Chryse-Xanthe vs Tempe through B Light in Early Feb 1995

Chryse-Xanthe vs Tempe through B Light in Early Feb 1995

From -- 1994/1995 Mars Note (3) -- "C M O" #167 ( 25 Sept. 1995 )
If a Martian image seen through a blue light filter looks quite bland or uniformly "dark" except for the limb hazes and polar areas, it is usually said that the surface is covered by the blue haze, or if some "dark" markings such as Syrtis Mj, M Acidalium and so on are evident, one may say that the "blue clearing" is occurring. However how can one discern whether blue cleared or not if some "dark" markings as well as some "light" markings appear to be dark while other "light" marking are light in B? Such was the case when the area of M Acidalium and Tempe as well as Chryse faced toward us in early February 1995.

ISHIBASHI (Is) pointed out that, concerning his photos taken on 7 Feb (055 degs.Ls, Phase Angle=07degs.), Tempe showed quite a different aspect through a Blue filter (B390 filter) from that taken through an R60 filter. Through R, Tempe was light while it was as dark as M Acidalium in B. Chryse was however rather light even in B.

Is phot ISHIBASHI's Phot (Is 006B)
07 Feb.
LCM=56 degsW
Ls=056 degs

This was also proven by the routine work by MORITA (Mo) from 5 Feb (056 degs.Ls, PhaseAngle=05degs.). These were already reported in CMO #156 p1571 and #157 p1588-89.

Mo phot MORITA's Phot (Mo 127B)
05 Feb.
LCM=72 degsW
Ls=055 degs

From our point of view, it should be quite natural that Tempe is as "dark" as M Acidalium because any light surface has scarcely the ingredient of blue light, and hence rather the fact that the area of Chryse was detected light through B was peculiar. This well suggests that the area was covered by a white matter which emitted a blue component; this being quite the same phenomenon as was the case of the white hazes or white clouds or the polar areas which are usually light apparent in B.

Table 1: Photos by the OAA members
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Table 1 lists out the photo work on our side during the period when the regions of Tempe and Chryse faced to us in Feb.
The photos by Mo consist of RGB sets, and those by Is of B and RG/Int. The colour emulsion used by Is was Fujichrome Provia 400 (RHP). Mt is a code of N MATSUMOTO (by use of a 44cm spec) and his emulsion is Fujichrome 100 (RD).
M Acidalium, Tempe, Tharsis and Chryse-Xanthe are abbreviated to as MA, T, Th and C-X respectively.

The above photo combinations thus show that Tempe near the noon was not seen through B light, while the area of the Chryse and Xanthe region was dimly light connecting the evening haze and the morning one. Note of course that the morning haze was much brighter than Chryse-Xanthe, as shown in Mo- 124B, Mt-020C etc. Tempe also behaved different also in B when it was at the morning limb or at the evening limb. This phenomenon will be mentioned in a coming issue when we will treat the case of the white cloud seen at Alba from the end of January.

Table 2:
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Mo-091 1 Jan LCM=72 degs.W: Npc large, MA dull
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Note also that the phase angle was rather small at the period since the planet was near at opposition. Table 2 is an example which corresponds to Mo -127B in Table 1. Ls was then 039 degs.Ls while 055degs.Ls when Mo-127B was taken. Since the CCD images by D PARKER (DPk) as mentioned below show that the difference remained also strongly in March and May, it may be possible to consider that the phenomenon occurs commonly after about 050degs.Ls.

Table 3: Visual observations associated
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Table 3 lists up the visual observations during the period by IWASAKI (Iw), MURAKAMI (Mk) and MINAMI (Mn). Visually Tempe was seen bright and very different from the area of M Acidalium which was of course quite dark, but it was noted several times that Tempe was strongly reddish. The brightness sometimes made a part of Tempe to be composed of a bright spot as in Mk-160D. On the other hand, the area of Chryse and Xanthe appeared to be just off- white, and sometimes showed a tint of cream as pointed by Iw (and also by Mk -171D). This must be caused because the ground surface was slightly transparent through the whitish covering.

Iw's observation Iw-127D was obtained under excellent seeing, but Iw made no mention of the bright regions in question: This may imply that the mist over Chryse and Xanthe was not so thick nor condensed.

As pointed out in CMO #158 p1613, Patrick RAPHAEL (PRp) at the WFS in Berlin visually observed the phenomenon: Tempe was comparably darker than Chryse visually in B on 14 Feb (059degs.Ls) at LCM=070degs.W. Photographically Don PARKER's colour prints of the CCD images listed in Table 4 well prove the difference between Chryse and Tempe.

Table 4: From D PARKER's CCD
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Left. .: 09 May LCM=088 degs.W
Middle: 12 May LCM=077 degs.W
Right..: 12 May LCM=088 degs.W

The (smaller)images in Mar and May much more clearly show the phenomenon: Especially on the image taken on 12 May (097degs.Ls), Chryse-Xanthe very whitish. The (larger) images on 25 Feb look however complexed or detailed: The area of Chryse and Xanthe has also such reddish components, and some part of Tempe is whitish: On the image on 25 Feb at LCM=043degs.W, the area from Niliacus L to M Acidalium is vastly dark reddish, and the northern part of Chryse-Xanthe is light reddish.

Tempe and Alba are the plateaux having the same altitude and situated nearly on the same latitude, and hence the atmosphercal difference between at Tempe and at Alba must be attributed to another factor (which shall be mentioned on the occasion when we treat the case of the white cloud phenomenon at Alba). On the other hand, Chryse is lower in altitude, and Xanthe is a slope rising up to Tharsis, and hence the phenomenon dealt with this time must be caused by the difference of the altitudinal and latitudinal structure. This must be very critical around this season, and must be a point to be resolved theoretically.