Carbon Dioxide Cold Traps on the Moon

Abstract

The rotation axis of the Moon is tilted by only 1.5° relative to the normal of the ecliptic plane and some craters in the lunar polar regions are therefore permanently shadowed. A portion of these PSRs are cold enough (<∼110 K) to trap water ice (Paige, Siegler, et al., 2010;Watson et al., 1961). Volatiles are delivered to the lunar surface by comets and (carbonaceous) meteoroids (Arnold, 1979;Berezhnoy et al., 2012). Among those common volatiles, the strongly polar H 2 O molecule has the lowest vapor pressure and sublimation rate (Watson et al., 1961). Other ices ("super-volatiles" or "hypervolatiles") are trapped at lower temperatures, and are therefore expected to be exceedingly rare. The sublimation rate of solid CO 2 becomes negligible at around 50 K (Zhang & Paige, 2009). Carbon dioxide cold traps, if they exist at all, would lie within the water ice cold traps. Carbon is found, at low concentration ∼100 ppm, in Apollo samples and likely of solar wind origin (Gibson, 1977;Haskin & Warren, 1991). If trapped in unusually cold areas near the lunar poles, carbon may exist at far higher concentration as dry ice, and would be valuable for the production of fuel and biological materials (Cannon, 2021).Diviner, on the Lunar Reconnaissance Orbiter (LRO), provides surface temperature measurements at hundreds of meters resolution and has extensive time coverage (

A Geoscientific Review on CO and CO2 Ices in the Outer Solar System

“…On the Moon, particularly at the lunar poles, there are cold regions with temperatures < 110 K, as observed by the Diviner radiometer instrument onboard the Lunar Reconnaissance Orbiter (LRO) [13]. Free carbon, even observed in meteoritic samples, has no gaseous phase at lunar surface temperatures and therefore cannot condense, leaving CO 2 as the primary carbon constituent at lunar cold traps [2]. Pockets of CO 2 should be stable within certain craters, such as Haworth, Amundsen (Figure 2a), de Gerlache, and others, over a cumulative area of ~200 km 2 [2].…”

“…Free carbon, even observed in meteoritic samples, has no gaseous phase at lunar surface temperatures and therefore cannot condense, leaving CO 2 as the primary carbon constituent at lunar cold traps [2]. Pockets of CO 2 should be stable within certain craters, such as Haworth, Amundsen (Figure 2a), de Gerlache, and others, over a cumulative area of ~200 km 2 [2]. The confirmation of CO 2 volatiles at the lunar poles was also confirmed by the LCROSS (Lunar Crater Observation and Sensing Satellite) probe, which impacted within the Cabeus crater and released CO 2 , validating thermal stability models [14].…”

“…The origin of this CO 2 is likely to be of solar wind origin [16] or micrometeoroids [1]. The sublimation rate of solid CO 2 at these cold traps would be negligible [2,17]. Exosphere models have observed that the capture rate of CO 2 on the Moon is rather high (compared to other volatiles), probably due to the low photodestruction rate of CO 2 in the gaseous state [18].…”

“…Exosphere models have observed that the capture rate of CO 2 on the Moon is rather high (compared to other volatiles), probably due to the low photodestruction rate of CO 2 in the gaseous state [18]. The age of the lunar cold traps has been estimated to be ~2 Gyr, with an accumulation of H 2 O ice being 50-500 kg/m 2 /Gyr, with the rate of CO 2 accumulations proposed to be similarly high [2].…”

“…Carbon-bearing (C-bearing) species are common throughout the Solar System, with the most abundant species observed in comets and planetary surfaces being carbon dioxide (CO 2 ), followed by carbon monoxide (CO), and methanol (CH 3 OH) [1,2]. CO 2 and CO have been observed (or inferred) through spectroscopic observations, either through groundbased and space telescopes, like the Spitzer Space Telescope, Infrared Astronomical Satellite (IRAS), United Kingdom Infrared Telescope (UKIRT), or planetary missions, such as Galileo, Voyager 2, and New Horizons.…”