Here's why:
* Definition of an atmosphere: An atmosphere is a layer of gases that surrounds a celestial body. It's held in place by the body's gravity.
* Outer space is essentially a vacuum: Outer space is incredibly vast and almost completely devoid of matter. There are a few particles floating around, but the density is so low that it's considered a near-perfect vacuum.
* No gravity to hold gases: There's no significant gravitational pull in outer space to hold onto any gases, even if they were present.
However, there are extremely thin and diffuse clouds of gas and dust scattered throughout space, known as interstellar medium. These are incredibly sparse and don't qualify as an atmosphere in the traditional sense.
So, while we can't say outer space has an "atmosphere" like Earth, it's not entirely empty. It's just incredibly thin and spread out.
