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Ryugu asteroid samples contain all DNA and RNA building blocks

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Re: Ryugu asteroid samples contain all DNA and RNA building blocks

#111

Post by asdff »

adrian_b wrote: post #70
make3 wrote: post #34

Earlier quoted context omitted.

read up on the RNA world theory, it's so cool

Parts of the RNA world theory are correct, but other parts are completely bogus and completely illogical. What is correct is that RNA must have existed a very long time before DNA, during which RNA was the only nucleic acid. Moreover, self-replicating RNA must have existed before ribosomes and proteins (where "protein" means a polypeptide that is synthesized using a RNA template). It should be obvious that neither ri…

>However, any RNA-based catalyst could have appeared only at a later time after the establishment of RNA self-replication.

RNA by virtue of its biochemistry is capable of self replication already. Sequence affinity alone is sufficient to drive structure formation. But without a template, structure can also form on its own (example of an open access paper exploring one such mechanism under certain conditions, 1).

This would be enough to kick start things.

1. https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002...

Re: Ryugu asteroid samples contain all DNA and RNA building blocks

#112

Post by pfdietz »

marcosdumay wrote: post #61
8bitsrule wrote: post #45

Earlier quoted context omitted.

The major flaw in Panspermia is that it all had to start somewhere without Panspermia. If it did that there, why not here?

We know 2 things that are apparently incoherent: 1 - Abiogenesis is incredibly rare. We don't know how much exactly, but it's a lot. 2 - Abiogenesis happened on Earth about as soon as it became possible. Where "as soon as" means within half a billion years, but it's still way quicker than its rarity implies. A lot of people think panspermia is what made those two happen. Life had about a full billion years to appear…

People make the inference that "early occurence of life" implies "life must be easy to start". But that inference requires the assumption that the chance of OoL (origin of life) remains mostly constant with time. An alternative would be that the conditions under which life could arise are transient, so life either starts early or not at all. We don't know enough about OoL to rule this out. Some chemicals that might be needed for OoL, like ammonia, are not stable for long. And if life originated in small asteroids, this might have only a few million years for it to occur while they are still warm enough from early short lived radioisotopes like Al-26.

Re: Ryugu asteroid samples contain all DNA and RNA building blocks

#113

Post by pfdietz »

adrian_b wrote: post #77
marcosdumay wrote: post #61

Earlier quoted context omitted.

We know 2 things that are apparently incoherent: 1 - Abiogenesis is incredibly rare. We don't know how much exactly, but it's a lot. 2 - Abiogenesis happened on Earth about as soon as it became possible. Where "as soon as" means within half a billion years, but it's still way quicker than its rarity implies. A lot of people think panspermia is what made those two happen. Life had about a full billion years to appear…

Life cannot appear in any of the small bodies that become meteors, because there is no source of energy for it. Life can appear only on big planets or on big satellites, like the big satellites of Jupiter and Saturn, if they have a hot interior and volcanism. Volcanism brings at the surface substances that are in chemical equilibrium at the high temperatures of the interior, but which are no longer at chemical equili…

> no source of energy

Asteroids early in the solar system would be very radioactive due to short lived isotopes formed during the formation of the solar system. The existence of these isotopes is known from the patterns of decay products found in asteroids. The current guess is the early protoplanetary disk was bombarded by intense GeV-scale protons accelerated in the shock of a nearby supernova, causing large scale transmutation in the disk.

Re: Ryugu asteroid samples contain all DNA and RNA building blocks

#114

Post by stouset »

dylan604 wrote: post #98
foxglacier wrote: post #88

Earlier quoted context omitted.

Wouldn't a big enough asteroid have an inner part which survives entry? You seem to be saying that it's impossible for any meteorite that might have these chemicals to not be completely vaporized which seems doubtful. Have you got a source?

So you survived re-entry. Now, you get to survive impact. Seems like the energy released would also be damaging

Most asteroids have slowed to terminal velocity by the time they impact. It’s not nothing, but it’s mostly going to be relevant to physical processes and not chemical ones.

You might consider that scientists advanced enough in their field to be launching missions to retrieve dust from asteroids are actually aware of basic facts relevant to their field of study.

Re: Ryugu asteroid samples contain all DNA and RNA building blocks

#115

Post by pfdietz »

kjkjadksj wrote: post #64
HarHarVeryFunny wrote: post #13

Earlier quoted context omitted.

