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 self-replicating mechanisms capable of evolution. I doubt an asteroid with a bit of organic dust is enough for that. If such small amounts suffice we should see the formation of new life forms from scratch, today, left and right I think?
The timing of the delivery is what's important here. These building blocks, organic matter, and water would have been depleted in the proto-Earth due to Solar irradiation. There needs to be some mechanism that delivers these ingredients from the outer Solar System. Bombardment by smaller rocks makes the most sense, and was likely triggered by the migration of Giant Planets, leading to a period of heavy bombardment (on a bare Earth -- no oceans, no volcanoes).. https://en.wikipedia.org/wiki/Nice_model
The smaller rocks are composed of those materials in solid state (e.g., ice not water). They are less irradiated as they are further away from the Sun (think the asteroid belt and beyond). Atmospheric entry (if that's what you mean) is irrelevant. What matters here is the transport of materials from a place where they could have formed, to a place where they couldn't.
> Atmospheric entry (if that's what you mean) is irrelevant.
I think the OP meant that Earths magnetic field and atmosphere shields any terrestrial matter far more than than a bare asteroid that has no such protections, so it seems implausible at first glance that these things would develop or survive in open space rather than here.
I guess it depends on how you define life, and whether we'd even recognize it when we see it, assuming we're looking in the right places.
I'd also imagine that any type of chemistry that harvests energy from the environment is liable to find itself as a food source at the bottom of the food chain now that earth is teeming with life.
I think that self-replication, and ability to harvest chemicals and energy from the environment to make more of what you're built of, is the point of complexification of chemistry that is best considered as the most primitive form of life. From there you can go on to things that are capable of encoding structure and more complex chemical factories.
I suppose one signature of these earliest type of "emergent life" chemistries would be localized concentrations of things like these nucleobases that we know are the building blocks of life as we know it, but there may be other types of self-replicating chemistries that emerge too, that don't lead anywhere.
He's an interesting person overall - the long interview is well worth watching if you haven't already seen it - but the relevance here are his experiments with the emergence of self-replicating computer programs out of random components.
His starting point is entire "programs" (random sequences of 64 characters, of which only ~7 have any meaning - the program "statements" of the BF language), so perhaps more suggestive of this RNA world stage, but perhaps also of what came before it when there may have been collectively self-replicating soups consisting of discrete components rather then entire structural encodings.
The bigger the pool the harder to create it here on Earth without introducing problems. For example, take a prion. Hard as hell to actually get rid of, how do you know you've not actually introduced something like this to your sterile pool that's going to make it do things you don't expect.
I don't think you'd want a single homogeneous "large pool", but rather a large variety of different types of micro-environment, including all those that have been suggested as possible environments for the emergence of life - the chemical and physical environments of hydrothermal vents, volcanic hot springs, shorelines, different types of rocks, clays, etc. You'd want to have environments that included all energy sources present on earth (solar, lightening, geothermal), all forms of mechanical agitation/mixing (hydrothermal, waves), etc, etc.
Yeah, but it seems impossible to experiment on the scale that would have happened in nature where there would have been millions of localized "test tube experiments" ongoing for millions of years.
Of course people can, and do, try to replicate early earth environments and self-assembling proto-cells, but I'm not sure how intellectually satisfying any self-replication success from these "designer experiments" would be, unless perhaps done on such a large scale (simulation vs test tube?) that any conclusions could be made about what likely happened in nature - just how specific do the conditions need to be?
My personal theory is that the conditions for life are plentiful in the universe but it probably took an unbelieavable number of random chemical/mechanical events to form the first proto-lifeform.
The discovery comes after these building blocks of life were detected on another asteroid called Bennu, suggesting they are abundant throughout the solar system.
We've barely started to look, other than on Mars, and notably we are seeing possible signs there. There may even still be primitive life there.
If we do find life of Mars, or say Europa, i.e. in the very first places we look for it, that that would be highly suggestive that it is extremely common (at least in primitive form).
This theory is called panspermia [1] and it has several alternatives. One of the most extreme is that in the very early Universe, these building blocks could spread easily because the ambient temperature of the Universe was significantly higher than it is now. This isn't the most popular version.
The most popular is that asteroids and other interstellar bodies spread the building blocks, be it anywhere from amino acids to more complex building blocks. As evidence of this, there are hundreds of surviving asteroids on Earth that have been positively identified as having coming from Mars, which is pretty crazy because that basically takes a violent impact throwing debris into space and it making it to us many times over.
