A major dust storm growing out of Hellas basin has been seen and recorded by members of the Mars Section of the Oriental Astronomical Association. Following are the e-mail texts I've been receiving on the matter from both the observers and some follow-up commentary. Further information and images can be found at the CMO Web-Site and in the June and July MarsWatch images pages.
The dust storm is now planet-encircling! It is a curiosity to have this much dust activity this early in the Mars season; does this imply a very dusty southern summer for Mars? What are the chances for a global dust storm? Where are the Vagas odds-makers now?
I will post information here as it becomes available. This page may become quite large, however I am going to refrain from putting images here and will instead provide links to points within the iamge pages. A warning: some of the image pages are getting quite large themselves and may take considerable time loading; I will consider breaking them apart or perhaps linking from here to individual images.
Note that many of the reports below come from mass e-mail from the several lists of Mars interested folks out there and some are personal e-mailings that have been passed around to said lists. I have taken the liberty of editing out some of the personal messages within the reports becuase they were A) personal messages, and B) not relevant to the report in general. I have not added any information to any of the posts, although there are some [Editor's Note]'s stuck in here and there.
A definite expansion of dust clouds inside and near Hellas has been observed by a number of CMO observers here in Japan.
The dust cloud has no more particularly bright area, and looks diffused, but it is definitely a dust phenomenon, as judged from the ccd images produced by KUMAMORI and MORITA on 26 June, covering a large region from Hellas to Hesperia. The eastern part of Hellas is covered by a bright dust streak, and at the same time M Tyrrhenum looks separated from M Cimmerium by a broad dust streak. The resonance between them is not clear at present, but the area inclusive is largely dusty.
KUMAMORI first sent to me a processed image (made from Sony Video images) taken on 26 June at LCM=277° W (at 14:29 GMT), and meanwhile I received a set of good ST-5C images from MORITA also on 26 June at LCM=275° W and 285° W.
One hour ago I had a conversation on the phone with ISHADOH at Okinawa (he was at the eyepiece with a wireless phone), and I am convinced that the phenomenon is surely developing on the area.
M Tyrrhenum has been slightly faded these days and looked weaker than Syrtis Mj and M Cimmerium, and showed a much fainter area inside it near the mouth of Hesperia on 24 June (184° Ls), as observed from Fukui. Most part of M Tyrrhenum is however apparent even today according to ISHADOH.
We are suffering from the rainy season in the main island of Japan, while it ended already in Okinawa, and according to ISHADOH, he is enjoying the clear skies every night these days, and has been chasing the dust phenomenon. He is about to send his drawings by FAX to me. I expect HIGA is also on an alert by the use of his Video recorder. As to the origin we have no definite information yet, but I expect to have more data and news within a few days. AKUTSU is now going to fly to Okinawa on 28 June JST to observe.
The area is at present facing to the Oriental countries, while its effect may be caught soon in Europe. And we also expect to receive the data from the US observers of pre-stage of the dust at the concerned region.
Further news as well as the images will be posted in our CMO Web-Site.
Masatsugu MINAMI at Kyoto on 27 June at 16 hours GMT Director, the OAA Mars Section
This is a second report:
The dust cloud now shows its vivid aspect, swirling from Hellas down to Hesperia. It now shows a bright core at the junction (at Ausonia Australis) of the two streaks (one at the eastern Hellas and the other at the area between M Tyrrhenum and M Cimmerium).
It is quite big and definite and looks stable.
I have just received two processed image-files from AKUTSU and KUMAMORI made this night on 27 June.
AKUTSU's set of good images were compiled at LCM=258° W this night on 27 June at 13:50 GMT, and the bright knot is just near the noon. It is shot in all wavelengths, IR, R, G, B as well as Int. The images are excellent to the extent that all of the known dark markings are clearly produced, and hence the strange meandering of the streak is well shown up. He was still at Home Observatory (using a 32 cm speculum with Teleris 2) at Tochigi this night, but he is going to fly to Okinawa to shoot the cloud by the use of a 40 cm spec chez WAKUGAWA from 28 June for four days.
KUMAMORI succeeded to shoot the dust cloud slightly earlier at LCM= 248° W by the use of a 60 cm Cassegrain at Sakai, Osaka equipped with a Sony TRV-900 Video Camera. The still image is a composite of 380 frames (this is nowadays possible!) and since he used an artificial colour to feature the cloud, the area covered by the dust is clearly identified.
The spc is still clearly seen (ina smaller size, but well whitish bright) and the nph also develops.
I hear HIGA was also aware of the phenomenon independently.
We are going to update the CMO Gallery with these images if the day breaks and our working colleague is not so busy.
PS or a third short report:
Yukio MORITA has just completed his images at LCM=264° W. It shows more Hellas side, and proves that the streak inside Hellas has further developed as well as the forgoing streak's winding.
Just a comment: Mare Cimmerium is completely out of the cloud, not affected by the cloud yet. The cloud is located to the west of the line of 250° W. Even the tip of the NW end of M Cimmerium is clearly visible.
I am sorry I must go to bed, and so details with a filing of the images will be done this evening JST.
See for example images from the 26th by Masahito Niikawa, T. Ikemura, and Maurice Valimberti; on the 27th by Masahito Niikawa; on the 28th by T. Ikemura, and Tan Wei Leong.
This is a fourth email on the dust at Hesperia-Hellas.
They still enjoy the clear sky and seeing at Okinawa. I hear AKUTSU arrived safely there.
