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MarsWatch

1998-1999 Apparition

Linking Amateur and Professional Mars Observing Communities.

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The International MarsWatch Electronic Newsletter


Volume 4; Issue 4
February 24, 1999
Circulation: 1492

Mars Symbol Mars Symbol


Dear Marswatch participant,

Happy opposition!

Four items in this latest (long) installment of the newsletter:

  1. HST Mars observations: April 27 through May 7

  2. Update on the Mars Global Surveyor Antenna Glitch

  3. Latest B.A.A. Mars observing update

  4. Latest A.L.P.O. Mars electronic newsletter

Also, remember that the 1998-1999 Marswatch Web Site is on line! Hundreds and hundreds of spectacular Mars images and drawings have been uploaded from observers all around the world, and they keep pouring in daily! To get to the site, point (and bookmark!) your browser to:
http://www.astroleague.org/marswatch/.

David Knighton of the Astronomical League is working hard to keep your posted images, ftp upload/download site, and other information updated.

--Jim Bell
Cornell University

Mars Symbol Mars Symbol


HST Mars observations: April 27 through May 7

All of the planned Hubble Space Telescope (HST) observations of Mars for this opposition have now been scheduled. HST will observe Mars at four central meridian longitudes (for full global coverage) between April 27 and May 7 (hopefully the recent failure of one of the HST gyros will not hinder this!). The exact times when HST will be observing Mars are indicated in the table below (times are given in Greenwich Mean Time or Universal Time, which is currently four hours ahead of U.S. Eastern Daylight Time). I am organizing these observations, and I am *especially* interested in obtaining supporting groundbased CCD images from amateurs and professionals during the times when the STIS instrument (Space Telescope Imaging Spectrograph) will be observing Mars. For the times when STIS is observing, we need high quality CCD images especially in the blue, so that we can determine where clouds, hazes, and fogs are most likely interfering with our spectroscopic measurements. If you are able to observe Mars in the blue at these times, we would greatly appreciate receiving copies of your images and their descriptions! We will be posting the HST images onto a Web site as soon as we get them processed.

1999 HST Mars Opposition Observations
Visit Instrument Start Time (GMT) End Time (GMT)
1 WFPC2 Apr 27 1999 17:55:38 Apr 27 1999 18:51:12
2 STIS Apr 27 1999 19:32:20 Apr 27 1999 23:23:27
4 WFPC2 Apr 28 1999 00:22:25 Apr 28 1999 01:17:59
7 WFPC2 May 1 1999 13:47:34 May 1 1999 14:43:08
8 STIS May 1 1999 15:24:53 May 1 1999 19:14:14
5 WFPC2 May 6 1999 11:28:10 May 6 1999 12:22:14
6 STIS May 6 1999 13:04:18 May 6 1999 16:51:20
3 STIS May 7 1999 06:52:54 May 7 1999 10:55:14

Mars Symbol Mars Symbol


Update on the Mars Global Surveyor Antenna Glitch

On April 15 the Mars Global Surveyor spacecraft experienced an "anomaly" (a glitch) with its main high-gain antenna. Apparently one of the hinges on the high gain antenna got stuck, meaning that the antenna can only swing in one direction instead of in two directions. JPL engineers are troubleshooting the problem, and mapping has been put on hold. The plan is to continue mapping next week because high speed communications with Earth can still work for now even if the antenna can only move along one axis. Check out the April 23 and earlier updates for many more details:

http://mars.jpl.nasa.gov/mgs/mgs-readme.html

Also, check out some of the spectacular early mapping data at:

http://www.msss.com/mars/global_surveyor/camera/images/index.html

Mars Symbol Mars Symbol


British Astronomical Association Mars Section Circular 1998-99, No. 5

By: Richard McKim, Director, B.A.A. Mars Section

(Here is the most recent compilation of telescopic observations to date, from Richard McKim of the British Astronomical Association. This and earlier reports can also be found on the B.A.A. Mars reports page, at http://marswatch.tn.cornell.edu/baa.html.)

