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Predicting Nitrogen Isotope Fractionation in Nitrate Deposition on Early Mars

JSHS · 2022

Jaylen Shawcross, Danica Adams · Bellarmine Preparatory School, Tacoma, WA

Overview

The habitability of early Mars was majorly impacted by nitrogen, which has undergone loss to space over time. Knowledge of nitrate deposition is valuable since it gives additional insight into the question of ancient Mars’ habitability. Nitrogen’s isotopic ratio can be used to constrain total N2’s escape. Two formation processes and corresponding ages are currently debated. Nitrates were deposited on the surface, either via lightning-induced fixation in an early warm climate or reactions over longer timescales in a cold climate. These nitrates record fractionation imparted by planetary processes at the time of formation. If observed by future scientific missions to Mars, predicting fractionation caused by these two processes will help to constrain the contribution of each formation mechanism. Processes influenced by the loss of Mars’ magnetic field including photochemistry are responsible for the loss of the atmospheric nitrogen reservoir to space (~4.0-3.7 Ga). We use the Caltech/NASA JPL 1D photochemical model, KINETICS, to conduct simulations of early and modern Mars with a primordial 15N/14N ratio. Near the surface of early Mars, where deposition occurs, the 15N/14N ratio in NOy species is slightly less than the primordial ratio. In the upper atmosphere, NOy species form via SEP events, so their ratio in the upper atmosphere decreases by 3.3% to match the primordial ratio scaled by the ionization potential. The dichotomy between the isotopic ratio in NOy and N2 is greater in the simulated modern atmosphere, especially in the lower atmosphere as lightning is no longer a means of formation. Inferring the Neutron Star Maximum Mass and Lower Mass Gap in Neutron Star—Black Hole Systems with Spin Christine Ye Eastlake High School, Sammamish, WA Gravitational-wave (GW) detections of merging neutron star-black hole (NSBH) systems probe astrophysical neutron star (NS) and black hole (BH) mass distributions, especially at the transition between NS and BH masses. Of particular interest are the maximum NS mass, minimum BH mass, and potential mass gap between them. While previous GW population analyses assumed all NSs obey the same maximum mass, if rapidly spinning NSs exist, they can extend to larger maximum masses than nonspinning NSs. In fact, several authors have proposed that the ∙2.6M∙ object in the event GW190814 -- either the most massive NS or least massive BH observed to date -- is a rapidly spinning NS. We therefore infer the NSBH mass distribution jointly with the NS spin distribution, modeling the NS maximum mass as a function of spin. Using 4 LIGO-Virgo NSBH events including GW190814, if we assume that the NS spin distribution is uniformly distributed up to the maximum (breakup) spin, we infer the maximum non-spinning NS mass is 2.7+0.5−0.4M∙ (90\% credibility), while assuming only nonspinning NSs, the NS maximum mass must be >2.53M∙ (90\% credibility). The data support the mass gap’s existence, with a minimum BH mass at 5.4+0.7−1.0M∙. With future observations, under simplified assumptions, 150 NSBH events may constrain the maximum nonspinning NS mass to ±0.02M∙, and we may even measure the relation between the NS spin and maximum mass entirely from GW data. If rapidly rotating NSs exist, their spins and masses must be modeled simultaneously to avoid biasing the NS maximum mass. West Virginia

Competition history

  • JSHS 2022 Category not listed

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Source: Junior Science and Humanities Symposium

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