September 11, 2003, 05:30 UT
Instrument: 10-inch Starfinder

Apparent diameter: 24".1
Phase: 99%
CM: 286°

Among the most fascinating of event to see on Mars is one of his wild and wooly dust storms. In June of the 2001 opposition, a storm which started in Hellas grew to encompass almost the entire planet. Albedo features which would otherwise have been as obvious as the nose on your face were shrouded behind the veil of a global Martian dust storm, one of the most dramatic weather events in the Solar System which can be viewed with amateur telescopes.

Tonight, another storm appears to be brewing in Hellas. The sketch at left, which portrays 247X and 388X views in my 10-inch Newtonian, shows a bright area in the northwest corner of the impact basin. This feature carries a yellowish tinge when viewed through a 0.9 neutral density Moon filter. With the 80A light blue filter in place, the jaundiced hue is even more striking. However, this feature appears brighter than the surrounding floor of Hellas in the 23A light red and this suggest a predominantly reddish hue. This is one of the signature signs of a dust cloud on Mars.

The other telltale sign is that the feature evolves and grows over time. Reading the reports in the marsobservers Yahoo forum, that is exactly what this feature seems to be doing. One report describes the bright spot as becoming larger over the course of a single 40-minute observation. Although I did not detect any noticeable change in size or shape during my observation, this evening, if the feature shows measurable change over the next 24-hours, I think we'll have a bonafied Mars dust storm on our hands.

By contrast with the possible dust storm in the northwest corner, the southeast corner of Hellas looks duskier. Of course, the most prominent feature gracing this longitude is the magnificent Syrtis Major. Its dramatic form is centered along the meridian. The slender form of Sinus Sabaeus snakes its way toward the following (west) limb. Just the slightest hint of Sinus Meridiani's bulbous shape is discerned.

The North Polar Hood is visible opposite the irregular North Polar Cap. Hazy clouds are visible along the both the preceding (east) and following limbs. But the big news is the developing dust storm in Hellas. Will it go global? Or will it fizzle? Time will tell.

Mars September 8, 2003

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Revised: September 11, 2003 [WDF]