I had a telephone call from Yasunobu HIGA at Naha, Okinawa this night. According to him, a small, but bright germ of dust has newly appeared today at the east coast of Syrtis Mj. It is interesting to note that the place looks following the area where the vanished Moeris Lacus was once located, if I have not misheard. HIGA assures that it is brighter than the spc at present, but very dim in the blue light. We expect to hear the aftermath of the germ tomorrow.
My email receiver has however been silent up until now; maybe since the observation time is not yet over (1:00 o'clock local time).
We are sorry since we were late in uploading the images of the dust cloud on 26 and 27 June (by AKUTSU, KUMAMORI and MORITA), but the CMO Gallery has been updated with these images, and so we hope you may make an access to http://www.mars.dti.ne.jp/~cmo/oaa_mars.html
There you will also find the images of the Edom brightening observed on 7 June at the Florida Keys (by courtesy of Tom DOBBINS and David MOOR).
Masatsugu @Kyoto
This is a fifth short communication from the CMO/OAA on the dust storm (on 29 June GMT):
No report from the observers in the main island arrived today because of the dismal weather, but the observers in Okinawa are still enjoying the seeing.
ISHADOH emailed me at 13:30 GMT that the dust storm looked to have further developed and M Cimmerium was nearly divided into two crossed by a thick streak of dust cloud coming from the southern side.
A moment ago, I received another detailed report from him together with several drawings made this night: According to the report and the drawings, almost all the markings on the southern hemisphere appear to have been affected by the dust, and as far as seen from LCM=240 - 270 degrees, no more than M Cimmerium (except for the crossed part) and the dark fringe of the spc look dark. ISHADOH assures that even the spc (especially its evening side) has become off-white because of the dust.
Don PARKER agrees with me in alerting the European observers since "it looks like the storm is still extending". Really the following side may soon be affected by the westward expansion of the storm. As well, as ISHADOH reports, the effect of the dust storm can also be soon checked from the south circumpolar region from any corner of the world.
Last night, just after I wrote "My email receiver has however
been silent up until now; maybe since the observation time is not
yet over (1:00 o'clock local time)", I received the following
message from TAN Wei-Leong in Singapore:
Date: Fri, 29 Jun 2001 01:49:58 +0800
From: "Tan Wei Leong"
Subject: Re: Dust still prevails
I've got some images from abt 12:00 to 14:00 Japan time, will be processing them after this. Not much images just 4 sets of images. Regards.
And after the day broke, I received from TAN a set of excellent images at LCM=274 degrees W in which the bright germ of dust at the eastern coast of Syrtis Mj was clearly shot as HIGA reported last night (already uploaded in the CMO Gallery).
According to ISHADOH, the germ still remains brightest tonight and looks to have made Syrtis Mj faded except at its northern tip. However such northern markings as Utopia, N Alcyonius and the dark patch following Elysium in Aetheria are normally dark. The nph is roundish large.
I returned home from Kyoto, but it's raining at Fukui.
Masatsugu MINAMI
The CMO/OAA
I am seeing the dust storm.
Now, 21h15m UT, MC~340°, I am seeing the dust storm near the east limb. I can't see the Syrtis Major. "It disappeared". I see only your north spike, but it is very faint. The dust storm is brighter over Hellas. I made good CCD images.
Nelson Falsarella
Rede de Astronomia Observacional - REA
Centro Integrado de Ciências de S. J. do Rio Preto - SP
BRAZIL
All images that have been submitted to MarsWatch regarding this have been posted to the images pages by the date upon which they were taken.
One week has passed since the dust cloud started on circa 24 June near Hesperia: We wonder thus how the cloud expansion westward is visible from the Occident.
This is a sixth CMO/OAA communication on the going-on dust storm from Japan.
As I returned from the Observatory, I heard from KUMAMORI, MORITA, MURAKAMI, and TSUNEMACHI that they all succeeded in observing Mars tonight on 1 July after a long absence of observation, while HIGA and ISHADOH are silent: They confessed the night before that they were dead tired because their observations had lasted every night since the beginning of the storm.
At Fukui, the sky was clear first tonight and we started from LCM~190 degrees W (at 11:30 GMT), but nearly at one o'clock am (16 hours GMT) mist hanged over the observatory (atop of a hill), and so we were not able to observe the surfaces west of LCM=250 degrees W.
Summing up the results obtained by our members including mine, the eastern procession of the storm reached M Sirenum, and Electris looked still brilliant with newly aroused dust; looking to cause something to M Sirenum tomorrow. The following areas appeared already covered largely by airborne dust to the extent that M Cimmerium was extraordinarily faint covered by several streaks of dust just leaving some dim markings. The spc looked whitish bright with a fine dark (black) fringe first, but became quite duller as the surface rotated.
In the northern hemisphere, Propontis I, Phlegra and the Aetheria dark patch were clearly seen, though even they looked slightly faded. One of dust streaks seemed to have come down to Elysium and the shape of the Aetheria dark patch has definitely changed. The dust disturbance should be said thus global. The Gyndes band was however seen up to Utopia, adjacent to the bright nph that was made of two (one outgoing and the other coming-in) white cloud patches.
Unexpectedly, Syrtis Mj came in to show up its whole shape though it was not fully dense. Morning terminator looked slightly hazy with dull white water vapour.
Gradually Syrtis Mj and Hellas are thus about to go out of sight from Japan, and so we expect a timely start of intensive observations of the present global dust storm in Europe. Late at night (or early morning), the covered or still uncovered M Sirenum might be caught in the US tonight.
