Mars Sketch (7)

1996/97 Mars Sketch (7)
from CMO #205

Elysium in March 1997
  We here review the Japanese observations of Elysium in March 1997 when the Martian season was near 090degreeLs. As reported in CMO No187 p2033 the region was impressively whitish bright in the afternoon side. From 7 Mar (087degreeLs) to 13 Mar (090degreeLs) there were obtained a number of observations (every forty minutes) in Japan and we here record the data.
  As a good example, we first introduce the observations by ISHADOH (Id) made on 10 March. His observations started from 13:20GMT and ended at 18:10GMT on the night and were made in the following way: 
  Id-076D    10 Mar (089degreeLs)   LCM=231degreeW
  Id-077D                           LCM=241degreeW
  Id-078D                           LCM=250degreeW
  Id-079D                           LCM=260degreeW
  Id-080D                           LCM=270degreeW
  Id-081D                           LCM=280degreeW
  Id-082D                           LCM=289degreeW
  Id-083D                           LCM=302degreeW

  Elysium was apparent from the outset (Id-076D), but it became very evident from around Id-079D. In Id-082D, Elysium was near the terminator and nearly vanished in Id-083D. Id made also at LCM=300degreeW on 9 Mar where the situation was the same. On 10 Mar the phase angle was 07degree, and Elysium was at around 4 o'clock local time when Id-080D (LCM=270degreeW) was made.
  Elysium Mons described by Id became whitish bright in the deep afternoon and hence this phenomenon was caused by such a white orographic cloud as reviewed in Mars Sketch (3) in No 201.
Fig. ISHADOH's drawing (Id-080D) on 10 Mar 1997 (089degreeLs)
at LCM=270degreeW showing a very whitish bright cloud at Elysium Mons

  At Fukui, NAKAJIMA (Nj) made a similar continual observations of the afternoon Elysium on 8 March (088degreeLs). On the day he witnessed that Elysium was whitish bright enough at LCM=244degreeW. On the following day on 9 Mar (088degreeLs), Nj however saw the off-white tint remain at the region of Elysium at LCM=235degreeW. MINAMI (Mn) on 9 Mar detected Elysium Mons through O56 atLCM=220degreeW while it became well whitish at LCM=240degreeW and very brilliant at LCM=260degreeW. Nj and Mn watched the region from 7 Mar to 11 Mar as follows: 

  Mn-332D    7 Mar (087degreeLs)   LCM=248degreeW
  Nj-093D                          LCM=252degreeW
  Mn-333D                          LCM=257degreeW
  Nj-094D                          LCM=262degreeW
  Mn-334D                          LCM=267degreeW
  Nj-095D                          LCM=272degreeW
  Mn-335D                          LCM=277degreeW
  Nj-096D                          LCM=282degreeW
  Nj-097D    8 Mar (088degreeLs)   LCM=224degreeW
  Nj-098D                          LCM=234degreeW
  Nj-099D                          LCM=244degreeW
  Nj-100D                          LCM=253degreeW
  Nj-101D                          LCM=263degreeW
  Nj-102D                          LCM=273degreeW
  Nj-103D    9 Mar (087degreeLs)   LCM=215degreeW
  Mn-336D                          LCM=220degreeW
  Nj-104D                          LCM=225degreeW
  Mn-337D                          LCM=230degreeW
  Nj-105D                          LCM=235degreeW
  Mn-338D                          LCM=240degreeW
  Nj-106D                          LCM=245degreeW
  Mn-339D                          LCM=250degreeW
  Nj-107D                          LCM=255degreeW
  Mn-340D                          LCM=259degreeW
  Mn-341D                          LCM=272degreeW
  Mn-342D                          LCM=281degreeW
  Mn-343D                          LCM=291degreeW
  Mn-344D                          LCM=301degreeW
  Mn-348D   11 Mar (089degreeLs)   LCM=203degreeW
  Mn-349D                          LCM=230degreeW
  Mn-350D                          LCM=240degreeW
  Mn-351D                          LCM=249degreeW
  Mn-352D                          LCM=259degreeW
  Mn-353D                          LCM=271degreeW
  Mn-354D                          LCM=281degreeW
  Mn-355D                          LCM=291degreeW
  Nj-110D                          LCM=295degreeW
  Mn-356D                          LCM=300degreeW
  Nj-111D                          LCM=305degreeW
  Mn-357D                          LCM=310degreeW
  Nj-112D                          LCM=315degreeW
We also have other observations among which the following are included: 
  Mo-054CCD  11 Mar (089degreeLs)  LCM=250degreeW
  Id-084D    11 Mar (089degreeLs)  LCM=251degreeW
  Id-085D                          LCM=261degreeW
  Id-086D                          LCM=271degreeW
  Id-087D                          LCM=281degreeW
  Mn-358D    12 Mar (090degreeLs)  LCM=216degreeW
  Mn-359D                          LCM=226degreeW
  Mn-360D                          LCM=236degreeW
  Mn-361D                          LCM=245degreeW
  Mn-362D                          LCM=255degreeW
  Mk-135D    12 Mar (090degreeLs)  LCM=260degreeW
  Id-088D    13 Mar (090degreeLs)  LCM=212degreeW
  Id-089D                          LCM=222degreeW
  Id-090D                          LCM=232degreeW
where Mo=MORITA, and Mk=MURAKAMI.

