Neutrino Geoscience: Geoneutrinos and Heat Production in the Earth

中微子地球科学：地中微子和地球产热

基本信息

批准号：
1650365
负责人：
William McDonough
金额：
$ 29.91万
依托单位：
University of Maryland, College Park
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-04-01 至 2021-09-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1650365&HistoricalAwards=false
关键词：
Neutrino Geoscience Geoneutrinos Heat Production

项目摘要

What powers plate tectonics, mantle convection, and the Earth's geodynamo? The Earth radiates 46 terawatts (46 million millon watts) to space, and this power emission reflects contributions from primordial and radiogenic sources, with the former constituting planetary accretion and core-formation sources. Inside the Earth, the decay of 3 radioactive elements (potassium, thorium, and uranium) produces 99% of the Earth?s nuclear power. Existing measurements of the Earth's flux of geoneutrinos, electron antineutrinos from terrestrial natural radioactivity, reveal the amount of uranium and thorium in the Earth, but these data come with considerable uncertainty. Given the understanding of the amount and distribution of these elements in the continental crust, it is known that they contribute about 7 TW of radiogenic power to the continental heat flux, and this component plus an underlying mantle flux accounts for about 1/3 of the total power lost from the Earth. The remaining 2/3 of the Earth's surface heat flux comes up beneath the oceans, but it is not known how much of this mantle flux is primordial versus radiogenic contributions. Compositional models of the Earth collectively allow for up to a factor of 30 in estimates of the mantle's radiogenic power. The understanding of the Earth's thermal evolutionary history is intimately linked to knowing the total radiogenic power of the mantle. Consequently, this project seeks to understand the rate and magnitude by which the planet is cooling. Thus, by determining the amount of radioactive energy that powers the Earth's engine, one can make a 'fuel gauge' that identifies the proportion of primordial to radioactive fuel left in the planet. In addition, there will be collaboration with particle physicists and members of the U.S. intelligence community in the detection of electron antineutrinos (from nuclear reactors and the Earth) for nuclear nonproliferation purposes. Reactor antineutrinos are the background for the analyses of geoneutrino research and geoneutrinos are the background for reactor monitoring.Despite best efforts there remains an order of magnitude uncertainty in the amount of radiogenic power driving mantle dynamics, given the competing models of the Earth's composition. Direct measurements of the abundance of radiogenic, heat-producing elements (K, Th and U) present in the mantle and much of the deep continental crust do not exist. Importantly, this picture is rapidly changing because of new, larger and more sensitive geoneutrino detectors that are coming on line in the coming years. In the next 8 years, a suite of 5 experiments will define the mantle's radiogenic contribution to the surface heat loss and when tested to a reference model these data can define the radiogenic heat from the mantle. These results will fix limits on the composition of the silicate Earth and will set bounds on permissible values for models defining the mode of mantle convection.The abundance and distribution of the heat-producing elements in the Earth will be studied, and the major tasks include: 1) Improve predictions and reduce systematic errors in defining the regional geoneutrino signal to SNO+ detector (Ontario, Canada), 2) Model geological, geochemical, and geophysical data of the regional lithologies surrounding the KamLAND, JUNO (Guangzhou, China) and Jinping (Sichuan, China) detectors to improve geological predictions, 3) Develop and improve the global reference model at the 1x1 degree scale, making it a community resource that goes beyond applications in geoneutrino studies, 4) Test existing and future data from all detectors against estimates of the regional and global contribution, assuming all detectors see approximately the same mantle signal (within +/-10%), and 5) Use above data to test models of the bulk silicate Earth. Data from current and planned detectors can bring resolution to several major issues in Earth sciences, such as 1) what are the building blocks used to make the planet; 2) what is the present-day proportion of radiogenic heat relative to the residual heat of accretion, core formation and extinct nuclides; 3) what is the present-day fraction of radiogenic heat in the continental crust relative to that in the mantle; and 4) what is the composition of the silicate Earth, upper mantle, and lower mantle? Answers to these questions will, in turn, define the power that is driving plate tectonics, mantle convection and the geodynamo, as well as the structure of mantle convection. Neutrino geoscience offers a great potential to address these broad interdisciplinary issues.