This evening (JST), HIKI's drawings made on 29 June and ccd images on 1 July by MORITA shall be uploaded in a just started corner of the CMO-Web.
Masatsugu MINAMI
Director, the OAA Mars
Today I saw Mars again, at 21h30 UT.
Syrtis Major appeared again, but it was faint in your south portion and Iapygia. The north portion of Syrtis Major was very dark again. Hellas was brighter than one month ago, when this region was visible to my observation site.
A very perceptible cloud crossed Syrtis Major east to west.
Nelson Falsarella
Rede de Astronomia Observacional - REA
Centro Integrado de Ciencias de S. J. do Rio Preto - SP
BRAZIL
Dear Masatsugu:
Thank you for your latest email "Storm is now global". This seems just a little premature, for I have not heard of there being any evidence that the longitudes of (for instance) Mare Erythraeum or Solis Lacus have been affected, at least not up to the time of writing this. The only thing global about the event is in terms of coverage by observers!
Of course, it may spread further, but if it did so it would be unusual for the current Ls. One cannot compare this disturbance with the only truly global storm of 1971, or even the encircling storms of the 20th century, from 1909 to the epoch of Viking. It seems in this case that dust has propagated largely to the east, invading the southern deserts including Hellas, Ausonia and Electris, and obscuring Tyrrhenum M., Cimmerium M. and even the Syrtis Major and parts of the N. hemisphere. In this respect the progression is reminiscent of aspects of the regional storms of 1894 October, 1907 July, 1941 November, 1943 September, 1958 October, etc...., though only the 1907 event was at a reasonably similar Ls. In some of these cases dust stretched three-quarters of the way around Mars, but one would not describe any of them as being global or even encircling. Historically, the great encircling events have only broken out later in the season, and seem to require a secondary, independent focus of activity to develop to enable them to reach encircling status. Thus the seasonally earliest encircling event commenced at Ls = 204. There have been many other Hellas regional events, but in many cases dust also spread substantially to the west, and in this case there has been little of that. What is unusual in the present case is the presence of initial cloud in the Hesperia region, and the bright patch of yellow cloud observed in the Libya-Isidis area shortly afterwards. The Libya-Isidis site had produced more dust storms than any other site according to E.C.Slipher, when writing in the 1960s. But since 1958-59 the site has not been active in producing events, and became a dust-sink, witness the gradual fading of the great Nepenthes curve over the next two decades. If the site is reestablished then that feature should reappear. Wait and see!
I was observing last night (July 1 U.T., with my 42-cm Dall-Kirkham Cassegrain) under CM = 325-335 and found a general loss of contrast, but the amrkings all clearly recognisable. The Syrtis Major was clearly visible though a little pale, except at the N. end. The Mare Serpentis area was well marked. Libya-Isidis and Hellas were bright and dusty on the evening side, and Hellas was brightest to the north. The SPC was seen, with a dusky boundary, but on the p. side I could not separate it from Hellas. Conditions were not good however, with Mars so low from England at present, and I hope other observers will be getting (and contributing) better views.
If the present storm reaches encircling status it will be a new martian record! Let us wait and see over the next few days.
Richard McKim
Director, Mars Section, British Astronomical Association.
This is a seventh communication on the present dust storm from the CMO/OAA, Japan.
Tonight near at 14:00 GMT (on 2 July), the Martian surface of LCM=220 degrees W faced to us near at meridian under a good seeing condition. The whole of surface was beautiful in a tint of bright yellow, just like a polished big ball. We should say the yellow cloud globally covered the surface all around except for the north polar region. Nobody calls it local or regional.
One of the characteristics of the present dust storm is its expansion deep to the northern hemisphere. The term "yellow cloud" is a good terminology to describe the aspect of the global expansion from the deep south to the deep north, but in order to understand the changing going on at the region from Phlegra to the dark patch in Aetheria (known since 1975), it is plausible to consider that the "dust" disturbance came down northward and still occurs frequently also on the northern hemisphere. The shape of the Aetheria dark patch looked today different from that observed yesterday, and the inside of Elysium showed more dusky areas than yesterday. Cebrenia is bright yellowish in the same way as Phaethontis is bright dusty. Gyndes adjacent to the north polar hood looked free from the dust and the darkest among other surviving dark markings on the disk. The white cloud patches at the npr were also beautiful.
Even in the case of the great dust storm in 1956, the northern hemisphere was not so affected: The storm encircled on the southern hemisphere upto the south polar region. Difference may come from a difference of the mechanisms of the dust arousing in different seasons (or different water supplies and the solar heating), but mostly the expansion difference comes from the difference of the global wind system. In 1956, the season was near 250 degrees Ls and the dust received the strong easterly. On the other hand, this time, the season is younger and milder yet when the south polar cap just started to thaw, and so the present wind system could not cause the hemi-sphere encircled expansion (as in 1956) nor the globular expansion (as just in 1971).
Even then the present yellow cloud storm have already shown a global expansion from Hellas to M Sirenum on the one hand and from the south polar region to the deep north on the other. Nearly it is thus covering a hemi-sphere (just like in 1956 though on different hemisphere). We should say this is rare and extraordinary and so this new kind of global phenomenon needs further attention.
