Slope streaks are prevalent and intriguing dark albedo surface features on contemporary Mars. Slope streaks are readily observed in the equatorial and subequatorial dusty regolith regions with low thermal inertia. They gradually fade over decadal timescales. The proposed mechanisms for their formation vary widely based on several physicochemical and geomorphological explanations. The scientific community is divided in proposing both dry and wet mechanisms for the formation of slope streaks. Here we perform a systematic evaluation of the literature for these wet and dry mechanisms. We discuss the probable constraints on the various proposed mechanisms and provide perspectives on the plausible process driving global-scale slope streak formation on contemporary Mars. Although per our understanding, a thorough consideration of the global distribution of slope streaks, their morphology and topography, flow characteristics, physicochemical and atmospheric coincidences, and terrestrial analogies weighs more in favor of several wet mechanisms, we acknowledge that such wet mechanisms cannot explain all the reported morphological and terrain variations of slope streaks. Thus, we suggest that explanations considering both dry and wet processes can more holistically describe all the observed morphological variations among slope streaks. We further acknowledge the constraints on the resolutions of remote sensing data and on our understanding of the Martian mineralogy, climate, and atmosphere and recommend continuous investigations in this direction using future remote sensing acquisitions and simulations. In this regard, finding more wet and dry terrestrial analogs for Martian slope streaks and studying them at high spatiotemporal resolutions can greatly improve our understanding.
We acknowledge the editorial board of Reviews of Geophysics for inviting the submission of this review article. We extend our gratitude to the efforts of the handling editor and the reviewers. We thank NASA, JPL‐Caltech, JPL/Goddard, University of Arizona, Malin Space Science systems, Arizona State University, USGS, ESA/DLR/FU Berlin, and Google Earth for providing various satellite images, maps, and JMARS software free of charge. The paper is theoretical, and no new data have been generated during the work. All the used satellite images of Mars can be rendered on JMARS software using the image ID provided in the respective figure captions, and the image sources have also been duly acknowledged in the respective figure captions. The maps in various figures have been created using ArcGIS version 10.4 (http://desktop.arcgis.com/en/arcmap/latest/get‐started/setup/arcgis‐desktop‐quick‐start‐guide.htm). Although we have cited all the previous research results used in the paper, we here acknowledge the efforts of all those researchers in providing the essential inputs for our study. A. B. acknowledges the Swedish Research Council for supporting his research in cold arid environments. L. S. acknowledges the German Academic Exchange Service (DAAD) for her PhD scholarship.
- slope streaks
- water activity
- formation mechanism