Gratteri crater is a young Martian crater which still retains secondary craters, and some of them have unique ejecta deposits similar to mudflows splattered by impacts, suggesting that they might have been formed on wet sand-like material. Interestingly, the morphologies of Gratteri secondary craters vary among regions. We conducted crater formation experiments onto wet sand targets with different water contents and observed that the crater size and morphology changed with target water content. We established a crater size scaling law for wet sand which can account for water content change. Our scaling law suggests that the region 103 km away from the Gratteri crater might have had a higher water content than the region 32 km away (≥4.6 wt.% vs. <2.0 wt.%, respectively), judging from the sizes and morphologies of its secondary craters in each region.

Knowledge of shock remanent magnetization (SRM) property is crucial for interpreting the spatial change in a magnetic anomaly observed over an impact crater. This study conducted two series of impact-induced SRM acquisition experiments by varying the applied field and impact conditions, and the remanences of cube-shaped subsamples cut from shocked basalt containing single-domain titanomagnetite were measured to investigate the pressure and temperature dependence of the SRM intensity. The peak pressure and peak temperature distributions in the shocked samples were estimated using shock-physics modeling. SRM intensity was proportional to the apple field intensity up to 400 µT. The SRM intensities under different projectile conditions were consistent at the same pressure values. An empirical equation of SRM intensity is proposed to be the power function of pressure and a linear function of temperature, which can express the experimental SRM intensity values in a range of pressures up to 10 GPa and temperatures up to the Curie temperature. The magnetic anomaly estimation over an impact crater was demonstrated using the empirical equation, and the anomaly distribution shows a distinct feature approximated as a combination of two dipoles located at the basement of the crater and a deeper part.

Knowledge of the shock remanent magnetization (SRM) structure is crucial to interpret the spatial changes in magnetic anomalies observed over the impact crater. This study reports the SRM intensity and stability structures of single-domain titanomagnetite-bearing basalt based on the SRM acquisition experiments, remanence measurements for divided subsamples, and impact simulations. The SRM properties systematically change with increasing pressure, and three distinctive aspects are recognized at different pressure ranges: (1) constant intensity below 0.1 GPa, (2) linear trend as intensity is proportional to pressure up to 1.1 GPa, and (3) constant intensity and increasing stability above 1.9 GPa. The SRM intensity and stability structures suggest that the crustal rocks containing the single-domain titanomagnetite originally had an SRM intensity structure according to the distance from the impact point, which changed depending on the remanence stability after the impact.