Why would our planet be lifeless without an atmosphere?

The atmosphere plays the role of a shield for our planet, protecting it from cosmic radiation. Without the atmosphere, the sun’s ray would reach the planet’s surface without obstacles, and the radiation level would be several times higher than it is now. In addition, without the atmosphere, the planet’s water resources would deteriorate, as happened with Mars. The temperature between day and night would begin to fluctuate greatly (the difference would reach over 100 ° C per day). All this would lead to the complete destruction of all life on our planet.