General

This Circular summarises the period 1999 March 1- April 15. On Mar 1, Ls = 104 deg., D = 10 arcsec., lat. of centre of disk = 15 deg. N, with the planet's declination at 13 deg. south. The planet will reach opposition on April 24 (Ls = 129 deg., D = 16 arcsec., lat. of centre of disk = 18 deg. N, decl. -12 deg.). The planet was becoming uncomfortably low for UK observers, but as can be seen, its declination will now be very slightly less southerly.

The UK weather has been less than cooperative during opposition month, but nevertheless there have been a fair number of observers, including the usual contributions from overseas that are essential to maintain good longitudinal coverage. During the present apparition I have had observational data from the following individuals, and acknowledge it herewith if not already done so by letter or by email: Leo Aerts, Sally Beaumont, Nicolas Biver, Ed Crandall, P.Devadas, Mario Frassati, Martin Gaskell, David Gray, Peter Grego, Walter Haas, Alan Heath, Carlos Hernandez, Frank Melillo, Cliff Meredith, Masatsugu Minami /OAA, Patrick Moore, Don Parker, Damian Peach, Tom Richards, Richard Schmude, David Strange, Paolo Tanga, Gerard Teichert, Rowland Topping, Dan Troiani/ALPO, Johan Warell, Sam Whitby and Jonathan Wojack.

More than one observer has supplied unreadable CCD image files: I do not always have the software to decode compressed files, and it would sometimes save time to mail a disc. I would also kindly point out to observers that I do not always have time to look for images on their personal Websites, much as I would like to; if you want your images discussed in these reports, kindly send them along in a readable format!

I am sorry that Dr Ebisawa's health has not been very good, so that he has not been able to make his usual meticulous visual and polarimetric observations so far. Is anyone doing polarimetric work this apparition?

Observations.

On Mars throughout March and April the N. polar cap remained small. A number of visual and CCD observations show haze around its S. perimeter. Despite this haze the outlying bright area of Olympia has been visible. Tanga saw it from Turin Observatory in fine seeing on April 18. White cloud activity remains quite high, but the Equatorial Cloud Band phenomenon (ECB) seemed much less conspicuous in April. The typical sites for white clouds have been active throughout the whole period, and a few observations will suffice to illustrate these locations and to describe some other features:

McKim, April 13, 22-cm refl., 2318h UT, CML = 218 deg. Elysium on mid-disk whitish. Bright am cloud over Libya-Isidis (and Syrtis Major). Hellas a brighter spot within the light S. limb area. Cebrenia lightish on the CM, some haze S. of NPC, but cap edge sharp. Some pm cloud over Amazonis, but Nix Olympica would have rotated off the disk at an earlier hour. The Aetheria secular darkening remains extensive and dark, and extends somewhat to the SW as in the last few apparitions. Propontis (I) is dark, and the Phlegra/Styx-Trivium Charontis-Cerberus complex, though not dark, was easy to see.

Meredith, April 14, 22-cm refl., 2355h UT, CML = 218 deg. CCD image much like McKim's visual drawing above. (Cliff's first really successful CCD work, well done to him.)

Parker, March 7, 0.4-m refl., ca. 0735h UT, CM = 321 deg. Evening cloud dims Syrtis Major, extending across it from Libya to Aeria! The evening Hellas is bright. Morning cloud occupies Chryse and partly hides SW Mare Acidalium. Haze south of the NPC.

Parker, March 12, ca. 0803h UT, CML = 282 deg. Hellas is very bright in white light. As Minami points out in the OAA's CMO, the brightness sometimes extends outside the contours of the basin: Gray found a similar phenomenon with Argyre in January.) Hellas was large and bright in green (VG9 filter) and blue (BG12), but was smaller and paler in red (RG610).

Parker April 3. This CCD image series even shows a little structure inside the Solis Lacus (which remains large and dark since the mid-'80s). The feature Gallinaria Silva, a small dark spot that was seen to the W. of the Solis Lacus in the apparitions immediately before the present one, seems to have nearly disappeared. This is therefore perhaps a small change since 1997. There is really fine structure in the Tithonius Lacus between Melas Lacus and Noctis Lacus! Aurorae Sinus appears detailed, with little northward projections including Baetis/ Juventae Fons, etc. Mare Acidalium and Niliacus Lacus are shown in fine detail. Hyperboreus Lacus is a dark spot adjacent to the small NPC.

