Inner planets are the four planets closest to the Sun: Mercury, Venus, Earth and Mars. They are collectively characterized by a solid surface and small size relative to the outer gas giants.

That's when the planets will make a brief appearance. Tokyo started seeing the parade first, on Feb. 22, according to Star Walk, a sky-gazing app. New York was expected to have the best view of ...

Most of the dense material in the dust cloud is attracted strongly and ends up here. The inner four planets (Mercury, Venus, Earth, and Mars) are rocky and have solid surfaces that can be walked on.