Mars Section Circular No. 1

1998 November

General

Mars is still very far from opposition, but the writer knows of observations as early as August 19. Six observers have reported their work, and this Circular describes some details seen from then until November 15 (Ls = 7–57 deg., D = 3.8–4.9 arcsec). Some notes about what to look for during the present apparition were published in the BAA Journal, 108 (5), 243–245 (1998). Although the planet is steadily drawing closer, its N. declination is decreasing, and will become S. of the celestial equator in early December.

North Polar Region

With these early observations, on occasion no dark markings can be seen on the tiny disk, due to lack of resolution rather than dust storm activity. Even then, sketches that just portray the NPC accurately will be useful. Drawings may be made every 15 or 20 minutes. Remember to estimate the cap in tenths of the planet’s diameter when transfering the mental impression to a Section report form.

Observations did not begin early enough this year to document the transition from polar hood to cap. Sketches do show the decline in size of the NPC, though no fine details could be expected. A dark collar was seen by Nicolas Biver on September 20, 26, by Richard Schmude on September 27, by David Gray in October and by Mario Frassati on October 28. Drawings by Martin Gaskell during October 12–13 (Ls = 42–43 deg.) place the NPC S. edge at latitude= 70–72 deg., and two by Gray on October 31 (Ls = 50 deg.) gave 74–75 deg. These results are very close to the BAA data for the earlier apparitions of the 1990s (and 80s). More measures please!

Atmospheric activity

Elysium: Gray reported slight whiteness here with the region near the CM, October 18, 19, and more so with the region on the morning side, October 22, 23, whilst Biver’s sketch of September 26 shows it light at the morning limb. (As Gray remarks, Elysium is sometimes detected not by its intrinsic brightness, but by the duskiness of its surroundings. Would observers therefore be explicit in their descriptions, please!)

Nix Olympica: detected as a light spot by Gray on the afternoon side on October 23.

Tharsis: On October 30 and 31 Gray reported a striking, large bright tongue of cloud, visible in white light and in W15 yellow, stretching from W. Tithonius Lacus (the latter feature, a dusky triangle, was near the CM, at CM long. 73 to 80 deg.), broadening towards the morning limb. Terrestrial cloud prevented a view in red or blue light. This seems to have been white morning cloud over Tharsis. The Director recalls a roughly similar view in February 1995, at a very slightly later seasonal date, so it may be a seasonal type of cloud. There is no real evidence for it having been a dust storm.

Chryse–Xanthe: bright on the evening terminator. Hellas: Under CML 254 deg. on September 20, Biver (10-inch refl.) did not draw it light. More data are needed for this region of the planet. The October work by Frassati and Gray reveals S. limb haze at all longitudes, sometimes very striking. A report by the OAA (Japan), October 2–9, confirms this.

Dark markings

These seem normal, like 1995 and 97. Using his 14-inch Dall–Kirkham Cass., Gray has already made detailed sketches showing such small details as Idaeus and Achilles Fons on the Nilokeras streak. Solis Lacus remains large, as in all the apparitions from 1984 through 1997. The Propontis area was dark (at lo-res), as were the S. maria, Syrtis Major, Mare Adidalium, etc. The SE dark border to Elysium (Trivium Charontis–Cerberus) remains invisible or virtually so.

Reporting data to the Section

Please note that since the last apparition I have moved house, and am now living at Cherry Tree Cottage, 16 Upper Main Street, Upper Benefield, Peterborough PE8 5AN; home telephone 01832 205387; office fax and answering machine 01832 274052; home e-mail Rmckim5374@aol.com. (Do not use the former e-mail number for my place of work (mckim@oundle.northants.sch.uk).)

Richard McKim, Director

1998 November 20