Research shows that comet impacts may have led to life on Earth—and perhaps elsewhere

August 18, 2015
comet
The momentum of light (along with the solar wind) creates the tails of comets by pushing material off the comets. Credit: European Southern Observatory

Comet impact on Earth are synonymous with great extinctions, but now research presented at the Goldschmidt geochemistry conference in Prague shows that early comet impact would have become a driving force to cause substantial synthesis of peptides - the first building blocks of life. This may have implications for the genesis of life on other worlds.

Dr Haruna Sugahara, from the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) in Yokahama, and Dr Koichi Mimura, from Nagoya University performed a series of experiments to mimic the conditions of impacts on the Early Earth at the time when life first appeared, around 4 billion years ago.

They took frozen mixtures of amino acid, water ice and silicate (forsterite) at cryogenic condition (77 K), and used a propellant gun to simulate the shock of a . After anyalysing the post-impact mixture with gas chromatography, they found that some of the had joined into short peptides of up to 3 units long (tripeptides).

Based on the experimental data, the researchers were able to estimate that the amount of peptides produced would be around the same as had been thought to be produced by normal terrestrial processes (such as lighting storms or hydration and dehydration cycles).

According to Haruna Sugahara:

"Our experiment showed that the cold conditions of comets at the time of the impacts were key to this synthesis, as the type of peptide formed this way are more likely to evolve to longer peptides.

This finding indicates that comet impacts almost certainly played an important role in delivering the seeds of life to the early Earth. It also opens the likelihood that we will have seen similar chemical evolution in other extraterrestrial bodies, starting with cometary-derived peptides.

Within our own solar system the icy satellites of Jupiter and Saturn, such as Europa and Enceladus are likely to have undergone a similar comet bombardment. Indeed, the NASA stardust mission has shown the presence of the in comets.

The production of short peptides is the key step in the chemical evolution of complex molecules. Once the process is kick-started, then much less energy is needed to make longer chain peptides in a terrestrial, aquatic environment.

Comet impacts are normally associated with mass extinction on Earth, but this works shows that they probably helped kick-start the whole process of life in the first place".

Commenting, Professor Mark Burchell (University of Kent, UK) said: "This is a new piece of work which adds significantly to the exciting field of the origin of complex molecules on the Earth. It has long been known that ices under shock can generate and break bonds in complex organics. The detection of amino acids on comet 81P/Wild2 by the NASA Stardust mission in the last decade, and the now regular exciting news from the Rosetta mission to comet 67P/Churyumuv-Gerasimenko indicates that comets are a rich source of materials. Two key parts to this story are how are initially generated on comets and then how they survive/evolve when the comet hits a planet like the Earth. Both of these steps can involve shocks which deliver energy to the icy body. For example, Zita Martins and colleagues recently showed how complex organic compounds can be synthesised on icy bodies via shocks. Now, building on earlier work, Dr Sughara and Dr Mimura have shown how amino acids on icy bodies can be turned into short peptide sequences, another key step along the path to life".

Explore further: Scientists discover cosmic factory for making building blocks of life

More information: Glycine oligomerization up to triglycine by shock experiments simulating comet impacts

H. SUGAHARA1* AND K. MIMURA2 1Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, 237-0061, Japan (*correspondence) 2Nagoya University, Nagoya, 464-8601, Japan

ABSTRACT
Abiotic peptide synthesis is one of key steps in prebiotic chemistry. Peptides are building block of proteins and also play a role as a catalyst to form other biomolecules (e.g., [1]). Although varieties of mechanisms for abiotic peptide synthesis in terrestrial environments have been proposed, extraterrestrial contribution, that is, cometary and asteroidal impacts has attracted little attention. Considering that the frequency of the extraterrestrial impacts on the early Earth was greater than present day and comets and chondrites contain amino acids (e.g., [2] [3]), extraterrestrial impacts could be a candidate for peptide synthesis.
In order to examine the feasibility of abiotic peptide synthesis by comet impacts, we conducted shock experiments on frozen mixtures of amino acid, water ice and silicate (forsterite) at cryogenic condition (77 K). In the experiments, the frozen amino acid mixture was sealed into a capsule and put into a container filled with liquid nitrogen to be kept at 77 K during the shock experiments. A vertical propellant gun was used to give impact shock.
The amounts of remaining amino acid and synthesized peptides in the recovered shocked samples were analyzed with gas chromatographs after the extraction and the derivatization. The results showed that amino acid was oligomerized into peptides up to tripeptide by impact shock. Furthermore, the yield of linear dipeptide was much higher than that of cyclic diketopiperazine. These results were contrasting to the results of shock experiments at room temperature, in which they resulted in the formation of comparable amount of cyclic peptides to linear peptides [4].
These results indicate that the cryogenic condition at impact shock is a key for the formation of linear peptide. Linear peptides are more useful than cyclic peptides for further elongation of peptide chain. Thus, comet impacts might have played an important role in chemical evolution by delivering linear peptides to the early Earth. [1] Barbier et al. (1993) J. Mol. Evol. 37, 554-558. [2] Elsila et al. (2009) Meteorit. Planet. Sci. 44, 1323-1330. [3] Burton et al. (2012) Chem. Soc. Rev. 41, 5459-5472. [4] Blank et al. (2001) Orig. Life Evol. Biosph. 31, 15-51

