Terraforming other planets is a common theme of sci-fi books and movies; humans need to leave Earth and inhabit new worlds, but first they have to make them livable. These maps are a play on that idea. I used digital elevation models of Mars (where a large northern ocean may actually have existed if/when the planet had a thicker atmosphere) and the Moon, and simply filled them with water to three elevations. I will note that many people have made far prettier versions of terraformed maps (e.g., Mars, Moon). The goal here was to show how changes in sea level relative to datum affect the land-sea balance.

Part of the reason I elected to show multiple sea levels was that the notion of datum on other planetary bodies is somewhat arbitrary. Without an actual ocean, we have to choose what will be considered zero elevation. For rocky planets and moons where we have a global DEM, we tend to use the average equatorial radius of the equipotential surface. So I flooded Mars and the Moon to their respective datums, then added and subtracted a kilometer to the sea level on each.

Without tectonics neither really has distinct continents; the topography and dichotomies result primarily from volcanism and cratering. I image that having only one large continent with a lot of crater lakes/oceans would be pretty bad. Fortunately, it’s not something we need to consider seriously…for now…

Data source: ftp://pdsimage2.wr.usgs.gov/pub/pigpen/