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RGClark
2005-Mar-10, 07:43 PM
Is it believed the Spirit Navcam images on this page show actual halos or is it just an optical artifact:

MER Spirit: Sol 345.
http://mars.lyle.org/bysol/2-345.html

This page has examples and explanations of halos caused by ice crystals on Earth:

Frequent Halos.
http://www.sundog.clara.co.uk/halo/common.htm


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.

Liquid water droplets can also form halos:

Fogbow.
http://www.sundog.clara.co.uk/droplets/fogbow.htm

Are there differences between the halos caused by ice and liquid water?


Bob Clark

ToSeek
2005-Mar-10, 07:51 PM
Is it believed the Spirit Navcam images on this page show actual halos or is it just an optical artifact:

MER Spirit: Sol 345.
http://mars.lyle.org/bysol/2-345.html


I'd vote for artifact. You can see very similar images in the exact same locations on Sol 400 (http://marsrovers.jpl.nasa.gov/gallery/all/opportunity_n400.html).

Swift
2005-Mar-10, 08:10 PM
I'm unconvinced it is a halo. But the site RGClark linked to is a great site about halos and sundogs and they in fact have some speculations about such things on other planets, including MARS! (http://www.sundog.clara.co.uk/halo/owmars.htm)

Bamf
2005-Mar-11, 06:33 AM
I'm unconvinced it is a halo. But the site RGClark linked to is a great site about halos and sundogs and they in fact have some speculations about such things on other planets, including MARS! (http://www.sundog.clara.co.uk/halo/owmars.htm)
We did experiments with MGS/TES to try to detect halos & sun dogs (TES has its own moving mirror and looks at the limb and space frequently). Nothing came of it, but with a point spectrometer we knew it was a long shot.