CAREER: GLOW: Investigation on the evolution of magnetic fields of early Earth and beyond with cutting-edge research opportunities for future scientists

职业：GLOW：研究早期地球及以后的磁场演化，为未来科学家提供尖端研究机会

• 批准号: 2237730
• 负责人: Miki Nakajima
• 金额: $ 55.63万
• 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: 2023
• 资助国家: 美国
• 起止时间: 2023-02-15 至 2028-01-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2237730&HistoricalAwards=false
• 关键词: CAREER; GLOW; Investigation; evolution; magnetic

In the inner solar system, Earth is the only terrestrial planet that has a strong magnetic field. The geomagnetic field provides a habitable environment for life by shielding it from harmful high energy particles. Thus, the presence of a magnetic field can help support life on the planetary surface. Mars appeared to have had a magnetic field in the past based on remnant magnetic fields in the Martian crust. Mercury currently has a magnetic field, but it is approximately 100 times weaker than that of Earth. Venus does not have any indication of a current or past magnetic field. Some observed planets in extrasolar systems (exoplanets) might have signs of magnetic fields, but further studies are needed. Currently, Earth’s magnetic field is produced by processes in the iron core, which consists of a solid inner core and liquid outer core with some light elements. As Earth cools, the solid inner core grows, releasing heat and light elements to the bottom of the liquid outer core. This facilitates convection in the outer core and contributes to generating a magnetic field. However, it is likely that this mechanism did not operate in the past because recent studies suggest that Earth’s core was completely molten in the early Earth and the solid inner core did not nucleate until recently (~ 0.5 – 1 Ga). Simultaneously, terrestrial rock records indicate that Earth had a magnetic field by 3.5-4.2 Ga. This may suggest that early Earth generated a magnetic field in a different mechanism from today’s process. It has been hypothesized that planetary magnetic fields may be influenced by meteorite impacts, but the details are not well understood. In this proposal, the team will investigate the mechanisms of Earth’s magnetic field over its history and apply the model to other planets, including Mars, Venus, and exoplanets, to achieve a comprehensive understanding of planetary magnetic fields. This will also help understand the habitability of a planet throughout its lifetime. One of the key aspects of the proposal is participation of local high school, undergraduate and graduate students, who will conduct cutting-edge research, numerical simulations, and learn scientific communication. This proposed work will provide a unique and enriching opportunity to a diverse group of students, encouraging them to pursue STEM career paths. This research will include the following tasks over the next five years to understand the history of magnetic fields of Earth and other planets: (1) Determine the Earth’s initial interior structure. Earth and other planets form by collisions among growing planets. This impact stage determines the initial structure of the planetary core and mantle, which strongly influences whether generation of a magnetic field in the core is likely or not. The team will calculate the planetary interior structure based on impact simulations using a smoothed particle hydrodynamics (SPH) method, which calculates fluid flows. (2) Using SPH, the team will investigate how meteorite impacts affect the magnetic field of Earth during the Hadean (4.5-4 Ga) and Archean (4-2.5 Ga) era. (3) Conduct shock experiments. The team will investigate the possibility that early Earth’s magnetic field was produced in an iron-rich silicate melt at the core-mantle boundary (basal magma ocean, BMO) instead of magnetic field generation in the core. For the BMO to generate a magnetic field, the BMO needs to have a very high electrical conductivity, which controls how quickly electrons move in the material. The team will calculate the electrical conductivity of a BMO analogue material based on laser-driven shock experiments at the University of Rochester Laboratory For Laser Energetics. (4) Simulate a magnetic field generation process in BMO using the electrical conductivities estimated in (3) as an input, and (5) apply the model developed for Earth to other planetary bodies, including the Moon, Mars, Venus, and exoplanets to predict the history of their magnetic fields. The proposed projects will be led by two graduate students and contributed by high school and undergraduate students. Four local high school students will join this project as summer interns and they will learn coding, data visualization, and cutting-edge research during Years 1 and 2. They will be responsible for data visualization of impact simulations, which will be used in paper publications and short public videos. During Years 3 and 4, the PI will develop a course focused on science communication and research primarily for first- and second-year undergraduate students, where they will learn planetary impact events, science communications, and how to conduct research. The course includes a field trip to the Sudbury impact basin, which is the second largest basin on Earth. During Year 5, the team will host an exhibit at the Rochester Science and Museum Center (RMSC) to present research output of the team over the past five years.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.

