Knowledge Resource Center for Ecological Environment in Arid Area
| 项目编号 | 200020_196955 |
| Nuclide Production in the Solar System | |
| Leya Ingo | |
| 主持机构 | University of Berne - BE |
| 开始日期 | 2020 |
| 结束日期 | 2023 |
| 资助经费 | 615000(CHF) |
| 项目类别 | Project funding (Div. I-III) |
| 资助机构 | CH-SNSF（瑞士国家科学基金会） |
| 语种 | 英语 |
| 国家 | 瑞士 |
| 中文简介 | Astronomy, Astrophysics and Space Sciences |
| 英文简介 | The proposal at hand is a continuation of the running proposal 200020_182447 “Nuclide Production in the Solar System”. The major focus of this proposal is on cosmogenic nuclide production in solar system objects, which is similar to the preceding proposal and which is our major expertise. Project A is on improving model calculations for cosmogenic production rates in meteorites, planetary surfaces, and planetary atmospheres. In the preceding funding period we developed the computer code 'Cosmic_Transmutation' to calculate the differential particle spectra for all possible meteorite types (also non spherical) and for planetary surfaces (with and without atmospheres and magnetic fields). The new code is for the first time reliable enough to fully implement galactic alpha-particles and to extend the model to higher energies. Here we propose to perform the next steps, i.e., combining the calculated particle spectra with the relevant cross sections and thereby providing the community with a complete and consistent database for cosmogenic nuclide production rates in meteorites and planetary surfaces. The new model will also be used by the other studies proposed here (Project B, C, D). This project will not only significantly increase the quality of cosmogenic model predictions for the entire community, it will also warrant our leadership in this important and increasing field. For cosmogenic nuclide studies but also for astronomy and astrophysics, there is one relevant question still unanswered: Was the galactic cosmic ray (GCR) fluency in the solar system temporal constant or not? If variations in the GCR fluency (if they occur) are not accounted for in studies of cosmic ray exposure histories, any interpretation of the dynamics of small bodies in the solar system will be wrong. Due to lack of knowledge, most studies simply assume that the GCR fluency was constant over time. This, however, is by no means granted as there are arguments for temporal variabilities. To tackle this question we started Project B, measuring K isotope concentrations in iron meteorites. This very challenging task has not been successfully tried for some time but it is of importance for a couple of reasons. Due to the long half-life of 1.25 Ga, only 40K offers the opportunity to study long term GCR variations. In addition, the so-called 40K-K ages are very reliable and robust. Having this in mind, it is difficult to accept that no 40K-K ages have been determined for more than 30 years and that there are hundreds of iron meteorites still waiting to be dated. A statistical meaningful number of cosmic ray exposure ages for iron meteorites will also have an impact on astrophysics (e.g., number of galactic spiral arms) and climate physics. In Project C we will study pre-irradiation effects in CAIs, starting with CAIs from Allende. In a new approach, we will first establish a database combining CAI chemical composition data with X-ray attenuation factors to determine a correlation between X-ray attenuation and cosmogenic production rates for, e.g., 3He, 21Ne, and Kr isotopes. This effort will enable us to extend the study to (the smaller) CAIs from other carbonaceous chondrite types. Based on the thus obtained correlation we can better distinguish whether measured noble gas excesses are due to a variable chemical composition of due to pre-irradiation effects. Together with the new model calculations developed in Project A we will obtain new constraints for CAI transport and storage mechanisms in the early solar system. Finally, in Project D we plan to continue our studies on 14C and 14C/10Be terrestrial ages of meteorites. Since we are one of only three laboratories world-wide able to measure cosmogenic 14C in meteorites, we plan to improve and extend our expertise in this important field. In parallel to some technical improvements, we also plan to re-determine initial 14C production rates and 14C/10Be production rate ratios, both are needed for reliable and precise terrestrial age determinations. In addition, we plan measuring a large variety of meteorites from the Atacama desert with the goal to i) study meteorite influx and accumulation in this so far unstudied desert and ii) to check whether old meteorites can bridge the gap between terrestrial and extraterrestrial nuclide production. |
| 英文关键词 | Meteorites Cosmogenic production rates Terrestrial ages of meteorites CAIs Galactic cosmic rays |
| 来源学科分类 | Astronomy, Astrophysics and Space Sciences |
| 资源类型 | 项目 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/356010 |
| 推荐引用方式 GB/T 7714 | Leya Ingo.Nuclide Production in the Solar System.2020. |
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