Violent young Sun may have seeded life on Earth: study

May 23, 2016
The sun rises over Jakarta, Inodnesia on March 9, 2015

Life on Earth may have sprung from bombardment by a youthful Sun lashing out with flares as potent as a thousand trillion exploding atomic bombs, a study suggested on Monday.

Such violence may explain how Earth became hospitable to about four billion years ago, when the planet, and its star, were much, much colder, a research team wrote in the journal Nature Geoscience.

While the Sun was about a third fainter than it is today, it was likely much more tempestuous, they found.

Repeated super-flares would have smashed nitrogen (N2) molecules in the atmosphere to yield a planet-warming greenhouse gas called nitrous oxide (N2O or "laughing gas"), as well as hydrogen cyanide, which produces amino acids—the building blocks of proteins.

While it is essential for all life, nitrogen in the form it would have existed in a young Earth's atmosphere is not chemically reactive, and needs to be transformed into more accessible forms.

Very high temperatures can achieve this.

The study was based on telescopic observations of other stars resembling our Sun in the first few hundred million years of life, as well as models of the chemistry of early Earth's atmosphere.

Without an efficient to trap the Sun's heat, "Earth would be a snowball rather than a wet and warm planet supporting life four billion years ago," study co-author Vladimir Airapetian explained.

The new model "resolves the currently unresolved 'Faint Young Sun' paradox by efficient production of laughing gas in the lower Earth's atmosphere" at the time.

"Our model describes the 'cosmic' ingredient required to produce biological molecules of life," Airapetian told AFP by email.

And it suggested that other planets subjected to similar violence by their star may have had similar outcomes.

"Geologic evidence suggests that Mars was also paradoxically warm and wet around the same time," planetary scientist Ramses Ramirez of the Carl Sagan Institute in New York noted in a comment on the study.

It may have experienced "similar solar-atmospheric interactions" than Earth.

"The findings may have implications for the climates and potential biology of terrestrial exoplanets orbiting very young Sun-like stars, particularly stars with exceptionally high magnetic fluxes and very intense super stellar storms," said Ramirez.

Explore further: Hunting for hidden life on worlds orbiting old, red stars

More information: Prebiotic chemistry and atmospheric warming of early Earth by an active young Sun, Nature Geoscience, nature.com/articles/doi:10.1038/ngeo2719

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ogg_ogg
2.5 / 5 (8) May 23, 2016
Article is behind a paywall. Abstract says that they can explain the Green House warming using NOx, but we need paleogeochemists/geologists to weigh in on this, they seem to be suggesting that the amounts of CO2, CH4 aren't sufficient for GHW. It's also not clear to me how important HCN is for abiogenesis. They claim it is "essential" for life. We don't know that, do we?
Otto_Szucks
1 / 5 (10) May 23, 2016
Within the article, I have counted:

may have - 4

would have - 2

suggests, suggested - 3

and then it says: "Without an efficient greenhouse gas to trap the Sun's heat, "Earth would be a snowball rather than a wet and warm planet supporting life four billion years ago," study co-author Vladimir Airapetian explained.

That statement makes it appear that there had been life on Earth 4bya. Good thing I caught it.
The article also states that without a GHG the Earth would become "snowball Earth".
IF that is the case, then exactly what volume of the several GHGs are conducive to keeping 'not too warm, not too cold, but just right'? IOW, in what proportions of gases in the atmosphere should be allowed to prevent GW or GC (global cooling)?
Nitrous Oxide to warm the planet and Hydrogen Cyanide to make amino acids. Awful concoction. Good thing life didn't exist at the time. Cyanide can kill you but you'll die laughing.
torbjorn_b_g_larsson
5 / 5 (11) May 23, 2016
@ogg_ogg: I have read some on this

The grand old man here, Kasting, thinks CO2 and CH4 is enough.

"Here, we argued that the upper limit on Archean pCO2 of 3 times present published by Rosing et al. based on the analysis of mineral equilibria in banded iron-formations is invalid. Two other critical comments were published along with ours. The faint young Sun problem would be hard to solve if Rosing et al. were right, but we think they are not."

[ http://www3.geosc...PDFs.htm ; seems the pdfs are removed, so you have to snoop around or ask Kasting for a copy.]

Personally I think the CO2/H2O would be enough, but if CH4 was around it should help.

HCN is a good starter for chemical evolution of soup theory, for example the new pathway to purines suggest it as starter material.