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22 comments

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EnsignFlandry
1 / 5 (1) Aug 18, 2015
What is really needed is evidence of comets, or something, leading to RNA or DNA, even a small nucleotide.
JVK
1 / 5 (7) Aug 19, 2015
What is really needed is evidence of comets, or something, leading to RNA or DNA, even a small nucleotide.


Agreed.

SARCASM ALERT: Until that experimental evidence becomes available, theorists can continue to assume that complex molecules are initially generated on comets and that they somehow survive and automagically evolve into intelligent humans. Perhaps this occurs via a series of mutations that link RNA-mediated gene duplication and nutrient-dependent RNA-mediated amino acid substitutions to the stability of organized genomes in all living genera.

Until then experimental evidence shows only that the sun's biological energy protects all life on earth from virus-induced entropic elasticity, which leads to genomic entropy when ecological variation limits the food supply.

Currently all experimental evidence confirms Schrodinger's claims in 1944. He linked sunlight from quantum physics to quantum biology and quantum smell to quantum consciousness.
JVK
1 / 5 (6) Aug 19, 2015
Re: He linked sunlight from quantum physics to quantum biology and quantum smell to quantum consciousness.

The sequencing of the octopus genome appears to have confirmed the role of achiral glycine in biophysically constrained cell type differentiation, which is nutrient-dependent and pheromone-controlled, via the chemistry of RNA-mediated protein folding in species from microbes to man.

In all vertebrates, the insertion of glycine in the GnRH decapeptide stabilizes their organized genomes via the finely tuned balance between nutrient uptake and the physiology of reproduction.

The sequencing of the octopus genome linked the epigenetic landscape to the physical landscape of DNA via olfaction and the nutrient-dependent de novo creation of receptors that enable nutrient uptake and ecological adaptation in marine invertebrates and primates.

See: Role of olfaction in Octopus vulgaris reproduction http://www.scienc...14004006
JVK
1 / 5 (6) Aug 19, 2015
Re: marine invertebrates and primates

And all other genera that must eat to survive and reproduce.

http://dx.doi.org...ure14668 The octopus genome and the evolution of cephalopod neural and morphological novelties

Excerpt: "Transposable element activity has been implicated in the modification of gene regulation across several eukaryotic lineages29. We found that in the nervous system, the degree to which a gene's expression is tissue-specific is positively correlated with the transposon load around that gene (r2 values ranging from 0.49 in the optic lobe to 0.81 in the subesophageal brain; Extended Data Fig. 8 and Supplementary Note 4). This correlation may reflect modulation of gene expression by transposon-derived enhancers or a greater tolerance for transposon insertion near genes with less complex patterns of tissue-specific gene regulation."

But, look over there -- it's a comet!
Da Schneib
5 / 5 (5) Aug 19, 2015
Fascinating. So, if this is correct, then, the first organic molecules were formed on comets as the comets accreted, and then deposited on Earth's surface during the Late Heavy Bombardment 4.1-3.8 billion years ago, during the late Eoarchaean and early Paleoarchean, at which time additional chemosynthesis occurred due to the impact. Interestingly, the oldest life fossil forms appear in the late Paleoarchean, some four hundred million years after the end of the LHB.
Torbjorn_Larsson_OM
5 / 5 (5) Aug 19, 2015
Interesting! Seems one can get peptides in about every non-equilibrium wet chemistry (dry/wet cycles, impacts, …).

@ EF: "What is really needed".

Not for astrobiology. All pathways that participate are of interest. Conversely one chemical pathway can inform on another. Incidentally, this last day precisely that was demonstrated, in impacts no less. (Since the Keller et al pathway to glucose/pentose means the nucleotide salvage pathway 'only' lack nucleobases in a disequilibrium situation.)

"They found the formation of a far larger variety of life's building blocks, including two kinds of nucleobases and nine kinds of proteinogenic amino acids. The results suggest a new route for how genetic molecules may have first formed on Earth." [ http://www.scienc...5751.htm ]

If you are adamant on nucletides, IIRC that was demonstrated as far back as 2009. (Check Wikipedia on OOL.)
Torbjorn_Larsson_OM
5 / 5 (5) Aug 19, 2015
@Da Schneib: "during the Late Heavy Bombardment".

