2024 October 10

Mars Opposition Blog 10 October 2024

Richard Mckim

October 10

Since the large Regional dust storm, there has been smaller scale dust activity in the same area. The weather was less cooperative, resulting in lower coverage. Initial observations were made – and promptly reported – by Foster in Namibia and Haigh in the UK, on the morning of Sep 18, when there were two small, bright dust cores in southern Chryse, and another dust cloud curving around the N. and W. of Lunae Lacus at the SW border of Tempe. Nothing had been seen in high resolution images by Haigh on the 17th. The Director immediately posted the news on the BAA Forum. On Sep 19, images were made by Foster, Haigh and Peach. Now there was dust along Valles Marineris bordering Chryse-Xanthe. There was a large, lightish patch of dust over Chryse, and an E-W dust streak obscured parts of Nilokeras and cut across Mare Acidalium, disfiguring Niliacus Lacus. Haigh’s Sep 18 and 19 image sets are shown here.

On Sep 20, images by Foster and Peach (posted here) showed the dust clouds more diffuse, causing a wide loss of contrast. The Valles Marineris dust now extended slightly to the SW. The immediate impression was of a N-S belt of dust (with a brighter core in Chryse) stretching from Niliacus Lacus into Mare Erythraeum. On Sep 21, the only coverage was from Europe: Basey, J.Sussenbach and Tickner participated. A large, bright dust cloud persisted just east of Aurorae Sinus, overlapping a part of Valles Marineris and Mare Erythraeum, and the bright core persisted in Chryse, while Mare Acidalium was returning to normal. On Sep 22, Foster’s images (posted here) showed all cores subsiding, with a slight residual loss of contrast. The two dark spots located upon Nilokeras, Idaeus and Achilles Fons, adjacent to the site of one of the initial dust cores, were now large and dark again.

Sep 23: Sedrani (Italy) showed Mare Acidalium normal, but the storm area was close to the morning limb. Sep 24: E.Sussenbach (Dutch Caribbean) showed residual dust over part of Nilokeras and (again) Mare Acidalium, though the latter was close to the evening terminator.

As this event was clearly subsiding, another, much more local storm arose on Sep 25, when images by Arakawa and Inoue (Japan) showed a small dust cloud at the E. border of Elysium. This may have persisted a day or two, but quickly vanished. See Inoue’s Sep 25 image posted here.

The N. polar canopy persists in white light over Mare Acidalium. In this longitude it has often been possible to see the lower part of Acidalium as a dark patch (sometimes an E-W oriented slit), due to thinning of the cloud. This feature was dubbed “Dawes’ slit” by the late Masatsugu Minami in honour of the English astronomer W.R.Dawes, who had been the first to observe it clearly, back in 1864-65.

Again my thanks to our 39 observers for their splendid early morning efforts which have brought in over 230 drawings and over 1,900 images so far.