Teichert, April 10, 28-cm SCT, 0056h UT, CML = 277 deg. Hellas bright on the CM. Nepenthes is invisible. Moeris Lacus forms a small protrusion on the E. side of Syrtis Major.

I do not intend a more complete analysis here. UK members may wish to know that I will be showing some illustrations of the Section's work in my presentation at the BAA Northampton Meeting on Saturday April 24.

Pic du Midi Website This is an excellent site (http://www.bdl.fr/s2p/mars.html), and contains some medium to high resolution images of Mars (1988-1999).

LPL Mars Water Group.

Ann Sprague emailed with more details of her LPL Mars Water Group's work at Catalina: see Rik Hill's communication from the same group in the last Circular. Anne writes that they have been measuring water vapour in the martian atmosphere every two weeks since 1998 September. "We are measuring CO2 molecular absorption with the hopes of using radiative transfer to measure atmospheric dust... the depth of the water vapor absorption line in Mars' Northern latitudes is much deeper than we have seen it in previous Northern summers."

February Dust Storm Follow-up.

Last time's Circular detailed a Regional storm over the Mariner Valley, whose observation was mostly due to David Gray. Todd Clancy emailed on March 10 to report that this event (which had first been detected on February 21) had had no apparent effect upon the atmospheric temperature (as deduced from radio waveband work), but, interestingly: "the overall trend in temperatures over the past two months is 5-10 K warmer than at this time in the previous Mars year." For those wishing to see David Gray's two sketches of the event, they may now do so thanks to Don Parker who scanned them and uploaded them to the Marwatch Website. Steve Lee emailed descriptions of the HST images of March 3 (CML 256, 280 deg.): these revealed ECB, but the CML was too high for them to show the Valles Marineris area.

Note that the results of Ann Sprague's spectroscopy and Todd Clancy's work seem to fit nicely together! It will be interesting to see if this relates to the regression rate for the NPC.

Yet More Dust Over Valles Marineris!

A further event occurred during the Director's absence on holiday abroad. Upon his return home on April 11, awaiting him was an email and observation by Carlos Hernandez, dated March 31 (22cm refl., CML = 53 deg.), which revealed an already mature dust storm in progress, in the form of a bright streak running E-W along (the S. edge of?) Valles Marineris. At first sight I thought it might just have been residual dust (see my comments upon Don Parker's March 3 CCD image in the last Circular), but Carlos had not noticed it earlier, and, moreover, it was too prominent, too well defined, and was bright through a W23A red filter. In his email Carlos mentioned that a CCD image by Antonio Cidadao taken 1h earlier had also shown the bright streak. Carlos observed again a few days later on April 2, finding that the area had returned essentially to normal. So when did it begin? Several days later, David Strange emailed a good CCD image taken on March 27 at 0100h UT under CML = 43 deg. This showed a bright area in Ophir which interrupted the Agathodaemon (also known as Coprates, part of W. Valles Marineris: a classical 'canal' which runs between Aurorae Sinus (Planum) and Tithonius Lacus (Chasma)). This was most probably the initial cloud of the storm, and the event subsequently spread eastward along the canyon. Don Parker's CCD images of April 1 show the area, but in very bad seeing; his work on April 2, 3 and 6 is high resolution, but apart from a possible faded appearance of Aurorae Sinus, the area seemed normal. Warell observed from Uppsala University Observatory, Sweden, with a 16-cm OG: on March 29, 30 and April 1 (CML = 23-34 deg.) he found a large am cloud over Tharsis and Thaumasia, etc., to appear distinctly yellowish. Johan's seeing conditions were not good enough for him to see the dust actvity in the Valles Marineris, but the yellow tint could represent dust diffused from the minor storm then underway. Ditto April 5, under CML = 322 deg., when a yellow tint was evident in the Chryse-Xanthe am cloud. In any case, a short-lived event.