Here is an interesting summary of years of painstaking research, now at the level of individual atoms, into the Jack Hill zircons and what they can tell us of crust and ocean fromation from John Valley himself: http://www.minsoc...1355.pdf

Turns out that the oldest ~ 4.40 Ga bp [billion years before present] zircon must be dismissed for the latter (but verify a crust), but figure 17 shows how a cluster of undamaged crystals verify an ocean before 4.3 Ga bp.

There is scatter, but one can even imagine a gradual hydration of Earth. That would fit with the recent agreeing clocks for dating the Moon producing collision which use an accumulating impact veneer, and with the resulting water content from Vesta type impactors.

[tbcdt]
Torbjorn_Larsson_OM
4.8 / 5 (5) Aug 19, 2015
[ctd]

With a collision ~ 90 Ma after the protoplanetary disk formation, that would put a hot, dry Earth emerging ~ 4.47 Ga bp, with a survivable (Late Heavy Bombardment scale) impact flow some 4.45 Ga bp. Perhaps the crust thought so too. =D

"the oldest life fossil forms appear in the late Paleoarchean".

That is an upper limit only, verified by that it is the earliest sediments that so far can yield such information. If we are lucky the Jack Hill zircon series can inform of a crust with biocycled carbon, or perhaps the Moon poles's impact record (from Earth ejecta), but it is young and iffy science. (There is a review that is looking into the preliminaries to do the first. It will take years...)

So who can say? At the moment I find the early habitable Earth a neat way to place the first split between Bacteria and Archaea, which is dated to 4.25 Ga bp in Timetree. [ http://www.timetr.../2/2157? ]
Dr_ Rock
3.9 / 5 (7) Aug 19, 2015
What is really needed is evidence of comets, or something, leading to RNA or DNA, even a small nucleotide.


Agreed.


Comets do not lead to RNA or DNA. Start to phrase your remarks scientifically and perhaps you can start a proper discussion.
Some progress for you morons: http://www.nasa.g...boratory
Dr_ Rock
4 / 5 (8) Aug 19, 2015
SARCASM ALERT: Until that experimental evidence becomes available, theorists can continue to assume that complex molecules are initially generated on comets and that they somehow survive and automagically evolve into intelligent humans. Perhaps this occurs via a series of mutations that link RNA-mediated gene duplication and nutrient-dependent RNA-mediated amino acid substitutions to the stability of organized genomes in all living genera.


If you'd actually read the above article ("Once the process is kick-started, then much less energy is needed to make longer chain peptides in a terrestrial, aquatic environment") you would perhaps refrain from passing off stupid remarks as knowledge.

JVK, isn't hubris one of the seven deadly sins? Isn't your God automagically creating intelligent humans from scratch? I think you should show some respect, to scientists who are actually doing validated research instead of placing cheap derisive comments.
Torbjorn_Larsson_OM
5 / 5 (5) Aug 19, 2015
Re polymeric (polybase) DNA, and this year RNA: They have been demonstrated from respectively nucleotides in vent thermophoretic reactors in PCR reactions. Pores in such are the only known reactors that select for strand elongation, so circumventing open pot synthesis problems.

Another potential stumbling block would have been doing this in racemic conditions, but earlier this year it was demonstrated that cross-chiral ribozymes work _better_ than chiral conditions. Since the genetic machinery has frozen in a today unnecessary double chiral selection (on tRNA choosing AA, and on ribosome choosing tRNA/AA pairs) - modern metabolism produces chirality - it is implicated that the earliest cells replicated on a racemic basis.

When a genetic code evolves it enforces chiral selection during the switch ribozymes -> enzymes, on the code and eventually on the early multi-use enzymes.
JVK
1 / 5 (4) Aug 19, 2015
I think you should show some respect, to scientists who are actually doing validated research instead of placing cheap derisive comments.


No serious scientists respect these pseudoscientists. Why should I not make derisive comments?

Re: ("Once the process is kick-started, then much less energy is needed to make longer chain peptides in a terrestrial, aquatic environment")

I tend to skip aspects of ridiculous misrepresentations that require kick-starting as the initial factor for the entirety of their ridiculous theoretical approach.

JVK
1 / 5 (4) Aug 19, 2015
if this is correct, then, the first organic molecules were formed on comets as the comets accreted, and then deposited on Earth's surface... 4.1-3.8 billion years ago


It is not correct. It is pseudoscientific nonsense.

When a genetic code evolves


A genetic code does not evolve.
See also: Symbiosis becoming permanent: Survival of the luckiest http://www.pnas.o...01.short

Ecological variation is linked to ecological adaptation via the biophysically constrained chemistry of nutrient-dependent RNA-mediated protein folding.

Scientific method: Defend the integrity of physics http://www.nature...-1.16535

"In our view, the issue boils down to clarifying one question: what potential observational or experimental evidence is there that would persuade you that the theory is wrong and lead you to abandoning it? If there is none, it is not a scientific theory. "
anonymous_9001
5 / 5 (6) Aug 19, 2015
It is not correct.


