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Tracing Water through the Stages of Planet Formation

The presence of water in the circumstellar disk of V883 Orionis, a protostar in Orion some 1300 light years out, is not in itself surprising. Water in interstellar space is known to form as ice on dust grains in molecular clouds, and clouds of this nature collapse to form young stars. We would expect that water would be found in the emerging circumstellar disk.

What new work with data from the Atacama Large Millimeter/submillimeter Array (ALMA) shows is that such water remains unchanged as young star systems evolve, a chain of growth from protostar to protoplanetary disk and eventually planets and water-carrying comets. John Tobin, an astronomer at the National Science Foundation’s National Radio Astronomy Observatory (NRAO), is lead author on the paper on this work:

“We can think of the path of water through the Universe as a trail. We know what the endpoints look like, which are water on planets and in comets, but we wanted to trace that trail back to the origins of water. Before now, we could link the Earth to comets, and protostars to the interstellar medium, but we couldn’t link protostars to comets. V883 Ori has changed that, and proven the water molecules in that system and in our Solar System have a similar ratio of deuterium and hydrogen.”

Image: While searching for the origins of water in our Solar System, scientists homed in on V883 Orionis, a unique protostar located 1,305 light-years away from Earth. Unlike with other protostars, the circumstellar disk surrounding V883 Ori is just hot enough that the water in it has transformed from ice into gas, making it possible for scientists to study its composition using radio telescopes like those at the Atacama Large Millimeter/submillimeter Array (ALMA). Radio observations of the protostar revealed water (orange), a dust continuum (green), and molecular gas (blue) which suggests that the water on this protostar is extremely similar to the water on objects in our own Solar System, and may have similar origins. Credit: ALMA (ESO/NAOJ/NRAO), J. Tobin, B. Saxton (NRAO/AUI/NSF).

V883 Ori is interesting in its own right as a star undergoing a so-called ‘accretion burst,’ a rarely observed occurrence in which a star in the process of formation ingests a huge amount of disk material, forcing an increase in its luminosity. Water reaches its condensation temperature at the ‘snow line,’ but finding the water snow line in a protoplanetary disk isn’t easy because for emerging stars similar to the Sun, it usually occurs as close as 5 AU, making the signal difficult to tease out through the dusty disk.

But V883 Ori has a disk massive and warm enough to allow these ALMA observations to distinguish the demarcation. The star masses 1.3 times the mass of the Sun, with a snow line now measured to have a radius of approximately 80 AU. Water is detected out to a radius of 160 AU according to the paper on this work, which recently appeared in Nature.

The water snow line is significant because water has much to do with the efficiency of early planetesimal formation as well as comets, not to mention its role in ice giants and gas giant cores. As we probe planet formation, we can also consider the implications of V883 Ori’s accretion burst, which raises the prospect that young stars in this stage of activity have water snow lines that can be highly dynamical, as a 2016 paper on V883 Ori points out (citation below). The new work finds gas phase water at a distance comparable to our own Kuiper Belt, with a composition that shows it remains unchanged through the stages of stellar system formation.

Merel van ‘t Hoff (University of Michigan) is a co-author on the 2023 paper:

“This means that the water in our Solar System was formed long before the Sun, planets, and comets formed. We already knew that there is plenty of water ice in the interstellar medium. Our results show that this water got directly incorporated into the Solar System during its formation. This is exciting as it suggests that other planetary systems should have received large amounts of water too.”

The paper is Tobin et al., “Deuterium-enriched water ties planet-forming disks to comets and protostars,” Nature 615 (08 March 2023), 227-230 (abstract). See also Cieza et al., “Imaging the water snow-line during a protostellar outburst,” Nature 535 (13 July 2016), 258–261 (abstract).

{ 13 comments… add one }
  • Alex Tolley March 10, 2023, 13:26

    Does this have any implications for planet formation, e.g. whether rocky worlds become water, desert, or goldilocks worlds?

    I had thought that the origin of Earth’s water was both possibly primordial and cometary and that the ratio was determined by assessments of the D/H ratio. The OP seems to suggest that there should be no D/H variation in the water in a system as it is all from a common interstellar source and isotropic across the system. Is this just the case for V883 Orionis or should it apply to all systems, if it does not in our solar system, what does that imply?

  • Alex Tolley March 10, 2023, 15:36

    The SETI institute is holding a web talk on the origin of water on Earth on March 22nd. The Origin of Water on Earth: Alien Meteors, Icy Comets, or Solar Wind?

    This is an opportunity to try to get an answer on the relevance of the V883 Orionis observations.

  • Alex Tolley March 10, 2023, 15:52

    This reference gives an overview of water and volatiles composition in the solar system, with info on the isotopic ratios.
    Constraints from Comets on the Formation and Volatile Acquisition of the Planets and Satellites

    These 2 papers are on the oxygen isotopic heterogeneity in the solar system:
    Molecular Cloud Origin for the Oxygen Isotope Heterogeneity in the Solar System.

    Oxygen isotopic heterogeneity in the early Solar System inherited from the protosolar molecular cloud

    My reading is that isotope ratios are used to infer the origin of the water because the “fractionation” of isotopes, particularly oxygen, does occur in the solar nebula.

    Hopefully, a knowledgeable commenter can clarify any discrepancy (if there is one) in the V883 Orionis paper and this isotopic heterogeneity evidence in our solar system.

