[BAA 00204] Martian dust storm alert

[Rick]

MARTIAN DUST STORM ALERT

A significant martian dust storm  is presently occupying much of the length of the great Valles Marineris canyon system, and is apparently still spreading.  The event began as a small yellow  cloud located just W. of Margaritifer Sinus on the S. border of Chryse on 2005  October 13. After a few days activity seemed to cease, but on October 18 there  was a strong resurgence, with dust moving north across Chryse, whilst a second  bright core appeared further west near Aurorae Sinus. Dust then rapidly spread  along Valles Marineris. The region was observed by the Director before dawn this  morning, October 20, when the dust storm was seen to have expanded further.

Another dust disturbance occurred on October 17, at the W. border of Mare Acidalium in SE Tempe.  Beginning at Ls = 306 degrees (October 13), this dust storm - in terms of both Martian date and location - is  similar to the large regional storm that took place at Ls = 315 degrees (2003 December 13) near the end of the last opposition. It also resembles local or regional events from the 1990 and 1992 oppositions (in a very similar location) that occurred at Ls = 308 and 316 degrees respectively. (For full details of the  2003 event, see the '6th Interim Report' on Mars at its 2003 opposition, available at the BAA Mars Section homepage:

        http://www.britastro.com/mars

For the historical storms see the writer's monograph on 'Telescopic martian dust storms', BAA Memoirs, volume 44 (1999).) Other historical examples could be quoted, at similar Ls and in a similar location, right back to 1879.  Historical records show that the present event is unlikely to develop into a planet-encircling event, but it could yet spread further. The seasonally  latest encircling storm commenced in 1924 December at Ls = 311 degrees, but only storms that begun in Hellas, Noachis or near Solis Lacus ever achieved  encircling status.

Further observations are desirable and should be sent to me at once.

Richard McKim, Director, BAA Mars  Section