[X] My Assistant

[Guest_BruceMoomaw_*]

...or at least those on Monday -- which is to say most of the important ones, dealing specifically with the latest results from ER and Mars Express. I've gotten another assignment from "Astronomy" to do a one-page piece on each of those subjects. (I would have loved to hang around for the remainder of the meeting to cover the Saturn and Titan meetings in particular -- but, alas I wasn't offered enough to even cover my motel expenses for that, since those meetings are spread across three more days. I do, however, intend to take careful note of the Saturn and Titan posters available on the first day.)

It's awfully late for me to give you this news -- but does anyone have any particular questions you'd like me to look into while I'm there?

[edstrick]

Those images have had strong contrast enhancement, but the Noctis Labrynthus clouds Viking imaged are fairly opaque. I do not see resemblence to cumulus, there's no relief on the cloud's and they are not sharp edged. Rather, they appear to be unusually dense ice-fog. Note that Labrynthus Noctis is at such high altitude, the valley floors are at lower pressure than the triple point of water and liquid is not stable at any time.

I've been frustrated that the only version of these images is the NASA press release with terrible uncorrected color shading caused by bad early-mission orbiter camera calibration files. They were never reprocessed into high quality images.

[Guest_RGClark_*]

Those images have had strong contrast enhancement, but the Noctis Labrynthus clouds Viking imaged are fairly opaque.  I do not see resemblence to cumulus, there's no relief on the cloud's and they are not sharp edged.  Rather, they appear to be unusually dense ice-fog.  Note that Labrynthus Noctis is at such high altitude, the valley floors are at lower pressure than the triple point of water and liquid is not stable at any time.

I've been frustrated that the only version of these images is the NASA press release with terrible uncorrected color shading caused by bad early-mission orbiter camera calibration files.  They were never reprocessed into high quality images.

I couldn't find direct MOLA measurements of Noctis but I found after a google search an article that gives elevations of Noctis in profile:

Mars: Northern hemisphere slopes and slope distributions.
GEOPHYSICAL RESEARCH LETTERS, VOL. 25, NO. 24, PAGES 4413-4416, DECEMBER 15, 1998.
http://ltpwww.gsfc.nasa.gov/tharsis/grl98_slopes.pdf


You see in Fig. 3, p. 3 that the deepest portions of Noctis extend down 2 km below, perhaps up to 3 km below, the Martian 0 elevation datum. This is deeper than the Viking landing sites which showed atmospheric pressures that never fell below the 6.1 mbar triple point for water, and sometimes reached to 10 mbars.
Since these clouds are described as lying in the low lying regions of this canyon system, I take it they extend over these lowest elevation portions as well.
The primary characteristic of precipitation bearing clouds is their denseness and thickness. They don't have to be separated into individual bulbous shaped clouds. For instance the sky over an area can be overcast and the area will generally be covered by an unbroken blanket of such clouds.
Such clouds can contain liquid water or ice. You can't know which without knowing their temperature. The clouds/fogs over Noctis appear to extend down to the surface. Since this is a near equatorial site, surface temperatures can exceed 20 C, 70 F during daytime.



- Bob