The varying brightness in Pluto's atmosphere is caused by atmospheric gravity waves, or buoyancy waves. Image: NASA/New Horizons/Johns Hopkins APL/SWRI

Gravity Waves On Pluto?

Article written: 19 Apr , 2016
Updated: 5 May , 2016
by

New Horizons’ historic journey to Pluto and beyond continues to provide surprises. As data from the spacecraft’s close encounter with Pluto and its moons arrives at Earth, scientists are piecing together an increasingly intriguing picture of the dwarf planet. The latest discovery is centred around Pluto’s atmosphere, and what are called ‘atmospheric gravity waves.’

Atmospheric gravity waves are a different phenomenon than the gravity waves that were detected for the first time in February, 2016. Those gravity waves are ripples in the fabric of space time, first predicted by Albert Einstein back in 1916. After years of searching, the LIGO instrument detected gravity waves that resulted from two black holes colliding. The discovery of what you might call ‘Einsteinian Gravity Waves’ may end up revolutionizing astronomy.

New Horizons has revealed surprise after surprise in its study of Pluto. Its atmosphere has turned out to be much more complex than anybody expected. It’s composed of 90% nitrogen, with extensive haze layers. Scientists have discovered that Pluto’s atmosphere can vary in brightness depending on viewpoint and illumination, while the vertical structure of the layered haze remains unchanged.

Scientists studying the New Horizons’ data think that atmospheric gravity waves, also called buoyancy waves, are responsible. Atmospheric gravity waves are known to exist on only two other planets; Earth and Mars. They are typically caused by wind flowing over obstructions like mountain ranges.

The layers in Pluto’s atmosphere, and their varying brightness, are most easily seen when they are backlit by the Sun. This was the viewpoint New Horizons had when it captured these images on its departure from Pluto on July 14, 2015. The spacecraft’s Long Range Reconnaissance Imager (LORRI) captured them, using time intervals of 2 to 5 hours. What they show is the brightness of the layers changing by 30% without any change in their height above the surface of the planet.

LORRI, as its name suggests, is a long range image capture instrument. It also captures high resolution geologic data, and was used to map Pluto’s far side. The principal investigator for LORRI is Andy Cheng, from the Applied Physics Laboratory at Johns Hopkins University, in Maryland. “Pluto is simply amazing,” said Andy Cheng. “When I first saw these images and the haze structures that they reveal, I knew we had a new clue to the nature of Pluto’s hazes. The fact that we don’t see the haze layers moving up or down will be important to future modelling efforts.”

Overall, Pluto and its system of moons has turned out to be a much more dynamic place than previously thought. A geologically active landscape, possible ice volcanoes, eroding cliffs made of methane ice, and more, have woken us up to Pluto’s complexity. But its atmosphere has turned out to be just as complex and puzzling.

New Horizons has departed the Pluto system now, and is headed for the Kuiper Belt. The Kuiper Belt is considered a relic of the early Solar System. New Horizons will visit another icy world there, and hopefully continue on to the edge of the heliosphere, the same way the Voyage probes have. New Horizons has enough energy to last until approximately the mid-2030’s, if all goes well.

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8 Responses

  1. btraymd says

    Holy Cow!! Before anybody else describes their findings of gravitational waves would someone have the courtesy to explain exactly what is the force of gravity. I mean. if you know it exists in wave form you must know it’s exact nature, right???
    Talk about putting the cart before the horse. No one can offer any scientific proof which defines the force of gravity. The only thing we know for sure is that it is infinitely weaker than the other known forces. Unless, of course, you create masses with impossible density, singularities, accretion discs, black holes. dark matter, neutron stars and the rest of the unproven concepts known as the “standard model”.
    The results that were sensationalized from LIGO about “gravity waves” were complete baloney. No one wants to mention that the “signals” received by the two observatories were received at different times, excluding gravity as a cause.
    But cosmologists that are wedded to the gravity based standard model are so desperate for some reason to continue their funding they are perpetrating one fraud after another.
    This article about gravity waves on Pluto caused by the wind over the mountains is equivalent to pornography. It sounds like a weak minded grad student sucking up to an equally weak minded professor.
    Before anyone else talks about gravitational waves they should be required to publish their research describing and confirming the exact nature of gravity.

    • mewo says

      Gravity waves and gravitational waves are not the same thing.

      Gravitational waves are distortions in space-time, definitively detected for the first time by LIGO earlier this year. Gravity waves are waves in a fluid, or the surface where two fluids meet, induced when buoyant or gravitational forces restore equilibrium. Despite the similarity in naming, the two phenomena have little to do with one another. A quick glance at Wikipedia might have spared you from this simple and embarrassing factual error.

      Of course, given your subsequent deranged ranting about fraud and pornography, I don’t think you have a problem with making a spectacle of yourself.

    • mewo says

      Also, your claim that “nobody wants to mention” the time delay between the two LIGO detectors is complete balderdash. The magnitude of the delay, in fact, is how the approximate location of the black hole merger event was determined. The scientists made a huge deal of it at the time. Saying it’s being swept under the rug is just completely backwards and shows that you haven’t been paying a lot of attention (just like you didn’t pay attention in high school physics and mathematics classes, apparently).

      Gravitational waves travel at the speed of light, so of course there will be a delay as the wave traverses the distance between two detectors on opposite sides of America. The length of the delay tells you the angle at which the wave is coming in. If the wave fronts are coming from directly above, perpendicular to the line joining the detectors, the wave will arrive at both locations simultaneously and there will be no delay. If the wave is perfectly parallel to the line joining the detectors, you get the longest possible delay. For all other angles, the lag will be an intermediate value. That’s how you can calculate the angle and approximately locate the position of the event.

  2. BlackWolfStanding says

    Gravity waves? Or maybe standing waves in the atmosphere possibly from picking up a resonance from the wind passing over the mountains or hills near them? Has somebody actually set up an enclosed gravity detector and established those are indeed waves in the air because of gravity?

    • Manu says

      A wave is the result of a propagating perturbation AND a recall force that tends to restore the initial state.
      A stone thrown into a pond pushes water out of its path, this is the perturbation, it propagates because that water in turns pushes more water, but gravity is the recall force that tends to restore the pond initial surface by filling the voids. In absence of gravity, the flat surface would never be restored, there would only be an expanding void instead.
      This is why waves at any fluid interface are called gravity waves. Gravity isn’t the cause of the perturbation, indeed wind/mountains/etc are.

  3. CJSF says

    The waves detected for the first time in February are rightly called gravitational waves, not gravity waves. I suggest updating the article to reflect proper terminology.

    CJSF

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