We suppose it is frustrating to wait the expansion whose speed is slower than the 40 minute rotation a day, but should wait until the yellowish hemisphere is seen to say something. We of course suppose the airborne dusts will soon subside away because of the season, but it is also possible for the thinner part of the airborne dust to have already influenced the other hemi-sphere. We should remember these airborne matters may cause another germ of storm in a latter season.
Tonight, Takashi NAKAJIMA and I witnessed the scene together at the Fukui Observatory: We both experienced the great dust storms in 1956, 1971 and 1973 at the same Observatory, but we both felt that we have never seen such a beautiful yellow storm expansion. It was apparently impossible to sketch such a glossy surface, and we are sure that neither photo-image nor literature can reproduce the globe wholly covered by the mildly bright yellow cloud.
Masatsugu MINAMI,
Editor, the CMO/OAA
"Our" hemisphere [viewing done at JPL, Pasadena, CA, USA] of Mars continues to appear largely dust-free, although since it's dominated by bright albedo features it's harder to be sure of this. The opposite-hemisphere large regional storm doesn't appear to have extended west into the Margaritifer and Acidalia regions yet, based on my visual observations last night in mediocre seeing (no imaging). Prominent polar clouds are visible in this image, as are morning clouds and wispy clouds across the planet's equator.
-Tim.
The recent Martian dust storm occurred at a great time for terrestrial observation, and that is how I first heard of it - the reports from Japanese observers. Excellent work, and some fine pictures!
The thermal signature of the storm in the Mars Global Surveyor horizon sensor data (15 micrometers wavelength in the infrared; this is a bulk measurement of the atmospheric temperature, which rises as sunlight heat the dust) appears to develop along with the visual evidence of bright yellow clouds. I made a series of thermal maps, one per day, and they show a gradual warming in the northern Hellas region starting about day of year 175 (June 24). The attachment is a Quicktime movie of the days 175-181. The data come from daytime hours only (0600 to 1800 hrs local time). I use west longitudes.
I would not expect the temperature to track the visual appearance of the dust storms exactly. What I am seeing is the heating due to dust that is mixed to considerable height in the atmosphere (many km). The behavior of the 1999 Ls 225 warming showed strong control by an existing thermal wave pattern rather than matching the dust storms seen in the MOC (MGS camera) image data.
The warming grows strongly after day 179, and begins to show up in the northern midlatitudes on day 180. The warming moves eastward in both the north and south after that. I will continue this movie as more data are processed. Because of this storm's early start within the dust storm season, it is particularly interesting.
Cheers, Terry
The Martian disk still remains wholly obscured from our side. Last night on 4 July, we (NAKAJIMA and I) first caught the planet at twilight before 20 h JST (11 hours GMT) at Fukui, and we thought the scene of the blurred M Sirenum (including an eastern part of M Cimmerium) was quite reminiscent of the scene we met in 1973 a few days after the occurrence of the great dust storm at the Solis L region. The season was largely different (Ls was 300 degrees in 1973) and the direction where the dust disturbance reached was opposite, while the scale of the obscuration seemed quite the same as judged from the distribution of the obscured dark markings. Furthermore, we noticed at the evening limb side a new brighter dust patch in Daedalia-Claritas preceding M Sirenum, and we thought this might have already been caught at the western countries of the US.
The bright dust patch must have certainly been caused by the dust disturbance at the following side, but this does not imply that the patch moved from the western side. Any encircling storm is a global storm, but any global storm does not mean it has a character of the encircling. Encircling is a minor index of the scale. When I met the late Professor Shotaro MIYAMOTO at Director's room of the Kwasan Observatory, Kyoto University, just after the brilliant occurrence of the dust at the Solis L region in October 1973, discussing about the possible expansion of the storm, he pointed out a possibility of the simultaneous occurrence of several dust cores at various areas, and suggested the scale of the storm is related more with the resonance than the expansion itself. The later depends more simply on the simple wind system, but resonance is more intrinsic. I suppose the present patch at the Daedalia-Claritas area is a resonant one.
As I have written, the dust storm has already been global (in the scale), and on 4 July we witnessed that the dust reached the north polar region and the morning side of the nph clearly showed an off-white tint, thought the evening cloud patch was still whitish bright. Attached here please find the image made by Teruaki KUMAMORI (by the use of a 60 cm Cass of the Sakai City Observatory) on 3 July, in which you see how the dust storm covers globally the disk. I don't suppose who call it local or regional. How many regions on Mars do you need to describe this covering as regional? The classification sounds almost primitive, and we should say the possibility of watching from every region on the Earth simultaneously (since encircling) is not related with the scale of the storm.
I was told from NAKAJIMA that the Martian disk covered wholly by the yellow cloud was branded on his mind even after he went home on 2 July late at night. It was not simply a disk, but it appeared to us as a glossy globular planet in beautiful perspective. We are of the opinion that the yellow cloud should not be observed with the use of the thick filters. The distribution is not necessarily made of the bright parts only, and if one can check it by a red filter, he will more easily be able to find it by the integrated light. Red or Infrared image may unearth the fainted dark markings, but the scale can more be checked by the naked eyes. We should say at least that the present beautiful disk with bright yellow cloud should be watched through the naked eyes.
Obscuration is however not the prime standard of the dust cloud. The scale of the dust disturbance is attributed to how it causes the change of the dark markings, to be temporal or to be secular. As I wrote repeatedly, the cloud is extraordinary since it already expanded from the spr to the npr, while at the same time it shows an every-day changing of the dark markings at the region of Phlegra and the Aetheria dark patch. Even Elysium and Cebrenia show tentative shadowy markings inside. It is quite interesting to know how the markings develop or not at the time the storm could have subsided. Fortunately, it happened at the opposition time, and so we may chase the aftermath within this season.
