Best Evidence Yet That Comets Delivered Water for Earth’s Oceans

by Nancy Atkinson on October 5, 2011

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New measurements from the Herschel Space Observatory have discovered water with the same chemical signature as our oceans in a comet called Hartley 2 (pictured at right). Image credit: NASA/JPL-Caltech

The idea isn’t new that Earth’s oceans originated from comets bombarding our planet back in its early days. But astronomers have now found the best evidence yet for this scenario. The Herschel infrared space observatory detected that comet Hartley 2, which originates from the distant Kuiper Belt, contains water with the same chemical signature as Earth’s oceans.

“Our results with Herschel suggest that comets could have played a major role in bringing vast amounts of water to an early Earth,” said Dariusz Lis, senior research associate in physics at the California Institute of Technology in Pasadena and co-author of a new paper in the journal Nature, published online on Oct. 5. “This finding substantially expands the reservoir of Earth ocean-like water in the solar system to now include icy bodies originating in the Kuiper Belt.”

Previous looks at various other comets showed water content different from Earth, with deuterium levels around twice that of Earth’s oceans, but those comets came from the Oort Cloud. Scientists theorized that if comets of this kind had collided with Earth, they could not have contributed more than a few percent of Earth’s water.

The Deep Impact spacecraft successfully flew past Comet Hartley 2 in November 2010 and is an example of the type of comet that the UCLA scientists describe in their research. Image: UPI/NASA/JPL-Caltech/UMD.

But Herschel’s observations of Hartley 2 are the first in-depth look at water in a comet from the Kuiper Belt — home of icy, rocky bodies that includes dwarf planets and innumerable comets — and it showed a surprising difference.

Using HIFI, a highly sensitive infrared spectrometer, Herschel peered into the comet’s coma, or thin, gaseous atmosphere, and found that Hartley 2 possessed half as much “heavy water” as other comets analyzed to date. In heavy water, one of the two normal hydrogen atoms has been replaced by the heavy hydrogen isotope known as deuterium. The ratio between heavy water and light, or regular, water in Hartley 2 is the same as the water on Earth’s surface.

“Comet Hartley’s deuterium-to-hydrogen ratio is almost exactly the same as the water in Earth’s oceans,” says Paul Hartogh, Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany, who led the international team of astronomers in this study.

The amount of heavy water in a comet is related to the environment where the comet formed, and by comparing the deuterium to hydrogen ratio found in the water in Earth’s oceans with that in extraterrestrial objects, astronomers were hoping to identify the origin of our water.

Astronomers know Hartley 2 comes from the Kuiper Belt, since they can track its path as it swoops into Earth’s neighborhood in the inner solar system every six-and-a-`half years. The five comets besides Hartley 2 whose heavy-water-to-regular-water ratios have been obtained all came from the Oort Cloud, an even more distant region in the solar system. This region is 10,000 times farther away than the Kuiper Belt, and is home to the most documented comets.

The team is now using Herschel to look at other Kuiper Belt comets to see whether they, too, carry the same type of water.

“Thanks to this detection made possible by Herschel, an old, very interesting discussion will be revived and invigorated,” said Göran Pilbratt, ESA Herschel Project Scientist. “It will be exciting to see where this discovery will take us.”

Paper: “Ocean-like Water in the Jupiter-family Comet 103P Hartley”

Sources: JPL, ESA

About 

Nancy Atkinson is Universe Today's Senior Editor. She also works with Astronomy Cast, and is a NASA/JPL Solar System Ambassador.

Anonymous October 5, 2011 at 10:04 PM

This doesn’t necessarily mean that comets delivered Earth’s water. It could mean that both comets and Earth got their water from the same source, or it could be just coincidence.

Anonymous October 6, 2011 at 12:59 AM

I agree.. and continue to wonder after Sol’s ‘birth’ location and early gravitational condensate fusion processes.

squidgeny October 6, 2011 at 12:18 PM

No, it doesn’t prove that comets delivered Earth’s water, but it’s evidence in support of the hypothesis that they did.

Anonymous October 6, 2011 at 12:24 PM

I would tend to second this. We really have at best a partial understanding of how planetary systems form. The proto-planetary disk contained some distribution of atomic and molecular substances which may have initially varied with radial distance from the sun. This likely changed with time as well. How that changed is not known. So we may have either that isotope distribution of water on Earth (and the other planets & moons) is connected to comets by either an inwards migration through bombardment, an outward migration of H_2O by photon pressure or the distribution has remained fairly constant.

