NO_xproduction and rainout from Chicxulub impact ejecta reentry

Abstract

The Chicxulub impact 66.0 Ma ago initiated the second biggest extinction in the Phanerozoic Eon. The cause of the concurrent oceanic nitrogen isotopic anomaly, however, remains elusive. The Chicxulub impactor struck the Yucatán peninsula, ejecting 2 × 1015 kg of molten and vaporized rock that reentered globally as approximately 1023 microscopic spherules. Here we report that modern techniques indicate that this ejecta generates 1.5 × 1014 moles of NOx, which is enough to cause the observed nitrogen enrichment of the basal layer. Additionally, reentry‐based NO production would explain the anomalously heavy isotopic composition of the observed nitrogen. We include N, O, N2, O2, and NO species in simulations of nonequilibrium chemically reacting flow around a reentering spherule. We then determine the net production of NO from all the spherules and use turbulence models to determine how quickly this yield diffuses through the atmosphere. Upon reaching the stratosphere and troposphere, cloud moisture absorbs the NOx and forms nitric acid. We model this process and determine the acidity of the resulting precipitation, which peaks about 1 year after the impact. The precipitation ultimately reaches the upper ocean, where we assume that the well‐mixed surface layer is 100 m deep. We then model the naturally occurring carbonate/bicarbonate buffer and determine the net pH. We find that insufficient NOx reaches the ocean to directly cause the observed end‐Cretaceous oceanic extinction via acidification and buffer removal. However, the resulting nitrates are sufficient to explain the concurrent nitrogen isotopic anomaly and facilitate an end‐Cretaceous algae bloom.

Nitric Oxide Production by Centimeter-Sized Meteoroids and the Role of Linear and Nonlinear Processes in the Shock Bound Flow Fields

“…Our approximation is thus reasonable, because much faster, strongly ablating meteoroids will have substantially higher peak mass fractions. In fact, a more recent modeling study [103] on the re-entry of spherules produced and ejected by the Chuxculub impact has shown that the NO mole fraction is consistent with the value adopted in our study. Consequently, the mass of produced NO is computed from 80 to 95 km within the volume corresponding to the initial radius of a bright meteor train.…”

HCN Production via Impact Ejecta Reentry During the Late Heavy Bombardment

“…To apply the aforementioned trace species transport model (Parkos et al, ), we must determine the diffusion coefficient. From Parkos et al (), …”

“…Existing work by the aerospace community (Ahmadjian et al, ; Arnold & Coleman, ; Zahn & Murad, ) demonstrates that nonequilibrium plays a crucial role in the production yield of certain chemical species. This effect was shown to be important for NO production during the Chicxulub impact (Parkos et al, ).…”

Adapting vibrational relaxation models in DSMC and CFD to ab-initio calculations

“…This can happen in shockwaves, plasma environments, and detonations. [1][2][3] When the gas is perturbed from a local thermal equilibrium, intermolecular interactions try to return the system back to equilibrium. However, regions of nonequilibrium can persist in the flow if the local convection or reaction rates are comparable to the relaxation rates of the internal energy modes.…”