Just concluded watching the fifth episode of 'Through the Wormhole' on http://topdocumentaryfilms.com/through-the-wormhole-how-did-we-get-here/
Bless the heart of the wise being who uploaded it! :)
I love the way documentaries give one so much food for thought and make scientists look like rock stars! About this particular one...
The origin of life on Earth is a much speculated and debated scientific and theosophic question. So many scenarios were played out on this episode. My take aways from it were :
- Source 1 of the 'seed' - An experiment conducted by scientists Miller and Ueri in the 50's attempted to replicate the environment during the Hadean period of the Earth involved two flasks, one with evaporating water linked to another with suspended electrodes in it. An electric discharge kept on between the electrodes causes the boiling water to get contaminated with HCn. Also, they found amino acids in the same solutions which are the building blocks of proteins and by extension, life. But even after all these years, proteins were never found in any of the samples of liquid preserved; they remained as unaggregated amino acids itself.
- Source 2 of the 'seed' - Meteors bringing amino acids to Earth - It has been shown by experiment that amino acids present within the meteor would have survived the entry through the Earth's atmosphere. This could then have been the seed of life on Earth. This is another possibility for amino acids to have entered the fray of the beginnings of life on Earth ( in contrast to the above explanation).
- Source 3 of the 'seed' - Mars could have harboured life before Earth - A meteorite that scientists have discovered the remains of in Antarctica is thought to have come from Mars. This meteorite (ALH84001) indicates signs of magnetization. Mars though is without an atmosphere today. This could indicate that it had an atmosphere and a magnetic field sometime in the past. It could have sustained life at that period. It is also logical because Mars, being half the size of Earth would have cooled faster and settled into a stable state much before Earth and hence could have had all the conditions that Earth now has inorder for it to have been inhabitable by life. It is also possible that after some time, around 4 billion years ago, when Mars started cooling even further, slowly losing its magnetic field and atmosphere, the life on Mars could have hitchhiked on a stray meteor broken out of itslef headed for Earth. This could then have been the third source of amino acids into the primordial soup that was present on Earth. We could all be martians!
- Life could have evolved in two different forms on the same planet (Earth) - Life in extreme conditions existing in a so-called shadow ecosystem have been discovered to be compatible with arsenic! In lake Mono in California, the levels of arsenic are around 40,000 times the maximum allowable levels. These organisms were collected and subjected to even higher concentrations of arsenic; they survived nonetheless. The reason arsenic is so toxic to human beings is that it molecule is similar to phosphorous and phosphorous is an integral component of the dna molecule. If As replaces the P molecule in dna, it could kill life. So these organisms are akin to alien life form (alien in the sense that they are different to life as we know it and not that they are from outer space). If life could evolve twice over in different ways on the same planet (Earth), then it is nearly impossible to say that life hasn't evolved anywhere else in the universe!
- Dna is a double helix while rna is a single helix. Rna's building blocks consist of sugar and and base molecules joined together. While it has been possible to create them individually, they have never been able to join them together. At the university of manchester, they tried to create an rna molecule ( something attempted by many many scientists before), but with a twist. This time, they simulated the conditions of Hadean Earth viz. heating, cooling, drying and wetting during the process and created two of the four fundamental building blocks!
The 'seed' for life is stated to be amino acids. In the episode, the sources of this seed are discussed. 'Where could the amino acids have come from?' is addressed.
This model of the start of life is called abiogenesis i.e. creation of biological life from inanimate chemicals under naturally occurring conditions.
My questions :
- How could it be proved that the meteorite was from Mars.
- In the Miller-Ueri experiment all that they used was evaporating water and electricity? Those weren't the only conditions in Hadean Earth I guess.
- Given the Miller-Ueri experiment, we know that only amino acids are not sufficient to create life. What are the other ingredients required for the same??