2024 November 8

Mars Opposition Blog 8 November 2024

Richard Mckim

With the US Presidential election taking place recently, I felt that some sort of parallel counting operation should be done in the UK, so on October 27 I tallied up the observations sent in to date, and there were 256 drawings and 2,285 images. I will not comment upon whether there were more blue images than red ones, but you will recall that I always hope for more blue ones! This blog post is complete up to and including Oct 31.

We have had new observations showing evening cloud over Arsia Mons and Olympus Mons (perhaps the first sign of the latter cloud). See the image by Gary Walker (USA) for Oct 23 posted here. Seasonally this is to be expected. Naturally the eye is drawn to the variable N. polar hood and its environs. Several observers have paid attention to the lower latitude of the hood in the vicinity of Mare Acidalium as well as its partial transparency over the north of the latter, while at some longitudes we have seen east-west elongated strips of cloud detached from the S. edge of the polar region.

Occasionally, frontal systems have moved off the cap to the south, and sometimes they have generated obvious small dust storms. A recent example (posted here) is a little yellow patch of dust caught in images by Luigi Morrone and Raimondo Sedrani (Italy) on Oct 30. This lay over E. Cydonia, NW of Ismenius Lacus. Note the very white morning limb cloud adjacent to the cap. Other such dust clouds at the cap/hood boundary have been seen.

Earlier, an even more dramatic storm in the form of an east-west shaped arc of dust was seen on Oct 13 by Flanagan and Mike Hood (USA), rapdily fading the next day. It was located west of the N. end of Syrtis Major, between it and Elysium. With its long dusty arc, the Oct 13 sharpened image gives a slightly unusual appearance to the planet. See the Oct 12-14 collage posted here. On this occasion the dust storm coincided with enhanced activity at the edge of the polar region. David Basey (UK) on Oct 11 drew attention to what appeared to be two bright projections off the edge of the cap, while closer inspection showed these to have been due to the presence of a horizontal cloud band that was transparent in the middle, with a dark feature (corresponding to the classical Sithonius Lacus) showing through. Sedrani captured the same activity. Johan Warell (Sweden) made a similar comment about enhanced hood activity at this longitude upon his images of Oct 12. The dust storm is the second of two recent events to have occurred near the boundaries of Elysium, an area where we know there has been a net accumulation of dust for some years now. (This is evident from the progressive fading of Cerberus, Trivium Charontis and the Aetheria dark marking.)

The N. polar hood will persist for some time into northern spring, particularly on the morning side of the disk, and in certain longitudes. N. spring (Ls = 0o) begins on Mars on Nov 12.

In the December Journal I have a note about the closely similar 1898-99 apparition, one of the earliest to be followed by the Mars Section, and I am suggesting that observers might challenge themselves to obtain images at very similar times and longitudes to the drawings published in the article, in order to make a comparison of albedo changes over 126 years. Let me know if you succeed.