As I am aware there has been some controversy about isotope distribution of water, both due to different concentrations of hydrogen-deuterium and oxygen isotope differences, with Earth’s oceans and comets. So the matter seems as yet not settled.

LC

Anonymous October 5, 2011 at 11:59 PM

Comets are major sources that likely seed habitable planets with water, and probably organic compounds including DNA. Scientists proved in an experiment that DNA self-assembles on carbon nanotubes near absolute zero vacuum. Amino acid base pairing takes place, and complex structures like proteins form by synthesis. Carbon nanotubes contain innumerable buckyballs inside. Buckyballs are believed discovered where supernovas blast them out, which is the material for new star formation. This means that oort cloud watery comets could contain DNA, and dead bacteria like Hoyle suggested are in nebula clouds using nanotubes to survive, and where water can remain liquid near absolute zero by merely contacting graphene! A primordial ribosome could have been out there in the early universe, that lead to life everywhere. Hoyle believed that Pamspernia caused life to begin on earth.

Anonymous October 6, 2011 at 1:11 PM

I think the existence of fullerenes and organic compounds in space indicates the universality of their formation. I don’t think it really means life started in space and then came to Earth.

I too have thought that carbon nano-tubes were a form of prebiotic ribosome. The spacing between carbon atoms is somewhat commensurate with the spacing of nucleotides. There is a winding number that is “resonant” in space. However, I am not sure of the electron-bonding affinities involved. Carbon matrix structures such as fullerenes also are hydrophobic for the most part.

LC

Sam Wilson October 6, 2011 at 4:03 PM

Do you have any good links regarding carbon nanotubes their space hosting properties? This is new to me.

Regards,
Sam

Anonymous October 6, 2011 at 9:05 PM

The distance between nucleotides in DNA is .34nm. The spacing between carbon atoms is .142nm. Now consider three bond lengths which form a “zig-zag” on graphene. The distance along the four carbon atoms is about 3*.142nm*cos(30-deg) = .37nm. So let us assume that a DNA, or RNA, single strand is floating around and it encounters a graphene sheet or similar fullerene. The graphene sheet has an sp^2 bonds, but which can hybridize with ?-orbitals. These ?-orbitals can have electron holes, a positive hole similar to an electron but with positive charge. A DNA or RNA has a phosphodiester PO_4 backbone, where one of these oxygens has a negative charge. Hence the DNA can line up on a graphene if the stretching of the DNA is energetically favorable. That part I am not sure about. However, it seem possible that a DNA or RNA could become tied down to a graphene or carbon tube. From there the complementary pairs of nucleotides in the aqueous solution would then line up.

So the early Earth may have had thermal vents with organic molecules floating around, including nucleotides. Volcanic activity is causing ash to fall into this pool with fullerenes. This process may then occur, and once a double strand is formed maybe some thermal cycling shakes it off of the carbon matrix. Hence graphene may have been the primordial replicase molecule. This could also maybe serve as a primordial ribosome as well.

LC

Torbjörn Larsson October 6, 2011 at 11:06 PM

The winding number is the number of windings around a point, not the pitch of the helix. The pitch can be widely different between different forms of DNA already, A-DNA has ~2.5 nm pitch and Z-DNA ~ 5 nm. It is difficult to see universality when we have factors that tend to orders of magnitude involved!

Assuming we have access to nucleotides, that could explain the DNA affinity part to a buckyball “ribosome” (see my above comment on wrapping/unwrapping. What is the amino acid to protein assembly part?

Anonymous October 7, 2011 at 1:05 PM

In the end experimental data is what will count. I am in discussions with a couple of people on how an experimental protocol might be derived.

Probably the precursor nucleotide chain was RNA, not DNA. I agree that it has to be uncoiled and it appears it has to be stretched a bit. I am not sure about the energetics of this. The process might be facilitated by various means, and indeed in an experimental setting it may require many trials with such proposed options.

The simplest system to look at is with the replication of DNA or RNA. A set of questions have to be answered. Does single stranded DNA or RNA bind onto a graphene sheet? Is there then complementary formation of a double strand? From there we can address additional questions, such as whether this can also act as a transcription mechanism.

LC

Torbjörn Larsson October 8, 2011 at 11:13 AM

“experimental data”.

That is great! I wish you luck in getting some, it will be much more fruitful than discussing pitch.

I agree that there are a few steps before hypotheses about translation (RNA readout to protein assembly) can be tucked onto this prototype transcription machinery.