Part of the evidence for all this is how soon after the Earth formed that life appeared. We have positive evidence that this only took a few hundred million years. That's kinda crazy if you think about it. Also consider that the oceans likely came after the EArth formed.
Our galaxy is over 10 billion years old. The Sun is less than 5 billion years old. So that's 5+ billion years for stars and Solar Systems to form, evolve and die before the first fusion reaction in the Sun. Some of this needed to happen just to form heavy elements that are relatively abundant. Even that's kind of crazy. Heavy elements like lead, uranium and gold take relatively rare and violent events to eject material into space and make it to us. So what else made it to us?
Admittedly, am layman, have only heard numerous sciencey folks talk about it, but we've found all these basic components in space already, naturally occurring, and while we've never to my knowledge recreated actual, genuine abiogenesis, we have observed every process required for abiogenesis to be a reasonable explanation for the origin of life.
As to your question on we should see the formation of new life everywhere, well, if we looked hard enough we might? The answer is competitive exclusion. Abiogenesis would've occurred on a remarkably clean earth: any life now emerging from the proverbial space dust is both almost certainly not preconfigured for this biosphere, and is instantly drowning in competing microorganisms that are. Anything that does form is likely quickly killed either by natural forces or competing organisms. Meanwhile, our life goes everywhere: We've found living bacteria on the outside of the ISS!
I wonder how they prevent contamination of the containers used to collect and store samples.
I assume they have to be ultra clean in every sense of the word 'clean' with the cavity pulled to a vacuum. And also the equipment that collects the sample and puts it into the canister has to be clean as well.
> Researchers from Imperial College London have discovered that a space-returned sample from asteroid Ryugu was rapidly colonized by terrestrial microorganisms, even under stringent contamination control measures.
> As described in the discussion of the journal paper, all samples received from JAXA have undergone the initial description, storage, and sealing in dedicated containers under a nitrogen atmosphere. The samples are distributed to researchers without exposure to the Earth's atmosphere. The possibility of microbial contamination is therefore considered extremely low. In addition, organic and microbial contamination assessment of the environment at the curation facilities within JAXA (clean chamber) in which the Ryugu sample grains undergo the initial description are conducted 1 ~ 2 times a year. It has been confirmed and reported that the concentration of organic matter is at or below the same level as that of the OSIRIS-REx asteroid return sample glove box at the NASA Johnson Space Center, and that no microbial colonies have been detected in the microbial contamination assessment conducted with swabbing and culture medium (Yada et al., 2023). Based on these facts, we agree that the microbial contamination described in the paper did not occur during a process within JAXA, but under the laboratory environment of the allocated researchers.
It contains nucleobases. But does it contain ribose, or ribose linked to the nucleobases, or to phosphates? And more generally, does it also contain a grab bag of related chemicals that are not building blocks? The existence of such blocks as minor constituents of a soup of random chemicals doesn't mean much, especially as the concentration of any such constituent declines exponentially with its complexity.
All it means is you can say "if life is rare, it's not because these specific small chemicals can't be produced". Which is a rather weak thing to say. It doesn't imply life isn't rare, or that further advancement the existence of these small building blocks is easy or inevitable.
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 collective replication/expansion exist, before we get anything as sophisticated as nucleic acids and structural encoding.
Fascinating that all five nucleobases were found in Ryugu samples. The fact that these formed abiotically in an asteroid environment strengthens the case that the building blocks of life are common throughout the solar system. The amino acid findings from the same samples were already compelling, but having the complete nucleobase set is a different level of evidence.
Doesn't multi-world interpretation pretty much answer how life originated?
I mean, even if the starting state require to bootstrap life have impossibly low chance to happen random, multi-world interpretation implies that there will be some worlds where it happened, and observation of life is only possible in such worlds..
Surface sample:
Hayabusa2's sampling device is based on Hayabusa's. The first surface sample retrieval was conducted on 21 February 2019, which began with the spacecraft's descent, approaching the surface of the asteroid. When the sampler horn attached to Hayabusa2's underside touched the surface, a 5 g (0.18 oz) tantalum projectile (bullet) was fired at 300 m/s (980 ft/s) into the surface.[72] The resulting ejected materials were collected by a "catcher" at the top of the horn, which the ejecta reached under their own momentum under microgravity conditions.
