Question

What would likely have happened to Earth if no icy debris had arrived?

Answer 1

Answer:

there will be no glaciers that could melt and can cause the shortage of. water.

Answer 2

If no icy debris had arrived,  the Earth would have released water from volcanic outgassing.

Explanation :

At the beginning before vegetation, the temperature was at high that made hot airs around the planet in the solar system. As earth had icy debris, the existence of water and the temperature level decreasing happened.

For other planets like Venus and Mars, it is believed that volcanic eruption caused created the atmosphere and the gases present comes from interspace comets.