Mercury is much denser than the other rocky planets in the solar system, and that may be because a collision vaporised its surface and the debris was blown away by the sun
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https://www.newscientist.com/article/2242893-a-large-chunk-of-mercury-may-have-been-blown-away-by-the-sun/?utm_campaign=RSS%7CNSNS&utm_source=NSNS&utm_medium=RSS&utm_content=home
