Venus has similar size, density and bulk composition as Earth, but has tectonically evolved clearly differently, and this divergence remains enigmatic. Surface observations such as gravity, topography and surface age constrain Venus' evolution, but interpreting these signals requires understanding of the surface-interior coupling and thus insight into the structure and evolution of the venusian mantle and lithosphere. Here, we investigate how such observables may be generated from interior dynamics using numerical forward models of global mantle convection that consistently link the thermochemical, magmatic and tectonic evolution of Venus. Venus' present surface gravity spectrum and its relation to topography is matched best by our models with a mantle viscosity profile featuring a sublithospheric minimum of ∼ 2 × 10 20 Pa s and a gradual increase by a factor of ∼ 100 down to a depth of ∼ 250 km above the core-mantle boundary. No pronounced viscosity jump around the mantle transition as inferred for Earth is favoured for Venus, which points to a relatively dry venusian upper mantle compared to Earth's as previously suggested. This holds true for both a pure stagnant-lid scenario and in the presence of episodic catastrophic overturns triggered by cumulative crustal growth due to ongoing magmatism and volcanism. Overturns strongly perturb the surface gravity spectrum up to ∼ 150 Myr after overturn cessation. Material deeply recycled by the resurfacing event annihilates the developed plume pattern, which needs much longer than those 150 Myr to recover to a state comparable to the pattern suggested by thermal emissivity anomalies observed on Venus. Moreover, overturns limit crustal thicknesses to reasonable values and are more capable than stagnant-lid evolutions in generating mean surface ages > 500 Myr. These findings seem to confirm previous suggestions that the episodic regime is more applicable to Venus than a purely stagnant-lid regime. Yet, the relatively long time span required to recycle the entire surface (∼ 150 − 200 Myr) and the presently ongoing volcanic resurfacing predicted by our models complicate the formation of a uniform surface age as indicated by Venus' crater population and may also suggest that the latest

Impact fragmentation is an energetic process that has affected all planetary bodies. To understand its effects in basalt, we studied Lonar Crater, which is a rare terrestrial simple impact crater in basalt and analogues to kilometer-scale simple craters on Mars. The Lonar ejecta consists of basaltic fragments with sizes ranging from silt to boulder. The cumulative size and mass frequency distributions of these fragments show variation of power index for different size ranges, suggesting simple and complex fragmentation. The general shape of the fragments is compact, platy, bladed, and elongated with an average edge angle of 100°. The size distribution of cobble-to boulder-sized fragments is similar to the fracture spacing distribution in the upper crater wall, indicating the provenance of those large fragments. Its consistency with a theoretical spallation model suggests that the large fragments were ejected from near surface of the target, whereas the small fragments from deeper level. The petrophysical properties of the ejecta fragments reflect the geophysical heterogeneity in the target basalt that significantly reduced the original size of spall fragments. The presence of Fe/Mg phyllosilicates (smectites) both in the ejecta and wall indicates the role of impact in excavating the phyllosilicates from the interior of basaltic target affected by aqueous alteration. The seismic images reveal a thickness variation in the ejecta blanket, segregation of boulders, fractures, and faults in the bedrock beneath the crater rim. The fracturing, fragmentation, and fluvial degradation of Lonar Crater have important implications for Mars.

Shallow moonquakes are thought to be of tectonic origin. However, the geologic structures responsible for these moonquakes are unknown. Here we report sites where moonquakes possibly occurred along young lobate scarps in the Schrödinger basin. Our analysis of Lunar Reconnaissance Orbiter and Chandrayaan‐1 images revealed four lobate scarps in different parts of the Schrödinger basin. The scarps crosscut small fresh impact craters (<10–30 m) suggesting a young age for the scarps. A 28 km long scarp (Scarp 1) yields a minimum age of 11 Ma based on buffered crater counting, while others are 35–82 Ma old. The topography of Scarp 1 suggests a range of horizontal shortening (10–30 m) across the fault. Two scarps are associated with boulder falls in which several boulders rolled and bounced on nearby slopes. A cluster of a large number of boulder falls near Scarp 1 indicates that the scarp was seismically active recently. A low runout efficiency of the boulders (~2.5) indicates low to moderate levels of ground shaking, which we interpret to be related to low‐magnitude moonquakes in the scarp. Boulder falls are also observed in other parts of the basin, where we mapped >1500 boulders associated with trails and bouncing marks. Their origins are largely controlled by recent impact events. Ejecta rays and secondary crater chains from a 14 km diameter impact crater traversed Schrödinger and triggered significant boulder falls about 17 Ma. Therefore, a combination of recent shallow moonquakes and impact events triggered the boulder falls in the Schrödinger basin.