  In the Mo image the afternoon Elysium is bright even though it was taken in Red. As seen from the example by MURAKAMI, Elysium this time proved most conspicuously whitish at LCM=250degreeW - LCM=260degreeW. The observations by Mn on 12 Mar was at Otsu, and Elysium Mons was detected at LCM=226degreeW.
  We have described mainly the trend of Elysium, but the region made of Cebrenia was also interestingly bright throughout the period.
  We also note that the afternoon Elysium shows the characteristic aspect in the Video images taken by HIGA (Hg) on 9 Mar, 10 Mar and 11 Mar. On 10 Mar at LCM=218degreeW, Elysium looks more whitish and brighter than Hellas. On the other hand the morning Elysium on the image on 15 Mar is not so whitish though bright.

  Elysium still faced to us. On 17 Mar (092degreeLs) at LCM=192degreeW, Elysium Mons was seen and the Elysium region of the morning was traced until 22 Mar. For example, in the observation: 

 Mk-141D    20 Mar (093degreeLs)   LCM=186degreeW
the morning Elysium and Cebrenia were apparent.

  Elysium came into sight again in mid-April. The Y-shaped Elysium-Cebrenia region was still light. But the apparent diameter went down to 12 arcsecs, and we could not catch well the activity of Elysium Mons. On 23 Apr (108degreeLs) at LCM=206degreeW (Mn-554D), there were seen a few areas of bright spots inside Elysium, but looked somewhat off-white. Id also recorded on 20 Apr (107degreeLs) at LCM=241degreeW (Id-110D) that Elysium was off-white. A CCD Red image by AKUTSU (Ak) shows a light Elysium on 22 Apr at LCM=235degreeW.
  Around 20 Apr (107degreeLs), the morning Elysium and the following area showed a white-cloud burst as seen visually and as proved by the Video images by Hg as reported in Sketch (1) in No 197 (see also No 204). The cloud was thought as the one developed from the morning mist which covers frequently the morning Syrtis Mj to make it to be quite blue-greenish in this season.

  Finally we record an aspect of Elysium in Feb 1997 from the notes of the present writer: Elysium was visible from around 5 Feb (074degreeLs). Elysium and Cebrenia were light enough in a Y-shape, and on 7 Feb (075degreeLs) at LCM=241degreeW, there was seen an activity inside Elysium. On 8 Feb (076degreeLs) at LCM=222degreeW, Elysium was off-white yet, but at LCM=242degreeW more whitish than Cebrenia. On 10 Feb (076degreeLs) at LCM=194degreeW, Elysium was not white but at LCM=233degreeW became bright. The apparent diameter was less than 12 arcsecs however.

(Mn : Masatsugu MINAMI)