Following are the e-mail messages I have received on all the various dust storms being seen by the MarsWatch community. Where possible, I will provide links to the images referenced as most of them were submitted to the MarsWatch site. Note that the page is set up from bottom-to-top so the most recent information will be at the top and the first message is at the bottom. Also, all e-mail addresses have been clipped so the spambots will not be able to use our site for harvesting.
I've attached a PDF [file] showing the TES view of the growth of the current dust storm on Mars. I plot these in groups of 12 MGS orbits, which is slightly less than one Earth day. So, the average date of the penultimate frame is just after midnight on the 20th, while the average date of the last frame is just before midnight on the 20th/21st.
As of the 21st, it appears as though the dust storm may no longer be rapidly intensifying. In particular, the MER Spirit site was still relatively clear, although I'd expect some of the dust at 300-0-60 W to advect over to 180 W even without new dust lifting. Storms of this size are often unpredictable, so we will continue to monitor it over the next days and weeks. Phil Christensen has been putting daily maps of atmospheric temperature and dust index on the TES web site.
In advance of a report to be written for the 2004 April BAA Journal, I am writing to give a few details of the recent significant martian dust storm, and to ask if anyone receiving this email letter has further observations to contribute.
Reports of the BAA observations up to the present are given on our Mars Section website.
On the night of December 12/13 UT (at Ls = 315 deg.) CCD images by Don Parker showed that a significant dust storm had arisen over southern Chryse (telescopic southern Xanthe) and the eastern part of Valles Marineris. Smaller, secondary dust cores were seen in northern Argyre and over Aram. (It seems that this really was the first day of the storm, but additional images from December 11-12 would be helpful.)
By December 13/14 a band of dust had extended SW from Argyre to higher latitudes and also westward across Thaumasia to the south of Solis Lacus (with the latter feature somewhat obscured). There was a general expansion of the original cloud to veil Eos-Aurorae Sinus-Mare Erythraeum.
On December 15/16, further images showed a belt of dust crossing Noachis and Pandorae Fretum-Deucalionis Regio diagonally from Argyre, and impinging upon Sinus Sabaeus. (Indeed, the Meridiani Sinus area was later affected by dust for a time.)
By December 17/18, activity was observed in Hellas in the form of a secondary bright core in the vicinity of the NW of the basin, its deepest part. However, the dust did not develop any further, probably having reached its maximum extent on this date. Observing visually, the Director (December 17/18 and 18/19, 41-cm Cassegrain, x410) detected a small projection of part of the Noachis dust cloud beyond the morning terminator.
A series of images by Ed Grafton at similar CML nicely demonstrated the progressive decline of the E. end of the storm during December 18-21. At the time of writing there remains but little suspended dust over Noachis, and the NW Hellas dust core is smaller and weaker. As of December 23, images by T.Akutsu (0740-0908 UT, CML = 63-85) show that the W. end of the activity has significantly declined, with the very little remaining dust in Thaumasia (just reaching the E. edge) connected to a bright persistent core in Argyre. Solis Lacus looks dark and well defined in these latest images.
There have been several albedo changes associated with the storm, and it will be interesting to see for how long they will persist. The Pandorae Fretum area looks broader and darker, and Noachis is now somewhat less bright than before the event. The whole area around Depressiones Hellesponticae (which marked the southern boundary of the Noachis dust) is much darker than before. A similar change occurred at the time of the great dust storm of 1956, and more recently during the event of 1988 November (see below). The Phasis area to the west of Solis Lacus should be watched closely for further possible albedo changes there as the dust gradually settles.
The general E-W extent of the storm at maximum was similar to that mapped by the writer for the 1988 November regional event, which had begun in Thaumasia to the south of Solis Lacus at Ls = 313. However, in 1988 the activity ultimately did not quite extend as far east as Hellas. In its initial development, the present event began more like the regional storm of 1990 November at Ls = 326. The Director actually cannot recall any historical event beginning in the location of the present one (S. Chryse-Xanthe/E. Valles Marineris) which showed such a considerable expansion in longitude! (Both the 1988 and 1990 events are illustrated and charted in R.J.McKim's monograph "Telescopic martian dust storms: a narrative and catalogue", published in Memoirs of the British Astronomical Association, Volume 44 (1999): see the Mars Section website for price and availability!) The Director (in BAA E-Circular No. 127) predicted that the event would not exceed regional status. This prediction was based upon the fact that the seasonally latest encircling storm ever observed had begun at Ls = 311 (in 1924 December).
Yesterday I made an image of Mars and the NW-part of Hellas looked unusally bright. Also that edge of the basin looks more square than round. It is definite not haze like the patch at the Southern part of the terminator. Seeing was 5/10 to 6/10. Can anyone confirm this?
On five different days I was now able to keep track of the bright region in Hellas which probably represents duststorm activity. There is a good correlation between the intensity in the R spectral domain and the thermal infrared results of the TES instrument on the Mars Global Surveyor Orbiter. I will try to compile my results in an appropriate way and make them available to the MarsWatch website.
