PI: Gareth Collins

On the 24th of December 2021, a bus-sized meteoroid struck the martian surface, producing a 150-m wide crater. The impact excavated an extensive field of m-scale blocks of water ice—the lowest-latitude water ice observed on Mars to date. We used 3D computer simulations of the formation of the crater performed on DiRAC (DIaL2.5) to understand properties of the meteoroid and the structure of local subsurface, including the origin of the ice.

From the simulated blast and ejecta pattern, we constrain the impact angle to be ~20 from horizontal (Fig. 1). Based on a comparison of the simulated and observed crater morphology, we find the preimpact subsurface likely contained a stronger bedrock layer overlain by 15 m thick regolith layer. Within the regolith, the ice most likely originated from a semi-continuous ice layer at a depth of 3.2–11 m below the surface. The presence of massive ice at accessible depths has important implications for future in-situ resource utilisation and human exploration of Mars.

Figure 1. (a) Observed blast zone and ejecta pattern around the Christmas Eve crater. Red lines mark the observed uprange forbidden zone. (b–f) Distal ejecta blanket for simulated impacts of a 6-m wide impactor striking a 15-m-thick regolith layer above bedrock, at impact angles between 15 and 45 degrees from the horizontal. Red lines mark the observed uprange forbidden zone from (a), determined between 1 and 2 km from the crater (marked with black circles). Green dashed lines show the location of the scimitars visible to the north and south of the impactor’s trajectory. These results imply the most likely impact is 20 degrees to the horizontal.

Wójcicka, N., Collins, G.S., Rangarajan, V.G., Dundas, C.M., Daubar, I.J., 2025. Origins of the Water Ice Excavated by the Christmas Eve Crater Formation on Mars. Journal of Geophysical Research: Planets 130, e2024JE008875. https://doi.org/10.1029/2024JE008875