Year: 2024
Type: article
Abstract: In the distant outer solar system, carbon monoxide (CO) and nitrogen (N2) ices tend to be colocated in the same deposits due to their similar molecular weights and sublimation properties. For instance, these volatiles are abundant on the surfaces of Pluto and Triton, so knowledge of their phase behavior is necessary for understanding surface evolution and geology. However, it is presently unclear how mixing between CO and N2 molecules affects the physical properties of such mixtures. Here, we measured the liquidus, solidus, and alpha–beta phase transitions for the N2 and CO binary system. We observed the liquidus by using visual inspection. The solidus and alpha–beta transitions were measured by using Raman spectroscopy. The laboratory results were later compared to a thermodynamic model, CRYOCHEM 2.0. The liquidus and solidus were consistent with CRYOCHEM 2.0. However, the alpha–beta coexistence region is shown to be narrower in the laboratory results than in the thermodynamic model. Finally, we present a method for deriving the compositions of a sample using Raman spectroscopy (Appendices A.1 and A.2).
Source: The Planetary Science Journal
DOI: 10.3847/psj/ad8fac
Language: English
Topic: Astro and Planetary Science
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,800
Awards: G2268656542, PREVIOUS STUDIES HAVE SHOWN THAT THE LAKES OF TITAN ARE COMPOSED OF METHANE AND/OR ETHANE BUT THE RELATIVE PROPORTIONS ARE MOSTLY UNCLEAR. UNDERSTANDING THE PAST AND CURRENT STABILITY OF THESE LAKES REQUIRES CHARACTERIZING THE INTERACTIONS OF LIQUID METHANE AND ETHANE ALONG WITH NITROGEN. PRIOR INVESTIGATIONS FOUND THAT THE FREEZING POINT OF METHANE IS DEPRESSED WHEN MIXED WITH NITROGEN. RECENT WORK SHOWS THAT ALTHOUGH METHANE AND ETHANE HAVE SIMILAR FREEZING POINTS WHEN MIXED THEY CAN REMAIN LIQUID DOWN TO 72 K. CONCURRENTLY WITH THE FREEZING POINT MEASUREMENTS WE ACQUIRE TRANSMISSION SPECTRA OF THESE MIXTURES TO UNDERSTAND HOW THE SPECTRAL FEATURES CHANGE WITH CONCENTRATION AND TEMPERATURE. ANY MIXING OF THESE TWO SPECIES TOGETHER WILL DEPRESS THE FREEZING POINT OF THE LAKE BELOW TITAN S SURFACE TEMPERATURE PREVENTING THEM FROM FREEZING. THE NEXT STEP IS TO DETERMINE HOW THE METHANE-ETHANE SYSTEM BEHAVES IN THE PRESENCE OF A NITROGEN ATMOSPHERE. PRELIMINARY RESULTS INDICATE THAT AT HIGH PRESSURE THE TERNARY SYSTEM CREATES TWO SEPARATE LIQUID PHASES. THROUGH SPECTROSCOPY WE DETERMINED THE BOTTOM LAYER TO BE NITROGEN RICH AND THE TOP LAYER TO BE ETHANE RICH. UNDERSTANDING THE FREEZING POINTS OF COMBINATIONS OF THESE SPECIES HAS IMPLICATIONS FOR NOT ONLY THE LAKES ON THE SURFACE OF TITAN BUT ALSO FOR THE EVAPORATION/CONDENSATION/CLOUD CYCLE IN THE ATMOSPHERE AS WELL AS THE STABILITY OF THESE SPECIES ON OTHER OUTER SOLAR SYSTEM BODIES. THESE RESULTS WILL GUIDE CURRENT THEORETICAL MODELS AND INTERPRETATION OF FUTURE OBSERVATIONAL DATA. WE WILL USE THE CRYOGENIC ASTROPHYSICAL ICE LAB AT NORTHERN ARIZONA UNIVERSITY TO MEASURE THE COMPOSITION AND STABILITY OF LIQUIDS AND ICES UNDER VARIOUS TEMPERATURES AND PRESSURES. OUR CRYOGENIC LABORATORY SETUP ALLOWS US TO EXPLORE ICES DOWN TO 30 K THROUGH IMAGING AND TRANSMISSION SPECTROSCOPY. SAMPLES WILL INCLUDE MIXTURES OF METHANE ETHANE AND NITROGEN. WE WILL ALSO PERFORM MODELING TO UNDERSTAND THE CHEMISTRY INTERACTIONS CAUSING THESE PHENOMENA. THE PROPOSED WORK WILL BE DIRECTLY APPLICABLE TO NASA S SOLAR SYSTEM WORKINGS OBJECTIVES OF CHARACTERIZING AND UNDERSTANDING THE CHEMICAL MINERALOGICAL AND PHYSICAL FEATURES OF PLANETARY SURFACES AND FLUID INVENTORIES THAT INTERACT WITH THE SURFACE. WE WILL ALSO DEVELOP THEORETICAL AND EXPERIMENTAL BASES FOR UNDERSTANDING THESE FEATURES IN THE CONTEXT OF THE VARYING CONDITIONS THROUGH TIME AFTER FORMATION.
OpenAlex ID: W4405541533