Also, in cells translation happens far away from transcription, reflecting its evolutionary path (from transcription only RNA world to translation protein world) but also enabling a copying multiplication (reuse of messenger RNA). That does not necessarily need to happen of course, assuming your protein centric metabolism is slow enough.

Torbjörn Larsson October 8, 2011 at 11:13 AM

“experimental data”.

That is great! I wish you luck in getting some, it will be much more fruitful than discussing pitch.

I agree that there are a few steps before hypotheses about translation (RNA readout to protein assembly) can be tucked onto this prototype transcription machinery.

Also, in cells translation happens far away from transcription, reflecting its evolutionary path (from transcription only RNA world to translation protein world) but also enabling a copying multiplication (reuse of messenger RNA). That does not necessarily need to happen of course, assuming your protein centric metabolism is slow enough.

Torbjörn Larsson October 6, 2011 at 10:55 PM

Comets are major sources that likely seed habitable planets with water, and probably organic compounds including DNA.

There are no observations as of yet that comets are “major sources” of volatiles, or that DNA is present outside of terrestrial environments.

Scientists proved in an experiment that DNA self-assembles on carbon nanotubes near absolute zero vacuum.

I would be happy if you could provide references. Meanwhile, interactions of carbon nanotubes with DNA seems limited to wrapping and unwrapping.

Also, nuclear bases are still to be observed outside terrestrial environments, and you need those to make DNA assemble in the first place.

Amino acid base pairing takes place, and complex structures like proteins form by synthesis.

That would make nanotubes the functional equivalent of ribosomes, and _that_ would have made major news!

Carbon nanotubes contain innumerable buckyballs inside

That seems improbable. For obvious reasons nanotubes prefer the buckyball size of ~ 1 nm. They wouldn’t fit!

Maybe what you want to say is that nanotubes looks like an aggregation of innumerable buckyballs?

Buckyballs are believed discovered where supernovas blast them out,

Buckyballs are everywhere, from carbon plasmas to soot, You can not not have them!

This means that oort cloud watery comets could contain DNA,

No, for the same reason they don’t contain DNA. Any self heated small body that starts to ‘differentiate’ in some form will have the chemical reaction zone migrating faster than abiogenesis can keep up. A result this year, IIRC.

dead bacteria like Hoyle suggested are in nebula clouds using nanotubes to survive,

Dead bacteria alive? Sound like Heisenberg zombies.

Hoyle believed that Pamspernia caused life to begin on earth.

Yes, for religious reasons and when he started to fall apart intellectually. Are you sure you want to rely on him for (non-empirical) authority?

Anonymous October 7, 2011 at 12:53 AM

The amazing carbon nanotubes ribosomal DNA link by Robert R Johnson, is at
http://dept.physics.upenn.edu/~robertjo/gallery

Proteins self-assemble on carbon nanotubes. Maybe there was a precursor primordial mother ribosome that was first to give life everywhere in the universe. Life did not have to begin on earth, but DNA could have came from outer space and landed on earth.

Buckyballs form quantum dots. Quantum dots have an energy gap that scales inversely with their size. I wonder if equations for black holes are similar in some ways to quantum dots. Gated bilayer graphene has more pronounced plasmonics. When graphene contains combined polymers that keep informational memory, its electrical properties are precisely organized by light. Graphene has Spin-Orbit electron interactions, the same as in nuclear magnetic resonance, which is the frame dragging component. Ferromagnetism similar to bubble universes would result if the vacancies in graphene are arranged in the right way, because growing numbers like Smolyaninov and Zhang are saying metamaterials are like the medium vacuum in outer space. The quantum foam, black holes, neutron stars, jets, and the big-bang are being modeled by metamaterials near absolute zero in vacuum. So, is there a metamaterial space-time fabric somewhat responsible for shaping the universe? Fantasy: Could the fourth dimension be part of a gigantic living ribosome that is our universe, organizing information beyond the non-living state? Fantasy: When supernovas form buckyballs could viral stars be exploding viruses spewing out functional equivalent ribosomes to copy again? The carbide signature at 11.5 mm for cool evolved carbon-rich giant stars shows buckyballs are everywhere. 1 atom thick for the space elevator, and known grown up to 5 inches thick, with far stronger strength.

Yes, it should be major news, but it doesn’t seem to be known today by cosmologists who publish papers. The references you requested I’ve provided. Protein synthesis takes place in these nanotubes by Robert Johnson. This makes carbon nanotubes the functional equivalent of ribosomes !

Torbjörn Larsson October 8, 2011 at 11:26 AM

Proteins self-assemble on carbon nanotubes.