In vent theory HCN isn't essential what I am aware of. (But every source for organic material would help.)
torbjorn_b_g_larsson
5 / 5 (10) May 23, 2016
@Otto: So? Your meaningless counting is no help in understanding the science here. I'm not sure you are interested in understanding how to read science, but FWIW:

Those precise statements elaborates on the inherent uncertainty of the observations et cetera. That statistical uncertainty can be so low that it is a claim beyond reasonable doubt, but you will still see the reminding clarity of the language.

"it appear that there had been life on Earth 4bya."

Exactly the point the paper makes if you read it as it likely should be understood. [ See? I use precise statements from time to time too.]

There are putative trace fossils that are at least 100 Myrs older et cetera, so you see fewer use the 3.5 Ga validated fossils and more that use the 4 Ga rounded value. But Earth was habitable > 4,3 Ga, if it comes to that and no need to think life didn't exists then.

"[a frozen Earth?]"

"the Sun was about a third fainter than it is today".

You do the math.

[tbctd]
torbjorn_b_g_larsson
5 / 5 (13) May 23, 2016
[ctd]

"Cyanide can kill you "

The composition of the oceans wouldn't mirror the atmosphere's upper layers, and you would have to account for dissociation of protons in solution et cetera.

More pertinent here, while HCN is bad for a modern aerobic organism https://en.wikipe...Toxicity], this was before atmosphere oxygenation.

HCN may be a nitrogen sink and source for prokaryotes. [ http://www.biotec...226.html ; http://www.ncbi.n...C546731/ ]
Otto_Szucks
1 / 5 (8) May 24, 2016
At ~4bya, the Earth was still in tremendous flux with the crust most likely extremely thin while being unable to carry the weight of present day oceans due to the crustal formation still in its early stages. Add to that the proto-continents heaving heavily above an almost fluidic crust with magma close to the surface of the land masses, it would have been impossible, IMO, for life, even anaerobic bacteria to have survived except in wet caves and shallow waters where even if the water was boiling, they could still subsist.
Since the atmosphere was poisonous for aerobic life forms, including in the waters, it's a wonder that the anaerobics were able to mutate much later when the atmosphere and waters became oxygenated to a degree where anaerobic bacteria could only survive where there was no oxygen, or very little. The evolution of bacteria was risky.
FYI, I had made a joke wrt the nitrous oxide and the Hydrogen Cyanide. Did you get it?
Otto_Szucks
1 / 5 (8) May 24, 2016
"the Sun was about a third fainter than it is today".

At 4bya the Sun would not have had much of an effect on Earth compared to what the Earth itself was experiencing while it was in the throes, upheavals of its "growing pains". Even now, she is experiencing volcanic eruptions. The thickness of the crust has had enough time to harden, and the anaerobic bacteria is now limited to certain volcanic hotspots of CH4 and other noxious gases. It is amazing that oxygen breathers were able at all to split off from the anaerobic to evolve into fish, etc.

Of course, it was inevitable, but I won't go further into why I believe it to have been inevitable.
Otto_Szucks
1 / 5 (9) May 24, 2016
Also, t_b_g_l - the reason why I counted all of the "may be", "would be", and "suggest, suggested" was that these words are included way too often in science articles, those words being what I call, "non-absolutes"...meaning that the "facts" that they offer aren't facts at all, but are negotiable and can be changed at a later time. The readers of Physorg are subjected to non-absolutisms and very often believe and accept them without thinking and considering their actual value.
MrData
4.5 / 5 (8) May 24, 2016
At that time, the early earth was regularly bombarded, had massive tidal forces (from the closer moon) as well as volcanic activity, all of which create massive amounts of heat. The question is, how much greenhouse gas was needed, considering the heat produced by the planet?
Da Schneib
5 / 5 (7) May 24, 2016
The reason HCN is important is because it brings nitrogen necessary to the synthesis of nucleic acids into the mix, and because it's a simple molecule that's very likely to have been present in the molecular cloud from which our Solar System formed (there's a fair bit of it out there in other molecular clouds we can see). Adenine, specifically, is easily formed from HCN.
torbjorn_b_g_larsson
5 / 5 (6) May 25, 2016
@Otto: Where to begin with this fractally wrong description!?

In short then: habitable oceans existed > 4.3 Ga [Valley zircon isotopic data], it is unknown if continental crust existed, it is known there were no aerobes since oxygen atmosphere existed first after 2.3 Ga.

"these words are included way too often in science articles", " "non-absolutes"...."facts"".

I have been over this. Those words are likely included too seldom for precision descriptions, and - I am sorry to note - you have no idea what an observable fact is. [ https://en.wikipe...ertainty ]

You should, in your own words, be thinking, studying and considering the actual values of observed facts.

@Da Schneib: Exactly!

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