We now have TES data through Sunday July 13 (Ls=220.6) processed. I think we can now pretty safely say that the dust storm has peaked and is now in decay. The peak was around July 5. The highest opacities (still about 0.7 in the IR) have drifted southward and in the July 13 data are at 50-60 S, 180-270 W. Although the longitude sector 180-330 W still has more dust than other longitudes, the "background" opacity in the entire southern hemisphere is now noticeably higher than it was before the storm, especially south of 30 S latitude (where it is roughly 0.4). We're still early in the dust storm season so we will keep watching for the next one.
As most of you probably know, there is a currently a growing dust storm on Mars. I just plotted the most current TES data (July 5, TES mapping day 20999, Ls=215.8). The storm has intensified and spread significantly since our last look on July 1. I now see IR optical depth of 1.0 in the core located at about 25 S, 310 W (just NW of Hellas). There is an extended region with optical depth greater than 0.7 from 10-40 S, 240-360 W. Unlike the 2001 storm, this storm seems to be spreading both west and east (2001 storm spread mostly eastward). Dust has also pushed southward since the 1st and there is now significant dust to at least 60 S in the 240-360 W sector. There doesn't seem to be much dust in the north yet.
Phil Christensen is putting up daily maps of "dust index" on the TES web site so you can track progress of the storm there.
As of the 5th, the storm is nearly as big as the 1997 and 1999 storms at Ls=225. The next week or so will tell whether it remains regional or expands to planet-encircling.
There was considerable surprise during the 2001 Mars apparition at the timing of the beginning of what would become a planet-encircling dust storm, virtually eight weeks prior to historical dust activity commencement. It is very obvious now that the current apparition's first dust activity has been observed and imaged, this time about six weeks later in the Martian season reckoning than the 2001 event. Japanese observers late last month noticed a peculiar appearance near the south polar regions, then, on [June] 28th at about 8:30 UT, the undersigned found regions to the preceding side and to the north of the impact basin Hellas that were uncharacteristically subdued in their albedo contrast, especially Mare Tyrrhenum and Iapygia. This observation was under pristine conditions on Little Torch Key, Florida using a six-inch f/8 borrowed from Don Parker. On the few subsequent dates, Parker and others have obtained images easily revealing a dust storm in northern Hellas. Parker also had noted a number of unusually strong blue clearings during the preceding couple of weeks; there is a suggestion that such clearings may be harbinger to dust activity. In any case, the alert is now in effect.
Jeff Beish has recently reminisced about long-time mentor Chick Capen and his detailed notes about the 1956 and 1971 global dust events and that Jeff's observations over the past two months were so eerily similar to Capen's vivid descriptions of what transpired in the days prior to the celebrated 1971 storm. As Jeff so poignantly stresses, we so much miss our great friend Chick. It is, of course, far too early to tell if this will go global and spoil the show for the anticipated legions who wish especially this time to have a an unsurpassable view. Let's hope all works out well.
I looked at Mars with a 16-inch SCT at 07:39 UT (about two hours before Don's images). The Hellas region S. from -25 to -55 latitude was yellowish as it came round the morning limb from longitudes ~320 (on the limb) to around 260.
I also looked with an 8-inch Newtonian about an hour after Don's image (10h UT). The whole region S. of the equator at Syrtis Major was of low contrast until one got near the SPC. Mare Tyrrhenum was lighter than Mare Serpentis.
The color of Aeria/Arabia particularly intrigued me, especially compared with Libya side of Syrtis Major. Aeria/Arabia had noticeable orange yellow color while Libya was a blander color. The difference seemed greater than normal.
Last Friday morning (2003/6/27) at dawn here in Nebraska I was looking at Mars (CM = 337) and I noted in my sketchbook that there was slightly yellowish diffuse cloud S. of Mare Erythraeum towards Argyre. The color was different from a whitish cloud over Chryse and the blue clouds/haze on the morning limb in the other (northern) hemisphere. Since the sun-angle between M. Erythraeum and Argyre was very favorable for dust scattering this might not be abnormal. I saw something similar a week or two before the 2001 dust storm. Compared to the 1988 opposition, overall contrast across the disk seemed to be down, but it was much better than in the summer of 2001.
My sketch of the SPC on June 27 showed the brightest area to be very clearly around longitude 50, rather than S. of Hellas as in Don's image of this morning.
Thanks for these images and the information. I agree a dust event has commenced, and will issue a BAA e-circular tonight. The bright SPC patch in the longitude of Hellas would be Novus Mons, or were you referring to another bright patch over the cap? It is not possible to predict how far the event will spread. I would be pleased to receive any further images at once. Many perihelic apparitions have dust events, some local, others larger. I am not yet sure what the focus of this event is, but will review the images closely. It seems to have arisen just north of the Hellas basin.
Let's keep watching!
Mare (310W, 20S) appears to have changed dramatically since 30 JUNE 2003 (yesterday) and is brighter now in orange (W23A filter) and blue-green (W64 filter) light. Areographic northwest Hellas (305W, 20S) brighter, light spot that was not there yesterday. Light/bright streak from Pandorae Fretum into Iapygia Mare. Also, Tyrrhenum Mare, Cimmerium Mare lighter than yesterday and Hesperia not as well-defined. Possible dust clouds.
[Editor's Note: see the images and notes for this date]