I don't understand why the HST distributes the images of this going-on global dust storm. I wrote previously to Tim PARKER as
By the way, do you not know any plan (or any alteration in the plan) of the HST to shoot this going-on spectacle on the half side of the planet? Do you think I or somebody else should write a letter to Jim Bell or Phil James?
Tim kindly replied (on 2 July at 18:30 GMT) as follows
I would go ahead and ask either Jim Bell or Phil James about HST plans to image Mars. I would be surprised if there aren't plans to do so already, but I could be wrong.
So I expect the HST is to work soon.
I am terribly busy: We have not yet completed the printed version of CMO #246 (25 June 2001 issue, too late). Furthermore I am bound to fly to Okinawa the day after tomorrow to observe the planet. I am looking forward to meeting soon HIGA and ISHADOH who have observed fully the early stage of the present dust disturbance under the clear skies every night at Okinawa (unfortunately MIYAZAKI does not stay near his Observatory at the Okinawa mainland, but in a different island at present on duty). AKUTSU already left Okinawa after shooting Mars and went home. Following me, several CMO members will visit Okinawa on to watch Mars by WAKUGAWA's 40cm. I hope the weather in Okinawa should be moderately poor: If not, the publication of the CMO will be much delayed. Alas!
Our CMO colleagues, MURAKAMI and TSUNEMACHI have also had a deep interest in the Solar activity from the 1970's. They are wondering at present whether this spontaneous Martian dust burst has any relation with the present violent activity on the Solar surface or not.
I suppose the dust brightening of Daedalia-Calaritas suggests a further development of the yellow cloud on the eastern side, and I hope it will remain amazing until you are able to catch the scene soon (though some of Japanese observers are now annoyed with this obscuration).
Masatsugu
Just a quick note that the dust storm noted in Daedalia on 3-4 July by De
Groff, Valimberti, D. Moore, and T. Parker has expanded to Thaumasia.
Multiple nodules are noted covering western Aurorae S., Ophir, and the
Tithonius complex. Bosporus and Nectaris P. remain dark, but dust clouds
noted in southern and western Thaumasia, curving around and partially
obscuring Solis Lacus and extending northward into Tharsis. The N.
hemisphere is largely unaffected.
Red light images attached.
Will send more when I wake up!
This set of maps
shows the initiation and growth of a very large dust storm
observed by the Thermal Emission Spectrometer (TES) during June and July
2001. Each panel is a map of 9-micron dust optical depth made from one day
of data. The Mars Global Surveyor is in a polar orbit with period 2 hours.
The 12 orbits taken during the course of one day provide 12 very narrow
strips of data running roughly north-south spaced about 30 degrees apart in
longitude. For these maps, dust optical depth has been interpolated in
longitude to "fill in" the gaps between the orbit tracks. The effect of
topography on dust optical depth has been removed by scaling to an
equivalent 6.1 mbar pressure surface. This scaling is accomplished by
multiplying the observed dust optical depth by the factor (6.1/psurf) where
"psurf" is the surface pressure in mbar. The color scale is the same for
each map. Blue and purple indicate low dust optical depth (clear
atmosphere), green indicates moderate dust optical depth, and yellow and red
indicate the high dust optical depth associated with dust storms. The
visible optical depth of dust is about twice the 9-micron optical depth
shown here, so anywhere that is yellow or red on these maps there are dust
clouds that are thick enough to obscure the surface in visible light images.
Michael Smith (Michael.D.Smith.1@gsfc.nasa.gov) NASA Goddard Space Flight Center I thought a little description of the visual appearance of Mars
from the US might be of interest since I think there are things that can
be appreciated visually but which can get lost in the processing of CCD
images.
I looked at Mars last night (2001-July-9 UT) with my favorite
planetary 20-cm Newtonian. The CM was around 18 degrees. I think it is
important to look at Mars through a familiar system to appreciate what is
going on right now. The subtle colors reveal a lot. The first obvious
thing is the lack of contrast. I've seen more contrast on Mars when it
has only been 5 arcseconds across. Normally my 20-cm Newtonian shows the
colors on Mars quite vividly; now it is a pale whitish-yellow. The lack
of contrast might not be obvious in CCD images where the contrast has been
artificially enhanced. Tonight (2001-July-10 UT) I think the contrast is
even lower.
Last night (2001-July-9) for a long time I thought I could not see
Sinus Meridiani at all. Then the seeing suddenly got better for a moment
and I clearly saw a ghostly presence of Sinus Meridiani! It was quite
eerie and a remarkable experience.
The line between Mare Erythraeum and the bright Aurorae Sinus dust
storm was quite sharp. The M. Erythraeum region was probably the highest
contrast part of the planet.
Niliacus Lacus and Mare Acidalium were visible, but at much
reduced contrast. Interestingly, the poorly-resolved Protonilus/
Deuteronilus/Dioscuria/Cydonia complex was almost as dark as the Niliacus
Lacus/Mare Acidalium region.
The strongest centers of dust activity were a deeper yellow than
the rest of the disk (they seemed almost brown), especially when they were
towards the limb. Optical depth effects are causing all of the limb to be
a bright yellow, except at the N pole (see below). The terminator is
noticeably more yellow than the evening limb. This will be because the
larger dust particles have a less forward-scattering phase function than
the high-altitude cloud particles.