  • John walker March 10, 2023, 18:49

    Water accretion vs water formation. How water actually chemically forms in the ISM is an interesting and separate question.

    • Michael March 12, 2023, 17:47

      Water would form near dying stars as the red giants throw off their tenuous atmospheres.

  • Geoffrey Hillend March 10, 2023, 20:58

    Interesting. I had an intuitive idea that I posted here on Centauri Dreams a while back which was a lucky educated guess. I thought why couldn’t our oceans have formed from water that came from a nearby source the gas, elements and dust from the accretion disk, so there is no need for comets and meteors to deliver water for our oceans. This is logical since it seems we got our oceans early and it’s a lot of time to depend upon comet collisions, and we already know there is a lot of water which is inside our mantle. Just because comets have the same D/H ratio as Earth does not necessarily mean that’s where our oceans came if the ratio exists throughout the whole solar system including inside the snow line. I think it should apply to all systems with stars comparable to ours. More research needs to be done, so the jury still might be out on this one. I hold the same view as this paper. D/H ratio may not be useful for determining if our oceans came from comets.

    • wdk March 12, 2023, 13:17

      If I am not mistaken, nucleosynthesis of deuterium does not occur in nature since the Big Bang. For example, you don’t have a hydrogen rich object enriched in deuterium by passage nearby a radiation source.
      On the other hand, an object enriched in hydrogen and its isotopes can become relatively enriched in deuterium by selective depletion of hydrogen due to escape. So, what I am driving at is that Jupiter would be a best example of the original heavy to light water ratio in the solar system vs. first pass comets falling from the Oort Cloud. After that it would get harder to determine. E.g., for the Earth, we could have volcano vented gas of original water vapor or water the result of chemical reaction. Or infall of comets, all producing oceans. But if the events are early enough in the Earth’s history, it would be hard to detemine which event was responsible for what: e.g., Hydrogen loss to the heat of formation or the Great Bombardment. Sounds to me that what we know for sure is that Mars, Venus and the Moon had it rougher than we had way back when. Largely due to size of atmosphere, gravitational force or lack of deflecting magnetospheres.

      On the other hand, the formation of water in individual stellar accretion /circumstellar disks in stellar nurseries with close proximity, leaves a door open for more mixing of chemistry between star systems. Even a chemical heritage across the galaxy. When the threshold reaches organic chemistry, that should not be ignored. As with hyperbolic comets, galactic networking might be greater than we were led to believe in pre-exoplanet days.

    • Michael March 12, 2023, 17:46

      Water could have formed when silicate material interacted with our hydrogen envelope as well, the silicate rocks been attracted to our hot forming planet via gravity and surface magma.

  • Mike Serfas March 12, 2023, 18:10

    I didn’t find a preprint for this one, but previous work for this system has proposed a complex structure of shells at which various organic compounds can be found: https://arxiv.org/pdf/2207.02252.pdf For example, methanol is between 40 and 125 au – the inner radius because it goes into gas phase around 80-100 K.

    What intrigues me at the moment is whether these results might lend any support to a fringe theory, namely abiogenic origin of petroleum ( https://www.intechopen.com/chapters/41889 ) … some of the compounds observed seem fairly reactive, so could they polymerize in place and be incorporated deep in the mantle or core of a planet? For purposes of science fiction this idea is highly convenient, because then Mars could have deep petroleum resources that can be reacted with perchlorates in some hidden deep ecosystem.

  • Michael Fidler March 13, 2023, 0:59

    This is a visible light image of variable star V883 Orionis and you can see the clouds it is embedded in. These same clouds are what our solar system travel through when we pass through the main galaxy arms. It is not too far to say the this is where much of the water on earth and other icey worlds in the solar system may of been enriched. These clouds are full of icy comets and planets like Mars may still contain a fossil record of these encounters. Our solar system may have had weather of a galactic scale!

    Scientists have traced Earth’s path through the galaxy via tiny crystals found in the crust.

    I would like all of you to take a close look at this image of our passage through the galaxies arms. There are not just the two main arms but a total six arms the last of which was passed through sixty-six million years ago and a small one we are just entering now. These passages vary tremendously because of the solar systems above and below orbit of the galactic plane and the density of different parts these galactic arms.


    So we are looking at a very complicated picture over time for the earth, that from this data of “V883 Orionis’s water during formation”, may be showing a continuing process of reintroducing water and organic material to planets like Mars and the earth.

  • Afterthought March 13, 2023, 2:40

    I’ve often wondered what a celestial body made almost entirely of water but sizable enough to retain an atmosphere would be like.

    • Michael March 14, 2023, 4:36

      Under the huge pressures it would be mostly ice.

      • Mike Serfas March 14, 2023, 10:36

        I asked a related question about whether Uranus has a liquid water surface at https://astronomy.stackexchange.com/questions/43887/
        could-there-be-liquid-water-on-uranus-are-there-any-indications-that-there-migh . Uranus and Neptune are both mostly supercritical fluid, but maybe Uranus has liquid water above that. As I recall Neptune may be too hot – if kicked out of the Solar system it might develop more potential for life. The planet imagined above is different, with no atmosphere but steam, perhaps with a crust of ice over an ocean. If it’s cold enough internally (few radioisotopes, smaller, etc.) the ocean could have an icy bottom like Europa or be frozen entirely.

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