2025 May 1

Mars Opposition Blog 1 May 2025

Richard McKim

1st May 2025

A short update this time. The tiny martian disk has now slipped below 7 arcseconds in diameter, and several observers consequently have now stopped their work for the season. However, daily coverage of most longitudes continues, and to illustrate this here are some images and drawings from the same date, April 17, from C.Foster (Namibia), C.Nuttall (UK), G.Walker (USA) and M.Adachi (Japan).

The band of orange-coloured atmospheric dust over the cap, mentioned in the last post, continued to be visible for some time. For example, images by M.R.Lewis (UK) on April 10 (posted here) and by G.Walker (USA) on April 17 show it clearly. The dust appeared close to the position where the polar area known as Olympia detaches from the rest of the cap.

The seasonal separation of Olympia from the N. polar cap has been observed. Images taken on April 19 (Ls = 73 degrees) onwards by T.Akutsu (Philippines) (and his image of April 22 is posted here) may have been the first to show it clearly on the evening side, and many subsequent images by others have confirmed it. It may have been caught on the morning side a little earlier, though the situation at that time was confused by the presence of the aforementioned streak of dust over the cap. With the current viewing geometry it is easier to spot on the evening side, where the gap between Olympia and the cap is widened by perspective. The seasonal date is typical. For example in 2010 separation was complete by Ls = 74 degrees.

The summits of the Tharsis Montes and Olympus Mons continued to show up through morning cloud. See the images by P.Tickner (UK) on April 19 for an example.

The equatorial cloud belt (or band) has continued to be strongly marked in the images, though not appearing equally intense all around the planet. It is also apparent visually. On April 24 Abel and the Director saw it under CM = 69 degrees. It was brighter in the morning and evening where it joined diurnal clouds, and around Ophir-Candor.

The seasonal brightening of Hellas, due to ground frost deposition, ought to be visible soon. The latest images from April 24 show it light in blue light, paler than the N. polar cap, but not yet bright in red. Akutsu’s April 22 series (see earlier) shows its current wavelength dependence.

I am hoping we shall be able to continue our daily patrol for as long as possible.