LAUSR

14 Longitudinal striae are a shared characteristic of long run-out landslides and layered ejecta 15 crater deposits. They appear to be a fundamental feature of disintegrated mass flows, 16 but their formation and the required conditions are poorly understood. We evaluated 17 their similarity using spectral analysis and assessed the possibility of a common forma18 tion mechanism. The topography of striae is scale-invariant in the form of a power law 19 relationship of the power spectrum and the derived spectral exponent and amplitude fac20 tor, which are a measure for roughness, show similar correlations on both types of de21 posit. There is no correlation to geologic substrate units, latitude or age. Parameter val22 ues are isotropic in horizontal direction for ejecta deposits and show a weak anisotropy 23 for landslide deposits. Spectral parameter values of substrate topography match well with 24 the values of the superposed deposit, which indicates that roughness is transferred from 25 substrate to deposit surface during emplacement. Testing different geometric models we 26 find that a simple superposition of topography with a semi-deterministic, anisotropic pat27 tern does not reproduce the patterns of our data. We find that phase-locking of a sur28 face with scale-invariant properties creates striae with fractal properties close to our nat29 ural datasets as well as recreating other morphological features that can form alongside 30 striae. Although the transferal of substrate roughness cannot be fully conciliated with 31 conventional flow models, we find that a model that combines advection with lateral dif32 fusion accounts for the unidirectional preservation of phase information and is also con33 sistent with the scale-invariance of striae. 34 Plain Language Summary 35 Longitudinal striae are a prominent surface feature of many types of mass move36 ments, e.g. long run-out landslides on Mars and Earth and layered ejecta crater deposits. 37 It is unclear how they form or whether they form by the same process on the different 38 types of deposits. Using high-resolution remote-sensing data of pristine martian land39 slides and layered ejecta craters, we find that the similar appearance of striae can be con40 firmed by shared morphometric properties. 41 Fourier methods reveal a scale-invariant topography where the roughness of lon42 gitudinal and perpendicular profiles is surprisingly similar. It is even similar to the rough43 ness of the topography outside the striated regions, so that it may be inherited from the 44 underlying substrate. This weak anisotropy in roughness cannot be responsible for the 45 distinct pattern of striae. The latter is probably related to the phases of the Fourier com46 ponents rather than to the amplitudes that are responsible for the roughness. 47 These characteristics include scale-invariance, weakly anisotropic fractal proper48 ties and a roughness that appears to be transferred from the substrate. Testing of for49 mation models shows that a formation process that conserves phase information of to50 pography is most consistent with our data. We suggest that a flow process that combines 51 advection with lateral diffusion of topography can enable phase-locking and is also con52 sistent with the fractal properties of striae. 53