
First Global Topographic Model of Mercury - Figs
http://www.nasa.gov/feature/first-global-topographic-model-of-mercury
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ygra
Looking at this I wonder how zero elevation is determined for other planets.
Simply the average elevation over the whole planet or are there similar guides
like on Earth where we use water level of the oceans?

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JoeAltmaier
Looks to be mostly craters - are there no volcanoes?

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dhritzkiv
The article does mention several volcanic plains and vents. The craters seem
to be a direct result of volcanic activity.

