The Acetylene-Ammonia
Co-crystal on Titan
Morgan L. Cable
Tuan H. Vu
Helen E. Maynard-Casely
Mathieu Choukroun
Robert Hodyss
10.1021/acsearthspacechem.7b00135.s003
https://acs.figshare.com/articles/media/The_Acetylene-Ammonia_Co-crystal_on_Titan/5956294
Titan,
the largest moon of Saturn, likely supports a rich organic
mineralogy that we are only beginning to understand. Photochemistry
in the upper atmosphere generates a complex array of organic molecules
from the simple precursors N<sub>2</sub> and CH<sub>4</sub>. These
organics continue to react and combine, forming aerosol layers and
ultimately depositing on the surface. Organics are transported via
pluvial (rain) and fluvial (rivers/flooding) processes into the methane-based
hydrocarbon lakes, where evaporation of volatile liquids can create
evaporite deposits of remnant dissolved molecules. Within such deposits,
chemical and physical processes may be occurring even at low temperatures.
We have demonstrated in previous work that benzene and ethane rapidly
form a unique and stable co-crystal at Titan surface temperatures
(90–95 K), akin to a salt on Earth, where the weak van der
Waals interactions in the benzene-ethane co-crystal are analogous
to the ionic bonds in a salt. Here, we report the formation of a second
co-crystal between acetylene and ammonia, which forms even more quickly
and is stable through anticipated conditions of Titan “rain”
events of liquid methane, ethane, and propane. Such co-crystals represent
an exciting new class of possible minerals for Titan’s surface
and may be responsible for processes such as selective sequestration
and storage of species as well as having new properties for construction
and erosive resistance of geological materials.
2018-02-27 00:00:00
evaporite deposits
methane-based hydrocarbon lakes
Such co-crystals
erosive resistance
van der Waals interactions
benzene-ethane co-crystal
CH 4
Acetylene-Ammonia Co-crystal
surface
precursors N 2
aerosol layers
molecule
Titan Titan