2025 February 27

Mars Opposition Blog 27 February 2025

Richard McKim

27th February 2025

This latest post offers a very incomplete summary of the main points of interest in the recent observations up to and including February 22.

Since opposition on Jan 16 the British weather has been rather variable, and often cloudy. Early February initially looked promising, but most British observers then endured a long cloudy period of more than a fortnight after Feb 6, which only now may be ending. But worldwide coverage by 79 observers (and our Far Eastern observers have been particularly energetic) ensured that no dates were missed. See the updated list on the main page. (And as usual, I have taken images and drawings from past and previous contributors from a variety of websites, but NOT from individual BAA members’ pages. Those members must SEND me their images to me direct if they are to be included!)

I show some images by two new Section members first: David Brett (notice the evening orographic cloud over Elysium Mons) and Ron Palgrave (Solis Lacus remains large, and the Phasis streak and the little dark spot Gallinaria Silva are well seen following it).

The Director on Jan 20 noticed the blueness of the Syrtis Major upon the morning terminator. Thin cloud surrounded it, and dimmed it slightly. By this time the equatorial cloud belt had thickened. A month or so later on Feb 22 (Ls = 48) the blue scattering effect was perhaps stronger, due to the completion of the ECB after about Ls = 45. Images by Mike Karakas in blue light (for example, Jan 23, Ls = 34) show an example of the as yet incomplete ECB.

I would encourage all imagers to actually look through the eyepiece. In several cases not enough emphasis is being given to the blue channel or to the blue filter in RGB combinations, and the colour balance is unrealistic. At this season, white clouds in the morning and evening are common, but not all observers are recording them.

The wavelength-dependence of the white diurnal clouds is nicely shown by C.Pellier on Feb 1. He adds: “I’m adding a simulation to show where the ring of 6 white patches locate on the surface. The most northerly one corresponds to Alba Patera and the weakest one [just to the south] corresponds to a small dome.” See his image below.

Observers should now be looking along the terminator for any high-altitude clouds that lie beyond it. On Feb 16 Tom Williams took just such an image (which I have annotated).

Once the morning terminator is displayed to advantage after opposition, it is always exciting to be able to catch the summits of the Tharsis Montes as dark spots poking through the surrounding morning white cloud. Without having seen images of the effect this year so far, the Director made such an observation on Feb 5. And an image showing this effect by Mike Hood for Feb 18 is shown here.

We must not ignore the far southern latitudes. Here, patches of white cloud are seen in certain locations. Argyre was mentioned in earlier posts. These isolated patches will later merge to form the S. polar hood. With Hellas just past the CM on Feb 17, the Director noticed white cloud along the S. limb, but even when viewed with a blue filter it hardly impinged upon the south of the basin. And of the other visual observers, David Graham on Jan 18 noted a wide bright area (Eridania and Ausonia) along the S. limb under CML = 222-232. See his drawings below. The Director found Ausonia very bright and conspicuous on the evening side on Feb 22.

Until recently, some observers continued to find traces of a warm tint over the NPC upon their images, due to ongoing minor dust storms and dust fallout. A fine image by Martin Lewis for Jan 15 is shown here: note the thin vertical streak of dust upon the cap near the CM. But this month, activity has been much reduced. The cap too, is considerably reduced in size. Next, observers should watch out for the seasonal separation of Olympia.

In January, Mars was occulted by the Moon. Efrain Morales in Puerto Rico captured the diminutive disk of Mars near the Moon on Jan 14, and for once I will allow north to be uppermost. I noticed that several observers, including Ethan Chappel in Texas, USA, obtained images of an actual occultation.

On Feb 9 observers in the north of Scotland had a chance to see a grazing lunar occultation of Mars, or a full occultation further north. Only Callum Potter (Rousay, Orkney, 59.17 N, 3.06 W) was successful in seeing and filming both ingress and egress with his Seestar S50 (50 mm f/5 OG). His collage is shown here. And Paula Wirtanen in Helsinki, Finland, also succeeded with good images and videos of the event, and one of her stills is appended.

In my experience it is very unusual for a planet to be occulted by the Moon in two successive months. In fact, I can’t actually recall such an instance. Can anyone comment upon this?

Finally, if anyone tried to telephone me in early February they will not have succeeded, as in renewing my contract with BT, the company instead unhelpfully cut off the phone for 16 days. Perhaps this was only to be expected: that, after all, is modern service for you!