They get protein subunits to assemble on chemically prepared nanotubes and, in the instance of coils it seems (paywall), induce the final protein conformation. That is a far cry from protein self-assembly out of monomers by a flexible translation machinery using RNA.*

So no ribosomes, despite your effort to redefine a clear functional system as something else entirely.

Since you don’t really answer any of the other questions you leave us with, but immediately switch to stream-of-consciousness oratory, I will just finish with a reminder that we have yet to observe DNA outside of Earth.

———–
* That said, it is always interesting to see chemical possibilities not explored by our biosphere.

Nanotubes are inimical to cells, and it has recently become clear why. Smooth tube ends aren’t discriminated by the eukaryote import machinery but they try to assimilate a tube as of it is a particle. They choke on long nanotubes.

Torbjörn Larsson October 8, 2011 at 11:26 AM

Proteins self-assemble on carbon nanotubes.

They get protein subunits to assemble on chemically prepared nanotubes and, in the instance of coils it seems (paywall), induce the final protein conformation. That is a far cry from protein self-assembly out of monomers by a flexible translation machinery using RNA.*

So no ribosomes, despite your effort to redefine a clear functional system as something else entirely.

Since you don’t really answer any of the other questions you leave us with, but immediately switch to stream-of-consciousness oratory, I will just finish with a reminder that we have yet to observe DNA outside of Earth.

———–
* That said, it is always interesting to see chemical possibilities not explored by our biosphere.

Nanotubes are inimical to cells, and it has recently become clear why. Smooth tube ends aren’t discriminated by the eukaryote import machinery but they try to assimilate a tube as of it is a particle. They choke on long nanotubes.

Anonymous October 9, 2011 at 5:01 AM

Nanotubes filled with metallofullerenes contain inside them tightly packed chains of buckyballs. They interact electromagnetically, and carbon nanotubes are known grown up to 5 inches thick. Perhaps in supernova winds these nanotubes could obtain this thickness, and could organize the buckyballs using metal atoms to apply magnetic fields to structures in the galaxy?

Anonymous October 8, 2011 at 1:02 PM

It appears that my idea is a couple of years behind. It looks as if the idea is already “scooped.”

LC

Anonymous October 8, 2011 at 1:02 PM

It appears that my idea is a couple of years behind. It looks as if the idea is already “scooped.”

LC

Anonymous October 9, 2011 at 4:52 AM

you were first to propose a primordial ribosome before, but isn’t it more logical to assume life on earth began from space DNA? As earth formed, our second generation star already would have interplanetary carbonaceous dust. Diamond nanoparticles are in this dust, but not as much as predicted have been found. Tiny amounts of DNA in this dust would contaminate the early earth, which replicate fast on habitable planets like earth. The wipe out of the dinosaurs saw man emerge rapidly, maybe from one DNA that made it to earth and found favorable conditions to adapt mutate to our form without being eaten by a dinosaur.

squidgeny October 6, 2011 at 12:34 PM

It’s my understanding that water is formed when the oxygen and hydrogen combust and can be disassociated by lightning and sunlight. Is there any way heavy water could be less or more susceptible to each of these processes than light water? I suspect not, but if so, that could bias the proportions on Earth relative to non-Earth reservoirs, where such processes would exist with different prevelance.

Torbjörn Larsson October 6, 2011 at 11:13 PM

So called fractionation seems to be processes where light and heavier isotope fractions separate under (mostly) diffusion.

On Earth it happens when geological or metabolic processes occurs. In a protoplanetary disk it should happen when molecules interacts on dust particles, where nearly all the interesting chemistry initially happens. But I assume minute differences in energy bands, especially for hydrogen, would also play some role during photodisassociation.

Sam Wilson October 6, 2011 at 4:02 PM

Do you have any good links regarding carbon nanotubes their space hosting properties? This is new to me.

Regards,
Sam

Michal Kowalski October 6, 2011 at 7:38 PM

http://www.lpi.usra.edu/books/MESSII/9038.pdf
(distribution of deuterium in solar system)
interesting numbers IMHO[table 1]

and a question: deuterium gradient for Jupiter, Saturn, Uranus and Neptune
why it exists?

Torbjörn Larsson October 6, 2011 at 11:25 PM

I think my above comment pertain to some of that. Different processes in different parts of the protoplanetary disk would result in different isotope ratios.

The giant planets gas reservoirs looks rather like the sun and interstellar dust particles (IDP) water primordial ratio. Then you have other ratios for IDP particles non-volatiles and comets. Terrestrials seems to result from a mixing of those.