在内太阳系中，地球是唯一具有强磁场的类地行星。地磁场通过保护生命免受有害高能粒子的伤害，为生命提供了一个宜居的环境。因此，磁场的存在可以帮助维持行星表面的生命。根据火星地壳中的残余磁场，火星过去似乎有过磁场。水星目前有一个磁场，但它大约比地球弱100倍。金星没有任何关于当前或过去磁场的指示。太阳系外的一些观测到的行星(系外行星)可能有磁场的迹象，但还需要进一步研究。目前，地球磁场是由铁核中的过程产生的，铁核由固体内核和液体外核以及一些轻元素组成。当地球冷却时，固体内核会增长，将热量和轻元素释放到液态外核的底部。这促进了外核中的对流，并有助于产生磁场。然而，这种机制很可能在过去并不起作用，因为最近的研究表明，地核在地球早期完全熔融，而固体内核直到最近才成核(~0.5-1Ga)。与此同时，陆地岩石记录表明，地球的磁场大小为3.5-4.2Ga。这可能表明，早期地球产生磁场的机制与今天的过程不同。有人假设行星磁场可能会受到陨石撞击的影响，但细节还没有被很好地理解。在这项提案中，该团队将研究地球历史上磁场的机制，并将该模型应用于其他行星，包括火星、金星和系外行星，以实现对行星磁场的全面了解。这也将有助于理解一颗行星在其整个生命周期中的宜居性。该提案的一个关键方面是当地高中、本科生和研究生的参与，他们将进行尖端研究、数值模拟和学习科学交流。这项拟议的工作将为不同的学生群体提供一个独特和丰富的机会，鼓励他们追求STEM职业道路。这项研究将在未来五年内包括以下任务，以了解地球和其他行星的磁场历史：(1)确定地球的初始内部结构。地球和其他行星是由不断增长的行星之间的碰撞形成的。这个撞击阶段决定了行星核和地幔的初始结构，这强烈地影响着核心是否有可能产生磁场。该团队将基于碰撞模拟，使用平滑粒子流体动力学(SPH)方法计算行星内部结构，该方法计算流体流动。(2)利用SPH，该团队将研究陨石撞击如何影响赫甸(4.5-4Ga)和太古宙(4-2.5Ga)时代的地球磁场。(3)进行冲击试验。该团队将研究早期地球磁场是在核-地幔边界(基底岩浆海洋，BMO)的富铁硅酸盐熔体中产生的，而不是在核心产生磁场的可能性。为了让BMO产生磁场，BMO需要有非常高的电导率，这控制着电子在材料中移动的速度。该团队将基于罗切斯特大学激光能量实验室的激光驱动冲击实验，计算BMO模拟材料的电导率。(4)使用(3)中估计的电导率作为输入来模拟BMO中的磁场产生过程，以及(5)将为地球开发的模型应用于其他行星体，包括月球、火星、金星和系外行星，以预测它们的磁场历史。提议的项目将由两名研究生领导，高中生和本科生参与。四名当地高中生将以暑期实习生的身份加入这个项目，他们将在一年级和二年级学习编码、数据可视化和前沿研究。他们将负责碰撞模拟的数据可视化，这些数据将用于纸质出版物和公共短视频。在第三年和第四年，PI将主要为一年级和二年级的本科生开发一门侧重于科学传播和研究的课程，在那里他们将学习行星撞击事件、科学传播以及如何进行研究。该课程包括对萨德伯里撞击盆地的实地考察，该盆地是地球上第二大盆地。在第五年，该团队将在罗切斯特科学和博物馆中心(RMSC)举办一场展览，展示该团队在过去五年的研究成果。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。