5:15 PM - 7:15 PM
[PPS09-P17] Simulation of the aerosol formation from meteoric metals in the Martian mesosphere
Keywords:Mars, meteorite, mesosphere
The thermal structure and water cycle in the Martian atmosphere had been thought to be dominated by micrometer-sized dust particles provided from the surface. However, the observed bimodal size distribution of dust particles in the lower atmosphere [Fedorova et al., 2014] indicated the continuous input of nanometer-sized particles into the atmosphere. Furthermore, model calculations of CO2 ice clouds observed in the mesosphere (40-90 km altitude) suggested that the dust in the lower atmosphere was insufficient to provide the required mesospheric condensation nuclei [Listowski et al.,2014]. One of the possibilities for solving these problems is that the ablation of meteoroids entering the atmosphere of Mars are responsible for providing the condensation nuclei [Määttänen et al.,2022; 2024].
Meteoroid smoke particles (MSPs) are nm-sized particles produced by chemical reactions between atmospheric molecules and metals released from ablating meteoroids. They are likely to form polar metal carbonates (e.g. MgCO3) which act as condensation nuclei of H2O and CO2 ice clouds in the mesosphere[Plane et al.,2018], or sediment and grow through coagulation with other MSPs and dust particles to form bimodal dust distributions. MSPs on Mars are thought to be water-bound carbonate dimers, but there has been little research on MSPs in Mars's atmosphere; for example, a modeling study focusing on their effects on their microphysics has never been done. In addition, it is difficult to directly detect the distributions and seasonal variations of MSPs by observation due to their expected grain size and density as a function of altitude.
Our research aims to develop a model that describes a series of physical processes from the formation of MSPs to their effects on microphysics, such as cloud formation and coalescence with dust, towards the evaluation of the impact of MSPs on the climate of Mars. As the first step, using the one-dimensional photochemical model PROTEUS [Nakamura et al., 2023], we calculated the chemical reactions for magnesium, one of the main components of meteroids, which are expected to occur in the mesosphere of Mars referring to Plane et al. [2018]. Then, we compared the Mg and Mg+ layers obtained in the model with MAVEN observations [Crismani et al., 2023], and investigated the amount of MgCO3 produced.
When cosmic dust was continuously injected into the atmosphere, metallic layers with a peak altitude of about 70-80 km were stably formed. The peak altitude and its number density varied with season and latitude. MgCO3 was consistently produced mainly by the MgO + CO2 reaction, with a peak at 60 km altitude, and diffused to the surface over several tens of days. At altitudes where mesospheric ice clouds formed, MgCO3 remained in steady state because it is removed by charge transfer with O2+.
Since MgCO3 has a huge dipole moment, clustering by dimerization occurs faster than the capture rate, which stays in the atmosphere as a particle. Therefore, atmospheric diffusion, sedimentation, and coalescence with tropospheric dust need to be considered in the next step. Based on the MgCO3 production rate obtained in this study, we plan to develop a model that describes clustering and the formation and dissipation of mesospheric ice clouds.
Meteoroid smoke particles (MSPs) are nm-sized particles produced by chemical reactions between atmospheric molecules and metals released from ablating meteoroids. They are likely to form polar metal carbonates (e.g. MgCO3) which act as condensation nuclei of H2O and CO2 ice clouds in the mesosphere[Plane et al.,2018], or sediment and grow through coagulation with other MSPs and dust particles to form bimodal dust distributions. MSPs on Mars are thought to be water-bound carbonate dimers, but there has been little research on MSPs in Mars's atmosphere; for example, a modeling study focusing on their effects on their microphysics has never been done. In addition, it is difficult to directly detect the distributions and seasonal variations of MSPs by observation due to their expected grain size and density as a function of altitude.
Our research aims to develop a model that describes a series of physical processes from the formation of MSPs to their effects on microphysics, such as cloud formation and coalescence with dust, towards the evaluation of the impact of MSPs on the climate of Mars. As the first step, using the one-dimensional photochemical model PROTEUS [Nakamura et al., 2023], we calculated the chemical reactions for magnesium, one of the main components of meteroids, which are expected to occur in the mesosphere of Mars referring to Plane et al. [2018]. Then, we compared the Mg and Mg+ layers obtained in the model with MAVEN observations [Crismani et al., 2023], and investigated the amount of MgCO3 produced.
When cosmic dust was continuously injected into the atmosphere, metallic layers with a peak altitude of about 70-80 km were stably formed. The peak altitude and its number density varied with season and latitude. MgCO3 was consistently produced mainly by the MgO + CO2 reaction, with a peak at 60 km altitude, and diffused to the surface over several tens of days. At altitudes where mesospheric ice clouds formed, MgCO3 remained in steady state because it is removed by charge transfer with O2+.
Since MgCO3 has a huge dipole moment, clustering by dimerization occurs faster than the capture rate, which stays in the atmosphere as a particle. Therefore, atmospheric diffusion, sedimentation, and coalescence with tropospheric dust need to be considered in the next step. Based on the MgCO3 production rate obtained in this study, we plan to develop a model that describes clustering and the formation and dissipation of mesospheric ice clouds.