And yet organic molecules have been observed on comets.

Direct observation: 1, Kohl's assumeptions: 0
JVK
1 / 5 (4) Aug 19, 2015
observed on comets

That seems to be a very unlikely thing to have anyone observe.
For comparison, on earth:
http://dx.doi.org...hem.2202 -- created nucleic acid precursors starting with just hydrogen cyanide (HCN), hydrogen sulfide (H2S), and ultraviolet (UV) light.

http://www.pnas.o...abstract -- linked them to light harvesting

http://genome.csh...abstract -- linked atoms to ecosystem in all living genera via RNA-mediated gene duplication and RNA-mediated amino acid substitutions that link nutrient-dependent protein folding from its biophysically constrained chemistry via changes in the speed of light on contact with water ON EARTH.

JVK
1 / 5 (3) Aug 19, 2015
One of the co-authors of "Scientific method: Defend the integrity of physics" co-authored with Stephen Hawking, and with Roger Penrose who wrote the forward to: http://www.amazon...07604664

Excerpt: "How often do we still hear that quantum effects can have little relevance in the study of biology, or even that we eat food in order to gain energy?"

Has anyone ever observed someone eating a comet in order to gain energy?
Vietvet
5 / 5 (7) Aug 19, 2015
observed on comets

That seems to be a very unlikely thing to have anyone observe.

@JVK

I'm not surprised at just how unaware you are.

https://www.googl...20comets
JVK
1 / 5 (3) Aug 19, 2015
http://www.popsci...es-comet

"We are currently investigating what kind of species these [molecules] are, and this will be published soon," says Ulamec. "We want to be sure. But it's definitely several species."

Does anyone know the difference between a molecule and a species that must eat and reproduce to become a species and to keep from becoming an extinct species?
gkam
2.7 / 5 (7) Aug 19, 2015
"Does anyone know the difference between a molecule and a species that must eat and reproduce to become a species and to keep from becoming an extinct species?"
---------------------------------------

Let me guess!!

RNA-mediated, mumbo-jumbo, mumble, oneanswertoeveryquestion.
Mike_Massen
3.4 / 5 (5) Aug 20, 2015
EnsignFlandry asked
What is really needed is evidence of comets, or something, leading to RNA or DNA, even a small nucleotide
Too easy :-

Early earth's atmosphere confirmed by archaeological & other studies being predominantly NH3 & other trace gases eg CO2, CO, H2O, H2, N2, O2 etc under influence of heat, sun's UV & lightning leads to stable formamide
https://en.wikipe...ormamide

Which, given only a little time leads to stable
https://en.wikipe.../Guanine

Leads to all other dna/rna bases given the initial conditions, eg deep oceans offering an almost ideal solvent/care happily extend permutation space leading to interactions between bases...

IOW: Universe is replete with chemicals constantly undergoing self-assembly & obviously given enough time, not too long (Hrs) for Guanine, leads to ALL essentials re DNA/RNA, rest is straightforward to anyone who understands permutation space re activation energy & meta-stability

Learn (Bio)Chemistry
Mike_Massen
3.4 / 5 (5) Aug 20, 2015
Adding to my last post, please observe that ALL constituents for life are VERY common & as such there must be a HUGE number of permutations offering not only the final forms but intermediate transitory forms with appropriate activation energy which allow sufficient time for even partial stability as bridges to more stable forms (now) & especially so in the deep oceans where UV sensitive molecules re dissolved & fall out of range of sufficient UV to force disassociation so the equilibrium re creation/denaturing favours stability upon the transition as they fall to lower depths, pretty obvious when you consider trillions of em per ml of seawater.

Note: Some 25 billion viruii found in seawater per litre = lottsa organic material for ALL life, so damn easy

See 3rd para this link AND of course aware references are real gold :-)
https://en.wikipe...i/Uracil

ir Not only see Biochem re permutation space of some 10^60 of C

BUT, also evaluate factorial of 10^60 :-)
JVK
1 / 5 (2) Aug 25, 2015
ALL constituents for life are VERY common


The first amino acid came from somewhere. Let's compare what's known about UV light and creation to theories about comets. http://phys.org/n...ory.html

Try to compare what's known about the de novo creation of the only achiral amino acid, glycine to claims about comets without sounding like a biologically uninformed science idiot.

Or not! You really have no choice, do you?

UV sensitive molecules re dissolved & fall out of range of sufficient UV to force disassociation so the equilibrium re creation/denaturing favours stability...


Dissolved in what? How do they fall out of range? What is the entropic force of disassociation that must be countered by the anti-entropic force that links the stability of all organized genomes to symbiosis across all living biomass that has not yet been destroyed by virus-driven entropic elasticity linked to genomic entropy?

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