Improved Meteoroid Characterization through Laboratory Experiments, Modeling, and Ground-based Observations

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A four-year research designs to investigate and improve the understanding of the relationship between the properties of a meteoroid and the resulting mesosphere and lower thermosphere (MLT) meteor optical emission and radar signatures. Laboratory experiments would be set up to simulate the ablation of meteors by the Earth's atmosphere by firing projectiles with known mass, speed, and composition into a laboratory chamber containing a known density of gas. The observed relationship found between the luminous brightness of the simulated meteor with the mass of the projectile used would help enable the use of ground-based radar and optical meteor measurements to determine the masses of individual meteoroids with considerably improved accuracy. This result would then quantify the estimate of the total meteor influx of objects into the Earth's atmosphere. This research would be done through experiments at the University of Colorado's Institute for Modeling Plasma, Atmospheres and Cosmic dusT (IMPACT) facility in which the goal would be the recreation of the ablation process in well-defined laboratory conditions. These experimental results would then be applied to meteor observational data derived from both radar and optical techniques, in order to estimate masses of individual meteor events and to validate experimental and modeling results. This award would further support the education and training of a graduate student pursuing a Ph.D at CU Boulder. In addition, undergraduate students would be involved in the program through the Discovery Learning Apprenticeship Program (DLAP) at CU Boulder. The DLAP program provides CU undergraduates a hands-on research experience, with pay, culminating in a final research report and a presentation to faculty and graduate students in the program. Finally, results from the research would be integrated into a new undergraduate course entitled 'Space: Environment and Effects', to begin in Fall 2018. This course is being developed under the auspices of a campus wide "Space Minor" open to students in all majors; as such, this curriculum would reach students beyond science and engineering. Meteors make up a key component of the space environment, and so this research would be used as a key topic to underline the fascinating complexity of the near-earth space environment. The researcher plans to include lectures on simulated meteor work in this series.Meteoroids enter the Earth's atmosphere with velocities between 10 and 70 km/s and masses from femtograms (fg) up to grams or larger; however, the total mass flux of meteoroids remains uncertain, with a range of estimates spanning two orders of magnitude. The ablation of meteoroids are suggested to be responsible for the creation of metal layers of the upper atmosphere, including atomic iron (Fe), magnesium (Mg), calcium (Ca), potassium (K), and sodium (Na) layers that all peak within the range of 85-95 km altitude. These metal layers lead into a variety of aeronomical phenomena, including the nucleation of noctilucent cloud particles, ocean fertilization with bio-available Fe, and creating a relationship between stratospheric aerosol content and O3 chemistry. Moreover, meteors of milligram size and larger pose a risk to spacecraft orbiting the Earth, with the potential to cause physical or electrical damage. Accurate assessment of the total mass flux is critical to improving the understanding of each of these areas. The total mass flux error is primarily caused by the inability to determine masses of individually observed particles. The major sources of uncertainty that lead to poor estimates of meteoroid masses are uncertainty in the parameters which map the mass to observables, such as optical emissions and radar cross section. These parameters are the luminous efficiency and the ionization probability. The project would possibly provide the best measurements to date for a range of velocities and for different materials representative of meteoroids. The foremost science objective in this award addresses a simple yet critical problem in understanding MLT aeronomy: what is the total mass flux entering our atmosphere from space? The ability to create artificial meteors in the lab provides a great opportunity to engage with the community in a way that non-specialists can understand.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.