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Recent Geologic Activity on the Moon?

Newly detected series of narrow linear troughs are known as graben, and they formed in highland materials on the lunar farside. These graben are located on a topographic rise with several hundred meters of relief revealed in topography derived from LROC stereo images. Image Credit: NASA/GSFC/Arizona State University/Smithsonian Institution


Recent images from NASA’s Lunar Reconnaissance Orbiter Camera provide evidence that the lunar crust may be pulling apart in certain areas. The images reveal small trenches less than a kilometer in length, and less than a few hundred meters wide. Only a small number of these features, known as graben, have been discovered on the lunar surface.

There are several clues in the high-resolution images that provide evidence for recent geologic activity on the Moon.

The LROC team detected signs of contraction on the lunar surface as early as August of 2010. The contractions were in the form of lobe-shaped ridges known as lobate scarps. Based on the data, the team suggests the widely-distributed scarps indicate the Moon shrank in diameter, and may be continuing to shrink. Interestingly enough, the new image data featuring graben presents a contradiction, as they indicate lunar crust being pulled apart and theorize that the process that created the graben may have occurred within the past 50 million years.

“We think the Moon is in a general state of global contraction due to cooling of a still hot interior, said thomas Watters from the Center for Earth and Planetary Studies. “The graben tell us that forces acting to shrink the Moon were overcome in places by forces acting to pull it apart. This means the contractional forces shrinking the Moon cannot be large, or the small graben might never form.”

Based on the size of the graben, the forces responsible for contraction of the lunar surface are assumed to be fairly weak. It is further theorized that, unlike the early terrestrial planets, the Moon was not completely molten during its early history.

“It was a big surprise when I spotted graben in the farside highlands,” said Mark Robinson, LROC Principal Investigator at Arizona State University. “I immediately targeted the area for high resolution stereo images so we could create a 3-dimensional view of the graben. It’s exciting when you discover something totally unexpected. Only about half the lunar surface has been imaged in high resolution. There is much more of the Moon to be explored.”

If you’d like to learn more about the recently discovered graben on the moon, you can watch a short video by Thomas Watters below:

To learn more about the Lunar Reconnaissance Orbiter Camera, visit: http://www.lroc.asu.edu/

Source: Arizona State University News

About 

In addition to being a published astronomer specializing in variable stars, Ray Sanders has blogged for Universe Today, and The Planetary Society blog, among others. He runs his own blog, Dear Astronomer, teaches classes for CosmoQuest, and is a NASA/JPL Solar System Ambassador.

Comments on this entry are closed.

  • Aqua4U February 21, 2012, 12:07 AM

    “It is further theorized that, unlike the early terrestrial planets, the Moon was not completely molten during its early history.”

    What does this do to the theory that the moon coalesced from the debris of a collision between Earth and another primordial planet? Doesn’t that theory imply that the collisional body would be entirely molten by the impact?

    • Sam February 21, 2012, 12:54 AM

      The mars sized body would have collided with the early Earth with a velocity around 11km/s which would have raised the temperature of the earliest rocks to around 13000K which most definitely would have made everything completely molten.

      • Jon Souter February 21, 2012, 10:05 AM

        But there’s a lot of other variables at play than speed and mass – such as trajectory (e.g. was it a glancing impact, or one that was more full-on) that affect the outcome.

        Stating without any qualification that the earliest rocks reached a very specific temperature is mis-leading at best.

    • John Miller February 21, 2012, 4:17 AM

      It does nothing to that theory. As was stated, “the Moon was not completely molten”. But it would have to have been at least partially molten. That is how the maria were formed.

    • Torbjörn Larsson February 21, 2012, 10:55 AM

      My 2 p above. Perfect melting seems less certain IMO, give or take the recent results.

      I don’t think there was ever a consensus on this, at least the textbooks I have leave it as an open question as I remember them.

    • lcrowell February 21, 2012, 3:48 PM

      If a Mars mass body collided with Earth and all of that energy was converted to thermal energy I would probably agree with you. The impact is thought to have spun off lots of matter which eventually coalesced into the moon. Hence a lot of that kinetic energy was preserved as kinetic energy in the spallation of the proto-Earth and this Mars massed planet. So it could be this material was not all melted and coalesced in a manner so the entire moon was not melted at once.

      I am a bit out of my element here, so one would have to research the literature and see what the primary researchers are thinking. There is a lot of numerical modeling which has gone into this as well. It is difficult to second guess the outputs of these complex codes.

