4 research outputs found
Fully coupled photochemistry of the deuterated ionosphere of Mars and its effects on escape of H and D
Although deuterium (D) on Mars has received substantial attention, the
deuterated ionosphere remains relatively unstudied. This means that we also
know very little about non-thermal D escape from Mars, since it is primarily
driven by excess energy imparted to atoms produced in ion-neutral reactions.
Most D escape from Mars is expected to be non-thermal, highlighting a gap in
our understanding of water loss from Mars. In this work, we set out to fill
this knowledge gap. To accomplish our goals, we use an upgraded 1D
photochemical model that fully couples ions and neutrals and does not assume
photochemical equilibrium. To our knowledge, such a model has not been applied
to Mars previously. We model the atmosphere during solar minimum, mean, and
maximum, and find that the deuterated ionosphere behaves similarly to the
H-bearing ionosphere, but that non-thermal escape on the order of 8000-9000
cms dominates atomic D loss under all solar conditions. The total
fractionation factor, , is --0.07, and integrated water loss is
147--158 m GEL. This is still less than geomorphological estimates. Deuterated
ions at Mars are likely difficult to measure with current techniques due to low
densities and mass degeneracies with more abundant H ions. Future missions
wishing to measure the deuterated ionosphere in situ will need to develop
innovative techniques to do so.Comment: 37 pages, 8 figures, published in Journal of Geophysical Research:
Planet
Nonthermal hydrogen loss at Mars: Contributions of photochemical mechanisms to escape and identification of key processes
Hydrogen loss to space is a key control on the evolution of the Martian
atmosphere and the desiccation of the red planet. Thermal escape is thought to
be the dominant loss process, but both forward modeling studies and remote
sensing observations have indicated the presence of a second,
higher-temperature "nonthermal" or "hot" hydrogen component, some fraction of
which also escapes. Exothermic reactions and charge/momentum exchange processes
produce hydrogen atoms with energy above the escape energy, but H loss via many
of these mechanisms has never been studied, and the relative importance of
thermal and nonthermal escape at Mars remains uncertain. Here we estimate
hydrogen escape fluxes via 47 mechanisms, using newly-developed escape
probability profiles. We find that HCO dissociative recombination is the
most important of the mechanisms, accounting for 30-50% of the nonthermal
escape. The reaction CO + H is also important, producing roughly as
much escaping H as momentum exchange between hot O and H. Total nonthermal
escape from the mechanisms considered amounts to 39% (27%) of thermal escape,
for low (high) solar activity. Our escape probability profiles are applicable
to any thermospheric hot H production mechanism and can be used to explore
seasonal and longer-term variations, allowing for a deeper understanding of
desiccation drivers over various timescales. We highlight the most important
mechanisms and suggest that some may be important at Venus, where nonthermal
escape dominates and much of the literature centers on charge exchange
reactions, which do not result in significant escape in this study.Comment: 47 pages, 4 figures, 3 tables. Accepted manuscript. An edited version
of this paper was published by AG
The Astropy Problem
The Astropy Project (http://astropy.org) is, in its own words, "a community
effort to develop a single core package for Astronomy in Python and foster
interoperability between Python astronomy packages." For five years this
project has been managed, written, and operated as a grassroots,
self-organized, almost entirely volunteer effort while the software is used by
the majority of the astronomical community. Despite this, the project has
always been and remains to this day effectively unfunded. Further, contributors
receive little or no formal recognition for creating and supporting what is now
critical software. This paper explores the problem in detail, outlines possible
solutions to correct this, and presents a few suggestions on how to address the
sustainability of general purpose astronomical software