Projectile cannon experiments show how asteroids can deliver water

Projectile cannon experiments show how asteroids can deliver water
Samples of impact glasses created during an impact experiment. In impact experiments, these glasses capture surprisingly large amounts of water delivered by water-rich, asteroid-like impactors. Credit: Terik Daly

Experiments using a high-powered projectile cannon show how impacts by water-rich asteroids can deliver surprising amounts of water to planetary bodies. The research, by scientists from Brown University, could shed light on how water got to the early Earth and help account for some trace water detections on the Moon and elsewhere.

"The origin and transportation of and volatiles is one of the big questions in planetary science," said Terik Daly, a postdoctoral researcher at Johns Hopkins University who led the research while completing his Ph.D. at Brown. "These experiments reveal a mechanism by which asteroids could deliver water to moons, planets and other asteroids. It's a process that started while the solar system was forming and continues to operate today."

The research is published in Science Advances.

The source of Earth's water remains something of a mystery. It was long thought that the planets of the inner solar system formed bone dry and that water was delivered later by icy comet impacts. While that idea remains a possibility, isotopic measurements have shown that Earth's water is similar to water bound up in carbonaceous asteroids. That suggests asteroids could also have been a source for Earth's water, but how such delivery might have worked isn't well understood.

"Impact models tell us that impactors should completely devolatilize at many of the speeds common in the solar system, meaning all the water they contain just boils off in the heat of the impact," said Pete Schultz, co-author of the paper and a professor in Brown's Department of Earth, Environmental and Planetary Sciences. "But nature has a tendency to be more interesting than our models, which is why we need to do experiments."

For the study, Daly and Schultz used marble-sized projectiles with a composition similar to carbonaceous chondrites, meteorites derived from ancient, water-rich asteroids. Using the Vertical Gun Range at the NASA Ames Research Center, the projectiles were blasted at a bone-dry target material made of pumice powder at speeds around 5 kilometers per second (more than 11,000 miles per hour). The researchers then analyzed the post-impact debris with an armada of analytical tools, looking for signs of any water trapped within it.

Hypervelocity impact experiments, like the one shown here, reveal key clues about how impacts deliver water to asteroids, moons, and planets. In this experiment, a water-rich impactor collides with a bone-dry pumice target at around 11,200 miles per hour. The target was designed to rupture partway through the experiment in order to capture materials for analysis. This high-speed video (taken at 130,000 frames per second) slows down the action--in real time, the experiment is over in less than a second. Credit: Terik Daly

They found that at impact speeds and angles common throughout the solar system, as much as 30 percent of the water indigenous in the impactor was trapped in post-impact debris. Most of that water was trapped in impact melt, rock that's melted by the heat of the impact and then re-solidifies as it cools, and in impact breccias, rocks made of a mish-mash of impact debris welded together by the heat of the impact.

The research gives some clues about the mechanism through which the water was retained. As parts of the impactor are destroyed by the heat of the collision, a vapor plume forms that includes water that was inside the impactor.

"The impact melt and breccias are forming inside that plume," Schultz said. "What we're suggesting is that the water vapor gets ingested into the melts and breccias as they form. So even though the impactor loses its water, some of it is recaptured as the melt rapidly quenches."

The findings could have significant implications for understanding the presence of water on Earth. Carbonaceous asteroids are thought to be some of the earliest objects in the solar system—the primordial boulders from which the planets were built. As these water-rich asteroids bashed into the still-forming Earth, it's possible that a process similar to what Daly and Schultz found enabled water to be incorporated in the planet's formation process, they say. Such a process could also help explain the presence of water within the Moon's mantle, as research has suggested that lunar water has an asteroid origin as well.

The work could also explain later water activity in the solar system. Water found on the Moon's surface in the rays of the crater Tycho could have been derived from the Tycho impactor, Schultz says. Asteroid-derived water might also account for ice deposits detected in the polar regions of Mercury.

"The point is that this gives us a mechanism for how water can stick around after these impacts," Schultz said. "And it shows why experiments are so important because this is something that models have missed."


Explore further

Study suggests Earth's water was present before impact that caused creation of the moon

More information: "The delivery of water by impacts from planetary accretion to present" Science Advances (2018). advances.sciencemag.org/content/4/4/eaar2632
Journal information: Science Advances

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Apr 25, 2018
This helps to add to the evidence for my opinion that what present water has been detected on Luna and Mars are from recent debris falls.

It has been pointed out that the isotopes for water on Luna and Mars does not match that detected on present asteroids. However the asteroids sampled are just a handful. There remains the declining possibility that different isotopes may still be found on rocks and comets that have not been sampled.

Apr 25, 2018
Neither this article nor Daly & Schultz discussed Mars at all, so how is that evidence that the detected water is from recent debris falls? Mars today has a far greater amount of water than the Moon (both on the surface and below), and I doubt you'd find a single planetary scientist alive who'd attribute all of it to geologically recent impacts given that and the strong evidence for an even greater amount of water in the past. Di Achille & Hynek's, "Ancient ocean on Mars supported by global distribution of deltas and valleys" Nature Geoscience Letters 2010, for instance, has an early Martian ocean occupying a volume of 124,000,000 cubic kilometers and nearly a third of the planet's surface.

If anything, this article supports the existing consensus that Mars obtained the bulk of its water through the same mechanism as the Earth: Through accretion of water bearing planetesimals. Mind you, Mars and the Earth did not go through a volatiles depleting reformation like the Moon.

Apr 25, 2018
detected on Luna
Hey. Thats the moon isnt it?

"Luna is the Latin name for the Moon"

By golly it is.

haha

Has anybody called you numbnuts today?

