What would have happened if the greenhouse gases were totally missing in the earth’s atmosphere?

Earth's most abundant greenhouse gases are $\mathrm{CO}_{2}, \mathrm{CH}_{4}, \mathrm{O}_{3}, \mathrm{CFCs}$, and water vapour. These gases are present near the Earth's surface. They absorb solar energy that is radiated back from the surface of the Earth. The absorption of radiation results in the heating up of the atmosphere. Hence, greenhouse gases are essential for maintaining the temperature of the Earth for the sustenance of life.

In the absence of greenhouse gases, the average temperature of the Earth will decrease drastically, making it uninhabitable. As a result, life on Earth would be impossible.