Sub-Surface Sample:
The sub-surface sample collection required an impactor to create a crater in order to retrieve material under the surface, not subjected to space weathering. This required removing a large volume of surface material with a powerful impactor. For this purpose, Hayabusa2 deployed on 5 April 2019 a free-flying gun with one "bullet", called the Small Carry-on Impactor (SCI); the system contained a 2.5 kg (5.5 lb) copper projectile, shot onto the surface with an explosive propellant charge. Following SCI deployment, Hayabusa2 also left behind a deployable camera (DCAM3)[Note 1] to observe and map the precise location of the SCI impact, while the orbiter maneuvered to the far side of the asteroid to avoid being hit by debris from the impact.
It was expected that the SCI deployment would induce seismic shaking of the asteroid, a process considered important in the resurfacing of small airless bodies. However, post-impact images from the spacecraft revealed that little shaking had occurred, indicating the asteroid was significantly less cohesive than was expected.[76]
Duration: 36 seconds.0:36
The touchdown on and sampling of Ryugu on 11 July
Approximately 40 minutes after separation, when the spacecraft was at a safe distance, the impactor was fired into the asteroid surface by detonating a 4.5 kg (9.9 lb) shaped charge of plasticized HMX for acceleration.[56][77] The copper impactor was shot onto the surface from an altitude of about 500 m (1,600 ft) and it excavated a crater of about 10 m (33 ft) in diameter, exposing pristine material.[15][32] The next step was the deployment on 4 June 2019 of a reflective target marker in the area near the crater to assist with navigation and descent.[33] The touchdown and sampling took place on 11 July 2019.[34]
The missing part is how do they form self-replicating mechanisms capable of evolution. I doubt an asteroid with a bit of organic dust is enough for that. If such small amounts suffice we should see the formation of new life forms from scratch, today, left and right I think?
They’d also have to contend with re-entry.
I think the OP meant that Earths magnetic field and atmosphere shields any terrestrial matter far more than than a bare asteroid that has no such protections, so it seems implausible at first glance that these things would develop or survive in open space rather than here.
I'd also imagine that any type of chemistry that harvests energy from the environment is liable to find itself as a food source at the bottom of the food chain now that earth is teeming with life.
I think that self-replication, and ability to harvest chemicals and energy from the environment to make more of what you're built of, is the point of complexification of chemistry that is best considered as the most primitive form of life. From there you can go on to things that are capable of encoding structure and more complex chemical factories.
I suppose one signature of these earliest type of "emergent life" chemistries would be localized concentrations of things like these nucleobases that we know are the building blocks of life as we know it, but there may be other types of self-replicating chemistries that emerge too, that don't lead anywhere.
https://www.youtube.com/watch?v=rMSEqJ_4EBk
He's an interesting person overall - the long interview is well worth watching if you haven't already seen it - but the relevance here are his experiments with the emergence of self-replicating computer programs out of random components.
His starting point is entire "programs" (random sequences of 64 characters, of which only ~7 have any meaning - the program "statements" of the BF language), so perhaps more suggestive of this RNA world stage, but perhaps also of what came before it when there may have been collectively self-replicating soups consisting of discrete components rather then entire structural encodings.
I've read about experiments like this but only at lab beaker scale.
Of course people can, and do, try to replicate early earth environments and self-assembling proto-cells, but I'm not sure how intellectually satisfying any self-replication success from these "designer experiments" would be, unless perhaps done on such a large scale (simulation vs test tube?) that any conclusions could be made about what likely happened in nature - just how specific do the conditions need to be?
We've barely started to look, other than on Mars, and notably we are seeing possible signs there. There may even still be primitive life there.
If we do find life of Mars, or say Europa, i.e. in the very first places we look for it, that that would be highly suggestive that it is extremely common (at least in primitive form).
You don't need to be an expert to be curious. Many here would surely like to know more. That's why non-IT stories are upvoted in the first place.
The most popular is that asteroids and other interstellar bodies spread the building blocks, be it anywhere from amino acids to more complex building blocks. As evidence of this, there are hundreds of surviving asteroids on Earth that have been positively identified as having coming from Mars, which is pretty crazy because that basically takes a violent impact throwing debris into space and it making it to us many times over.
Part of the evidence for all this is how soon after the Earth formed that life appeared. We have positive evidence that this only took a few hundred million years. That's kinda crazy if you think about it. Also consider that the oceans likely came after the EArth formed.
