Mars Has Watery Insides, Just Like Earth

Researchers from the Carnegie Institution have found that water is present in surprisingly Earthlike amounts within Mars’ mantle, based on studies of meteorites that originate from the Red Planet. The findings offer insight as to how Martian water may have once made its way to the planet’s surface, as well as what may lie within other terrestrial worlds.

Earth has water on its surface (obviously) and also within its crust and mantle. The water content of Earth’s upper mantle — the layer just below the crust —  is between 50 and 300 ppm (parts per million). This number corresponds to what the research team has identified within the mantle of Mars, based on studies of two chunks of rock — called shergottites — that were blasted off Mars during an impact event 2.5 million years ago.

“We analyzed two meteorites that had very different processing histories,” said Erik Hauri, the analysis team’s lead investigator from the Carnegie Institute . “One had undergone considerable mixing with other elements during its formation, while the other had not. We analyzed the water content of the mineral apatite and found there was little difference between the two even though the chemistry of trace elements was markedly different. The results suggest that water was incorporated during the formation of Mars and that the planet was able to store water in its interior during the planet’s differentiation.”

The water stored within Mars’ mantle may have made its way to the surface through volcanic activity, the researchers suggest, creating environments that were conducive to the development of life.

Like Earth, Mars may have gotten its water from elements available in the neighborhood of the inner Solar System during its development. Although Earth has retained its surface water while that on Mars got lost or frozen, both planets appear to have about the same relative amounts tucked away inside… and this could also be the case for other rocky worlds.

“Not only does this study explain how Mars got its water, it provides a mechanism for hydrogen storage in all the terrestrial planets at the time of their formation,” said former Carnegie postdoctoral scientist Francis McCubbin, who led the study.

The team’s research is published in the July edition of the journal Geology. Read more on the Carnegie Institution for Science’s site here.

Image: The remains of what appears to be a river delta within Eberswalde crater on Mars, imaged by ESA’s Mars Express. Credit: ESA/DLR/FU Berlin (G. Neukum).

27 Replies to “Mars Has Watery Insides, Just Like Earth”

  1. Well, it seems to me that the younger Mars had water. But now, unless they find a hot spring, I am not yet convinced that underneath it has large amount of water.

    1. The Phoenix lander found ice under a layer of regolith. Much of the surface of Mars is a thin layer that covers glaciers.

      1. I see. The Mariner 4, the Phoenix and the Spirit all found thin glaciers on the surface. However, the meteorites from Mars only provide us the scenario of early Mars. The large-scale water underneath still needs to be proven.

      2. Thank you! You prompted me to look into this a bit. This article is a bit dense, but it looks to be a summary of someone who knows the field. (On Wikipedia, nonetheless.)

        It describes why scientists believe there is a vast subsurface water ice cap 100s to 1000s meter under the surface. It would fit the surface features that indicate ~ 500 m “Water Equivalent to a Global layer (WEG)” surface water. No more than 50 m of that is believed to have been lost to space, indicating the rest was buried as ice.

        Notable is that while it doesn’t contain the result described in the post, it describes how this could come about:

        “An alternative to the cometary and asteroidal delivery of H2O would be the accretion via physisorption during the formation of the terrestrial planets in the solar nebula. This would be consistent with the thermodynamic estimate of ~2 earth masses of water vapor within 3AU of the solar accretionary disk, which would exceed by a factor of 40 the mass of water needed to accrete the equivalent of 50 Earth hydrospheres (the most extreme estimate of Earth’s bulk H2O content) per terrestrial planet.[8] Even though much of the nebular H2O(g) may be lost due to the high temperature environment of the accretionary disk, it is possible for physisorption of H2O on accreting grains to retain nearly 3 Earth hydrospheres of H2O at 500 K temperatures.[8] This adsorption model would effectively avoid the 187Os/188Os isotopic ratio disparity issue of distally-sourced H2O. However, the current best estimate of the nebular D/H ratio spectroscopically estimated with Jovian and Saturnian atmospheric CH4 is only 2.1×10-5, a factor of 8 lower than Earth’s VSMOW ratio.[8] It is unclear how such a difference could exist if physisorption were indeed the dominant form of H2O accretion for Earth in particular and the terrestrial planets in general.”