Does anyone else have pertinent observations? If so, kindly let the Director know! Looking at the Pic du Midi website will reveal a March 24 image which does not show the storm, so we appear to have pinned it down quite well. The location of the 1984 June Regional storm fell in a similar location; in that case, dust also spread to the east over the same area, as well as dispersing generally over Mare Erythraeum. This storm was fully described in the writer's published 1984 BAA apparition report.

The Director looked up the work of the group that are analysing solar radio occultation data from MGS to determine atmospheric temperatures. There is a section on the MGS homepage. Joe Twicken of that group kindly (and rapidly) responded to a query from the Director with the following email. " We have not processed the raw data that we do have for the dates that you mention. We do have a lot of data from the February period, but very little from the March period. MGS did not begin normal mapping operations until this month. Precise reconstructions of the spacecraft orbit are required to process our raw data, and the orbit reconstructions from JPL for the February and March periods were not sufficiently accurate for us to retrieve meaningful atmospheric profiles. Other members of our Team are in the process of reconstructing the orbits, and we will process the data when we can. I will let you know if we see anything interesting. You should be aware that the spacecraft occultations during the periods you mention occurred at very high northern and southern latitudes, so we will not have any atmospheric data from the vicinity of Valles Marineris." Thus it seems that the only record of the March storm is again that of the groundbased observers. Keep up the good work, everybody! But for your observations, these two small but important events would have been completely missed!

Mars as seen through the eyes of the Global Surveyor:  MGS has begun to image the planet from orbit again, after achieving final orbit about March 1. In the current (May) Sky & Telescope Jonathan McDowell's Mission Update column mentions a dramatic incident at Mission Control which nearly interfered with the attainment of the final orbit...

Since the release of the Aerobraking Image Set, the MGS website has been posting full-disk and closeup images from March and April. These show how successfully the craft is behaving, and whet the appetite for more! Polar dune fields, craters, clouds, Valles Marineris (including a fine shot of E. Tithonium Chasma, image MOC2-109)... But telescopic observers will be most interested in two full-disk 'images', reconstructed from a sequence of nine strip-maps obtained on successive orbits. These were obtained in March during the calibration phase of the mission. The Director has emailed for a more precise date in case the images can support the discussion of the latest Valles Marineris dust storm. The colours will not be perfect as the Martian Orbiter Camera (MOC) makes red and blue images, and averages them to make a 'green' image to combine with the others to make a colour composite. Another consequence of this process would seem to result in rather low albedo contrast compared with that telescopic observers can enjoy. (No matter, just try Adobe Photoshop or similar program on your PC, and you can make them look more like telescopic images - and put south at the top at the same time!!)

MOC2-117 shows Syrtis Major central, partly covered by the bluish-white 'Syrtis Cloud'. Iapigia shows the location of the large Huygens crater. Hellas is bright and looks mostly (but not entirely) frost-covered. The NPC shows fine rifts and the broad dark Chasma Boreale (Iaxartes). The fine albedo details around Utopia-Boreosyrtis-Propontis look to be very similar (if not identical) to 1997, as 1997 looked identical to 1995 in the HST images.

MOC2-118 is an image of the Tharsis and Thaumasia regions. The morning clouds cover Olympus Mons, Alba Patera, Ascraeus Mons, but affect Pavonis and Arsia Mons less.

The Mars Dust Storm Memoir.

At last I can report that everything is finished and checked, and that I will be taking the text and figures to the printer, University Printing Services, Cambridge (the printers of the BAA Journal), in the next couple of days. It is to be hoped that it can be published in the next few months. The printed text will occupy about 168 pages, equivalent to THREE 56-PAGE ISSUES of the Journal!

Reporting Data to the Section.

