Distribution of once-watery basins on Mars

This image shows the distribution of a number of deep craters (marked as dots) recently explored as part of a study into groundwater on Mars.

The background image is shown in colours representing topography: reds and oranges are lower elevations, and blues and greens are higher ones.

The study found that the floors of the basins, which sit over 4000 m deep, show signs of past water – the first geological evidence that the Red Planet once had a system of interconnected groundwater-fed lakes that spanned the entire planet.

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