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Seen here is the 70 km wide volcanic dome of Rümker, the target landing site for the Chinese Chang’e 5 sample return mission.
Unlike most features that are formed by impact processes (mountains, craters, mare basins), lunar domes are formed by volcanic processes. Domes like Rümker are typically formed when lava slowly oozes out through a central opening (or caldera). This lava stacks layer by layer and forms multiple small domes, as seen in the featured image.
The highest point of the feature, Mons Rümker, is about 1 km above the local surface, much lower than typical mountains. As apparent in the featured image, domes have very gentle slopes, making a landing mission feasible.
Rümker dome is younger than all previously brought back samples from Apollo and Luna missions. Accurately determining the age of rocks in Rümker dome is key to improving how we use crater distribution to determine lunar feature ages. Which is why every lunar enthusiast is looking forward to the launch of Chang’e 5 in 2019, which will bring back samples from Rümker. A lunar sample return mission after more than 40 years!
Like Rümker, the Gruithuisen domes are volcanically formed too.
For amateur astronomers to observe domes through home telescopes, Sky & Telescope has an excellent guide.
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