        Bar “the nebular D/H ratio spectroscopically estimated with Jovian and Saturnian atmospheric CH4”, the physisorption theory fitted better to other observations already before the discovery of a generic water content. Otherwise you have to have a peculiar contribution of asteroid belt protoplanets not seen today.

        In the tension between the new results and the spectroscopic data, I don’t know which gives. But I note the latter data is more remote from the estimated initial water content.

  2. Without water in the Earth’s mantle the oceans and water vapor in the atmosphere would disappear in about 500 million years. Water in the very upper atmosphere is chemically changed to H_2 and O_2 by UV radiation from the sun. This process has actually been measured from space. The result is that without a replenishing mechanism water would be gone after a time period shorter than the geological age of the Earth. Volcanism causes water from the interior to reach the surface and replenishes water lost through photo-chemical action.

    1. But then isn’t the volcanism using up the reserves in the interior? So we lose the water in the atmosphere due to the chemical reactions you describe, it’s replaced by volcanism, we lose more, replaced, etc. It seems that eventually that would run out too.

      1. Of course it is not eternal. The Earth itself is running down. The weak nuclear radioactive decay in the center of the Earth, mostly due to potassium 40 as I understand, will become exhausted as well. As the mantle cycles in its convection process it probably loses a percentage of water. Of course the time scale for serious depletion is several billion years, so this is not a practical concern, just as the sun over heating in a couple of billions of years.

    2. Does this mean that the oil and gas fracking boom of injecting water deep into the underground is actually saving our water 😉

    3. Fascinating! I’d like to say thanks for your many informative and knowledgeable posts

    4. Most of Earth atmosphere loss is by sequestration into rocks, not by escape to space.

      Earth currently looses ~ 3 kg/s H2, see the link and its ref. One hydrogen molecule masses ~ 2 g/mol, one water molecule ~ 18 g/mol, giving an equivalent loss of 3*18/2 ~ 30 kg/s H2O.

      The Earth water content is ~ 0.05 % by mass, or ~ 0.0005*6*10^24 kg = 3*10^21 kg. Half of that is buried in the crust and mantle, giving ~ 10^21 kg as surface and atmosphere water.

      To loose that water to space would take 10^21/30 ~ 3*10^19 s or ~ 10^12 years. Earth is ~ 5*10^9 years of age, so at the current rate it has lost ~ 0.5 % of its ocean water over its history.

      Of course, I haven’t figured in the gains yet.

      Earth gains ~ 6*10^10 g/year mass of debris from asteroids and dust (Barker & Anders, 1968, based on isotopic abundance ratios in sea floor sediments; Ceplecha 1996), or ~ 2 kg/s. If we take the chondrite value of ~ 20 % water by weight, it means Earth gains ~ 0.4 kg/s water.

      Other hydrogen sources are solar wind influx and diverse forms of radioactivity in atmosphere and Earth bulk, but I think I’ll give it a rest. The point is that either I have messed up my estimate or we need a source for the 500 million lifetime.

      Sure it wasn’t during the young Sun and with a potential hydrogen wind loss? (The hydrogen wind would be a hydrodynamical flow loss if the young Earth had more than 30 % hydrogen in its atmosphere. Essentially the hydrogen escapes and drags some other light gases with.)

      1. I spent a little time trying to find a reference for my claim about photoionization or photochemical loss of H_2O. I remember reading about this some time ago, even with a picture formed from the spectral lines of this process as seen from space. I seem to remember the time for total loss of water was about 5×10^8 years. I ran the numbers from the Wiki site and got the same answer.

  3. I wonder what this says about the possibility for water under the surface of Ceres. If anything. Oh well, I guess we’ll know before too long.

  4. Locked up in the rock, eh? No doubt…. This comment: “Like Earth, Mars may have gotten its water from elements available in
    the neighborhood of the inner Solar System during its development.” represents the currently accepted theory of planetary formation and subsequent elemental composition and is quite plausible if not fact. BUT I’d like to point out that there is yet another mechanism which might add to this cosmic brew and is one that is usually overlooked.