Still pretending youre black?

haha

Apr 25, 2018
Earthly water was likely created in the same manner as water is created at comets, electrochemically.

https://www.suspi...arwater/

Apr 25, 2018
I've always wondered about that. Could it have possibly been that the impacter that hit the earth and created the moon might have been a great big huge chunck of mostly Ice?

Apr 25, 2018
@24volts
Given that the impactor's size is typically described as being around the mass of Mars, probably not. Even if it formed well beyond the Earth, a significant amount of its interior volume would've still been rock and metal like other large bodies in the Solar System.

Though it would hardly matter as far as the Moon's concerned. Volatiles contained within the debris would've likely been depleted prior to their accretion into the new body (or simply left out of the accretion disk) and further loss would have occurred during any subsequent volcanism. For more, see Kato et al.'s, "Extensive volatile loss during formation and differentiation of the Moon" Nature Communications 2015 and Canup et al.'s, "Lunar volatile depletion due to incomplete accretion within an impact-generated disk" Nature Geoscience Letters 2015.

Apr 25, 2018
Earthly water was likely created in the same manner as water is created at comets, electrochemically.

https://www.suspi...arwater/


Wrong. Whoever came up with that idea is very obviously scientifically illiterate. Not going to happen.

Apr 25, 2018
But the, "O" in, "Observer" was replaced with a, "0". Surely that attempt at wordplay accounts for something!?

Apr 25, 2018
Wrong. Whoever came up with that idea is very obviously scientifically illiterate. Not going to happen.

This coming from the guy who said, "where's the electrolyte?" When it's suggested electrochemistry occurs in plasmas. LOL! Scientifically illiterate indeed.

Apr 25, 2018
Wrong. Whoever came up with that idea is very obviously scientifically illiterate. Not going to happen.

This coming from the guy who said, "where's the electrolyte?" When it's suggested electrochemistry occurs in plasmas. LOL! Scientifically illiterate indeed.


So, please explain how this woo is happening. Where is your H? Where is your O? How are they getting together? Show me the chemical pathways and the the necessary number of reactants to account for ~ 1000 litres/s. Or 200 000 l/s, if you want to try Hale-Bopp. Like I said, it is scientifically illiterate nonsense.

Apr 26, 2018
H in the solar wind, O in the rock. Electrochemistry via cathode sputtering and charge exchange.
With regards to Earth, plenty of H in the solar wind along with O fountains spewing into near-Earth space.

Apr 26, 2018
H in the solar wind, O in the rock. Electrochemistry via cathode sputtering and charge exchange.
With regards to Earth, plenty of H in the solar wind along with O fountains spewing into near-Earth space.


Oh dear. Such ignorance! Firstly, there is no rock on a comet. As confirmed by multiple instruments. Secondly, the solar wind H+ is getting nowhere near the comet for months on end, around perihelion. Thirdly, there is nowhere near enough H+ to account for even 1 l/s of water. Fourthly, the SW H+ is travelling far too quickly to combine with anything. Fifthly, there is no O- for it to combine with, even if it could. Sixthly, what cathode? Seventhly, there was sod all O when Earth was getting its water, and the SW would get nowhere near the surface.
Other than that............ lol.

Apr 26, 2018
Water molecules origins are where planets obtained their water, not comets
looking through the article and the comments does not give any leads of where the comets got their water from, ice freezing on billions of particles is not where the comets got their water from, the water is present in the Cometary particles orbital paths, is a surface for water molecules to attach to, whether its collision or electrical attraction/surface tension before it freezes, it has be in molecule form - water only freezes when molecules combine. As each molecule lands on a single grain it does not freeze till other molecules land forming water then freezing, once frozen the comet can deposit its billions of grains any where it impacts, but all this does not explain where the water molecules arrived in the comets orbital path. The water molecules origins are where the earth, moon and mars obtained their water, not comets.

Apr 26, 2018
And the same proccess applies to asteroids or any cold region of orbital space in our solar system.

Apr 26, 2018
Below a certain size/volume of impactors masses I can see the water and other light volatiles evaping away from the mass, however, once you get above a certain size/mass, then the water and other volatiles will stick around due to the gravity of that mass until you have a full atmosphere. After that, when you get impacts the volatiles will stick around and just build atmosphere, liquids as well as rock. Even Luna holds a tenuous atmosphere.

Apr 26, 2018
The difficulty I see in these comments about water sources for Mars is the absence of the concept of time. Mars has been around for billions of years.

Billions of years ago the proto-planet that survived to become Mars underwent billions of impacts from asteroids and comets.

During the first billion or so years, as the crust cooled sufficiently, Mars developed at least shallow oceans. Based upon the available evidence to date, it is a reasonable supposition that an Early Mars was wet.

Unless some new, radically disruptive evidence is discovered? I can accept that expectation.

Then billions of years passed where Mars, for a multiple of reasons, lost it's oceans. Until we are left with the present dead rustball.

Now, from a distance, we are trying to ascertain whether or not there any available water in the crust.

It still remains to be proven or disproven the originating source of any water to be found. What we know is a constantly changing scale.

Apr 26, 2018
Scientists are not, "trying to ascertain whether or not there any available water in the crust": They already know there is and have for decades now. The only debates concern particular phenomenon, the total inventory and the evolution of the Martian hydrosphere. There is absolutely no debate as to whether Mars has near surface water or not, even if we're to exclude the ice caps.

For example: Stuurman et al.'s, "SHARAD detection and characterization of subsurface water ice deposits in Utopia Planitia, Mars" Geophysical Research Letters 2016 confirmed the presence of around 14,300 cubic kilometers of water ice beneath Utopia Planitia using data from ground penetrating radar. Prior to that Carr & Head's, "Martian surface/near-surface water inventory: Sources, sinks and changes with time" Geophysical Research Letters 2015 noted that Mars noted that, "a global layer of water about 34 m thick is present at the Martian surface and near surface today".

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