The structure of the NPC is interesting. During rare moments of
good seeing it was exceptionally bright so there would seem to be less
general diffuse dust down there. However, the NPC seemed to be cut in two
by a small brown cloud sitting almost exactly at the pole! A W25 filter
showed neither cap to be bright so the poles must be showing mostly blue
haze rather than white ice.
Tonight (2001-July-10, UT) I could see "the ghost of Syrtis
Major". It is a little hard to tell with variable seeing from night to
night, but I wonder if anything at all will be visible anywhere in a few
more days.
Martin Gaskell
TES Finds June-July 2001 Martian Dust Storm now Planet-Encircling
This map continues the TES dust storm
observations posted on July 6. As
before, each panel is a map of 9-micron dust optical depth made from one day
of data. The Mars Global Surveyor is in a polar orbit with period 2 hours.
The 12 orbits taken during the course of one day provide 12 very narrow
strips of data running roughly north-south spaced about 30 degrees apart in
longitude. For these maps, dust optical depth has been interpolated in
longitude to "fill in" the gaps between the orbit tracks. The effect of
topography on dust optical depth has been removed by scaling to an
equivalent 6.1 mbar pressure surface. This scaling is accomplished by
multiplying the observed dust optical depth by the factor (6.1/psurf) where
"psurf" is the surface pressure in mbar. The color scale is the same for
each map. Blue and purple indicate low dust optical depth (clear
atmosphere), green indicates moderate dust optical depth, and yellow and red
indicate the high dust optical depth associated with dust storms. The
visible optical depth of dust is about twice the 9-micron optical depth
shown here, so anywhere that is yellow or red on these maps there are dust
clouds that are thick enough to obscure the surface in visible light images.
The use of spectral information in the thermal infrared for
tracking dust storms has advantages over the use of visible data:
In addition, normalizing for the depth of the atmosphere using
surface pressure provides further insights:
Spawned by modest dust activity near the retreating seasonal south
polar cap and in central Hellas, a major dust storm developed in
June. Thermal infrared observations showed that a modestly active
storm center advanced NE out of Hellas into Trinacria around 15 June
(Ls=179°). From here, explosive growth commenced on 26 June
(Ls=185°), with optically thick dust advancing 180 degrees of
longitude in five days. The storm spread south to the cap, and north
as far as Cebrenia and north of Syrtis Major by July 4 (Ls=190°). By
July 7 (Ls=191°) the storm had encircled the planet at low latitudes,
while the atmosphere remained clear in NE Arabia and much of Utopia.
Considerable dust was present as far north as S Arcadia. A region of
relatively thin dust remained in N Noachis and W Deucalionis Regio.
The storm has two unusual characteristics. First, it is the earliest
planet-encircling storm on record. Second, it has advanced much
farther north than usual for large storms. In addition, atmospheric
temperatures have risen dramatically. For example, by July 4, at 20
km altitude, they had increased more than 20K at the equator, and
more than 10K at 45°N. The changes in atmospheric thermal structure
have strongly intensified the north polar vortex above 45°N. The
overall heating of the atmosphere should strongly suppress the
formation of the north polar hood until the dust dissipates.
Michael Smith (Michael.D.Smith.1@gsfc.nasa.gov) NASA Goddard Space Flight Center Thank you for your precious information on the visual appearance of
the nearly opposite side of the planet Mars. Since you reached the
ghost of Syrtis Mj from Nebraska, I suppose the present dust
disturbance has now been watched all around the world.
Yes, the so-called contrast has often been artificially enhanced in
ccd images as you correctly point out, and so it has been highly
possible for the markings that are now ghostly present to have been
haunted much earlier by a pre-storm of thinner dust even when the
aspect was just claimed to be normal by judging only from the ccd
images. For instance, the images by Don PARKER on 9 July clearly
shows that S Meridiani is thickly covered by dust, while, as I
think, his clearer and more excellent images on 7 July also show
that S Meridiani has already been affected by a thinner spread of
airborne dust. There have been observed multifocally a lot of thick
and bright cores or their flows of dust on a disk, showing a
resonance effect among them, but the resonance might have been
impossible if there is no haunting of airborne dust in its pre-stage.
On our side, for instance Propontis I looks normal sometimes, but
another time it turns to be abnormal or vanishing (depending of
course on the seeing). It is however apparent the disk is wholly
dusty at present even if its minor shape shows up normal or not.
If we don't have any effective and handy method to measure the
optical depth throughout the disk at hand, we should watch
carefully the subtle difference of contrast and colour by the use
of a familiar instrument, as you did, when we hear something global
has happened on another surface.
Unfortunately or fortunately the present global storm started at
opposition, and so we have much time to watch the reverse course
how the ghosts will turn out to take the original or secularly
changed form meantime. Again, we should say we need to ask a timely
encounter of the Occident and the Orient.
Masatsugu MINAMI (9th CMO communication on the present dust)
Recent images from the US bring about interesting information on the
resonance of the dust cores or their flows. The
images on 5 July taken by Ed
GRAFTON show a dust core to the west of Solis L, and the ones on
6 July by Don PARKER
[Editor's Note: these images are from 7 July]
do a bright band made of several bright spots to the east of
Solis L: The latter further developed on the following days. Finally
Don PARKER showed on 9 July
that the dust over S Meridiani and Edom became thicker.
