Planetary collision that formed the moon made life possible on Earth

Planetary collision that formed the moon made life possible on Earth
A schematic depicting the formation of a Mars-sized planet (left) and its differentiation into a body with a metallic core and an overlying silicate reservoir. The sulfur-rich core expels carbon, producing silicate with a high carbon to nitrogen ratio. The moon-forming collision of such a planet with the growing Earth (right) can explain Earth's abundance of both water and major life-essential elements like carbon, nitrogen and sulfur, as well as the geochemical similarity between Earth and the moon. Credit: Rajdeep Dasgupta

Most of Earth's essential elements for life—including most of the carbon and nitrogen in you—probably came from another planet.

Earth most likely received the bulk of its carbon, and other life-essential volatile elements from the planetary collision that created the moon more than 4.4 billion years ago, according to a new study by Rice University petrologists in the journal Science Advances.

"From the study of primitive meteorites, scientists have long known that Earth and other rocky in the inner solar system are volatile-depleted," said study co-author Rajdeep Dasgupta. "But the timing and mechanism of volatile delivery has been hotly debated. Ours is the first scenario that can explain the timing and delivery in a way that is consistent with all of the geochemical evidence."

The evidence was compiled from a combination of high-temperature, high-pressure experiments in Dasgupta's lab, which specializes in studying geochemical reactions that take place deep within a planet under intense heat and pressure.

In a series of experiments, study lead author and graduate student Damanveer Grewal gathered evidence to test a long-standing theory that Earth's volatiles arrived from a collision with an embryonic planet that had a sulfur-rich core.

The sulfur content of the donor planet's core matters because of the puzzling array of experimental evidence about the carbon, nitrogen and sulfur that exist in all parts of the Earth other than the core.

"The core doesn't interact with the rest of Earth, but everything above it, the mantle, the crust, the hydrosphere and the atmosphere, are all connected," Grewal said. "Material cycles between them."

One long-standing idea about how Earth received its volatiles was the "late veneer" theory that volatile-rich meteorites, leftover chunks of primordial matter from the outer solar system, arrived after Earth's core formed. And while the isotopic signatures of Earth's volatiles match these primordial objects, known as carbonaceous chondrites, the elemental ratio of carbon to nitrogen is off. Earth's non-core material, which geologists call the bulk silicate Earth, has about 40 parts carbon to each part nitrogen, approximately twice the 20-1 ratio seen in carbonaceous chondrites.

Grewal's experiments, which simulated the high pressures and temperatures during core formation, tested the idea that a sulfur-rich planetary core might exclude carbon or nitrogen, or both, leaving much larger fractions of those elements in the bulk silicate as compared to Earth. In a series of tests at a range of temperatures and pressure, Grewal examined how much carbon and nitrogen made it into the core in three scenarios: no sulfur, 10 percent sulfur and 25 percent sulfur.

"Nitrogen was largely unaffected," he said. "It remained soluble in the alloys relative to silicates, and only began to be excluded from the core under the highest sulfur concentration."

Carbon, by contrast, was considerably less soluble in alloys with intermediate sulfur concentrations, and sulfur-rich alloys took up about 10 times less carbon by weight than sulfur-free alloys.

Planetary collision that formed the moon made life possible on Earth
A study by Rice University scientists (from left) Gelu Costin, Chenguang Sun, Damanveer Grewal, Rajdeep Dasgupta and Kyusei Tsuno found Earth most likely received the bulk of its carbon, nitrogen and other life-essential elements from the planetary collision that created the moon more than 4.4 billion years ago. The findings appear in the journal Science Advances. Credit: Jeff Fitlow/Rice University

Using this information, along with the known ratios and concentrations of elements both on Earth and in non-terrestrial bodies, Dasgupta, Grewal and Rice postdoctoral researcher Chenguang Sun designed a computer simulation to find the most likely scenario that produced Earth's volatiles. Finding the answer involved varying the starting conditions, running approximately 1 billion scenarios and comparing them against the known conditions in the solar system today.

