is an odd little planet, tiny but incredibly dense, relatively close by but hard to study via telescope. The MESSENGER probe
's latest findings, 57 papers
presented two days ago at conference, bring new weirdness to our understanding of the planet closest to the Sun. Take, for instance, the new revelations about Mercury's core. We always knew that Mercury had a proportionally larger core than Earth does; geologists thought that it might make up a whopping 42% of the planet's volume, in comparison to Earth's 17%. The newest estimate, though, blows that out of the water: We now think the number is 85%. To boot, there appears to be an extremely dense layer more than a hundred miles thick encasing the core, perhaps a shell of iron sulfide. That makes the mantle and crust---to use the memorable analogy of a planetary scientist interviewed by Wired
---like a mere orange ...
