Halos On Mars?

[exoscientist]

Is it believed the Spirit Navcam images on this page show actual halos or is it just an optical artifact: <br /><br />MER Spirit: Sol 345. <br />http://mars.lyle.org/bysol/2-345.html <br /><br />This page has examples and explanations of halos caused by ice crystals on Earth: <br /><br />Frequent Halos. <br />http://www.sundog.clara.co.uk/halo/common.htm <br /><br /><br />If the Navcam images are real halos that might suggest there were thin non-visible ice water clouds over the Spirit site as were the visible cirrus clouds seen over Meridiani. <br /><br />Liquid water droplets can also form halos: <br /><br />Fogbow. <br />http://www.sundog.clara.co.uk/droplets/fogbow.htm <br /><br />Are there differences between the halos caused by ice and liquid water? <br /><br /><br />Bob Clark <br /> <div class="Discussion_UserSignature"> </div>

 

[CalliArcale]

Yeah, I noticed some pictures like that too! I didn't immediately think anything of them, however, since I was specifically looking for another picture at the time. But I remember seeing those. It would be interesting to know which way the camera was pointing in relation to the Sun. That's neccesary to figure out whether they were atmospheric halos. They are suspiciously well-centered in the images, however, which has me thinking that they may be internal to the camera. Sun-halos are generally centered around the Sun, which is not visible in those shots, and rarely will be centered around other locations in the sky (such as the zenith and the anti-solar point).<br /><br />Now, I do seem to remember reading that there was a scientist or two actively working to get MER to take some pictures specifically to hunt for atmospheric effects like this, since of course it can reveal a lot about the atmospheric composition. If he was successful, then images intended to search for halos would logically be targeted at the likely locations for such effects -- such as the Sun, the zenith, and the anti-solar point. And then the halos WOULD be centered. So I guess we can't really draw any conclusions there. <img src="/images/icons/wink.gif" /><br /><br />Maybe that scientist will release information once he's had time to analyze the data. I hope so! That would be very nice.<br /><br /><blockquote><font class="small">In reply to:</font><hr /><p>Are there differences between the halos caused by ice and liquid water? <p><hr /></p></p></blockquote><br /><br />Yes, and in fact you can get different halos from different shapes of ice crystals (and different orientations of them as well). For instance, the most popular and colorful halo is the rainbow. On Earth, this is produced exclusively by liquid water droplets, and it is centered around the anti-solar point. (Yes, the rainbow theoretically is a circle; it's just that you can never see the whole thing.) You can even make your own rainbows, w <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>