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.
Gravity waves, really? (Score:1)
Re:Gravity waves, really? (Score:5, Insightful)
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.
Re:Gravity waves, really? (Score:5, Informative)
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It's a different phenomena, same name.
It's not even the same name. To quote the same article [wikipedia.org]
This article is about the movement of fluids. For the phenomenon of general relativity, see gravitational wave [wikipedia.org].
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Lee waves are used by gliders to reach great heights, they result from mountain ranges (forming lenticular clouds) , and at the edges of different air masses..
Standing waves ocour too, the Morning Glory wave is caused by the collision of two airmass.
The cloud streets, form when the wind aligns rows of Cumulus clouds, which then form the "mountain" that triggers a wave in the atmosphere above. This is known as thermal wave, and can at times be seen in the form of a Pilious cloud.
Strong wind shears can induce
Re:Gravity waves, really? (Score:5, Informative)
This is not the cosmological kind of gravity waves (the ones we are building complex detectors for that have been in the news during the last few years) but a much more down to earth, I mean Mars, weather phenomenon. Happens on earth all the time, not really that special. Probably only made the news because of confusion with the other kind of GW,
Re: Gravity waves, really? (Score:1)
This is more like cloudy tidal waves, nothing to do with gravitons.
Re:Gravity waves, really? (Score:5, Informative)
They are easily detectable on earth - for example see here [wikipedia.org] (picture here [wikipedia.org]). They've also been detected [nature.com] in the atmosphere of Venus, which has winds over 200 miles per hour.
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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.
Re:Gravity waves, really? (Score:5, Informative)
Gravitational_wave [wikipedia.org] - General Relativity
Wikipedia does not constitute proof, but it's probably right in this case.
Re: Gravity waves, really? (Score:2)
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.
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Score:-5, Pwned (Score:1)
Witness BitZtream getting pwned! [slashdot.org]
OUCH! (Score:1)
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Would a properly maintained hosts file have helped prevent this from happening to him?
Re: Gravity waves, really? (Score:1)
You're pretty much completely wrong. Gravity waves is a name that has been around for nearly a century in multiple fields for cases where gravity is the dominant restoring force for the wave, including large oscillations in flow without compression in air and in incompressible liquids. That has nothing to do with compression, hence why they are not called compression waves...
So (Score:1)
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"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.
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Gravity waves != gravitational waves (Score:5, Informative)
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).
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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.
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Let's see if I got this straight:
Cloud particles gravitationally pull on each other such that if there is a disturbance in their movement, ripples form in the attraction movement pattern somewhat similar to ripples on a pond after tossing in a pebble: the particles bunch up and then some other force (???) pushes them back apart after a period of time. What's this other force? (On a pond, the weight of the peak of the wave pushes it back down.)
It seems we normally don't see these on Earth because our thicker
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Let's see if I got this straight: Cloud particles gravitationally pull on each other
No. At least not to any significant amount.
It seems we normally don't see these on Earth because our thicker atmosphere and magnetosphere overwhelm gravity's direct influence.
What is it you think that keeps our "thicker atmosphere" where it is if it isn't "gravity's direct influence"?
Gravity waves are waves in something that are moderated by the force of gravity. E.g. regular waves at the beach are gravity waves. The properties depend directly on the difference in densities between the two layers in contact. For surface waves this is air/water. For subaqueous (or "internal") waves, it is a water/water interface.
There are also infragr
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"Gravity waves" seems misleading or confusing. Maybe it stuck for historical reasons?
Pond and sea waves involve multiple forces interacting in a rhythmic way. Labeling their cause as one force among multiple is problematic communication.
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"Gravity waves" seems misleading or confusing. Maybe it stuck for historical reasons?
It stuck because it is accurate.
Labeling their cause as one force among multiple is problematic communication.
All scientific communities have their terminologies, and "gravity waves" is an accurate use of the words for fluid dynamics. It is not gravity that CAUSES the waves, it is gravity that moderates them.
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Possibly... (Score:1)
I am confused (Score:1)
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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Why is it so unlikely?