The First Billion Years of the Geodynamo

地球发电机的第一个十亿年

• 批准号: 1015269
• 负责人: John Tarduno
• 金额: $ 48.66万
• 依托单位: University of Rochester
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-10-01 至 2014-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1015269&HistoricalAwards=false
• 关键词: First; Billion; Years; Geodynamo

The onset and nature of the geomagnetic field is important for understanding the evolution of the core, atmosphere and life on Earth. The geomagnetic field is generated in the liquid outer core, and hence is a probe of core conditions. The field also protects Earth from energetic particles streaming from the Sun (the "solar wind"); without this protective shield Earth might have developed into a dry and barren planet. A record of the early core geodynamo that generated the field is preserved in ancient silicate crystals from igneous rocks that contain minute magnetic grain inclusions. Our data indicate the presence of a geodynamo between 3.4 and 3.45 billion years ago, near the limit for the start of growth of the solid inner-core. While the magnetic field sheltered Earth's atmosphere from erosion at this time, the standoff of the solar wind was greatly reduced, and similar to that seen during modern extreme solar storms. These conditions suggest that intense radiation from the young Sun may have modified the atmosphere of the young Earth by promoting loss of light elements and water. Such effects would have been more pronounced if the field were absent prior to 3.45 billion years ago, as suggested in some hypotheses, or if an older geodynamo prior to inner core growth produced a weak field. In general, these considerations suggest the young Earth was more water-rich than today. The new frontier to learn more about these issues is obtaining geomagnetic field records that are more than 3.45 billion-years-old.We are investigating the first billion years of geodynamo history and its implications for Earth evolution through the study of well-dated rock units from 6 ancient cores of continents (cratons). We are using a combination of existing methods of single silicate crystal magnetic measurements from in situ igneous host rocks and new approaches involving magnetic analyses of grains from sedimentary units. These measurements are achievable using highly sensitive magnetometers at the University of Rochester. Determination of the presence and strength of the geomagnetic field during the first billion years of Earth history is of broad interest to a range of scientists who study early Earth environments (atmosphere and biosphere) and the core. The investigation involves international collaboration with geologists from several countries, and multidisciplinary collaborations spanning astrophysics and space physics. Our program also integrates research and educational efforts. The study is contributing to graduate theses and undergraduates are receiving training in the field and the laboratory.

地磁领域的开始和性质对于理解地球上核心，大气和生命的演变很重要。地磁场是在液体外核中产生的，因此是核心条件的探针。该场还保护地球免受从太阳流出的能量颗粒（“太阳风”）；没有这种保护性的盾牌地球可能已经发展成为一个干燥而贫瘠的行星。产生该场的早期核心Geodynamo的记录保存在含有微小磁性颗粒夹杂物的火成岩中的古代硅酸盐晶体中。我们的数据表明，在3.4至34.5亿年前的地球杂志的存在接近固体内部核心增长的限制。虽然此时磁场掩盖了地球的大气层侵蚀，但太阳风的僵局大大减少了，并且类似于现代极端太阳风暴中看到的侵蚀。这些条件表明，年轻太阳的强烈辐射可能通过促进光元素和水的流失来改变年轻地球的大气。如果在34.5亿年前没有该领域（如某些假设中，或者在内部核心生长之前的较旧的Geodynamo产生弱场），这种影响将变得更加明显。通常，这些考虑表明，年轻的地球比今天更富含水。了解这些问题的新领域是获得超过34.5亿年历史的地磁田间记录，我们正在研究Geodynamo历史的首次十亿年，及其对地球进化的影响，通过研究来自6个古代大陆（Cratons）的良好的岩石单元（Cratons）。我们使用了现有的单硅酸盐晶体磁性测量方法的组合，来自原位火成岩宿主岩石以及涉及沉积单元晶粒的磁分析的新方法。这些测量方法是可以使用罗切斯特大学高度敏感的磁力计实现的。 在地球历史的前十亿年，确定地磁领域的存在和强度对于研究地球早期环境（大气和生物圈）和核心的一系列科学家而言，这是广泛的关注。该调查涉及与来自几个国家的地质学家的国际合作，以及涵盖天体物理学和太空物理学的多学科合作。我们的计划还整合了研究和教育工作。这项研究为研究生和本科生提供了在野外和实验室的培训。