Final answer:
Mercury's large iron core and significant silicate loss is primarily due to early giant impacts or the vaporization of silicates by the young Sun. Its dense metallic composition generates a weak magnetic field, distinguishing it from other terrestrial planets.
Step-by-step explanation:
Mercury is a body dominated by its iron core. Astronomers believe this unique characteristic is a result of the planet's early history, which involved extreme conditions leading to significant silicate loss. The most plausible explanation is that Mercury, like the Moon, was subjected to giant impacts early in its formation. These colossal collisions could have stripped away a portion of its mantle and crust. Consequently, a significant portion of Mercury's composition is metallic, accounting for about 60% of its total mass, while the remainder is primarily made up of silicates. Another hypothesis suggests that in its formative years, the intense heat from the young Sun may have vaporized much of Mercury’s lighter silicates, leaving behind a planet rich in metals.
Mercury's internal structure is noteworthy not just for its large metal core, which is about the same size as our Moon, but also for the generation of a weak magnetic field. This field is evidence that part of Mercury's core is liquid, which allows for the dynamo effect that produces the magnetic field. This stark difference in composition compared to other terrestrial planets like Earth or Venus, which have a more even metal-to-silicate ratio, continues to intrigue scientists and prompts ongoing research into Mercury's origins and the conditions of the early solar system.