From our side, the dust remains globally spread. Propontis I has been
however rather evident these days. ISHADOH identified Olympus Mons as a dark
spot since it appeared on the evening limb side. On 9 July ISHADOH and I at
Naha (together by the use of a 25cm Newtonian) checked it at LCM=144 degrees
W and onward, and on 10 July from LCM=135 degrees W (so that it lied quite
near the CM). The spot is rather large and looked roundish in a tint of dark
brown. It is apparent the summit has not yet been affected by the dust while
the outskirts are light dusty to show the summit up. The three Tharsis
Montes are also evident as a series of dark spots. To the south of Arsia
Mons, there is a strange dark marking.
It may sound strange, but the north polar hood (nph) remains quite large and
whitish bright: It seems it recovers soon its whiteness even if it is often
affected by the dust. It is usually believed that the nph recesses when the
dust storm develops, but this time it proved not the case. The spc is now
quite obscure or quite smaller (than expected) from this side, while its
morning side is followed by a condensed/bright white cloud along the morning
terminator. This is a characteristic fact observed successively these days.
TAN W-L in Singapore produces every day excellent images and posts readily
within a few hours (cf CMO-Web). His images on
9 and
10 July show Olympus
Mons on the afternoon side. We are sure he will capture it on 11 July near
the CM, because there is only one hour difference or so between us. His blue
colour of the nph implies the whiteness of the white cloud.
We are about to observe an aftermath of Solis L and the following Daedalia
whether such a shading seen in 1973 is appearing or not.
Masatsugu MINAMI@ Naha, Okinawa on the morning of 11 July JST.
Just a quick note that JPEG versions of all of the HST 2001 Mars
opposition images obtained to date are available online at the
following web site:
http://marswatch.tn.cornell.edu/hst01.html
The June 26 images were featured in a recent press release (and all
over the media) that can be found at:
http://oposite.stsci.edu/pubinfo/PR/2001/24/index.html
and
http://heritage.stsci.edu/public/2001jul/display.html
We hope to collect a global set of 12-color images in early August.
As far as I know, this will represent all of the HST Mars imaging
that will be conducted in 2001.
Enjoy the rest of the Mars Show this summer!
-Jim
You might be interested in another TES web site located at:
http://tes.la.asu.edu
We are putting up daily globe images of dust opacity and temperature.
Philip Christensen 10th CMO Short Report on the Present 2001 Great Dust Storm
Edward GRAFTON's images on 11 July at 3:31 GMT (LCM=342 degrees W)
showed that the storm obscured the final tip of Grand Syrtis (cf
CMO-Web).
Just before the Grafton images reached, we had heard from Samuel WHITBY,
Virginia, as follows:
I was able to observe Mars with my reflector this evening for about half
an hour. The seeing was good. At 2 UT (on 10 July) the planet looked
very strange. Sinus Sabaeus and Sinus Meridiani were unrecognizable.
What seems to have been the northern part of Syrtis Major was visible,
detached from other dark albedo markings. The preceding limb of Mars was
very bright. I made a sketch which I will send to you later. I am not a
very experienced observer of Martian dust storms, but it looks like the
"easy" side of Mars is largely obscured by dust!
Sincerely, I was able to observe Mars again tonight, July 11, at 2 UT. Mars seems
heavily obscured by dust, with only a vague Syrtis Major and a dim hint
of Sinus Sabaeus visible. The seeing was not as good as last night, but
it was still fair. I think the extent and degree of obscuration were
greater tonight than last night. I made a sketch and will mail it to you
later.
Sincerely, We are otherwise not well informed from the European side how the
western procession of the storm had proved out, but we think we can thus
suppose the obscuration scale has now become globulous ever since the
first obscuration started faintly near at M Tyrrhenum on 24 June.
There have been produced a lot of RGB or LRGB images since the start of
the dust storm, while we do scarcely come across with the images that
may reproduce the realistic tint of 'yellow' intrinsic to the expanding
airborne dust cloud. Especially it was strange to us some of LRGB images
continued to produce some 'normal' surfaces regardless of the obvious
fact that the yellow dust had already proved globally covering the same
surfaces. It seemed it was claimed that it was just abnormal only when
some bright local dust bursts occurred or some dark markings were
definitely obscured or deformed in the enhanced images. Obscuration is a
matter of degree, but when we are to discuss how the storm will turn
out, we should pay much attention to the subtle obscuration due to the
expanding yellowish airborne dust, without depending much on the ability
of the infrared penetration. The LRGB image is sometimes powerful, but
as is widely known, it has not been well established yet as far as the
Martian images are concerned, and we should sometimes refrain from
saying something concerning the atmospheric matters if any depends only
on the LRGB images.
Although the heavy obscuration was completed, we think rather there are
arisen a lot of work to be done. This unexpected great event is of a
novel type, in the sense it occurred in quite a younger season, it first
rapidly expanded to the north, it invited several resonant cores while
its start was never brilliant and so on. We suppose so any old styled
comments may be boring, and no prediction by the so-called experts is
possible: In other words any observation concerning the outcome of the
storm might be significant and it is a good opportunity to watch this
rare yellow Mars when its angular diameter is still large and it stays
long in the evening sky.
At present, the areas from 90 degrees W to 150 degrees W are facing to
us in Japan. Solis L does not show up; maybe some eastern part of the
so-called Valhalla looks darkened, while M Sirenum is invisible yet.
