Determine the late-season physical state of Martian CO2 ice at Sisyphi Cavi

Determine the physical state of the seasonal CO2 ice at Sisyphi Cavi during the final stages of sublimation after solar longitude 227°, when the ice is no longer directly characterized by the available observations.

Background

The study uses CRISM observations at solar longitudes 183° and 227° to infer that the CO2 ice at Sisyphi Cavi is translucent during most of the observed ice season. OMEGA observations indicate that CO2 ice persists at solar longitude 249° but is no longer detected at solar longitude 253°.

Because the physical state of the ice during this final interval is not established, the observations do not fully constrain whether the late-stage gully-modification processes operate beneath translucent ice, within a granular deposit, or during a transition between these states.

References

CO2 ice observed by CRISM at two different times ($L_\mathrm{S}\,183\circ$ and $L_\mathrm{S}\,227\circ$) exhibits a translucent behaviour in both cases. This suggests that CO2 ice remains in a translucent state during most of the ice season, although its state during the very last stages (after $L_\mathrm{S}\,227\circ$) remains uncertain.

— Properties of Seasonal Ice at Sisyphi Cavi and Implications for Current Modification of Martian Gullies  (2609.03885 - Leclef et al., 3 Sep 2026) in Conclusion, bullet-point summary