As you may have read from the alerts and follow-ups that I posted upon the BAA Forum, we have recently had a major Regional dust storm. I will cover this in some preliminary notes below which extend up to and including September 4. But first, to follow up upon the previous happenings….

The local dust storm described in the previous blog post lasted only a few days, but in late July and early August there was a slight resurgence of activity when a local dust cloud appeared in southern Chryse. This too lasted only briefly. On Aug 3 there was virtually no trace of it on the morning side to the Japan observers, while on the same date J.Warell (Sweden) caught the now inactive region at the evening terminator, proving that no activity had spread to the west.

It was to be in a similar location that more significant activity began on Aug 18, when images by Clyde Foster from 05:10 UT onwards showed very bright dust activity along eastern and central Valles Marineris, with two bright cores overlapping the southern deserts of Chryse/Xanthe. At Ls = 313.5 degrees, it had commenced at a point fractionally beyond the last moment for an encircling storm to have developed, but a large Regional event could not be ruled out at that stage, and indeed turned out to be the case. The eastern bright core was centred at -8.7, 034.4 degrees according to images at 00:23 UT taken by the MARCI instrument aboard the Mars Reconnaissance Orbiter (MRO), as provided by A.Sanchez-Lavega. (This location is close to Eos or Pyrrhae Region on the classic albedo maps.) Eric Sussenbach caught the western end of the event at 10:04 UT.

Next day, Aug 19, the storm expanded to the north over Chryse-Xanthe, and to the south over Mare Erythraeum. At this time I suggested that secondary dust cores would probably arise, perhaps over some or all of Meridiani Sinus, Margaritifer Sinus and Argyre, as they have done in similar events in the past.

By Aug 20 the storm had definitely reached Regional status (its long axis extending over 2000 km, or 34 angular degrees). Foster’s images (from Namibia) and Nick Haigh’s (UK) show that it had reached and faded E. Meridiani Sinus on the eastern front, while Peter Tickner’s full daylight IR image (from the UK) timed at 08.45 UT showed dust surrounding a still dark Aurorae Sinus to the west, and still expanding south west, with apparently one discrete cloud near Solis Lacus. Dust continued to occupy Chryse and Xanthe, with Mare Acidalium to the north largely unaffected. Although UK observers were now losing the emergence site over the morning limb at dawn, the eastern end would remain in view.

Further secondary cores now emerged, and I cannot mention all of them here. The dust core located near Solis Lacus became large and extremely bright on Aug 22 according to images by Gary Walker, Frank Melillo and others. Gregory Terrance, using a 50 cm aperture, showed that this new core was in fact highly condensed. However, little further development on the western side occurred. On Aug 21, Haigh caught a bright dust core between Meridiani Sinus and Margaritifer Sinus which lasted a few days, while to the south, dust was invading western Noachis.

A new (or resonant) core formed in Hellas: it is shown on the Aug 19 and 21 MARCI maps that have been forwarded by colleagues in the USA. Dust remained within the basin. On Aug 25 however, Haigh and Peach showed a bright yellow cloud in the NW corner of the basin spilling out of it into Iapigia, which was confirmed by Foster next day. The core was small and bright in early September, but by then dust was confined to the basin. An image by Walker dated Sep 4 shows this aspect. Furthermore, a new dark patch had developed adjacent to it on the west, as often happens as a result of events here. (Larger events cause a broadening and darkening of all of Mare Serpenis-Yaonis Fretum, bordering Hellas.)

Dust had covered Mare Erythraeum and Argyre and environs in the form of several parallel E-W belts. Within days these bright areas would become static, indicating that fallout was occurring. Sussenbach’s images on Aug 23 and 24 show daily changes.

On Aug 25 I posted the following at the Forum: “As of today this event seems to be ending. The eastern secondary core at Meridiani Sinus and more prominent western ones at or near Solis L. did not last long; for a time there was a bit of atmospheric dust raised in Hellas. The area around Argyre is still bright, but its lack of daily movement suggests it is now dust fallout from the storm. This area is larger than Argyre, as was the case with the similar event in 2022. Compared with the 2020 and 2022 regional storms at similar seasonal dates, the present one was less energetic and less extensive.”

