Small-scale topographic irregularities on Phobos: image and numerical analyses for MMX mission

Tomohiro Takemura,Takafumi Niihara,Hideaki Miyamoto,Patrick Michel,Ryodo Hemmi

doi:10.1186/s40623-021-01463-8

Abstract

The mothership of the Martian Moons eXploration (MMX) will perform the first landing and sampling on the surface of Phobos. For the safe landing, the 2.1-m-wide mothership of the MMX should find a smooth surface with at most 40 cm topographic irregularity, however, whose abundance or even existence is not guaranteed based on current knowledge. We studied the highest resolution (a few meters per pixel) images of Phobos for possible topographic irregularities in terms of boulder (positive relief feature) and crater distributions. We find that the spatial number densities of positive relief features and craters can vary significantly, indicating that the surface irregularities vary significantly over the entire surface. We extrapolate the size-frequency distributions of positive relief features to evaluate the surface roughness below the image resolution limit. We find that the probabilities that topographic irregularities are < 40 cm for the areas of 4 × 4 m and 20 × 20 m are > 33% and < 1% for boulder-rich areas and > 88% and > 13% for boulder-poor areas, respectively, even for the worst-case estimates. The estimated probabilities largely increase when we reduce the assumed number of positive relief features, which are more realistic cases. These indicate high probabilities of finding a smooth enough place to land on Phobos’ surface safely.Graphical

Highlights

Introduction Phobos andDeimos, the two moons of Mars, are intriguing for their high scientific interests, and as targets of potential human missions
The Landing Operation Working Team (LOWT) and the Surface Science and Geology Sub Science Team (SSG-SST) of Martian Moons eXploration (MMX) are organized by scientists and engineers to evaluate Phobos’ surface conditions
Assuming that the cm to meter-scale topography on Phobos mostly results from craters and boulders distributions, we might evaluate the topographic roughness by creating an artificial terrain model (DTM) based on such information

Summary

Introduction

Introduction Phobos andDeimos, the two moons of Mars, are intriguing for their high scientific interests, and as targets of potential human missions. Geological studies find that dominant topographic landforms on Phobos’ surface differ in scale and location and are typically classified into three major morphologies: craters, grooves, and boulders (Basilevsky et al 2014). A high-resolution image of an area at least wider than about 1 km2 is needed for the statistical study of the distributions of meter-scale craters and boulders.

Results

Conclusion