The formation of sulfate, nitrate and perchlorate salts in the martian atmosphere

Funding: 2011 NAI Director’s Discretionary Fund award titled ‘‘Perchlorate, Water, and Life’’, along with a NASA postdoctoral program award to work at the Virtual Planetary Laboratory.In extremely arid regions on Earth, such as the Atacama Desert, nitrate, sulfate and perchlorate salts form in the atmosphere and accumulate on the surface from dry deposition according to diagnostic evidence in their oxygen isotopes. Salts of similar oxyanions should have formed in the atmosphere of Mars because of comparable photochemical reactions. We use a 1-D photochemical model to calculate the deposition rates of sulfate, nitrogen oxyanions, and perchlorate from Mars' atmosphere, given a plausible range of volcanic fluxes of sulfur- and chlorine-containing gases in the past. To calculate integrated fluxes over time, we assume that throughout the last 3. byr (the Amazonian eon), the typical background atmosphere would have been similar to today's cold and dry environment. If the soil has been mixed by impact perturbations to a characteristic depth of ~2. m during this time, given a time-average volcanic flux 0.1% of the modern terrestrial volcanic flux, the model suggests that the soil would have accumulated 1.0-1.7. wt.% SO42- and 0.2-0.4. wt.% N in the form of pernitrate (peroxynitrate) or nitrate. The calculated sulfate concentration is consistent with in situ observations of soils from rovers and landers and orbital gamma ray spectroscopy. However, nitrates or pernitrates are yet to be detected. The modeled formation of perchlorate via purely gas-phase oxidation of volcanically-derived chlorine is insufficient by orders of magnitude to explain 0.4-0.6. wt.% ClO4- measured by NASA's Phoenix Lander. The far smaller amount of ozone in the martian atmosphere compared to the terrestrial atmosphere and the colder, drier conditions are the cause of lower rates of gas phase oxidation of chlorine volatiles to perchloric acid. Our calculations imply that non-gas-phase processes not included in the photochemical model, such as heterogeneous reactions, are likely important for the formation of perchlorate and are yet to be identified.Publisher PDFPeer reviewe

Consequences of Giant Impacts on Early Uranus for Rotation, Internal Structure, Debris, and Atmospheric Erosion

We perform a suite of smoothed particle hydrodynamics simulations to investigate in detail the results of a giant impact on the young Uranus. We study the internal structure, rotation rate, and atmospheric retention of the post-impact planet, as well as the composition of material ejected into orbit. Most of the material from the impactor's rocky core falls in to the core of the target. However, for higher angular momentum impacts, significant amounts become embedded anisotropically as lumps in the ice layer. Furthermore, most of the impactor's ice and energy is deposited in a hot, high-entropy shell at a radius of ~3 R ⊕. This could explain Uranus' observed lack of heat flow from the interior and be relevant for understanding its asymmetric magnetic field. We verify the results from the single previous study of lower resolution simulations that an impactor with a mass of at least 2 M ⊕ can produce sufficiently rapid rotation in the post-impact Uranus for a range of angular momenta. At least 90% of the atmosphere remains bound to the final planet after the collision, but over half can be ejected beyond the Roche radius by a 2 or 3 M ⊕ impactor. This atmospheric erosion peaks for intermediate impactor angular momenta (~3 × 1036 kg m2 s−1). Rock is more efficiently placed into orbit and made available for satellite formation by 2 M ⊕ impactors than 3 M ⊕ ones, because it requires tidal disruption that is suppressed by the more massive impactors

Ridge Formation and De-Spinning of Iapetus via an Impact-Generated Satellite

We present a scenario for building the equatorial ridge and de-spinning Iapetus through an impact-generated disk and satellite. This impact puts debris into orbit, forming a ring inside the Roche limit and a satellite outside. This satellite rapidly pushes the ring material down to the surface of Iapetus, and then itself tidally evolves outward, thereby helping to de-spin Iapetus. This scenario can de-spin Iapetus an order of magnitude faster than when tides due to Saturn act alone, almost independently of its interior geophysical evolution. Eventually, the satellite is stripped from its orbit by Saturn. The range of satellite and impactor masses required is compatible with the estimated impact history of Iapetus.Comment: 19 pages, 3 figures; Icarus, in pres

The Eons of Chaos and Hades

We propose the Chaotian Eon to demarcate geologic time from the origin of the Solar System to the Moonforming impact on Earth. This separates the solar system wide processes of planet formation from the subsequent divergent evolution of the inner planets. We further propose the division of the Hadean Eon into eras and periods and naming the proto-Earth Tellus

Atmospheric Erosion by Giant Impacts onto Terrestrial Planets: A Scaling Law for any Speed, Angle, Mass, and Density

We present a new scaling law to predict the loss of atmosphere from planetary collisions for any speed, angle, impactor mass, target mass, and body composition, in the regime of giant impacts onto broadly terrestrial planets with relatively thin atmospheres. To this end, we examine the erosion caused by a wide range of impacts, using 3D smoothed particle hydrodynamics simulations with sufficiently high resolution to directly model the fate of low-mass atmospheres around 1% of the target's mass. Different collision scenarios lead to extremely different behaviors and consequences for the planets. In spite of this complexity, the fraction of lost atmosphere is fitted well by a power law. Scaling is independent of the system mass for a constant impactor mass ratio. Slow atmosphere-hosting impactors can also deliver a significant mass of atmosphere, but always accompanied by larger proportions of their mantle and core. Different Moon-forming impact hypotheses suggest that around 10%–60% of a primordial atmosphere could have been removed directly, depending on the scenario. We find no evident departure from the scaling trends at the extremes of the parameters explored. The scaling law can be incorporated readily into models of planet formation

The Impact-Flood Connection: Does It Exist?

https://deepblue.lib.umich.edu/bitstream/2027.42/155790/1/Deutsch_et_al_1994_Impact-flood_connection.pd