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Mars Space Science

Mars Rover Spots Clouds Shaped By Gravity Waves (sciencemag.org) 56

sciencehabit writes from a report via Science Magazine: NASA's Curiosity rover has shot more than 500 movies of the clouds above Mars, including the first ground-based view of martian clouds shaped by gravity waves, researchers reported this week at the Lunar and Planetary Science Conference. The shots are the best record made so far of a mysterious recurring belt of equatorial clouds known to influence the martian climate. Understanding these clouds will help inform estimates of ground ice depth and perhaps recurring slope lineae, potential flows of salty water on the surface, says John Moores, a planetary scientist at York University in Toronto, Canada, who led the study with his graduate student, Jake Kloos. "If we wish to understand the water story of Mars's past," Moores says, "we first need to [separate out] contributions from the present-day water cycle." Using Curiosity's navigation camera, Moores and Kloos recorded eight-frame movies of this wispy cloud belt for two martian years. They've used two angles to capture the clouds: one pointed directly up, to see wind direction and speed, and another that keeps the rover's horizon in the frame, allowing a view into the clouds' depth. Given the limited water vapor, solar energy, and atmosphere, the martian clouds lack the variety of shapes seen on Earth. But during one day of cloud gazing -- Curiosity's 1302th martian day, to be precise -- the team got lucky and saw something unusual. That day, when Curiosity looked to the horizon, it saw a sequence of straight, parallel rows of clouds flowing in the same direction: the first ground-based view of a gravity wave cloud. Similar to the waves that follow a pebble tossed into a pond, gravity waves are created when some unknown feature of the martian landscape causes a ripple in the atmosphere that is then seen in clouds. Such waves are common at the edge of the martian ice caps, but thought to be less frequent over its equator.
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Mars Rover Spots Clouds Shaped By Gravity Waves

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  • And the reason why we do not have those gravity waves here on Earth is?
    • by Calydor ( 739835 ) on Thursday March 23, 2017 @03:13AM (#54093771)

      We probably do, but our atmosphere is so many times more active than that of Mars that any effect by gravity waves is drowned out (heh) by all the other things happening at the same time - air pressure, air humidity, wind etc.

    • by Anonymous Coward

      We do, undular bores for example.

      Note that fluid dynamics' gravity waves (what's discussed here) and relativity's gravitational waves (e.g. as detected by LIGO) are two entirely different things.

    • We do - do an image search for gravity waves satellite photo.

      Admittedly, the only reason I know is from a Rogue NASA tweet. I couldn't understand how you could see them until I realised I was getting them confused with gravitational waves.

    • by Chrisq ( 894406 )
      We do [wikipedia.org]. All you need to do to see them is go to the ocean or a reasonably large lake. These are not gravitational waves [wikipedia.org], simply waves in a fluid surface under gravity.
    • "Gravity Wave", here, means a wave wherein the restoring force is gravity, such as waves on the ocean. It is not the same as the cosmological gravity waves caused by coalescing black holes sought by the LIGO experiment.

    • by dbIII ( 701233 )
      We do. It turns out that the term is used for two different things and this is the atmospheric physics use of the term instead of the gravitational physics use.
  • by Anonymous Coward on Thursday March 23, 2017 @03:26AM (#54093795)

    Just a reminder: the gravity waves (waves resulting from gravity restoring an equilibrium) discussed in the article are different from gravitational waves (wave functions describing gravity itself).

    • Just a reminder: the gravity waves (waves resulting from gravity restoring an equilibrium) discussed in the article are different from gravitational waves (wave functions describing gravity itself).

      In layman's terms it's the difference between waving at someone, and having a seizure. One is an external phenomena caused by gravity, the other is an internal (sorta) phenomena of gravity.

    • So it is just the same as waves on water? Very interesting story then.
  • FTFA: "It’s far from certain those are gravity waves, though."
  • Don't we call these things tidal forces? When large masses (like our Moon) moves, its gravitational influence also moves along with it. That changes the graviatational effects on other bodies near by. The general term used for this is Tidal forces. Because the ocean tides are the most common and observed phenomena due to this.

    Gravitational waves on the other hand are extremely hard to observe, and they do not involve moving large massive bodies locally.

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