Comparing Ice-Atmosphere Interaction on Mars, Pluto, and Triton – PSI

The past decade has yielded major observational advances for bodies with atmospheres that are in vapor-pressure equilibrium (VaPE) with condensed surface ices. In 2011, radar observations revealed a massive CO2 deposit at the martian south pole and, in 2015, the New Horizons mission revealed Sputnik Planitia, Pluto, the surface of a vast basin of N2 ice. Triton’s southern hemisphere also hosts a vast deposit of N2 ice. These reservoirs buffer the sublimation-deposition cycle of Mars’ CO2 atmosphere and Pluto’s and Triton’s N2 atmosphere. While the climates of Mars, Pluto, and Triton have been individually studied, no high-level framework exists for determining where VaPE climates can exist throughout the Solar System.

Therefore, the goal of the proposed work is to answer: Where in the Solar System are VaPE climates like those of Mars, Pluto, and Triton viable? Characterizing the pressure regime of worlds with VaPE climates is important because pressure is a key determinant of climatic behavior, including liquid surface water stability and available habitable surface environments. Pressure also directly influences surface modification processes, such as aeolian erosion rates, ice-sculpting rates, and the size range of meteors reaching the surface to create craters. The presence and location of ground ice deposits also influences the climate and geologic record of VaPE worlds. PAC ice deposits trap and consolidate less-volatile species, acting as a long-term sink of these materials and providing a stratigraphic record encoding the orbital and climatic history of these worlds. PAC ice deposits also create topographic highs and cold traps that modify atmospheric circulation and weather patterns and host processes that efficiently rework planetary surfaces, like pressure geysers. Developing an overarching understanding of VaPE worlds and applying such a framework to Mars, Pluto, and Triton will elucidate the geologic and climatic histories of worlds across our solar system.

The importance of understanding how VaPE worlds operate leads to the following objectives:

Objective 1: Find the parameter space of orbital, ice, and ground properties required for VaPE worlds and PAC deposits. Objective 2: Characterize the pressure behavior and PAC ground ice distribution for worlds in the region of VaPE stability. Objective 3: Determine the PAC ground ice and pressure history of Mars, Pluto, and Triton

Methodology – We approach our Objectives with the following Tasks:

Task 1: Establish conditions for onset of PAC ice deposition and perennial PAC ice stability. Task 2: Identify stability regions for VaPE worlds and PAC ice distributions.
Task 3: Model influence of PAC ice surface morphology on energy balance.
Task 4: Determine the ground ice and pressure history of Mars, Pluto, and Triton.