型当我们观察地球上的大中型陨石坑时，它们被从陨石坑快速、湍流中喷出的物质所包围。这些喷发出的沉积物类似于火星上火山和一些陨石坑周围的所谓“火山碎屑流”。前者被认为会导致气候变化，而后者被认为只有在火星表面下有冰的情况下才有可能。以前从撞击地点喷出的物质模型以一种简单化的方式处理喷出的物质。柯林斯和阿尔特米耶娃将使用SOVA适当地模拟喷射物与大气之间的相互作用，以及这种物质在撞击地点周围的沉积。他们将使用他们的模型来测试：陨石撞击是否会导致气候变冷(就像火山碎屑流一样)，以及火星表面下是否有冰。3)确定K-T撞击的角度65 Ma的陨石如果以与地表的低角度撞击行星，可能会对环境造成更大的破坏，因为它们可以从近地表岩石中释放出更大体积的气体。因此，一个低角度可以解释为什么6500万年前在墨西哥希克苏鲁布发生的撞击具有如此毁灭性的影响，并导致包括恐龙在内的大规模灭绝。摩根从世界各地收集了喷射物的样本，并确定了每个地点的颗粒大小。Morgan和Artemieva将使用SOVA来模拟粒子如何在不同的撞击角度下从撞击地点喷射出来。然后，他们将比较观察到的数据和建模的数据，以确定这颗陨石撞击地球的角度。由此，我们将能够更好地计算这次撞击释放到大气中的具有气候活性的气体的体积。