There were a few final flourishes. Mike Hood and Walker on Aug 29 recorded a new bright dust cloud in SE Chryse more or less following the line of Oxia Palus-Indus. It did not develop, and more recent images show that the emergence site has returned to normal, in spite of the strong activity that had taken place there, while the Oxia Palus-Indus dark feature and other halftone streaks crossing Chryse are well seen again.

Several Japanese observers were very active as usual, but could hardly watch the storm. However, their work showed that the evening orographic cloud at Arsia Mons remained bright throughout its course, showing that dust did not significantly warm the atmosphere beyond the confines of the event. Great storms warm the entire atmosphere, causing all white crystal clouds to disappear.

In the north, although the polar hood presently persists (and should continue to do so for a long time) we have witnessed the first signs of the ground cap. Around Aug 9 the polar region had become brighter and sharply defined in red images (and to a lesser extent in IR images), at Ls = 309 degrees, though the larger overlying hood was visible in blue light. Makoto Adachi and myself consider that the ground cap was captured on this date by S.Ito and S.Watanabe, while Adachi may have seen it visually on Aug 7. (In 2012 BAA data showed the ground cap was first sighted at Ls = 312 degrees.) It is usual for the polar region to be changeable at this Ls, and indeed the hood is often more prevalent than the ground cap in the longitude of Mare Acidalium. We did not see the hood recede during the current Regional dust storm, confirming that dust was obviously not penetrating very far north of the equator.

Posted here are several daily compilations showing different stages of the Regional dust storm. This is in no way intended to be a complete account. I would like to thank all those who responded to the Forum posts and to personal email alerts. We now have over 36 observers sending or posting data, and the list of them on the front page has been updated.

Front page teaser image – Eastern End of Dust Storm, Clyde Foster. Western End of Dust Storm, Eric Sussenbach.

Previous Post – 5 August 2024

This is a summary of observations up till July 31.

By early July a trace of bluish-white N. polar hood along the limb had been discernible for some time. It had never been prominent. Tomio Akutsu’s images of June 27-28 and Clyde Foster’s images of July 9-10 clearly show how some cloud had moved south to cover the N. end of Mare Acidalium, as is often the case. The hood will become very prominent over the next few months. A nice image of it was secured by Damian Peach on July 28.

O.Inoue on Jul 20 imaged an evening cloud at Arsia Mons at Ls = 297 deg. It was clearly confirmed by MacNeill’s work two days later. These may be the first images of it this apparition.

Indus continues to be easily visible. It is now quite clear that Sinus Gomer (at the northern edge of Mare Cimmerium) has faded greatly since 2022. This had been suspected some months ago, but we could not be certain with such a tiny disk diameter back then. See the July 28 image of Peach. I also suspect that Lunae Lacus may now be somewhat darker than it has been for some time. East of Syrtis Major there is a hint of the southern part of Nepenthes being weakly imaged, while to the north, Nodus Alcyonius remains small and weak compared with a decade ago. And Solis Lacus may be a little smaller, particularly in the N-S sense.

During July 27-29, imaging and visual observations from Japan revealed a small dust storm upon the western edge of Margaritifer Sinus, in the eastern part of Valles Marineris. See the July 28 image by Inoue. As of today it does not appear to be expanding, and is now fading out. This continues the trend of recent years with, Hellas less active in producing storms and Valles Marineris (upon the border of Chryse-Xanthe) exhibiting greater activity.

I am posting Foster’s image of July 10 here, plus others from Casely (June 23), Haigh (June 17), Inoue (July 28), Ito (July 6), Akutsu (June 27) and Peach (July 28).

At July 31 we are at Ls = 303 degrees. A large planet-encircling storm might yet commence within the next 10 degrees in Ls, so please keep watching intensively

Front page teaser: Another dust storm and some small albedo changes. Image by O Inoue

Previous Post – 5 July 2024

The SPC continues to shrink, and is too tiny upon the sub-6 arcsecond diameter disk to offer any interior details. There is little sign of any white cloud, though some weak cloud has sometimes been visible along the north limb, indicating a nascent N. polar hood. The evening orographic clouds have not yet been sighted, and I remind observers that to detect them easily one needs a deep blue or violet filter, at least when the disk diameter is as tiny as it still is. Little dust activity has been evident of late, but on June 23 Foster imaged a small (and hardly detectable) dust storm to the south of Propontis (in the light region labelled Azania upon the Ebisawa standard map), which was also seen by the MRO spacecraft. His images of June 22 and 25 do not obviously show it. His June 23 image is posted here, together with drawings by Makoto Adachi and an image by Niall MacNeill.