      LC

  • Torbjörn Larsson February 21, 2012, 10:04 AM

    The Moon is an interesting body.

    My own interest comes from what it can tell us of early Earth history. As Universe Today readers may remember, the Moon rocks dating the Earth-Moon impactor may be younger than earlier thought, maybe dating as late as 4.36 Ga bp (billion years before present). The latest dating of the solar system is 4.5672 +/- 0.0005 Ga bp, making the Moon originating at most ~ 210 My after system formation (asf).

    However, that last reference has an interesting update on Earth formation, which may tie into the current find. Earlier it was believed for good reason that when the Earth formed, the incoming impactors melted fully and made the mantle composition uniform. This is because the metals that readily dissolve in lighter silicide rocks (siderophiles) are slightly depleted to match such a process.

    The new model shows that it is possible to fit observations of siderophiles to impactors that only contribute ~ < 40 % of mantle material. The upshot is that the time of Earth formation becomes more relaxed and the models of impact rates simpler. (See their fig. 4.) Now a simple draining impact supply fits a basic exponential decreasing rate. I eyeball the latest time for the Earth-Moon impactor as ~ 180 My asf. (You have to go to their model paper for that.)

    This goes back to how much melting occurs during impact formation, on the impactor but also on the impacted body. And suddenly there seems to be observations that says there could be less than perfect melting. Here is results implying that large impactors have problems emulsifying as neatly as the old models assumed. And And here is direct observation of mantle survival during the Earth-Moon impactor:

    “Unexpected new findings by a University of Maryland team of geochemists show that some portions of the Earth’s mantle (the rocky layer between Earth’s metallic core and crust) formed when the planet was much smaller than it is now, and that some of this early-formed mantle survived Earth’s turbulent formation, including a collision with another planet-sized body that many scientists believe led to the creation of the Moon.”

    “We have discovered 2.8 billion year old volcanic rocks from Russia that have a combination of isotopes of the chemical element tungsten that is different from the combination seen in most rocks — different even from the tungsten filaments in incandescent light bulbs,” says the first author, Touboul, a research associate in the University of Maryland’s Department of Geology. “We believe we have detected the isotopic signature of one of the earliest-formed portions of the Earth, a building block that may have been created when the Earth was half of its current mass.”

    All of this ties in with the late, late tail of bombardment which could have supplied the remaining superabundance of highly siderophile elements or not. It would be interesting to see a planetary scientist synthesize a working model.

    In the context, one can well ask how we can have graben without having lava flows? Well, maybe the answer is that some Moon lava is untypically dense:

    “Nearly all the lunar magmas were found to be less dense than their solid surroundings, similar to the situation on Earth. There is one important exception: small droplets of titanium-rich glass first found in Apollo 14 mission samples produce liquid magma as dense as the rocks found in the deepest parts of the lunar mantle today. This magma would not move towards the surface.

    Such titanium-rich magma can only be formed by melting titanium rich solid rocks. Previous experiments have shown that such rocks were formed soon after the formation of the Moon at shallow levels, close to the surface. How did they get deep into the mantle? The scientists conclude that large vertical movements must have occurred early in the history of the Moon, during which titanium-rich rocks descended from near the surface all the way to the core-mantle boundary. “After descending, magma formed from these near-surface rocks, very rich in titanium, and accumulated at the bottom of the mantle – a bit like an upside-down volcano.”

    Btw, Mars has been rocked by recent geological activity too:

    “Gerald Roberts, an earthquake geologist with Birkbeck, an institution of the University of London, who led the study, said that the images of Mars included boulders that ranged from two to 20 meters (6.5 to 65 feet) in diameter, which had fallen in avalanches from cliffs. The size and number of boulders decreased over a radius of 100 kilometers (62 miles) centered at a point along the Cerberus Fossae faults.

    “This is consistent with the hypothesis that boulders had been mobilized by ground-shaking, and that the severity of the ground-shaking decreased away from the epicenters of marsquakes,” Roberts said.”

  • Torbjörn Larsson February 21, 2012, 10:15 AM

    Btw, Mars has been rocked by recent geological activity too:

    “Gerald Roberts, an earthquake geologist with Birkbeck, an institution of the University of London, who led the study, said that the images of Mars included boulders that ranged from two to 20 meters (6.5 to 65 feet) in diameter, which had fallen in avalanches from cliffs. The size and number of boulders decreased over a radius of 100 kilometers (62 miles) centered at a point along the Cerberus Fossae faults.

