Les Kuriata asked:
Firstly, keep up the great work in putting out the Astronomy Podcast. I have only recently discovered the Podcast and am currently working my way through previous episodes.
Anyway, back to my question. We live is an amazing Solar System in which nothing surprises me anymore, however there is one thing that has always bugged me regarding the origins on water on planet Earth. My understanding is that water arrived on Earth in the early solar system in the form of comet like bodies as part of a extensive bombardment. Is this scenario widely accepted and unchallenged or are there other possibilities as to the presence of water on the Earth? If the bombardment scenario is correct, could anyone come up with some numbers to underpin this theory. For example, taking a estimation of the amount of water which could have arrived on one body, how many impacts and for how long would the bombardment have had to endured in order to account for all the water on our planet?
Kind regards, Les Kuriata
We put this question to Dr Jonathan Shanklin, director of the Comet sections of the British Astronomical Association and the Society for Popular Astronomy...