Water worlds of Solar System

About 71% of our planet is covered in water, so our planet is sometimes called a water world.

Unfortunately, only one planet in our solar system can boast so much liquid water. Nevertheless, let’s fantasize and imagine that Earth is not the only planet covered with water.

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Mean radius: 2,440 km (1516 miles) / 0.3829 Earths
Length of the equator: 15,329 km (9,525 miles)

Surface area: 7.48×107 km2 (2.89×107 mi2) / 0.147 Earths
Mass: 3.3011×1023 kg / 0.055 Earths

This topographical map created by PythonMaps using Python libraries: raster, NumPy, and matplotlib show the first planet from the sun, with the ocean covering ~71% of the surface, like Earth. Data comes from NASA observations.

What a wet Venus look would like

On this topographical map, low altitude areas are shown in dark blue, and high altitude areas are dark red. For comparison, the highest and lowest points on Mercury are about 8.9 km (5.5 miles) apart. On Earth, the highest and lowest points are about 19 km (12 miles) apart.

If we consider that the Earth’s mean radius is 6,371 km (3959 mi), Mercury’s radius is 2,440 km (1516 miles). So the elevation difference is slightly more significant for Mercury than for Earth compared to the overall radius.

Below on the enlarged topographic map of Mercury’s surface, many flow channels on Mercury look like on Earth, but in fact, these channels have been created by lava.

Channels on Mercury mapped

If there were water on Mercury, then after a relatively short period, most of these channels, small islands, and highly irregular coastlines would get worn down by the water and look more like Earth’s landmasses.


Mean radius: 6,052 km (3,761 miles) / 0.9499 Earths
Length of the equator: 15,329 km (9,525 miles)

Surface area: 4.6023×108 km2 (1.7761×108 mi2) / 0.902 Earths
Mass: 4.8675×1024 kg / 0.815 Earths

Scientists believe that Venus might have had oceans several billion years ago, perhaps much like those on Earth.

The topographical map below created by data scientist Alexis Huet shows what a wet Venus looks like with a similar amount of water to Earth.

Map of Venus with water

Flat, volcanic plains cover roughly 80% of the Venusian surface, consisting of 70% plains with crinkle ridges and 10% flat plains. Nearly a thousand impact craters on Venus are equally scattered across the planet’s surface.

Here the physical map of terraformed Venus created by Neneveh.

The physical map of Venus with oceans


Mean radius: 6371.0 km (3958.8 mi)
Length of the equator: 40075.017 km (24901.461 mi)

Surface area: 5.1007×108 km2 (1.9694×108 mi2)
Mass: 5.97237×1024 kg

Oceans, seas, lakes, and rivers of water on Earth are hard to surprise anyone. We are used to seeing our hospitable planet like this.

physical world map

Our planet looks much more unusual without water.


Mean radius: 3389.5 km (2106.1 mi) / 0,5320 Earths
Length of the equator: 21,297 km (13,233 mi)

Surface area: 1.4480 x 108 km2 (0.5591 x 108 mi2) / 0.284 Earths
Mass: 6.4171×1023 kg (0.107 Earths)

The surface of Mars resembles plains, deserts, polar caps of Earth. Above the surface of Mars towers the highest volcano in the solar system – Olympus Mons. Its height is 21 kilometers, which is 2.5 times higher than Mount Everest.

The Martian polar ice caps are mainly composed of water. If only the south polar ice cap melted water to cover the planet’s surface to a depth of 11 meters (36 feet).

Here the map of Mars built by Reddit user Crikey, with the surface 71% covered by water.

Below is the hypothetical map of a terraformed Mars.

Map of terraformed Mars

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