"What we found is that all the evidence—isotopic signatures, the carbon-nitrogen ratio and the overall amounts of , nitrogen and sulfur in the bulk silicate Earth—are consistent with a moon-forming impact involving a volatile-bearing, Mars-sized planet with a sulfur-rich core," Grewal said.

Dasgupta, the principal investigator on a NASA-funded effort called CLEVER Planets that is exploring how life-essential elements might come together on distant , said better understanding the origin of Earth's life-essential elements has implications beyond our solar system.

"This study suggests that a rocky, Earth-like planet gets more chances to acquire life-essential elements if it forms and grows from giant impacts with planets that have sampled different building blocks, perhaps from different parts of a protoplanetary disk," Dasgupta said.

"This removes some boundary conditions," he said. "It shows that life-essential volatiles can arrive at the surface layers of a planet, even if they were produced on planetary bodies that underwent core formation under very different conditions."

Dasgupta said it does not appear that Earth's bulk silicate, on its own, could have attained the life-essential volatile budgets that produced our biosphere, atmosphere and hydrosphere.

"That means we can broaden our search for pathways that lead to volatile elements coming together on a planet to support life as we know it."


Explore further

Earth's carbon points to planetary smashup

More information: D.S. Grewal el al., "Delivery of carbon, nitrogen, and sulfur to the silicate Earth by a giant impact," Science Advances (2019). DOI: 10.1126/sciadv.aau3669 , http://advances.sciencemag.org/content/5/1/eaau3669
Journal information: Science Advances

Provided by Rice University
Citation: Planetary collision that formed the moon made life possible on Earth (2019, January 23) retrieved 24 June 2019 from https://phys.org/news/2019-01-planetary-collision-moon-life-earth.html
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Theories that require fine tuning should raise a red flag, as in requiring Theia to be so similar to Earth as to lie on the 3-oxygen-isotope terrestrial fractionation line, yet so volatilely different as to differentiate Earth (after the supposed Giant Impact) from its comparatively volatilely-depleted twin-planet Venus.

Alternatively, why isn't Venus the odd man out, with its 'recent' resurfacing, and its thick, sulfurous Hadean atmosphere?

How about Earth as the quiescent twin, with Venus having suffered a giant impact from a retrograde moon in a decaying orbit that spiraled in to merge at 541 Ma, contaminating Earth with Venusian lifeforms, causing the Cambrian Explosion (of ALL modern phyla) on Earth, and with Venus losing (rather than gaining) volatiles in the 'Venusian Cataclysm'.

Jan 23, 2019
Seems even less likely that life exists, anywhere.

Jan 23, 2019
A major problem with this theory is that there is no model that can show how a moon forms from an impact. It's all made up stuff. Without some simulation results, even with the best initial conditions, it is best to ignore such theories.

Jan 23, 2019
So this adds extra layers of fine-tuning? Holy cow!!!

ps1: I guess planet hunters must now look for such collisions among other criteria.
ps2: I guess god orchestrated that too....even the collision angle was estimated!! lol
ps3: Had my grandma been my grandpa if she had.....y chromosome?

Jan 23, 2019
A major problem with this theory is that there is no model that can show how a moon forms from an impact.

So if Bart says that it's never been modeled, that obviously means that it has been modeled: https://justin.va...6073.pdf . ;)

Jan 23, 2019
This comment has been removed by a moderator.

Jan 23, 2019
I am not convinced that impact ever took place. It is only a hypothesis, if you tell a lie a thousand times, it might appear as truth. Moons do not form by impacts.

Jan 23, 2019
I may be taking this out of context, but saying that the core does not interact with the Earth is incorrect. The generation of the magnetic field definitely interacts with the Biosphere. Without it no life would exist.

Jan 23, 2019
I am not convinced that impact ever took place. It is only a hypothesis, if you tell a lie a thousand times, it might appear as truth. Moons do not form by impacts.

I believe the fact that the moon is moving away from the Earth is one of the reasons for the impact theory.

