RE: Panspermia theory?
May 23, 2017 at 11:09 am
(This post was last modified: May 23, 2017 at 11:44 am by Anomalocaris.)
Actually, I believe recent analysis of zircon crystals dating to 4.2-4.3 billion years ago suggests the Hadean eon wasn't very hellish at all. Earth had solid crust, a heat trapping atmosphere, moderate temperature and abundant liquid water on the surface as long as 4.4 billion years ago. The earliest known life on earth is 3.8 billion years old. So there is a 500 million year gap between earliest evidence of hospitable environment and earliest evidence of life on earth.
At the end of hadean eon, things on earth actually got much worse. There seemed to have followed a period of unusually heavy meteror bombardment. Age dating of intact ancient rocks shows an abrupt cut off in age coinciding with the end of the period of bombardment, although crustal minerals such as zircon dating to before the bombardment has been found incorporated into rocks that formed after the bombardment. This shows there was a modern looking crust before the bombardment but little if anything sizeable portion of the crust dating to before the bombardment survived the bombardment. But life appear to have arisen very shortly after the end of the bombardment.
This raises intriguing questions.
1. Obviously, did life arrive on the earth through the heavy meteror bombardment? This could account for life appearing to arise so quickly after the bombardment.
2. If life did not arrive but arose through abiogenesis after the bombardment, then it appears abiogenesis is a rapid acting process requiring little time to operate. If that is the case, would life have also arisen in the 300-400 million years of pleasant watery warm environment that appeared to prevail before the bombardment?
3. If life did arise before the bombardment, was it sniffed out by the bombardment, or did it survive the bombardment and reemerge quickly after the bombardment?
4. If life did arise in earth before the bombardment and survive the bombardment, this implies early life is extremely resilient and have good chance of hitching a ride on ejecta from the bombardment to land elsewhere in the solar system.
At the end of hadean eon, things on earth actually got much worse. There seemed to have followed a period of unusually heavy meteror bombardment. Age dating of intact ancient rocks shows an abrupt cut off in age coinciding with the end of the period of bombardment, although crustal minerals such as zircon dating to before the bombardment has been found incorporated into rocks that formed after the bombardment. This shows there was a modern looking crust before the bombardment but little if anything sizeable portion of the crust dating to before the bombardment survived the bombardment. But life appear to have arisen very shortly after the end of the bombardment.
This raises intriguing questions.
1. Obviously, did life arrive on the earth through the heavy meteror bombardment? This could account for life appearing to arise so quickly after the bombardment.
2. If life did not arrive but arose through abiogenesis after the bombardment, then it appears abiogenesis is a rapid acting process requiring little time to operate. If that is the case, would life have also arisen in the 300-400 million years of pleasant watery warm environment that appeared to prevail before the bombardment?
3. If life did arise before the bombardment, was it sniffed out by the bombardment, or did it survive the bombardment and reemerge quickly after the bombardment?
4. If life did arise in earth before the bombardment and survive the bombardment, this implies early life is extremely resilient and have good chance of hitching a ride on ejecta from the bombardment to land elsewhere in the solar system.