    “This is consistent with the hypothesis that boulders had been mobilized by ground-shaking, and that the severity of the ground-shaking decreased away from the epicenters of marsquakes,” Roberts said.”

    “Because the area of displaced boulders in the marsscape stretched across an area approximately 200 km124-miles) long, the quakes were likely to have had a magnitude greater than 7, the researchers estimated.”

  • Ashar Azhar February 21, 2012, 12:48 PM

    the Quran has already stated about this event 1500 years ago!!

    http://www.answering-christianity.com/moon_split.htm

    ^please visit above website^

    • squidgeny February 21, 2012, 12:58 PM

      Yes but the Quran is full of rubbish, like every other holy book.

      • Really20 February 22, 2012, 12:21 AM

        You, sir, are a very intelligent and understanding person who thinks that all religion is in perpetual and necessary conflict with science, and with no respect for views beside your own. I applaud your wisdom.

        • Torbjörn Larsson February 22, 2012, 10:12 AM

          Indeed, it is the very basis of empirical derived wisdom to not respect any view, of course including your own. Eternal criticism and vigilance against the tendency to fool oneself (science) or others (religion) is the only way forward.

          I applaud you misdirected criticism.

          • Really20 February 23, 2012, 1:01 AM

            I consider science and religion to be entirely different realms. At least in my belief, they do not conflict because there is no playing field on which they must conflict.

          • Ken Lord February 23, 2012, 5:22 AM

            What you describe as your belief … your ability to hold two conflicting views (religion and science) in your head at the same time without apparent mental discomfort, is what the rest of us feel as real mental and even physical discomfort known as Cognitive Dissonance.

            If you think the realms don’t overlap and therefore can’t conflict, you haven’t given it much thought. Apparently Ignorance really is bliss to you.

            Any real claim made by religion (real as in affecting the universe in an observable way), for example the claim that a great global flood occurred as stated in Genesis in the Christian bible, or the claim made by some creationists that the Earth is only 6,000 years old can be tested and is therefore very much overlapping the realm of science.

            Dissonance time: There is no evidence of such a flood, and tree ring records by themselves prove the earth is more than 12,000 years old (let alone the reams of evidence for an age billions of years greater).

          • Torbjörn Larsson February 23, 2012, 10:48 AM

            Again, what is your _data_ to shore up your unwarranted belief? Claiming that there is no conflict is not the same as showing that there is no conflict (as described above).

          • Really20 February 24, 2012, 12:47 AM

            Religion is philosophical in nature, and cannot be reduced to mere data. You think that ALL religion is in necessary conflict with science. By that logic, only atheists can be “true scientists” who do not “pollute their data.”

            What you are saying is no better than religious extremism. I’m not in denial that religious texts are often filled with hate and rubbish, but you think that I hold a completely irrational belief because it differs from your own.

          • magnus.nyborg February 29, 2012, 11:10 AM

            Religion is in conflict with REALITY, as has been demonstrated numerous times.

          • Really20 March 1, 2012, 2:30 AM

            Only if you are extremely socially conservative and do not know the difference between religion and science.

          • magnus.nyborg March 1, 2012, 1:01 PM

            Society is not a religous concept, and there the demonstrable factors for societal wellfare that indicates that relgion lowers the wellbeing of society (statistically significant studies)

          • Really20 February 24, 2012, 12:49 AM

            I use religion in the sense of personal morality and decency and the underlying purpose to our universe while I look to science for directly observable phenomena. Therefore science and religion are not in conflict. I feel that if it crosses the previously mentioned line, religion is not religion, it’s pseudoscience.

        • squidgeny February 22, 2012, 3:28 PM

          I didn’t say that religion conflicts with science. I said that holy books are full of rubbish. I’ll grant you that those claims are related and overlap somewhat, but they’re not the same.

      • Raja Ikram February 29, 2012, 10:45 AM

        it seems you have no religion. so thats why you dont consider any of the book as a “not important”…Quran taught the scientists how to explore things…Quran gave hints to the universe… by all the way the term “science” have been started and explored and by muslims first…. so if you dont have knowledge about any thing dont come around these plaecs.. because you are creating anxiety among religion.

        • squidgeny February 29, 2012, 1:26 PM

          I do read the articles of great scientists and have never once need the Quran quoted or referenced in any way. Care to cite?

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