[BAA-ebulletin 00956] Mars: monitoring for major dust storm activity

[BAA electronic bulletins service]

Mars: monitoring for major dust storm activity
Mars is now well placed again in our evening skies, but its diameter is less than 6 arcseconds. The S. polar cap is tiny, and the martian skies are free from any major dust activity according to our latest observations. At the present time, the areocentric longitude (Ls) of the planet is 300 degrees, corresponding to the first half of the summer season in the southern hemisphere. According to our past records, the latest seasonal date at which any planet-encircling dust storm began was at Ls = 311 degrees, towards the end of the 1924-25 apparition, when the Rev. T.E.R.Phillips had been the first to see a bright streak of dust breaking out from the west of the Hellas basin. Days later the whole planet was covered in an impenetrable yellow veil. 
We are keen to know if any such event will occur in the current martian year, but owing to the smallness of the disk the number of observers has lately become very small. If you are able to get any decent images over the next few weeks please do send them to the Mars Section. Likewise any observer able to view the planet at the eyepiece could also make a useful contribution. On January 14 the Director made his 100th drawing of the current apparition: despite the tiny disk, the major features in the longitude of the Syrtis Major and Hellas were still distinctly visible with a magnification of at least x250. To achieve our objective, we shall need to observe a little way beyond Ls = 311 degrees, which means at least until mid-February. The planet cannot be observed for long after sunset, so observations from around the world are necessary to build a full picture over all longitudes of the planet. On average, planet-encircling dust storms occur once in every three martian years, but so far no-one has succeeded in accurately predicting them. What will happen this time round? Your work could help to answer the question.
Dr Richard McKim (Director, Mars Section)
richardmckim at btinternet.com
2017 January 16