It's a sample of one, but I think the takeaway is just that if the nucleobases are present on a random asteroid then they probably commonly occur. Of course as you note it takes a lot more than that to form these into nucleic acids. I would guess there is a more primitive stage in the emergence of life where self-replicating soups (Kaufmann: metabolisms), including things like nucleobases and amino acids, capable of…

The nucleobases can self polymerize into nucleic acids

Since nucleobases contain neither sugars nor phosphates, no they can't.

Re: Ryugu asteroid samples contain all DNA and RNA building blocks

#117

Post by asdff »

adrian_b wrote: post #77
marcosdumay wrote: post #61

Earlier quoted context omitted.

We know 2 things that are apparently incoherent: 1 - Abiogenesis is incredibly rare. We don't know how much exactly, but it's a lot. 2 - Abiogenesis happened on Earth about as soon as it became possible. Where "as soon as" means within half a billion years, but it's still way quicker than its rarity implies. A lot of people think panspermia is what made those two happen. Life had about a full billion years to appear…

Life cannot appear in any of the small bodies that become meteors, because there is no source of energy for it. Life can appear only on big planets or on big satellites, like the big satellites of Jupiter and Saturn, if they have a hot interior and volcanism. Volcanism brings at the surface substances that are in chemical equilibrium at the high temperatures of the interior, but which are no longer at chemical equili…

>Solar energy cannot be used for the appearance of life. Capturing light requires very complex structures that can be developed only after a very long evolution and which cannot form spontaneously in the absence of already existing living beings.

I think that is putting the cart well before the horse. Earliest "life" I would say looks something like a short sequence of random RNA, in some structure (as in secondary), in some solution, among some nucleotides, where brownian motion lead to collision with nucleotides in the chain that grow the chain and/or template off the chain and make a copy. The energy requirements for this sort of pre cell life are far less than cell based life which has to spend energy on cell membrane or wall building. Energy could be quite low, it would just reduce the number of interactions over time. Likely also that this pre cell "life" would not die either so long as it is protected somewhat by cosmic radiation bombarding the chain (although to an extent this is also a ripe source of mutagenic potential).

Re: Ryugu asteroid samples contain all DNA and RNA building blocks

#118

Post by asdff »

dan_hawkins wrote: post #57
0x000xca0xfe wrote: post #8

One longstanding theory is that life first began on Earth when asteroids carrying fundamental elements crashed into our planet long ago. I'm no expert but this sounds strange. Surely those fundamental elements would also form in vast quantities on their own on an entire planet with volcanoes and oceans? Wouldn't a couple asteroids be the literal drop in the ocean in comparison? The missing part is how do they form se…

My layman guess would be that shortly after formation Earth was just a ball of lava that destroyed every organic component so when the surface solidified it was sterile.

It was probably a ball of lava again when the moon formed after the impact too

Re: Ryugu asteroid samples contain all DNA and RNA building blocks

#119

Post by asdff »

Vrondi wrote: post #85
0x000xca0xfe wrote: post #8

One longstanding theory is that life first began on Earth when asteroids carrying fundamental elements crashed into our planet long ago. I'm no expert but this sounds strange. Surely those fundamental elements would also form in vast quantities on their own on an entire planet with volcanoes and oceans? Wouldn't a couple asteroids be the literal drop in the ocean in comparison? The missing part is how do they form se…

Comets is where many astronomers have long thought the ocean came from. Comets are literal drops in our ocean. LOTS of comets. The atmosphere and the Earth at large would have been very different, and being bombarded by many giant space snowballs (along with asteroids) would have contributed materials. The missing part is, um, missing. We still do not know. However, these samples contained building blocks, not actual…

One thing that is beginning to be appreciated is, if you have building blocks, under the right conditions, you also have self replicating RNA.

https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002...

Re: Ryugu asteroid samples contain all DNA and RNA building blocks

#120

Post by ekianjo »

0x000xca0xfe wrote: post #8

One longstanding theory is that life first began on Earth when asteroids carrying fundamental elements crashed into our planet long ago. I'm no expert but this sounds strange. Surely those fundamental elements would also form in vast quantities on their own on an entire planet with volcanoes and oceans? Wouldn't a couple asteroids be the literal drop in the ocean in comparison? The missing part is how do they form se…

> One longstanding theory is that life first began on Earth when asteroids carrying fundamental elements crashed into our planet long ago.

That theory is bullocks. When an asteroid enters the atmosphere and crashes as high speed on the surface, you get a huge amount of energy that creates an explosion and a destruction of most complex chemical material in the process. It's no mistake that these kind of impacts are counted in the same range as multiple atomic or hydrogen bombs.

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