pavelcherepan

What is your view on 'RNA world' hypothesis? If it's correct and self-replicating RNA existed before DNA came to existence, they didn't require living hosts to replicate as there wouldn't have been any. Maybe I was wrong in speaking about viruses, since in this case these RNA would act differently from a modern day virus, which indeed needs a living host to replicate.

Sure. I just specified RNA viruses since according to relatively well accepted RNA-world hypothesis, this is what precluded the more modern DNA-based life. Ooops! Sort of agree. Mostly the discussion is centered around beecee's statement: "certainly we know that at one time there was no life [universally speaking] then there was". The way this is phrased alludes to some relatively sharp boundary between 'living' and 'non-living'. while in fact there seems to have been a progressive transition from one to another.

Normally these days viruses are not considered 'living' even though they are based on an extremely complex self-replicating RNA molecule. Preons that I mentioned are even simpler - they are proteins but they work in such a way that when coming into contact with proteins in your body they will modify them to assume the same structure, causing nasty things like mad cow's disease. Simply put, the boundary between life and non-life is not really well defined at all.

But it's really hard to discuss the question of abiogenesis since it really depends on what we define as 'living'. Otherwise the discussion is quite meaningless.

Well, fair enough. Maybe a bad analogy, but all analogies are. By the way, I totally forgot to ask a very important question - for the purposes of this discussion what do we define as 'life'? Are viruses 'life'? What about preons? Where is the boundary between life and non-life?

Taking it in a literal sense - yes, but on the other hand the term 'abiogenesis' currently refers to a mix of several hypotheses on origin of life, neither of which has gives any understanding of what might have happened. It's like dark energy - it's used as an explanation to an observed phenomena, but no one has any clue as to what it actually is, just guesses.

Just to be a devil's advocate, I'd say that even without any kind of blind faith in creation myths or religion that you mentioned in the other (now closed thread), there can be plenty of valid reasons to question abiogenesis. Personally, I surely don't, but let's face the facts. Apart from a few experiments where simple simulations of conditions in primordial oceans have been done and resulted in some rather complex molecules being formed as the end product, there are no real facts or models of how exactly simple chemistry could've lead to forming of something as complex as DNA or RNA.

I think you're over-reacting a bit. First of all, this is not a great way to start a discussion unless you want it to go downhill from the very start. Secondly, the statement in question holds true in most cases, even where religion is concerned so I doubt that that other member was a creationist.

Sure, but also due to a sheer weigh of numbers, it's highly unlikely to have the first life brought to Earth even from one of the planets of Solar System. There's been quite a few meteorites from Mars found on Earth, most of those came during Late Heavy Bombardment. Those that have been studied so far, haven't shown any sign of life. It's even far less likely that an asteroid from another star system in our galaxy managed to land on the Earth. The odds of that happening are so extremely small that it's not sensible to even consider them as an option while you have an entire planet capable of developing life. And I agree, there's likely life elsewhere in the universe, and Fermi did think so too, hence it's a 'paradox'.

Here you run into both the Occam's razor and Fermi paradox. It's both extremely unlikely for the life to have been brought to us from outside the solar system and also there's no indication that complex life has in fact evolved in one of those billions and billions of other planets. Until we know for certain that abiogenesis was impossible on Earth, we should really stick to the idea that life did in fact form here.

Don't have a citation. Just a generalisation. I agree it's possible that for a short periods there could've been other places where conditions have been just as good. Should paraphrase it to: For majority of history Earth has had the best conditions for life developing. Mars could have had decent atmosphere and liquid water but those ended very early on, water was almost completely gone by 3.5 bya. Venus also could have had conditions to support life, but then very early into the history underwent a runaway greenhouse effect and since then has most certainly been completely lifeless. Moons of giant planets have liquid water oceans, but depending on the size of the moon, there can be too little of valuable nutrients coming into the water which limits the chances of favourable chemical reactions. Also the low temperature slows down reactions.

The reason I can't accept Panspermia is rather simple application of Occam's razor. If life has developed from 'non-life' somewhere, why would we assume it happened somewhere other than the Earth which (in our Solar system) has and always had the best conditions for life developing? I'm not saying it's impossible, but we would have to accept a) life forming first in a less hospitable environment, say Mars; then the life would have b) to survive some asteroid impact that would kick bits of the rock that it lives on into space; then c) the rock would be so lucky as to hit the Earth, then d) life would have to have survived the journey and e) life has to have survived the re-entry into Earth's atmosphere. How likely does this set of coincidences look compared to life simply forming on Earth?

I always find it fascinating that people consider the possibility of panspermia when exactly the same chemical components were available on Earth combined with an environment much more conducive of a complex chemistry.

One of them died in 2005 from heart condition so he was awarded posthumously. Two others are still alive. There are recent interviews with two of them, for example here: https://www.thesun.co.uk/news/9298446/chernobyl-diver-averted-second-blast-devastated-europe/ Here Ananenko does in fact state that they didn't consider it an act of heroism and that they were just doing their job.

Bodies of firefighters were radioactive due to neutron activation. Even after clothes were removed they were still dangerously radioactive https://en.wikipedia.org/wiki/Neutron_activation