Gardening of the Martian Regolith by Diurnal CO₂ Frost and the Formation of Slope Streaks

Abstract

The seasonal transfer of CO 2 between the atmosphere and the surface at high latitudes is associated with a wide range of exotic processes shaping the surface morphology (

Diurnal and Seasonal Mapping of Martian Ices With EMIRS

“…Even the retrieved nighttime temperatures are not low enough to allow the formation of CO 2 ice at the surface of the planet in these regions. This formation of CO 2 frost late during the night with a quick sublimation at sunrise was expected from the models (e.g., Lange et al, 2022) with implications on the formation of gullies and slope streaks (Khuller et al, 2021;Lange et al, 2022;Pilorget & Forget, 2016). But as previous nighttime observations were conducted only around 03:00, this is the first time we are able to confirm it with direct observations of the diurnal cycle of the surface CO 2 frost at low latitudes.…”

Diurnal and Seasonal Mapping of Martian Ices with EMIRS

“…Even the retrieved nighttime temperatures are not low enough to allow the formation of CO 2 ice at the surface of the planet in these regions. This formation of CO 2 frost late during the night with a quick sublimation at sunrise was expected from the models (e.g., Lange et al, 2022) with implications on the formation of gullies and slope streaks (Pilorget & Forget, 2016;Khuller et al, 2021;Lange et al, 2022). But as previous nighttime observations were conducted only around 03:00, this is the first time we are able to confirm it with direct observations of the diurnal cycle of the surface CO 2 frost at low latitudes.…”

“…Figure 2 shows the CO 2 surface ice detections for each local time between L s = 152 • and L s = 203 • . We can see that apart from the polar caps, CO 2 ice is detected at night under equatorial and mid-latitude regions mostly around 100 • W (Tharsis region), and also around 40 • E (Arabia Terra), which corresponds to low thermal inertia areas (Putzig & Mellon, 2007) where nighttime surface CO 2 frost have been detected through MCS or THEMIS measurements (Piqueux et al, 2016;Khuller et al, 2021;Lange et al, 2022). Regarding the daily evolution of these CO 2 frost deposits, we observe that it starts to appear at midnight (panel a) and last after 6 am to disappear during daytime, with a maximum of intensity between LST of 03:00 and 06:00 (panel b).…”

“…While the ices are essentially located in the polar regions, both CO 2 & H 2 O ices can also be observed seasonally under low latitudes, in the shadows of pole-facing slopes or at the bottom of some craters (Schorghofer & Edgett, 2006;Brown et al, 2008;Carrozzo et al, 2009;Vincendon et al, 2010;Conway et al, 2012;Lange et al, 2022). From a more transient perspective, frost has also been observed to be deposed on the surface during nighttime, and remaining until early morning (Landis & Mer Athena Science Team, 2007;Piqueux et al, 2016).…”

“…From a more transient perspective, frost has also been observed to be deposed on the surface during nighttime, and remaining until early morning (Landis & Mer Athena Science Team, 2007;Piqueux et al, 2016). The presence of this daily cycle of CO 2 frost has been shown to have an impact on surface processes such as gullies or slope streaks formation (Pilorget & Forget, 2016;Khuller et al, 2021;Lange et al, 2022). Thus, better constraining this diurnal frost cycle and the properties of the CO 2 ice in these regions is of importance to better understand current active processes at the surface of Mars.…”