Pluto
	Pluto is the farthest planet from the sun, except when it rotates in the opposite direction of all the other planets, and then it is closer then Neptune. Clyde W. Tombaugh discovered Pluto by accident in 1930. No space craft has ever visited Pluto. Pluto's atmosphere is unknown to humans but it probably contains nitrogen with some methane and carbon monoxide. Since Pluto is so small it can barely be seen with an amateur telescope.