Torbjörn Larsson October 6, 2011 at 10:32 PM

Interesting, but I don’t think Kuiper objects warrant being thought of as standard comets. They are part of the short-period comet population.

As lcrowell notes, there are molecular and aggregate (asteroid, comet) migration processes. And while the Oort cloud comets may in part have been subjected to that (scattering by Jupiter) a large part would have been native distant aggregates. (In some scenarios a hefty subpopulation from other planetary systems in the cluster that spawned our own system.)

If most KBOs are formed just beyond the original orbits of Uranus and Neptune, the resemblance to Earth isotopic ratios are encouraging. That means the scenarios of LHB and the continuous characteristics between asteroids (especially rubble piles) and comets looks validated.

What would be put back on the table would be “the late veneer” (LHB delivery) scenario of Earth water aggregation. However, at the same time the asteroid and hence planetesimal population may have more water content than in earlier scenarios, AFAIU recent results. (The asteroid-comet continuity.)

That Earth had an early large water reservoir doesn’t seem to be in doubt (Jack Hill zircons), with what that implies for abiogenesis scenarios.

Anonymous October 7, 2011 at 3:09 PM

Water on our planet came from many sources, as did all other elements, even now, as our planet travels through space, we steadily pick up particles, mainly due to the planets well established orbit. Maybe we could analyze this upcoming meteor shower[the draconid meteor shower]. There is some documented proof of a comets impact on our planet from c/1811 f1. If this may interest you, I invite you to this link at http://www.wix.com/koolkreations/kalopins-legacy ,”documents and links”, “a few comments on 1811-2011″. You will find the truth behind “A Comet and A Quake”.

Anonymous October 8, 2011 at 2:14 AM

Carbon rich chondritic interplanetary dust particles comprise 60% of the total interplanetary dust particles. Surely DNA here can land on earth and other planets. Of interest is that alpha the fine-structure constant is tuned to life, and has the value 1/137.036. A very similar value is the measured, fractal dimension of 1.4 for graphene quantum dots at low temp, having fractal magneto-conductance with perpendicular magnetic field. Carbon life as ribosomal nanotubes might be fine tuned to alpha, I suggest. Telescopes have measured alpha in outer space, and don’t know if it is constant everywhere, but life cannot exist if it changes slightly far away. Maybe we have life because these numbers have nearly the same value. Alpha is dimension one.

Anonymous October 8, 2011 at 2:14 AM

Carbon rich chondritic interplanetary dust particles comprise 60% of the total interplanetary dust particles. Surely DNA here can land on earth and other planets. Of interest is that alpha the fine-structure constant is tuned to life, and has the value 1/137.036. A very similar value is the measured, fractal dimension of 1.4 for graphene quantum dots at low temp, having fractal magneto-conductance with perpendicular magnetic field. Carbon life as ribosomal nanotubes might be fine tuned to alpha, I suggest. Telescopes have measured alpha in outer space, and don’t know if it is constant everywhere, but life cannot exist if it changes slightly far away. Maybe we have life because these numbers have nearly the same value. Alpha is dimension one.

Torbjörn Larsson October 8, 2011 at 11:32 AM

As I remarked above, we have yet to observe DNA outside our biosphere and in particular we find the environments on bodies smaller than Ceres or Mars scale planetesimals prohibitive for DNA and abiogenesis assembly.

We know that the finestructure constant is really constant to large precision. It has nothing to do with ability of abiogenesis, since nothing in the general process is sensitive to physical parameter changes.

Torbjörn Larsson October 8, 2011 at 11:32 AM

As I remarked above, we have yet to observe DNA outside our biosphere and in particular we find the environments on bodies smaller than Ceres or Mars scale planetesimals prohibitive for DNA and abiogenesis assembly.

We know that the finestructure constant is really constant to large precision. It has nothing to do with ability of abiogenesis, since nothing in the general process is sensitive to physical parameter changes.

Anonymous October 9, 2011 at 5:35 AM

bs

Anonymous October 8, 2011 at 12:55 PM

The question is what interactions might there be with nucleotide sequences and graphene, or carbon tubes. It is difficult to predict this by theory or trying to estimate things from molecular data. It might have been that they formed a sort of stage for various interactions with DNA and RNA.

LC

Anonymous October 8, 2011 at 12:55 PM

The question is what interactions might there be with nucleotide sequences and graphene, or carbon tubes. It is difficult to predict this by theory or trying to estimate things from molecular data. It might have been that they formed a sort of stage for various interactions with DNA and RNA.

LC

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