Jan 24, 2019
I believe the fact that the moon is moving away from the Earth is one of the reasons for the impact theory.

So what you're saying is that the moon could only have been in place for 1.3 billion year according to the Roche limit. Or else according to tidal friction it should only have gottten there 1.7 billion years ago. However, the current age estimate of the moon is about the same as the earth. Plus the iron poor moon requires an impact angle that contradicts the impact theory. So does rare titanium composites which are very much the same as that of earth itself. The impact theory fails miserably- according to evolutionist analysis.
The generation of the magnetic field definitely interacts with the Biosphere.

There is no generation of the magnetic field. The field strength shows a simple impulse response curve decay with major disturbance a few thousand years ago. Similarly the moon had a very strong magnetic field with no sign of a generator whatsoever.

Jan 24, 2019
"What we found is that all the evidence—isotopic signatures, the carbon-nitrogen ratio and the overall amounts of carbon, nitrogen and sulfur in the bulk silicate Earth

This article makes some really ridiculous assumptions. The very fact that it is assumed the earth formed naturalistically forces them to introduce some even more mythical speculations to overcome the actual real life observations that contradict any notion of a naturalistic self-formation. According to the current core accretion theory(or any other prior ones for that matter) there should not be as much volatile material around on earth as the actual real life evidence shows, So they have to go fishing in an imaginary pond to find it. With even more fantastic contradictions along the way: Water still exists on the moon, the moon had a very strong magnetic field with no generator in sight, etc., etc. etc.
Much easier to accept the earth was purposefully created to be inhabited by LIFE.

Jan 24, 2019
There just is no naturalistic explanation for how the moon formed all by itself given the huge size, composition, recession, remnant rock magnetic field, position, inclination and very precise orbital plane, distance to the sun, size relative to the sun and the spectacular stabilization of the earths spin.
Secularists are on a hiding to nothing. Their speculations border on sheer lunacy with regards to real life observations and actual physics. The Psalmist has it right: The fool said in his heart there is no God -Psalm 14:1.

Jan 24, 2019
There just is no naturalistic explanation for how the moon formed all by itself given the huge size, composition, recession, remnant rock magnetic field, position, inclination and very precise orbital plane, distance to the sun, size relative to the sun and the spectacular stabilization of the earths spin.

Have you ever thought that it might be because we are the observers and we might have been fooled by our perspective bias?

Jan 24, 2019
So these guys had a hypothesis that made predictions and they fulfilled it. Not to say it's the only way but after 9 billion tries, it looks pretty likely.

Jan 24, 2019
zz5555, nice try. I read through this paper, which is about how the compositions of the earth's and moon's materials could have been made. There is precious little on how a moon can form and start orbiting the earth. Please try again.

Jan 24, 2019
Bart, when you read a paper, you need to read past the title. The 2nd sentence in the abstract talks about previous simulations and the abstract itself discusses the simulation the paper is about. You can see the results of that simulation in Fig. 1. This results in a planetary disk of the correct proportions and elemental makeup. The only thing left is for the particles in that disk to form the moon. But as the paper points out, that work has already been done (see reference 20: https://www.scien...00964960 ). You do need to read past the title to get this information, though.

Jan 24, 2019
What about the fact that the Giant Collision vaporized the resulting system of rock-silicates-and-all and drove volitiles out during the thousand(s) of years it took to cool? I don't mind the addition of sulpher this way, makes sense. But overall? does this model take the vaporized result into account? See things like arxiv.org/abs/1802.10223

Jan 24, 2019
zz5555, thanks for your kind response. Yes, I did read much past the title, even all the way to the end. The next reference you gave can be seen in detail at this link:
http://www.cfca.n...vie.html

Basically it is about how a moon can form from an already orbiting disc of debris.
What this and the previous link that you provided don't simulate, is how such an orbiting disc of debris can happen from a giant collision. Please do keep providing links, and I will look at each one.


Jan 24, 2019
IF our sun has passed thru the red giant phase and into a lesser sun of a pending white dwarf which has 'burped' its gases onto the Earth, perhaps this scenario would be a perfect fit.