什么能力板块构造，地幔对流和地球的geodynamo？地球辐射了46吨（4600万毫米瓦）到达空间，这种功率发射反映了原始和放射原源的贡献，前者构成了行星积聚和核心形成源。在地球内部，3个放射性元件（钾，th和铀）的衰减产生了地球99％的核能。地球地球通量的现有测量值，来自陆地自然放射性的电子抗体，揭示了地球中铀和th的数量，但这些数据具有相当大的不确定性。鉴于对这些元素在大陆地壳中的数量和分布的了解，众所周知，它们为大陆热通量贡献了约7个TW的放射性功率，而该组件以及一个基本的地幔通量约占从地球中损失的总功率的1/3。地球表面热通量的其余2/3出现在海洋下方，但尚不清楚多少这种地幔通量是原始的，而是放射原贡献。地球的估计值估计地球的成分模型允许高达30倍。对地球热进化史的理解与知道地幔的总放射力密切相关。因此，该项目试图了解地球冷却的速度和幅度。因此，通过确定为地球发动机供电的放射性能量的量，可以制作一个“燃油表”，以识别原始燃料与地球中留下的放射性燃料的比例。此外，还将与粒子物理学家和美国情报界的成员合作，以检测电子抗肿瘤（来自核反应堆和地球），以实现核不扩散的目的。反应堆抗腐殖质是地球素研究分析的背景，而地球植物是反应堆监测的背景。尽管最佳努力仍然存在着驱动地幔动力学的放射力动力量的数量级不确定性，鉴于地球竞争模型的组成模型。直接测量了地幔中存在的放射原性，产生热元素（K，Th和U），并且不存在许多深层大陆地壳。重要的是，由于未来几年即将到来的新型，更大，更敏感的地球植物检测器，因此这张照片正在迅速变化。在接下来的8年中，一个5个实验的套件将定义地幔对表面热量损失的放射性贡献，并且在对参考模型进行测试时，这些数据可以定义地幔的放射热。 These results will fix limits on the composition of the silicate Earth and will set bounds on permissible values for models defining the mode of mantle convection.The abundance and distribution of the heat-producing elements in the Earth will be studied, and the major tasks include: 1) Improve predictions and reduce systematic errors in defining the regional geoneutrino signal to SNO+ detector (Ontario, Canada), 2) Model geological, geochemical, and Kamland，Juno，Juno（中国广州）和Jinping（中国四川，中国的探测器）围绕区域岩性的地球物理数据，以改善地质预测，3）3）3）3）3）在1x1度度尺度上的全球参考模型，使其成为社区资源，使其成为一个超出了Geoneutrino研究的社区资源，4）对现有的贡献和未来的数据进行了估计，所有估计的人都会估算出所有估算的估算，并且估算了所有估计的估计，该数据估算了所有估计的估计，该数据估计了，该数据估计了，估算了估算的估计，该数据估计了，并且估算的是，估算了估算的估计，请参阅大约相同的地幔信号（在+/- 10％之内），5）使用上述数据来测试散装硅酸盐地球的模型。来自当前和计划的探测器的数据可以解决地球科学的几个主要问题，例如1）用于制造地球的构件是什么； 2）相对于积聚，核心形成和灭绝的核素的残留热，放射热的比例是多少？ 3）相对于地幔中的大陆地壳中的放射热的当今比例是多少？ 4）硅酸盐地球，上地幔和下地幔的组成是什么？这些问题的答案反过来将定义驱动板块构造，地幔对流和geodynamo的力量，以及地幔对流的结构。中微子地球科学为解决这些广泛的跨学科问题提供了巨大的潜力。