http://www.abc.net.au/science/articles/2011/04/29/3203610.htm
The poisonous organic compound Formaldehyde has turned out to have been a deciding factor in enabling life on Earth to survive the gigantic impact that created the Earth`s moon. The impact would have melted the entire crust of the Earth and vaporised any water and organic materials that existed on the planet at that time, but after the Earth cooled, the planet Earth would have been seeded by comets and their impacts on the embattled planet would have brought new organic compounds to re-new the building blocks of life. If the giant impact of the Mars sized planetoid had not happened, then life would have developed sooner on the young Earth;, but it would not be the same as the life we now see around us. With no tides due to the lack of a moon, we would have a totally different climate and totally different lifeforms on the Earth now if any at all. So of course I am grateful for the massive impact that created our companion in the sky and gave the Earth a relatively stable orbit to sustain life as we know it. It is amazing that a poisonous compound that we use to keep dead animals in jars was the instigator for life on this planet after such a cataclysmic impact that vaporised all water and life on the new Earth. But it has been known for a while that comets can harbor organic compounds and ice, but they are carrying even more water than scientist previously believed.
The comet has been used the plot device in movies like Armageddon, and I know they said it was an asteroid, but I believe it was a comet as it was out gassing steam when it faced the sun just like a comet does, and that is what I think. But that movie really did science a disservice as far as the solution to the problem of the large rock heading towards Earth that had enough energy in it to vaporise the worlds oceans and all life on Earth.
The object coming to hit Earth in this YouTube video is only 500 KM in diameter and it has half of the destructive power of the asteroid in the movie Armageddon which is about 1400 KM across and would have twice the destructive ability of this small planetoid. It would release so much energy when impacting into the ocean that the water would be turned into superheated plasma and not steam as it would be too hot at the impact zone, but the rest of the ocean would boil away and all life in the oceans and on land would be vaporised and vanish forever. Sorry about posting a video with the stupid doomsdaytube text on it, but the 2012 thing is everywhere. Let us all raise our glasses to Formaldehyde, the compound responsible for life on this planet we all share.