Computer Simulations Suggest Building Blocks of Life Didn't Arrive on Prehistoric Comets (cnn.com) 42
CNN reports:
The popular theory that comets were crucial in kick-starting life on Earth billions of years ago may not hold up, according to new computer simulations that counter decades of scientific thinking. The finding suggests the fragile organic molecules supposedly carried by the icy objects would have been destroyed on impact, upending an established origin of life theory that dates back to at least 1961 [with earlier versions postulated in 1908]...
Early in its history — over 4 billion years ago — Earth may have experienced a period of heavy bombardment from more than 100,000 comets larger than 100 meters (328 feet), according to the new study, published Wednesday in the journal Scientific Reports. Those impacts, however, were mostly too heavy for life-starting molecules to withstand. The team used the latest models of comet formation and evolution to simulate this early planetary period 100,000 times. "Given what we know about surface environments on the early Earth, on average, our simulations found that there were no successful impacts," said lead study author Richard Anslow, who conducted the research while completing his doctorate at the Institute of Astronomy of the University of Cambridge in the United Kingdom... "The typical velocities of these comets when they impact the Earth meant that actually very few, if any, would have been able to deliver intact organic molecules, so comets actually don't seem to be as useful for prebiotic chemistry as was previously thought," Anslow said.
More precisely, 54% of the simulations showed no impact at all, while the remaining 46% had at least one and a "tiny minority" returned up to three collisions, Anslow said. "We can't rule out confidently that there was never a successful impact — there could have been one of these fluke impacts." However, such flukes had to occur in a "perfect location" that already met several important conditions, including the presence of liquid water and other chemicals needed to support life. That combination makes the overall process unlikely, he added.
The article notes his argument that even if a successful impact occurred, it's unlikely an important chemical like hydrogen cyanide (HCN) could survive the impact, and would've dissolved in an ocean impact. Plus, "many other precursor molecules are also needed, such as compounds that contain phosphorus and sulfur, but these are not routinely found in comets, Anslow said." An alternative cosmic source of organic material could have been asteroids, which typically struck Earth more slowly and in greater numbers. Anslow pointed to recent findings on samples from asteroids Bennu and Ryugu, which contain the majority of protein-building amino acids. The recent study also raises another intriguing possibility: While Earth may not have had the ideal conditions to foster HCN from comet impacts, ancient Mars might have been better suited. "Because Mars is much smaller than Earth and further away from the sun, the typical impact velocity of comets is much lower, so while these impacts on Earth were destroying most of the HCN, this wasn't the case so much for Mars," Anslow said. This idea could add another dimension to the long-standing question of whether the red planet once supported life.
While the authors closely analyzed how HCN could have survived comet impact, the chemical may have undergone reactions before the icy bodies entered Earth's atmosphere, said Queenie Chan, an associate professor of Earth sciences at Royal Holloway University of London, who was not involved with the study. This process could have created biologically important compounds, such as those protein building blocks, that are less volatile and more likely to survive.
Early in its history — over 4 billion years ago — Earth may have experienced a period of heavy bombardment from more than 100,000 comets larger than 100 meters (328 feet), according to the new study, published Wednesday in the journal Scientific Reports. Those impacts, however, were mostly too heavy for life-starting molecules to withstand. The team used the latest models of comet formation and evolution to simulate this early planetary period 100,000 times. "Given what we know about surface environments on the early Earth, on average, our simulations found that there were no successful impacts," said lead study author Richard Anslow, who conducted the research while completing his doctorate at the Institute of Astronomy of the University of Cambridge in the United Kingdom... "The typical velocities of these comets when they impact the Earth meant that actually very few, if any, would have been able to deliver intact organic molecules, so comets actually don't seem to be as useful for prebiotic chemistry as was previously thought," Anslow said.