I am always happy to receive CCD images by email. Any URGENT and important drawing can be scanned and sent as an image file, but I do not want to receive routine drawings by email, because the vast majority are sent to me as hard copies, and that is the form I like to compare (and archive) them in. I have to write that I am spending an enormous amount of time downloading files sent to me over the Internet, then decoding, analysing and refiling them in the Section's records! Send mail to Cherry Tree Cottage, 16 Upper Main Street, Upper Benefield, Peterborough PE8 5AN, Great Britain; home telephone 01832-205387; home email Rmckim5374@aol.com. (Do not use the former email address for my place of work (mckim@oundle.northants.sch.uk).) Urgent faxes can be sent to my place of work on 01832-274052.

The Next Circular.

Please report observations April 16 to May 31 by June 7, so that the next Circular can be published in the second or third week of June.

Good observing!

Richard McKim, Director, 1999 April 23 (Opposition Day minus one!)

Mars Symbol Mars Symbol


The Martian Chronicle: Newsletter of the International Mars Patrol
An Observing Program of the Association of Lunar and Planetary Observers
April, 1999

Daniel M. Troiani
ALPO Mars Section Coordinator
E-Mail: dtroiani@triton.cc.il.us or dantroiani@Earthlink.net
ALPO Home Page: http://www.lpl.arizona/~rhill/alpo

Happy Martian Opposition!!!!!!

     By: Jeff Beish A.L.P.O. Mars Section

Although rarely seen, immense global dust storms are firmly entrenched in Martian lore. The late Leonard J. Martin (Planetary Research Center, Lowell Observatory, Flagstaff, Arizona) wrote that there have been only five well-documented "planet-encircling" Martian storms. These storms occurred in 1956, 1971, 1973, and two storms in 1977 (these were discovered by Viking Spacecraft).

Smaller dust storms or dust clouds are observed on Mars more frequently. Dust clouds are very difficult to identify in their beginning stages and, in some cases, go undetected even after they have fully developed. They might appear during any season; however, very few dust clouds are reported during the Martian northern hemisphere late-winter and spring. Although these reports are rare we do receive several observations each apparition of small transient dust clouds roaming around Chryse and into Eos and Aurorae Sinus.

Recently observers have reported bright cloud features in the regions of Chryse and several observers have identified these as dust clouds. It is gratifying to see our observers using the A.L.P.O. International Mars Patrol (I.M.P.) revised standards for identifying Martian dust clouds. It may be beneficial to repeat the method for identifying Martian dust clouds as a gentle reminder to observers.

Chryse is a bright equatorial region just south Niliacus Lacus and Achillis Pons, part of the Mare Acidalium region. During the northern hemisphere late spring and summer seasons Chryse can be seen as bright in blue and green light, at times fairly bright in red light. We may assume that the red component is dust. Occasionally bright spots are seen near the southern edge of Chryse near Aurorae Sinus and Eos. These clouds will appear bright in red light and will move south east, or towards the morning limb. They are most likely dust clouds. Dust clouds may form a long wave or stream of dust that will pass over Solis Lacus and then move towards the evening limb into Argyre I.

For a good description and how to report these small dust clouds see the article, "A Martian Dust-Storm Watch," Sky and Telescope Magazine, Volume 85, Number 1, January 1993.

Identifying a Martian Dust Storm.

Numerous reports of yellowish hazes have appeared in the literature and in the I.M.P. archives. Mars observers frequently report "albedo features" lacking in contrast, the planet is "washed out," or Mars' atmosphere is "dusty." These terms have been employed in the past by the A.L.P.O. Mars Recorders (Coordinators). While such descriptions may have merit, generalized yellow hazes and temporary losses in surface contrast is usually omitted in our reports. Photographic evidence for these phenomena is also weak, since the proper sensitometric calibration is usually lacking.

In the past observers referred to dust storms as "yellow clouds" and "yellow dust storms." We felt that this description was misleading and began to change our observing techniques and reporting methods for Martian dust clouds. First, it is virtually impossible to see or even photograph accurate colors on Mars without employing very specialized techniques. Traditionally, observers have employed yellow filters to better reveal dust clouds. The problem is that nearly every light feature on Mars appears bright through a yellow filter!

