what all bombarded on earth during this phase?
But how do we know that comets have ice?
Did you remember any missions that humans did to study comets which we learnt in previous chapters.
Did you remember one comet for every 75 years we can watch?
If earth is too hot all water will vaporize again, if it is too cool everything will be frozen. So how did the water cycle continue for longtime and we got oceans?