Scientists Simulate Ancient Lunar Atmosphere at NCCS
Using NASA Center for Climate Simulation (NCCS) computing resources, NASA Goddard Institute for Space Studies (GISS), Columbia University, University of Colorado, and NASA Langley Research Center scientists simulated a thin, relatively short-lived atmosphere thought to arise from erupting volcanoes that could have brought substantial amounts of water to the Moon's poles over 3 billion years ago.
“This water could have been trapped in permanently shadowed regions or buried under the lunar dust to be preserved until the modern day,” said Igor Aleinov, an associate research scientist affiliated with NASA GISS and Columbia University. Indeed, several NASA missions show water ice deposits at the poles, particularly in the permanently shadowed regions.
Since polar water would be vital to any human lunar outpost, the computational research focused on determining if the ancient atmosphere could be stable enough and have the right meteorological characteristics and chemical composition to transport water. This interdisciplinary endeavor required two computer models—the GISS planetary general circulation model ROCKE-3D and a zero-dimensional chemistry model.
The NCCS Discover supercomputer hosted over 50 ROCKE-3D simulations, each running at approximately 150-kilometer resolution and using 44 computing cores. Serving as simulation data inputs were NASA Lunar Reconnaissance Orbiter (LRO)/Lunar Orbiter Laser Altimeter (LOLA) observations of the Moon's topography, albedo (reflectivity), and permanently shadowed regions.
The published study considers 12 ROCKE-3D simulations: pure carbon monoxide (CO) and pure carbon dioxide (CO2) atmospheres with three different thicknesses (10-, 2.5-, and 1-millibar) and two different amounts of water (“dry” and “wet”). The researchers stored model output on Discover's online disk and shared their core results on the NCCS DataPortal. Climate characteristics from ROCKE-3D then served as inputs to the workstation–hosted, zero-dimensional chemistry model for deciding on the likely atmospheric composition.
Across the studied cases, the lunar atmosphere was generally stable and capable of transporting water volcanically outgassed from large (now dark due to volcanic basalt deposits) plains called maria to the polar regions. The quantity of delivered water could be substantially more than that from solar wind deposits and comet or meteorite impacts. Future simulations using more realistic atmospheric and surface conditions will aim at predicting the distribution and abundance of polar water. Such water could be used for human consumption and as a catalyst for rocket fuels when astronauts return to the Moon under NASA's Artemis Program.
“Access to the NCCS computers allowed us to simulate a large-parameter space within a couple months' time that would have taken us over a year in other circumstances,” Aleinov said. “The ease of use, fast I/O, and storage capacities also contributed to our modest success. Finally, the NCCS DataPortal has become a vital resource to our team and increases the visibility of our results.”
Aleinov, I., M.J. Way, C. Harman, K. Tsigaridis, E.T. Wolf, and G. Gronoff, 2019: Modeling a transient secondary paleolunar atmosphere: 3-D simulations and analysis. Geophys. Res. Lett., 46, no. 10, 5107-5116, doi:10.1029/2019GL082494.
NASA News Release: The Moon and Mercury May Have Thick Ice Deposits, Aug. 2, 2019
NASA/GSFC Scientific Visualization Studio: Tour of the Moon 4K Redux, Apr. 9, 2018