More precisely, 54% of the simulations showed no impact at all, while the remaining 46% had at least one and a "tiny minority" returned up to three collisions, Anslow said. "We can't rule out confidently that there was never a successful impact — there could have been one of these fluke impacts." However, such flukes had to occur in a "perfect location" that already met several important conditions, including the presence of liquid water and other chemicals needed to support life. That combination makes the overall process unlikely, he added.
The article notes his argument that even if a successful impact occurred, it's unlikely an important chemical like hydrogen cyanide (HCN) could survive the impact, and would've dissolved in an ocean impact. Plus, "many other precursor molecules are also needed, such as compounds that contain phosphorus and sulfur, but these are not routinely found in comets, Anslow said." An alternative cosmic source of organic material could have been asteroids, which typically struck Earth more slowly and in greater numbers. Anslow pointed to recent findings on samples from asteroids Bennu and Ryugu, which contain the majority of protein-building amino acids. The recent study also raises another intriguing possibility: While Earth may not have had the ideal conditions to foster HCN from comet impacts, ancient Mars might have been better suited. "Because Mars is much smaller than Earth and further away from the sun, the typical impact velocity of comets is much lower, so while these impacts on Earth were destroying most of the HCN, this wasn't the case so much for Mars," Anslow said. This idea could add another dimension to the long-standing question of whether the red planet once supported life.
While the authors closely analyzed how HCN could have survived comet impact, the chemical may have undergone reactions before the icy bodies entered Earth's atmosphere, said Queenie Chan, an associate professor of Earth sciences at Royal Holloway University of London, who was not involved with the study. This process could have created biologically important compounds, such as those protein building blocks, that are less volatile and more likely to survive.
Re: Still not complete (Score:2)
The person isn't but lots of chemicals and microorganisms are. Plus some things could have melted off prior to impact, gone airborne, or any other possible things.
Re: (Score:3, Interesting)
No that's not what is being said. People please.
The comet theory never held up because that relies on there being another source of life out there. So that is as much as a "god theory" as anything else.
No the most logical theory has always been that the combination of plate techtonics creating mountains, which in turn creates stable wind (all planets with an atmosphere have wind) which eventually leads to lightning, which eventually leads to random particles being created. You've all smelled ozone from a li
Re:Still not complete (Score:5, Insightful)
No that's not what is being said. People please.
Good start.
The comet theory never held up because that relies on there being another source of life out there.
But then you completely miss the point. This isn't about "life came from space," this is about "the building blocks of life came from space." There's a difference, whether you can understand it or not.
Re: (Score:3)
Doesn't everything come from space?
Re: (Score:2)
Everything came from space there was no planet until it coalesced from the debris field left over from the sun's formation. Or so I've been told. Not sure where the space came from, the big bang, I guess.
I'm no Brian May so I may be wrong.
Re: (Score:3)
No, panspermia, actual life coming from space isn't what's being discussed. It's the idea that some or all of the complex organics, like amino acids, could have been delivered by comets. We observe lots of these in space and we know how they can be made there via processes that involve things like lots of UV that might not be as common on the surface of a planet.
Re: (Score:2)
I find it interesting that the article says the building blocks of life didn't arrive on COMETS, but specifically states that there is an alternative chance they might have arrived on ASTEROIDS, which typically struck Earth more slowly and in greater numbers.
Comets create huge craters, many lined with fused quartz and silica from the intense heat. Asteroids often reach the surface or explode in the atmosphere and arrive on Earth as meteorites, many of which can be found sitting on the surface even today.
Re: (Score:2)
And? Whether or not there's some other element involved doesn't change the fact that the other element alone isn't enough. It also needs the building blocks.
This is just "God did it" (Score:1)
Re: (Score:3, Funny)
Re:This is just "God did it" (Score:4, Insightful)
There is no god. But this argument isn't the Prime Mover Conjecture. [wikipedia.org]
Think of an island in the Pacific. Animals arriving from a nearby continent is a reasonable explanation for the native fauna. It doesn't mean that all fauna everywhere on every continent must be explained as immigration from the outside.
