Sand Dunes On Mars In Motion 55
TheNextCorner writes with news that NASA's Mars Reconnaissance Orbiter has detected ripples and shifts in the sand dunes on Mars, which means the surface of the planet is more dynamic than previously thought. Planetary scientist Nathan Bridges said, "Mars either has more gusts of wind than we knew about before, or the winds are capable of transporting more sand. We used to think of the sand on Mars as relatively immobile, so these new observations are changing our whole perspective." The article explains, "The air on Mars is thin, so stronger gusts of wind are needed to push a grain of sand. Wind-tunnel experiments have shown that a patch of sand would take winds of about 80 mph to move on Mars compared with only 10 mph on Earth. Measurements from the meteorology experiments on NASA's Viking landers in the 1970s and early 1980s, in addition to climate models, showed such winds should be rare on Mars."
Local storms... (Score:5, Interesting)
Measurements from the meteorology experiments on NASA's Viking landers in the 1970s and early 1980s, in addition to climate models, showed such winds should be rare on Mars.
Yeah, and 80+mph winds were rare in Miami in the 1970s and early 1980s too.
What about gravity? (Score:5, Interesting)
I can understand how they could have a low pressure wind tunnel to simulate the lower Martian atmospheric pressure, but how did they reduce the gravity by almost 2/3? There's no mention of Mars' lower gravity anywhere in the article.
Re:What about gravity? (Score:3, Interesting)
Theoretically, you can, indeed, do the same for the pressure difference. After all, you can calculate the necessary forces to move any particular grain of sand. You can calculate various forces from the wind. You can even throw in electromagnetic effects. However, the volume of calculation makes that difficult at best. So the wind tunnel is useful, and would be a faster way to see how different air pressure, air composition, etc., affect the result. And what's to say there weren't dozens or more different experiments calibrated to measure different aspects of the problem?
And no, I don't have a specific formula to share. But I also have not conducted a detailed study (and I never claimed I did) so I do not have a detailed understanding of the dynamics in play. Still, I would expect formulas used in fluid dynamics and, get this, the formulas related to gravity, would likely apply. And given there is probably an electrostatic effect of some kind with the small particles, formulas related to electricity and magnetism might be involved.
In any event, my assertion was that it *should* be possible. I don't have any special knowledge of the problem.
Also, sure, there are suspended particulates in the Martian atmosphere. However, those are not the particles that form the dunes in the first place. The dunes would be composed of the larger (heavier) particles that need more force to move. And before you ask, I'm basing that statement on having observed drifting sand.
Finally, let me direct to you my signature, "If it works in theory, try something else in practice." I have no delusions that my "theory" is any more correct than any other.
Re:Controlled for all factors? (Score:4, Interesting)