Our galaxy is over 10 billion years old. The Sun is less than 5 billion years old. So that's 5+ billion years for stars and Solar Systems to form, evolve and die before the first fusion reaction in the Sun. Some of this needed to happen just to form heavy elements that are relatively abundant. Even that's kind of crazy. Heavy elements like lead, uranium and gold take relatively rare and violent events to eject material into space and make it to us. So what else made it to us?
[1]: https://en.wikipedia.org/wiki/Panspermia
As to your question on we should see the formation of new life everywhere, well, if we looked hard enough we might? The answer is competitive exclusion. Abiogenesis would've occurred on a remarkably clean earth: any life now emerging from the proverbial space dust is both almost certainly not preconfigured for this biosphere, and is instantly drowning in competing microorganisms that are. Anything that does form is likely quickly killed either by natural forces or competing organisms. Meanwhile, our life goes everywhere: We've found living bacteria on the outside of the ISS!
I assume they have to be ultra clean in every sense of the word 'clean' with the cavity pulled to a vacuum. And also the equipment that collects the sample and puts it into the canister has to be clean as well.
The logistics aren't obvious to me at all
https://phys.org/news/2024-11-ryugu-asteroid-sample-rapidly-...
> Researchers from Imperial College London have discovered that a space-returned sample from asteroid Ryugu was rapidly colonized by terrestrial microorganisms, even under stringent contamination control measures.
https://www.isas.jaxa.jp/en/topics/003899.html
> As described in the discussion of the journal paper, all samples received from JAXA have undergone the initial description, storage, and sealing in dedicated containers under a nitrogen atmosphere. The samples are distributed to researchers without exposure to the Earth's atmosphere. The possibility of microbial contamination is therefore considered extremely low. In addition, organic and microbial contamination assessment of the environment at the curation facilities within JAXA (clean chamber) in which the Ryugu sample grains undergo the initial description are conducted 1 ~ 2 times a year. It has been confirmed and reported that the concentration of organic matter is at or below the same level as that of the OSIRIS-REx asteroid return sample glove box at the NASA Johnson Space Center, and that no microbial colonies have been detected in the microbial contamination assessment conducted with swabbing and culture medium (Yada et al., 2023). Based on these facts, we agree that the microbial contamination described in the paper did not occur during a process within JAXA, but under the laboratory environment of the allocated researchers.
> The five-carbon sugar ribose and, for the first time in an extraterrestrial sample, six-carbon glucose were found.
The soup does matter, as does finding that the ingredients are everywhere.
It doesn't demonstrate the existence of Shakespeare's works, but it's a building block that's good to know exists.
This is absolutely a good finding to have in your pocket.
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 collective replication/expansion exist, before we get anything as sophisticated as nucleic acids and structural encoding.
I mean, even if the starting state require to bootstrap life have impossibly low chance to happen random, multi-world interpretation implies that there will be some worlds where it happened, and observation of life is only possible in such worlds..
Sub-Surface Sample: The sub-surface sample collection required an impactor to create a crater in order to retrieve material under the surface, not subjected to space weathering. This required removing a large volume of surface material with a powerful impactor. For this purpose, Hayabusa2 deployed on 5 April 2019 a free-flying gun with one "bullet", called the Small Carry-on Impactor (SCI); the system contained a 2.5 kg (5.5 lb) copper projectile, shot onto the surface with an explosive propellant charge. Following SCI deployment, Hayabusa2 also left behind a deployable camera (DCAM3)[Note 1] to observe and map the precise location of the SCI impact, while the orbiter maneuvered to the far side of the asteroid to avoid being hit by debris from the impact.
It was expected that the SCI deployment would induce seismic shaking of the asteroid, a process considered important in the resurfacing of small airless bodies. However, post-impact images from the spacecraft revealed that little shaking had occurred, indicating the asteroid was significantly less cohesive than was expected.[76]
Duration: 36 seconds.0:36 The touchdown on and sampling of Ryugu on 11 July Approximately 40 minutes after separation, when the spacecraft was at a safe distance, the impactor was fired into the asteroid surface by detonating a 4.5 kg (9.9 lb) shaped charge of plasticized HMX for acceleration.[56][77] The copper impactor was shot onto the surface from an altitude of about 500 m (1,600 ft) and it excavated a crater of about 10 m (33 ft) in diameter, exposing pristine material.[15][32] The next step was the deployment on 4 June 2019 of a reflective target marker in the area near the crater to assist with navigation and descent.[33] The touchdown and sampling took place on 11 July 2019.[34]
https://en.wikipedia.org/wiki/Hayabusa2#Sampling