    Mr. Sol is an evolved representative of the G2 class of stars. To reach this relatively calm state Sol has processed, using fusion, a wide range of elements in it’s interior. Today we see in the solar wind ionized Hydrogen (KEY here), 8% Helium and trace amounts of Carbon, Nitrogen, Oxygen, Neon, Magnesium, Silicon, Sulfur and Iron. The SOHO satellite also identified traces of some elements for the first time such as
    P, Ti, Cr and Ni and an assortment of solar wind isotopes identified
    for the first time: Fe 54 and 56; Ni 58,60,62

    It is quite possible, that Sol’s later evolution has included episodes where certain elements became much richer and more dominant and were then expelled in the solar wind. In particular there may have been episodes where Hydrogen and _Oxygen_ become the dominant outflow from Sol.

    Ice Ages on Mars (concurrent with those on Earth) anyone?

    1. Stars sized as the Sun or smaller mainly fuse using the p-p chain, resulting in He. So the processing it does with heavier nuclei would be gravitational sorting in settling, convection and diffusion of already existing nuclei.

      The Sun is pretty well mixed, so I don’t think outflow would vary much over its surface until the scale of magnetic field variations. I don’t know how much such flows would vary over time, but FWIW this paper discusses solar origins of terrestrial water:

      “While the water production by solar wind capture is very small today it may have been significant during the first billion years after planetary formation because solar wind was much stronger at that time and Earth magnetospheric configuration may have been different. We estimate that the contribution of solar wind hydrogen to the Earth water reserves can be up to 10% when we assume a that the Earth dipole acted as a collector and early solar wind was 1000 times stronger than today. We can not even exclude that solar wind hydrogen was the main contributor to Earth water reserves [sic]”.

      Note that the current paper nicely rejects the last suggestion. Then the at most 10 % constraint of hydrogen contributed by the Sun would be order of magnitudes stricter for oxygen. ‘Metals’ like oxygen is ~ 1 % of a recent generation star by mass, and a more massive molecule would be harder to eject.

    2. It is quite possible, that Sol’s later evolution has included episodes where certain elements became much richer and more dominant and were then expelled in the solar wind. In particular there may have been episodes where Hydrogen and _Oxygen_ become the dominant outflow from Sol.

      No, the sun does not produce any of the elements beyond Helium (yet), wich means the possible inflow remains a constant (so far).

      1. Please double check your notes… This is from a Stanford physics dept. web page:

        “The composition of the solar wind is a mixture of materials found
        in the solar plasma, composed of ionized hydrogen (electrons and
        protons) with an 8% component of helium (alpha particles) and trace
        amounts of heavy ions and atomic nuclei: C, N, O, Ne, Mg, Si, S, and
        Fe ripped apart by heating of the Sun’s outer atmosphere, that is, the
        corona (Feldman et al., 1998).

        SOHO also identified traces of some elements for the first time such as
        P, Ti, Cr and Ni and an assortment of solar wind isotopes identified
        for the first time: Fe 54 and 56; Ni 58,60,62 (Galvin, 1996)”

      2. Please double check yours.
        The content of elements heavier than helium remains the same as it was when the sun was originally formed some 4.5 billion years ago, because none of those elements are currently produced by the sun.
        That means that there will be no large variations in the influx towards planets, or ‘constant influx’ of the same proportions, making your origonal comment…

        It is quite possible, that Sol’s later evolution has included episodes where certain elements became much richer and more dominant and were then expelled in the solar wind. In particular there may have been episodes where Hydrogen and _Oxygen_ become the dominant outflow from Sol


      3. Stellar nuclesyntesis.
        The Sun is fusing Hydrogen into Helium, and has been since it was formed some 4.5billion years ago.
        The Sun does not fuse anything heavier then Helium. So provide me with a mechanism that would allow the Sun to expell variating ratios of elements when its own ratios does not change (Except for the ratio Hydrogen/Helium)

      4. Did you even read the above link? ( I’ll repeat it for you here: “…The solar wind has trace amounts of heavy ions and atomic nuclei: C, N, O, Ne, Mg, Si, S, and Fe. Also, as discovered by SOHO P, Ti, Cr and Ni and an assortment of solar wind isotopes identified
        for the first time: Fe 54 and 56; Ni 58,60,62…”