If the Earth is an island, then this may in fact be what happened locally, provided it can actually be proved. The real issue with Panspermia [wikipedia.org] is that cosmic distances are so vast and timescales so long that chance arrivals of chemical compounds from elsewhere in the galaxy (or even the wider universe) is exceedingly unlikely and shouldn't be taken seriously with what we currently know.
There's a variant wherein Life As We Know It may have originated on another planet in our solar system, and later injected into Earth. But that's a much weaker idea, because it raises the question why Earth, which is clearly in the most hospitable band for Life As We Know It, wouldn't have evolved its own variant. Instead of waiting for a comet that traveled all the way from a more inhospitable region bringing Life from there.
The good news is that these arguments can be tested scientifically by drilling into the proposed mechanisms directly, no faith needed.
Re: (Score:2)
The moon is smaller in the sky than the sun, and it's getting smaller because it's moving away. 2.5B years ago the moon was noticeably larger.
Let me help make your argument still work: maybe god was planning for this moment and just overshot it by tiny bit? I'm fine with whatever makes you comfy (hopefully we can keep Noah's Ark out of it).
Re: (Score:2)
Science answers questions. We don't get to choose which ones.
Re: (Score:2)
Not a scientist but personally I find the odds of propagating human life from a comet to be astronomical.
But I don't believe in god either, so I'm not sure where this leaves me overall.
Re: This is just "God did it" (Score:2)
There's no theory about the origin of life that doesn't require acceptance of astronomically small odds.
Re: (Score:2)
Why should this be god did it? If you say "Life came to earth from somewhere else" you do not claim "Somewhere else it came from nothing"
Re: (Score:2)
If life came here from comets, where did the life come from, originally, that these comets carried here? Where they carried to other planets from even more comets?
We don't know, but note that the hypothesis of extraterrestrial origin doesn't just move the problem of abiogenesis from Earth A to Earth(like) B. Theories that assume life arose on Earth need to explain how it happened in the conditions existing on primordial Earth (to the extent we understand them). If life (or at least life's basic blocks) came from somewhere else, on comets or asteroids, they may have originated in places with wildly different physical and chemical conditions. This greatly widens the ra
Playing KSP is not the same as running simulations (Score:2)
Re: (Score:2)
Sure thing. Let's put you on a snowball in space then have you blaze through the atmosphere and slam into the ground. This assumes the snowball doesn't explode in the atmosphere. We'll see how you make out.
The issue is not if you'll make it back from space, that part'll happen pretty definitely. The issue is in what condtion.
Re: (Score:2)
I was unaware organic molecules had developed protective gear and spaceships. Thanks for the info!
Comet is a disinfectant, duh (Score:5, Funny)
The scientist's name was Ajax (Score:2)
Wasn't Ajax an Ancient Greek (super) Hero ?
Not going back far enough (Score:2)
Re: (Score:2)
ok thanks! I'll message this doctoral candidate at the literal Cambridge University Institute of Astronomy and tell him he needs to go back in history a little bit farther. Thanks for the tip.
Re: (Score:2)
It's not like they miraculously just appeared.
Mechanisms for that have been demonstrated. Your unawareness of this is irrelevant.
I did it (Score:1)
Hopped into the ol' Delorean, cranked it up to 88 mph, and when I got there...well I found a nice cozy spot, wipped out a vintage dead-tree copy of Playboy (from before it went woke) and well...the rest is history.
You're welcome.
Re: (Score:2)
Uuuhh.....
How did you come back, Professor 1.21 Gigawatts?
Where you've gone there are no roads!
We will find out... (Score:2)
This idea could add another dimension to the long-standing question of whether the red planet once supported life.
...when we colonize Mars.
Which Bias is This? (Score:2)
So, life on Earth appears to be extremely unlikely given our inability to locate any life anywhere else.
Study says... purported source of life would be extremely unlikely to actually result in life. But it could?
An extremely unlikely event doesn't need a cause that was likely to cause it.
In other news (Score:1)
Yeah right.. (Score:2)