Geospatial data from a global survey of martian fan-shaped sedimentary landforms.

Data in this article are related to the research article "The global distribution and morphologic characteristics of fan-shaped sedimentary landforms on Mars". We used globally available image and topographic data to document the location of every fan-shaped sedimentary landform on the surface of Mars. We mapped fan outlines and associated drainage basins and collected a number of morphologic metrics. These data can be used as a boundary condition for studies of global scale studies of Mars, including climate and hydrologic modeling. Data files publicly available on Figshare include point shapefile of fan apices, and polygon shapefiles of fan outlines and drainage basins.

Changing spatial distribution of water flow charts major change in Mars's greenhouse effect.

Early Mars had rivers, but the cause of Mars's wet-to-dry transition remains unknown. Past climate on Mars can be probed using the spatial distribution of climate-sensitive landforms. We analyzed global databases of water-worked landforms and identified changes in the spatial distribution of rivers over time. These changes are simply explained by comparison to a simplified meltwater model driven by an ensemble of global climate model simulations, as the result of ≳10 K global cooling, from global average surface temperature [Formula: see text] ≥ 268 K to [Formula: see text] ~ 258 K, due to a weaker greenhouse effect. In other words, river-forming climates on early Mars were warm and wet first, and cold and wet later. Unexpectedly, analysis of the greenhouse effect within our ensemble of global climate model simulations suggests that this shift was primarily driven by waning non-CO2 radiative forcing, and not changes in CO2 radiative forcing.

Persistence of intense, climate-driven runoff late in Mars history.

Mars is dry today, but numerous precipitation-fed paleo-rivers are found across the planet's surface. These rivers' existence is a challenge to models of planetary climate evolution. We report results indicating that, for a given catchment area, rivers on Mars were wider than rivers on Earth today. We use the scale (width and wavelength) of Mars paleo-rivers as a proxy for past runoff production. Using multiple methods, we infer that intense runoff production of >(3-20) kg/m2 per day persisted until <3 billion years (Ga) ago and probably <1 Ga ago, and was globally distributed. Therefore, the intense runoff production inferred from the results of the Mars Science Laboratory rover was not a short-lived or local anomaly. Rather, precipitation-fed runoff production was globally distributed, was intense, and persisted intermittently over >1 Ga. Our improved history of Mars' river runoff places new constraints on the unknown mechanism that caused wet climates on Mars.