        The statement(s) in the link(s) above indicate that the Solar Wind’s composition includes traces of elements heavier than Helium. Sol’s composition is assumed to be due to it’s initial nebular elemental variety and then through nuclear processing within the core. I contend that the variation and distribution of these elements in the solar wind is reliant upon Sol’s internal state and stages of fusion and gravitational condensation. Therefore it is entirely possible that during Sol’s early evolution, fusion processes evolved where the percentage of ionized hydrogen and oxygen in the solar wind increased, providing elemental ‘seed’ stock for an increase in the creation of water molecules.

      5. Aqua, seriously, if you cannot even grasp the simple fact that the Sun currently (and historically) pretty much only fuses Hydrogen into Helium, and DOES NOT fuse any heavier elements, then talking to you is a complete waste of time.
        Yes, I understand that stars can fuse heavier elements, DO YOU UNDERSTAND THAT THE SUN DOES NOT?

      6. @magnus.nyborg: Obviously you have missed my point entirely. Yes… fusion within Sol is that of Hydrogen turning into Helium as the Hydrogen fuses. In my statement I was asserting that there were other elements in the gaseous and dust filled ‘soup’ which condensed out of the interstellar medium and formed our star. Those elements have been detected in solar wind particles. (As noted above) Those elements were created (Of course!) very early on in the supernova of first, second or perhaps third generation of stars… Then LATER those elements were incorporated into the next generation of stars like our sun.

        Check out Frazer’s explanation?

        You will note that in the diagrams shown there are assumed layers as one approaches the core: Basically the Convective zone, the Radiative zone and the Inner core. WHERE do _you_ think those early incorporated metals might be in this mix? What I am saying, is that as Sol processes Hydrogen there may have been episodes where, even though miniscule in comparison to the abundance of Hydrogen and Helium, layers of heavier elements may have evaporated into the solar wind stream.. thereby altering the abundance ratios of those elements in the solar wind which were later captured and processed by planetary gravity wells and magnetic fields.

        Then again… we certainly don’t know everything there is to know about the goings on within stars, now do we? Instead we have the best scientific estimate of those processes. I contend that there may be processes of elemental shuffling within Sol that we don’t completely understand which MAY have lead to the episodic expulsion of heavier elements in the solar wind.

  5. I believe I said on this the other day here on UT, tremendous news! But I should lay it out here under the relevant post:

    – Mars had as much water as Earth originally. ;

    By looking at two martian meteorites where one was relatively pristine and another mixed geochemically they could see the same water contents in the same minerals. This argues for a sustained water storage through martian history.

    The derived water content in the martian mantle is ~ 70 – 300 ppm, compared to tellusian mantle 50 – 300 ppm. It is notable that this water should affect the mantle and make it more malleable, sustaining geological activity longer.

    But wait, it gets better!

    The original parent magma contained 10 times as much water, or ~ 700 – 3000 ppm water, see the abstract.

    – This predicts the generic water evolution and content on terrestrials!

    They are pretty dry compared to your average asteroid chondrite, that has ~ 15-20 % water by mass. Earth-Moon and Mars now initially had ~ 0.5 % water by mass which Earth mostly retains. 5 times less and we would likely not have plate tectonics (Earth is a runt, as terrestrials go, so plate tectonics is marginal), 5 times more and we would have no continents.

    This has been a long standing concern for me, re habitability “as we know it” elsewhere. But with a generic fine dryness after the aggregation process, there should be extensive habitability as we know it in exoplanets placed in the habitable zone.

    And as the press release has the scientists note, water volatile evolution after aggregation by volcanic activity should now suffice – here, on Mars and everywhere.

    “There has been substantial evidence for the presence of liquid water at the Martian surface for some time,” Hauri said. “So it’s been puzzling why previous estimates for the planet’s interior have been so dry. This new research makes sense and suggests that volcanoes may have been the primary vehicle for getting water to the surface.”

    Presumably Moon vented as much water and hydrogen after the Earth-Moon impact formation, but it didn’t stick around. Except maybe those polar craters got the last whiff.

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