It was once generally believed by most astronomers that a planet called Vulcan existed amid the orbit of Mercury and the sun.
However, the presence of such a planet was never confirmed.
Ice on Planet Mercury
Despite being so near to the sun, pictures from the Messenger have shown that the planet’s north and south poles are dark and chilly. There’s even proof of ice in the shadows of some pits.
Some astronomers have recommended that comets and meteorites might have brought ice to those frozen areas of the planet.
A Large, Liquid Core
With a radius of 1,100 to 1,200 miles, the center in Mercury secures up about 85 percent of the planet’s radius. Radar photographs taken from Earth exposed that the center is molten liquid rather than solid.
Additionally, Mercury’s center has more iron than any other planet in the solar system.