Several more observers have joined in our programme, and I have now produced a Word document listing all of them, which is posted upon the front page of the Mars Section. It will be updated as necessary.

Front page teaser image:

A shrinking S. polar cap, and a very small dust storm near Propontis. By Clyde Foster

Previous Post – 31 May 2024

Next Post – 5 August 2024

More observers have now joined in. Highlights since the last post are: (1) During April 21-25 Clyde Foster caught a light patch of dust lying along the E. part of Valles Marineris, east of Aurorae Sinus, which was then accessible to him fairly close to the evening terminator. Spacecraft data show that this was a regional dust event that had spread somewhat further. Regions to the immediate E. looked nearly normal as they became visible from his longitude, but were lacking somewhat in contrast. During April 23-25 what appears to have been a dust streak elongated in the E-W direction can be made out near the N. edge of the SPC. (If Pandorae Fretum subsequently darkens, it will show that dust excavation had occurred as far as those longitudes.) (2) Some other local dust activity has been spotted along the N. edge of the S. polar cap. For example Foster’s image of May 27 shows a streaky bright area which can be seen in IR, R and G, but not in B. (3) The seasonal separation of Novus Mons from the spring SPC was complete at Ls = 238^o in 2020. At that seasonal date in 2024 the disk diameter was below 5”, but nevertheless Foster’s images of Apr 29-May 6 (Ls = 245-250^o) show the cap elongated in the correct longitude, with a hint of separation on the best images on some days. A trace of the much decayed outlier was caught by Mark Lonsdale on May 22 (Ls = 260^o), but only the best images will have a chance of resolving it.

Now is the best time to watch for more significant dust storm activity and I encourage those of you able to rise early to monitor the planet whenever you can in order to maintain continuity of coverage.

Previous Post – 7 April 2024

Next Post – 5 July 2024

The 2024-25 apparition of Mars has begun. In fact, ever since 2024 January 10 we have been receiving a series of excellent images from Clyde Foster (Namibia). These are remarkably good given that the planet’s disk diameter has so far hardly exceeded 4 arcseconds. Several of the results are posted here, with south up as usual, including images until the last few days. These show the gradual shrinkage of the S. polar cap, and the usual seasonal development of dark patches and rifts within it. The Hellas basin now appears lighter in the centre than it did in February, but no specific dust storm event has yet been recorded. The Mare Serpentis area is broad and dark, which is suggestive of a recent past event in Hellas. On March 14 Clyde even resolved some of the Tharsis Montes as tiny dark patches. The Indus streak (which in the past would have been called a canal), which runs between Oxia Palus (at the N. tip of Margaritifer Sinus) and the SE corner of Mare Acialium/Niliacus Lacus, has already been imaged. This is an area of particular interest, darkening during the 2018 planet-encircling dust storm, and persisting throughout the next two oppositions.

I am hoping that other early morning observers will soon join in the programme, and in particular I am keen that observers at other terrestrial longitudes will do so, enabling us to watch all sides of the planet simultaneously. By not doing so we risk missing short-lived local dust storms.

For a detailed Mars map, and lots of martian names, see the 2022 chart by Martin Lewis posted on the front page.

Opposition is still a long way off, and will not occur until 2025 January 16. A detailed note about which seasonal phenomena can be observed (and when) will be appearing in the June issue of the BAA Journal. I am including here only a copy of the ‘seasonal protractor’ showing the current 15/17-year cycle of oppositions, to include 2025.

An early pre-opposition preview was given by the Director at the 2024 March BAA Meeting; if you are interested, the presentation is still available on our YouTube channel simply by following the link below from around 2 minutes onwards:

https://m.youtube.com/watch?v=jHMM4efBYw4

This blog will be updated at irregular intervals. Keep watching for the latest news.

Next Post –  31 May 2024