Fortunately the summits of Tharsis Montes as well as Olympus Mons are
spotted. Arsia and Olympus Montes look brownish dark perhaps because of
the contrast effect since the outskirts are bright yellow due to the
dust sea. On 12 July, the dark spot of Olympus Mons was visible from its
morning at LCM=090 degrees W onward. Yesterday night I had a talk with
ISHADOH who assured he saw first the stain on 7 July, and this night
HIGA showed me a Video where it was taken on 6 July. At the same time we
concluded that Olympus Mons looked 'normal' until circa 4 July at least
in the evening although the dust was shown to have already reached
Arcadia at the beginning of July. The dust must have been fully/thickly
stable at the outskirts since around 5 or 6 July.
The CMO Web still keeps a page to upload the up-to-date images of the
2001 great dust storm, and it invites you to make an access to
http://www.mars.dti.ne.jp/~cmo/oaa_mars.html
Thank you in advance, Storm under storm... that's a bit the way I can describe my only
observation of the event, recently.
I don't know if you got some information from European observers, but our
longitude should have favored the observation of the obscuration of Syrtis
Major by the dust for the last 2 weeks.
Unfortunately I left France on July 1, so
my last drawing in France was
dated June 30.9 UT when Syrtis Major seemed hard to
see close to the limb, likely partly covered by dust.
Since then, I got a telescope (25cm on the week-ends and 20cm in the week)
to use after July 7, but weather did not cooperate much, either in France
or in Noordwijk, Netherlands, where I finally got in touch with Mars on
July 12.9 UT.
From there Mars culminates barely at 10 degrees above horizon (52.2 deg.
N), and I actually observed it at 8 degrees (Second drawing)...
For those who can get it 40 degrees high in the sky, I observe it through
4 times thicker atmosphere and turbulence!
Fortunately this Netherland countryside is flat like sea and seeing not so
bad as wind is more likely laminary: On July 12.9 the seeing was good for
what you would expect so low, fair to poor in absolute.
The problem was that sky cleared up (it took a bit longer to clear Mars
low at the southern horizon) thanks to the wind of a storm system, blowing
more than 60 km/h, and I had also the problem of not getting my scope
blown away! [even behind (low) buildings I couldn't find some rest from
these though windy conditions]
In any case, at CML 253, Syrtis Major should have been clearly visible (by
comparison to a drawing of June 5 --
see
http://wwwusr.obspm.fr/biver/planetnews.html#mars) but was not identified
although the NPC and Utopia seemed clearly identified (so not too much a
seeing/wind shake effect). The SPC was tentatively seen small, also, most
of disk beeing patches of low contrast albedo features, one likely related
to Mare Cimmerium?
I wish you all better observing conditions for this on-going storm [on
Mars, please not on Earth!!],
Nicolas BIVER
Subject: Dust Storm
Date: Fri, 06 Jul 2001 09:01:44 +0100
From: Donald Parker
Some news from the Mars Global Surveyor Thermal Emission Spectrometer
Subject: Latest dust storm figure
Date: Fri, 6 Jul 2001 12:12:11 -0400
From: Michael Smith
John Pearl
Greenbelt, MD
A view from the (Earth's) Western Hemisphere
Subject: A Ghostly Mars
Date: Tue, 10 Jul 2001 01:45:16 -0500 (CDT)
From: C Martin Gaskell
More from MGS-TES
Subject: Dust storm update for MarsWatch
Date: Tue, 10 Jul 2001 10:27:37 -0400
From: Michael Smith
John Pearl
Greenbelt, MD
Some more comments by ground-based telescopic observers
Subject: RE:A Ghostly Mars
Date: Wed, 11 Jul 2001 06:04:23 +0900
From: Masatsugu MINAMI
Director, the Mars Section of the Oriental Astronomical Association
Editor's Note:
In light of the questions regarding enhanced contrast to CCD images,
perhaps observers could note something like "false color" or "contrast
enhanced" on their images or in their notes. In order to make a "true"
color image one should expose Mars in Red, Green, and Blue for a time
long enough to get good signal-to-noise, but then each image should be
ratioed to its exposure time before being combined with the other
images into the three-color representation. Such images would then
present a more true contrast appearance.
Subject: The dust does not invade Olympus Mons yet
Date: Wed, 11 Jul 2001 13:31:21 +0900
From: "MINAMI, Masatsugu"
News from the HST folks
Subject: 2001 HST Mars images online
Date: Wed, 11 Jul 2001 00:55:29 -0400
From: Jim Bell, Cornell University
The continual monitoring of dust storm activity by MGS-TES
Date: Wed, 11 Jul 2001 08:47:15 -0700
From: Philip Christensen
Principal Investigator, MGS Thermal Emission Spectrometer
Subject: 10th CMO Short Communication
Date: Fri, 13 Jul 2001 07:47:34 +0900
From: Masatsugu MINAMI
To: cmo@mars.dti.ne.jp
Date: Mon, 9 Jul 2001 22:33:52 -0700
From: "Sam and Uta Whitby"
Sam
Date: Tue, 10 Jul 2001 22:46:53 -0700
From: "Sam and Uta Whitby"
Sam
With best wishes,
Masatsugu MINAMI@Okinawa
Director, the OAA Mars Section
Subject: Re: Mars Storm under stormy weather!
Date: Sat, 14 Jul 2001 17:54:34 +0200 (MET DST)
From: Nicolas Biver
Some new dust activity
Subject: Re: Mars Storm under stormy weather!
Date: Sat, 14 Jul 2001 17:54:34 +0200 (MET DST)
From: Nicolas Biver
