Labels:car | lepton | road | rock | sculpture | sky | tree OCR: STRUCTURE Crust: 180 km thick Mantle 460 km thick Core Radius: 800 km Composition Mercury's high mean density 5.5 grams/cc as compared to 3. .34 grams/cc for the Moon) prompts researchers to speculate that the planet has thin mantle and relatively large iron core approximately 3,600 km (2 200 miles) across. With core composition of 65-70 percent iron (by weight), Mercury is twice as rich in iron as any other planet in the solar system ross