2024 December 10

Mars Opposition Blog 10 December 2024

Richard Mckim

December 10

The weather has not been very cooperative lately, but we have still managed to get observations on nearly every date. This entry continues the story up till and including December 4, but is not intended to be a complete account. As ever, I can only post and discuss here a small fraction of the observations received.

Albedo feature changes are often slow and subtle, and one such example has been the gradual fading of the so-called “Aetheria darkening”, which was first apparent in the late 1970s, when a broad, triangular shading developed at the NW corner of Elysium. It was sometimes contracted to a small dark spot, but basically remained in place till recently. In 2010 there existed a tenuous streaky extension to the south, but after 2018 and the global dust storm the dark shading gradually faded. Now it has all but disappeared. Other features in the region have also changed. Trivium Charontis and Cerberus were dark areas until the late 1980s, but have progressively narrowed and faded. Thus the whole area around Elysium has seen a net accumulation of dust fallout, hiding albedo markings. Here I show comparative images by Damian Peach (UK) from 2010 and 2024, with some annotations. These really show the change well.

Of the changeable features elsewhere that have remained dark, the Indus streak from Oxia Palus to SE Mare Acidalium remains dark, and the streaky Hydaspes to the west of it remains noticeable.

In terms of high resolution imaging, Tom Williams used his new 60 cm (24-inch) reflector to obtain an amazingly detailed image on December 2. Of course, technical skill in processing is also needed for such results! Note the parallel belts of faint white cloud near the NPC, and the intricate details (for example) around the W. end of Valles Marineris at Tithonius Lacus.

The north polar hood has largely cleared now, but streaks and patches are sometimes seen in the morning.

Cutting across the N. polar cap near the CM, a coloured streak of airborne dust could be seen in the fine images by Peach and Peter Tickner (UK) on December 4. The dust streak was darker than the cap and brighter than the dark border of the cap. (See the 2010 report for an account of a conspicuous dust storm over the NPC.) Another, much less prominent dust streak at the cap edge was captured by Gary Walker (USA) at a higher longitude (close to the CM of the image, 082o) on the same date.

The orographic clouds over the Tharsis Montes are well visible in the image of November 26 by C.Foster (Namibia) shown here, which also shows cloud at Alba near the CM in the north. Notice how a blue/violet filter increases their contrast. The Alba orographic is also beautifully shown in an image of November 30 by E.Sussenbach (Dutch Caribbean), where the tailing off of the cloud to the west can be well seen. On December 2 T.Akutsu (Philippines) imaged a slight terminator projection due to high cloud, located near +2o, 202o (NE Aeolis).

I include other typical images by M.Hood (USA): note the partial morning clouds off the edge of the NPC; T.Arakawa (Japan): note the fine details NE, N and NW of the Syrtis Major, including Nodus Alcyonius; and T.Kumamori (Japan): the region of Indus and Hydaspes.

Opposition is fast approaching, so naturally more observers are joining in. The list of contributors posted on the front page has been updated, and already contains 53 names. If you are reading this as a BAA member please note that to start contributing to the Section you must first get in touch with the Director.

Expect another update shortly after the date of opposition.