Here's why:

* Cosmic rays originate outside our solar system. They are high-energy particles from distant sources like supernova explosions and active galactic nuclei.

* Mars is not a gateway for cosmic rays. It's a planet in our solar system, and its atmosphere and magnetic field act as a barrier to cosmic rays, just like Earth's.

* Cosmic rays can reach both Earth and Mars. They travel through space and interact with the planets' atmospheres and magnetic fields.

Think of it this way: Imagine cosmic rays as rain. Mars is like another umbrella in the same storm, not a path for the rain to reach Earth.