Jan 25, 2019
I think the first error that many of the previous commentator are making?
That there has only been a single collision event for the Earth. Those readers want a simple soundbite that magically resolves all possible questions.

However as we observe current proto-planetary disks around other stars? The process of forming planets & clearing out the orbital lanes, seems to be a chaotic series of random collisions & unpredictable expulsions into Interstellar Space.

& that's the way it goes folks. Even if you disapprove of the disorderly results?
The Cosmos does not seek your satisfaction & ignores your demands for an orderly existence.

Is this pop-science article reasonably accurate?
I don't know.

I will read the supporting material to clarify some of the issues I have with what is posted.
For instance, the source of phosphorous in the Earth's crust?
Since the article claims there is no metal being exchanged between the Earth's core & the crust?

Jan 26, 2019
The hypothesis as is puts a lot of constraint into the last large accretion impactor, besides the rarer glancing angle impact that spawned the Moon. As a non-specialist reader it is striking that the paper do not seem to consider that earlier accretion could have pushed the mantle state too.

That impression is shored up in an interview with geoscientist James Day, who besides other problems noted that: "In reality however, the "abundance of these elements in the Earth's mantle before the Moon-forming impact is unknown," [Day] said."

[ https://gizmodo.c...31984838 ]

Jan 26, 2019
@SSS: "Theories that require fine tuning should raise a red flag, as in requiring Theia to be so similar to Earth as to lie on the 3-oxygen-isotope terrestrial fractionation line, yet so volatilely different as to differentiate Earth (after the supposed Giant Impact) from its comparatively volatilely-depleted twin-planet Venus."

Yes, the proposed model - which is fine in its mechanism - is used in an unnecessary unlikely scenario as scientists already pointed out, see my first comment. But the glancing angle impact that mixed Theia and protoplanet Tellus into both Earth and Moon did not require either the same oxygen isotope ratios (due to the mixing) nor a finetuned impact (since a heft percent are glancing, c.f. the Mars north polar region glancing impact analog).

-tbctd-

Jan 26, 2019
-ctd-

And Venus differentiation came later and is due to the distance to Sun, it is believed to have gone moist greenhouse after 0.5 Gyrs and cooked out the volatiles into the atmosphere, lose its magnetic field and hence its hydrogen and water. The reverse of finetuning, actually. To go into all the differences feel like having another and lengthy discussion, though, I'll stop here.

@michael_frishberg: You seem to imply you think life is unlikely? Geologists and biologists disagree.

@guptm: "Moons do not form by impacts."

Wrong. It is likely our did, as a counter example.

@BrainMeeps: "Without it no life would exist."

That is an open question, since Earth lies so far from Sun (so no Venus) and has a massive enough atmosphere (so even loosing hydrogen preferentially may be no problem).

Jan 26, 2019
@BartA: "What this and the previous link that you provided don't simulate, is how such an orbiting disc of debris can happen from a giant collision."

The first paper did that. Again, read through the title and look at the paper.

Finally, the creationist Gish galloping erroneous and irrelevant claims and questions is trivially boring and need no science response. Bollocks, how trolls are boring.

Jan 26, 2019
What this and the previous link that you provided don't simulate, is how such an orbiting disc of debris can happen from a giant collision.

Again, you actually need to read the paper before criticizing it. From the paper:
We describe the impactor and target as differentiated objects with iron cores and overlying silicate mantles. We simulated impacts using smooth particle hydrodynamics as in (1–3, 15, 16), representing the impactor and target with 300,000 SPH particles. Each particle was assigned a composition ... and its evolution was tracked with time as it evolved due to gravity, pressure forces, and shock dissipation.

We simulate a given impact for approximately 1 day of simulated time. We use an iterative procedure to determine whether each particle at the end of the simulation is in the planet, in bound orbit around the planet (i.e., in the disk), or escaping.

Sounds like a fun simulation to see how the disk forms.

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