In November, 1989, we were fortunate to have Leonard Martin spend several with the A.L.P.O. Mars Section reviewing I.M.P. dust storm data. Under his guidance we have revised our definition of dust clouds/storms. He pointed out that dust clouds usually appear bright in red light since the major past of the planet's surface is composed of reddish volcanic dust particles. Dust clouds can be bright in all spectral regions, including violet, but if they are not bright in red, they are most likely not dust. Also, spacecraft observations indicate that these dust clouds are caused by high winds and usually can be seen to obscure previously well-defined albedo features as they move across the Martian surface.

Martian dust clouds form rapidly when finely divided surface materials are raised by the Martian wind. These clouds may be small, localized, and short lived, or they may expand to cover most or all of the planet in a matter of days. Dust clouds brighten faintly in yellow filters and reveal sharpened boundaries through orange and red filters. During the initial stages of formation, they often appear very bright in violet and ultraviolet light (photo graphic), suggesting the presence of ice crystals. Thus dust clouds are frequently confused with bright white areas, frosts, or high localized clouds on Mars. Because these dust clouds are often confused with bright surface deposits it becomes more difficult to determine the extent of the dust cloud expansion once the observer identifies it as dust on the move. Fresh surface deposits of dust tend to brighten the area where its has fallen and appears to blend with the dust cloud on the move.

While working with Leonard Martin and Richard W. Zurek (JPL) on problems of correctly identifying and classifying Martian dust clouds or storms, new guidelines have been established by the A.L.P.O. Mars Recorders (Coordinators) for interpreting Martian dust clouds and dust storms, they are classified as:

I. Type of Observation.

  1. White cloud or bright area mistaken for dust cloud.
  2. Visual observation(s) of dust clouds in a dust storm.
  3. Instrumental observation(s) of dust cloud/storm (Includes photographic, polarimetric, spacecraft data, or other data obtained by instrumental means).

II. Martian dust clouds.

  1. Obscuration (obstruction) -- Not sure if surface or atmospheric.
  2. Dust Haze -- Partial obscuration with displacement.
  3. Bright dust cloud -- Bright obscuration with displacements.
  4. Limb projection/terminator protrusion by dust cloud.

III. Martian dust storms.

  1. Local -- Dust storm with major axis not to exceed 2000 km (1,243 miles or less than 34 degrees).
  2. Regional -- Dust storm with major axis that exceeds 2000 km (1,243 miles or less than 34 degrees) but not encircling either or both hemispheres.
  3. Planet Encircling -- Dust storm with major axis that completely encircles either one or both hemispheres of Mars.


Summary.

If we consider the color of Mars is predominately RED, with a mix of features displaying dark gray-orange and brown hues, it becomes interesting when attempting to describe Martian dust clouds as "yellow."

So, we may wish to define Martian dust clouds by their color, movement, and in some cases, the two dimensional aspect of the clouds. As a general rule, a Martian dust cloud will qualify if they 1) are bright in red light, 2) show movement with obscuration of previously well-defined albedo features, and 3) may cast a shadow.

Chryse has been show to be an area where small dust clouds form and then to move southward into dark areas of Mars. These reports are important in the understanding our reddish neighbor, Mars.

Mars Symbol Mars Symbol



Jim Bell will continue to maintain the email distribution list as well as the various Cornell and JPL Marswatch-related WWW archives. If you are receiving duplicate copies of the International MarsWatch Electronic Newsletter, or you want your name added to or removed from the distribution list, please send him an email at jimbo@marswatch.tn.cornell.edu.

Jim Bell
Cornell University
Department of Astronomy
Center for Radiophysics and Space Research
424 Space Sciences Building
Ithaca, NY 14853-6801
Phone: 607-255-5911; fax: 607-255-9002
Email: jimbo@marswatch.tn.cornell.edu
WWW: http://marswatch.tn.cornell.edu


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This page is maintained by David Knighton for the International MarsWatch. The 1998-1999 MarsWatch site it hosted by the Astronomical League as a service to the astronomical community. Comments, corrections, and suggestions can be addressed to webmaster@astroleague.org. This page last updated June 1, 1999.