Photophoresis/Thermophoresis and Dust Motion

[yevaud]

<b>By simple light and heat mechanisms, dust particles seem to defy gravity and leap up into the air. The effect, which once played a role in the formation of the Earth and asteroids, could also have applications in dust removal and even propel small probes on Mars.</b><br /><br /><i>When shining a red laser beam on a pile of dust, some dust particles will jump up, apparently erupting in a fountain of dust strands (see image). In studying the mechanisms behind the erupting dust, scientists Gerhard Wurm and Oliver Krauss from the University of Munster found two causes working together that explain their observations: photophoresis and the solid state greenhouse effect.<br /><br />Photophoresis – or the movement of particles due to light – is based on a long-known effect called thermophoresis – or the movement of particles due to heat transfer. Essentially, in environments with temperature gradients, particles will migrate from hotter to cooler regions due to the thermophoretic force. When light absorption serves as the heat source, the mechanism is called the photophoretic force.<br /><br />In addition to the presence of a temperature-gradient surface, Wurm and Krauss found that the solid state greenhouse effect also plays a role in dust eruptions. This greenhouse effect occurs because the laser beam heats up dust particles slightly below the surface (at least 100 micrometers, which encompasses several tens of particle layers) the most. In a recent Physical Review Letters, the scientists describe how coupling photophoresis with this greenhouse effect means that surface dust particles will strive to migrate away from hot underlying particles – and that direction is up.</i><br /><br />Full Story <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[silylene old]

That's cool ! <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[yevaud]

<i>Could this be the cause of the "mysterious" dust removal on Oppy's solar panels?</i><br /><br />Entirely possible. Since the solar panels would tend to heat up more easily than the surrounding atomsphere, in fact likely. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>