Exploring the Atmosphere of Neoproterozoic Earth: The Effect of O2_{2} on Haze Formation and Composition

Previous studies of haze formation in the atmosphere of the Early Earth have focused on N$_{2}$/CO$_{2}$/CH$_{4}$ atmospheres. Here, we experimentally investigate the effect of O$_{2}$ on the formation and composition of aerosols to improve our understanding of haze formation on the Neoproterozoic Earth. We obtained in situ size, particle density, and composition measurements of aerosol particles produced from N$_{2}$/CO$_{2}$/CH$_{4}$/O$_{2}$ gas mixtures subjected to FUV radiation (115-400 nm) for a range of initial CO$_{2}$/CH$_{4}$/O$_{2}$ mixing ratios (O$_{2}$ ranging from 2 ppm to 0.2\%). At the lowest O$_{2}$ concentration (2 ppm), the addition increased particle production for all but one gas mixture. At higher oxygen concentrations (20 ppm and greater) particles are still produced, but the addition of O$_{2}$ decreases the production rate. Both the particle size and number density decrease with increasing O$_{2}$, indicating that O$_{2}$ affects particle nucleation and growth. The particle density increases with increasing O$_{2}$. The addition of CO$_{2}$ and O$_{2}$ not only increases the amount of oxygen in the aerosol, but it also increases the degree of nitrogen incorporation. In particular, the addition of O$_{2}$ results in the formation of nitrate bearing molecules. The fact that the presence of oxygen bearing molecules increases the efficiency of nitrogen fixation has implications for the role of haze as a source of molecules required for the origin and evolution of life. The composition changes also likely affect the absorption and scattering behavior of these particles but optical properties measurements are required to fully understand the implications for the effect on the planetary radiative energy balance and climate.Comment: 15 pages, 3 tables, 8 figures, accepted in Astrophysical Journa

Camilla: A Centaur reconnaissance and impact mission concept

Centaurs, minor planets with a semi-major axis between the orbits of Jupiter and Neptune (5–30 AU), are thought to be among the most diverse small bodies in the solar system. These important targets for future missions may have recently been Kuiper Belt Objects (KBOs), which are thought to be chemically and physically primitive remnants of the early solar system. While the Kuiper Belt spans distances of 30–50 AU, making direct observations difficult, Centaurs' proximity to the Earth and Sun make them more accessible targets for robotic missions. Thus, we outline a mission concept designed to reconnoiter 10199 Chariklo, the largest Centaur and smallest ringed body yet discovered. Named for a legendary Centaur tamer, the conceptual Camilla mission is designed to fit under the cost cap of the National Aeronautics and Space Administration (NASA) New Frontiers program, leveraging a conservative payload to support a foundational scientific investigation to these primitive bodies. Specifically, the single flyby encounter utilizes a combined high-resolution camera/VIS-IR mapping spectrometer, a sub-mm point spectrometer, and a UV mapping spectrometer. In addition, the mission concept utilizes a kinetic impactor, which would provide the first opportunity to sample the composition of potentially primitive subsurface material beyond Saturn, thus providing key insights into solar system origins. Such a flyby of the Chariklo system would provide a linchpin in the understanding of small body composition, evolution, and transport of materials in the solar system

Visualizing Nanoparticle Dissolution by Imaging Mass Spectrometry

We demonstrate the ability to visualize nanoparticle dissolution while simultaneously providing chemical signatures that differentiate between citrate-capped silver nanoparticles (AgNPs), AgNPs forced into dissolution via exposure to UV radiation, silver nitrate (AgNO₃), and AgNO₃/citrate deposited from aqueous solutions and suspensions. We utilize recently developed inkjet printing (IJP) protocols to deposit the different solutions/suspensions as NP aggregates and soluble species, which separate onto surfaces <i>in situ</i>, and collect mass spectral imaging data <i>via</i> time-of-flight secondary ion mass spectrometry (TOF-SIMS). Resulting 2D Ag⁺ chemical images provide the ability to distinguish between the different Ag-containing starting materials and, when coupled with mass spectral peak ratios, provide information-rich data sets for quick and reproducible visualization of NP-based aqueous constituents. When compared to other measurements aimed at studying NP dissolution, the IJP-TOF-SIMS approach offers valuable information that can potentially help in understanding the complex equilibria in NP-containing solutions and suspensions, including NP dissolution kinetics and extent of overall dissolution

Training Curriculum: Human Resources and Administrative Investigations (Facilitator’s Guide)

The enclosed Human Resources and Administrative Investigations curriculum was developed by the Project on Addressing Prison Rape at American University, Washington College of Law as part of contract deliverables for the National PREA Resource Center (PRC), a cooperative agreement between the National Council on Crime and Delinquency and the Bureau of Justice Assistance (BJA). The Prison Rape Elimination Act (PREA) standards served as the basis for the curriculum’s content and development, with the goal of the Human Resources and Administrative Investigations curriculum to satisfy specific PREA standards requirements. It is recommended that the Human Resources and Administrative Investigations curriculum be reviewed in its entirety before choosing which modules to use. Any alterations to the original materials require either acknowledgement during their presentation or removal of the PRC and Project on Addressing Prison Rape logos. BJA is currently undergoing a comprehensive review of the enclosed curriculum for official approval, at which point the BJA logo may be added

Training Curriculum: Human Resources and Administrative Investigations (Facilitator’s Guide)

The enclosed Human Resources and Administrative Investigations curriculum was developed by the Project on Addressing Prison Rape at American University, Washington College of Law as part of contract deliverables for the National PREA Resource Center (PRC), a cooperative agreement between the National Council on Crime and Delinquency and the Bureau of Justice Assistance (BJA). The Prison Rape Elimination Act (PREA) standards served as the basis for the curriculum’s content and development, with the goal of the Human Resources and Administrative Investigations curriculum to satisfy specific PREA standards requirements. It is recommended that the Human Resources and Administrative Investigations curriculum be reviewed in its entirety before choosing which modules to use. Any alterations to the original materials require either acknowledgement during their presentation or removal of the PRC and Project on Addressing Prison Rape logos. BJA is currently undergoing a comprehensive review of the enclosed curriculum for official approval, at which point the BJA logo may be added