This week’s map is an artistic rendition of the geologic map of Mars designed by the USGS. I used the same geology data as the original map, but I added more topographic and label data, redesigned the visual style, and also edited the key for a more general audience.

One of the most difficult parts of making this map was translating the key into plain English. The original USGS map was designed for geologists, so I had to look up almost all of the vocabulary. For example, my abbreviated definition for a caldera rim was “The rim of an empty magma chamber left behind after a volcanic eruption.” The original description was “Ovoid scarp, outlines single or multiple coalesced partial to fully enclosed depression(s); volcanic collapse, related to effusive and possibly explosive eruptions.”

In many cases my translated labels were approximate or less informative than the original, so I decided to also include the original acronyms for each type of geologic unit. These labels can be cross-referenced to the original data to learn more about each type of geologic formation in scientific terms.

Some of the distinctive geologic features on Mars. 1: Olympus Mons, the largest volcano in the Solar System. 2: Valles Marineris, a deep canyon system more than 4000km long. 3: Hellas Planitia, the largest visible impact crater in the Solar System. 4: Mars is divided geologically into the Northern lowlands (pale green) and Southern highlands (brown). Impact craters formed by colliding asteroids and comets (neon yellow) are scattered across the planet.

I also spent a long time trying out different map projections for this design. I wanted to accurately show how much of the planet was made up of each geologic formation, so in the end I decided to use an Eckert IV equal-area projection. This type of map distorts object outlines, but it preserves the relative area of shapes across the globe. Eckert IV is not great for visualizing the polar regions, so I also added four inset maps to the corners to show each hemisphere of Mars (North, South, East, and West).