Neutrino Geoscience: Geoneutrinos and heat production in the Earth

PI试图了解驱动地球发动机的动力，以及为其发动机提供动力的燃料将持续多久，并使地球保持活跃和可居住。地球内部有两种能量来源：原始能量和辐射能。原始能量是在碰撞过程中产生的动能：粒子对粒子，小行星对小行星，大行星对大行星碰撞。根据陨石的速度和地球的质量，对这种能量进行简单的估计，得到1032焦耳，或者说超过现有所有核电站功率的万亿倍。不幸的是，我们缺乏一个燃料表的能源，因此我们不知道还有多少功率来驱动地球的引擎，也不知道还有多少能量（和时间）来保持它的可居住性。地中微子是在这些发热元素的β衰变过程中自然产生的电子反中微子。这些中微子是微小的基本粒子，几乎不可能被探测到，因为它们比质子小10亿倍，几乎没有质量，也不带电。2005年，粒子物理学家首次用大型地下探测器探测到地球的地中微子发射，现在正在告诉我们地球内部的放射性热量。然而，通过计算地中微子来阅读地球的燃料表，需要地质学家了解这些产热元素在大陆和地幔中的丰度和分布。通过量化地球的地中微子通量，我们可以精确地确定其组成，并确定用于建造地球的陨石积木。关于地球成分的相互竞争的理论模型将被中微子技术无偏见地询问，并告诉我们哪个地球化学模型是正确的。日本和意大利的地中微子探测器的新结果呈现出关于地球引擎中还剩多少燃料的对比故事。地质学家正在通过建立地球各大洲的三维物理和化学模型来解决这些复杂问题。我们试图解决这些复杂性。该奖项将资助研究生的研究和PI的推广工作。关于地球地幔的对流能力和地球中放射成因元素的丰度的争论仍在继续。地球具有不均匀的3D物理和组成结构。因此，产热模型之间的一致性最小。来自当前和计划中的地中微子探测器（主要的100万美元的粒子物理实验）的数据可以解决地球科学中的几个主要问题，我们试图回答：1。地球是由什么组成的？2.放射成因热与吸积和成核余热的比例是多少;3.大陆地壳中的放射成因热相对于地幔中的放射成因热的比例是多少;块状硅酸盐地球的成分是什么？它现在的上地幔和下地幔的成分是什么？这些问题的答案将反过来定义驱动板块构造、地幔对流和地球发电机的力量。从这一点上，我们也将了解地幔对流的结构。中微子地球科学提供了一个潜在的解决广泛的跨学科问题，超过传统的方法。地中微子测量是对地球仪进行采样，不会受到地幔熔融过程的干扰。目前关于地幔的Urey比率（值从0.1到0.8不等; UR =（放射性地幔功率）/（总地壳放射性功率））的争论混淆了对地球的南极难熔元素丰度（36种元素，包括Ca，Al，Th，U），其冷却速率和板块构造开始的预测。让地球科学家与物理学家一起确定地中微子信号的地壳模型和地幔对产热的贡献，将促进互利的跨学科合作。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The PI seeks to understand the power driving the Earth’s engine and how long the fuel, which powers its engine, will last and keep the planet active and habitable. There are two sources of energy within the Earth: the primordial energy and radiogenic energy. Primordial energy is the kinetic energy that comes from heating during a collision: particle to particle, small planet to small planet, and big planet to big planet collisions. A simple estimate of this energy, derived from the velocity of meteorites and the mass of the earth, gives 1032 joules, or more than a trillion, trillion times the power of all nuclear power plants in existence. Unfortunately, we lack a fuel gauge for either energy source and consequently we do not know how much power is left to drive the earth's engine, nor how much energy (and time) is left to keep it habitable. Geoneutrinos are naturally occurring electron antineutrinos produced during beta-decays of these heat producing elements. These neutrinos are tiny fundamental particles that are almost impossible to detect, because they are about a billion times smaller than a proton, near-massless and chargeless. In 2005, particle physicists first detected the earth's emission of geoneutrinos with large underground detectors and are now telling us about the amount of radiogenic heat inside the earth. Reading the earth's fuel gauge by counting geoneutrinos, however, requires that geologists understand the abundance and distribution of these heat producing elements in the continents and the mantle.By quantifying the planet’s geoneutrino flux we can establish precisely its composition and define the meteoritic building blocks used to construct the Earth. Competing theoretical models of the Earth’s composition will be unbiasedly interrogated by neutrino technology and tell us which of the competing chemical models of the Earth is the right one. New results from geoneutrino detectors in Japan and Italy present contrasting stories as to how much fuel is left in the earth's engine. Geologists are addressing these complexities by building 3-D physical and chemical models of the earth’s continents. We seek to resolve these complexities. This award will fund the research of a graduate student and the outreach efforts of the PI. Debate continues regarding the convective power of earth's mantle and the abundances of radiogenic elements in the earth. The earth has a nonuniform 3D physical and compositional structure. Consequently, there is minimal consistency between heat production models. Data from current and planned geoneutrino detectors (major 100’s of million dollars particle physics experiments) can bring resolution to several major issues in earth sciences which we seek to answer:1. what are the building blocks used to make the planet;2. what is the proportion of radiogenic heat relative to the residual heat of accretion and core formation;3. what is the fraction of radiogenic heat in the continental crust relative to that in the mantle; and4. what is the composition of the bulk silicate earth, and its present upper and lower mantle?Answers to these questions will, in turn, define the power that drives plate tectonics, mantle convection and the geodynamo. From this we will also get insights into the structure of mantle convection. Neutrino geoscience offers a potential to address broad interdisciplinary issues over conventional methods. Geoneutrino measurements sample the globe and are not confounded by mantle melting processes. The current debate about the mantle's Urey ratio (values ranging from 0.1 to 0.8; where UR = (radiogenic mantle power)/(total - crustal radiogenic power)) confound predictions for the Earth's abundances of chondritic refractory elements (36 elements, including Ca, Al, Th, & U), its cooling rate, and the onset of plate tectonics. Having geoscientists working with physicists to determine the crustal model for the geoneutrino signal and the mantle's contribution to heat production will promote mutually beneficial interdisciplinary collaborations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.