Suzy B Software 2/Suzy B Software CD-ROM 2 (1994).iso/nasa/mars_c/mc6.txt

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 .................................................................
 .        = T H E   M A R T I A N   C H R O N I C L E =          .
 .                                                               .
 .  The electronic newsletter by the International Mars Patrol,  .
 .                  an observing program of the                  .
 .          Association of Lunar and Planetary Observers         .
 .                     Edited by: J.D. Beish                     .
 . June 1991                                              No. 6  .
 .................................................................
                  1990-1991 OBSERVATIONAL SUMMARY

    Although participation fell short of  the  7,063  observations
 turned in during 1988, the Association  of  Lunar  and  Planetary
 Observer's International Mars  Patrol  program  successfully con-
 vinced seventy-five Mars observers to watch  the  Red  Planet  in
 1990 and 1991.  Using 95 telescopes, these dedicates  astronomers
 contributed 1,669 visual, multi-colored photographic observations
 of Mars, polar cap measurements, and 44 video tapes of CCD images
 during the 1990-91 apparition of Mars.
    During this period, the planet's south pole was tilted  toward
 Earth, allowing detailed observations of the highly cratered  and
 topographically interesting southern hemisphere of the Red Planet
 Mars.
    A Mars apparition is a period that useful observations the Red
 Planet can be obtained and  usually  covers  one  or  more  Earth
 years.  Mars has an average 15.8-year seasonal opposition  cycle,
 which consists of three or four  aphelic  oppositions  and  three
 consecutive perihelic oppositions.   The 1990-91 apparition   was
 considered transitional because opposition occurred almost exact-
 ly 90 degrees of perihelion.  Mars reached opposition on November
 27, 1990 and was closest to Earth on November  20,  1990  with  a
 distance of 48,050,617 miles (77,330,127 km) and an apparent disk
 diameter of 18.10 arcsecs.
    Gerard Teichert of Hattstatt, France was the first and last to
 send observations of Mars during the last apparition.  Apparition
 observational coverage was adequate, with 54% of the Martian year
 being observed.
    The study of dust storms has been one of the priorities of the
 IMP. The dust program has two goals:  1)  to  alert  professional
 astronomers as soon as dust clouds are detected, and 2)  to moni-
 tor the progression and boundaries of the dust clouds. The system
 worked well for the two dust storms of 1988, but it was the  1990
 apparition that provided the opportunity to demonstrate the  true
 international character of the IMP.

                    MARTIAN DUST STORMS OF 1990

    One of the most exciting events for the Mars  observer  is  to
 catch a dust storm on the move.  It is rare indeed  when  one  is
 abler to watch great dust clouds slowly  move  over  the  Martian
 landscape,  covering  features  previously  were  dark  and  well
 defined, just hours before.
    While no two dust clouds appear  the  same  they  nevertheless
 exhibit similar  characteristics.   Dust  clouds  are  frequently
 confused with bright white areas, frosts, or localized fogs,  and
 some dense white clouds.  In addition,  after  identification  is
 made, it becomes difficult to distinguish active dust clouds from
 fresh surface dust deposits.

                  TRANSIENT DUST CLOUDS OF OCTOBER

    During the first week of October 1990  the  phone  at   ALPO's
 International Mars Patrol (IMP) headquarters began to ring.  News
 of bright spots on Mars,  "maybe  a  dust  cloud  or  something,"
 scoffed the cautious observers.  Their words were restrained  and
 with good reason -- past experience has led them to  a  more con-
 servative approach and not to  jump  to  conclusions,  especially
 about this Martian dust storm business.  After all, these  storms
 are very rare and often mislead the most experienced Martian dust
 storm watchers!
    The genesis of the these dust disturbances  may  be  a  sudden
 increase in meteorology in one of the  dust  sensitive  areas  on
 Mars.  Reporting from Paragould, Arkansas, Kermit Rhea noted,  on
 September 25, 1990,  that Chyrse (where  Viking  1  Lander  sits)
 appeared brighter than usual over an extended period of time. His
 observations indicated unusual meteorological activity in several
 regiopns on Mars.
    On 03 October, Dan Troiani observed Chryse as very  bright  in
 red light, indicating possible dust activity.  The next  day,  04
 October, calling from New York, Frank  Melillo  reported  to  the
 ALPO Mars Recorders a dust cloud in Chryse.  On October 4th,  the
 Recorders observed a bright streak  bordering  northern  Aromatum
 Promontorium, in the south of Chryse, and suspected it  might  be
 the beginning of a  dust  storm.   The  following  night  the  we
 watched with delight as the dust  cloud had  moved  southwest  of
 Chryse.  The morning side of Mars had lost its  usual  effect  of
 limb darkening and was replaced by a bright pole  to  pole  haze.
 Subsequent visual reports and photographs show that a dust  cloud
 extended 575 miles further southwest.
    The next day, 07 October, the main dust cloud had  moved  west
 southwest another 475 miles to a longitude of 50W and latitude of
 20S.  A peculiar Y-shaped dust cloud hung over Aurorae Sinus that
 extended into Ophir, (regions near the great canyon  Vallws Mari-
 neris).
    At last, the next day the small Martian dust storm appeared to
 be over. With perfect "seeing" on October 8th the Mars  Recorders
 saw a familiar Martian landscape.  Only a few alterations to  the
 usually dark and well defined "maria" were obvious.  The  morning
 limb was bright with blue and  reddish hazes.

                 TRANSIENT DUST CLOUDS OF NOVEMBER

    Observational  reports  of  unusual  atmospheric  activity  in
 Chryse on 31 October. CCD images by T. Platt of  England  reveals
 what must be a dust cloud over Chryse-Candor.
    Dust clouds were  definitely  identified  on  04  November  by
 ALPO's Frank Melillo. Don Parker's photographs from 04 through 09
 November show several small bright and well defined  dust  clouds
 crossing from Chryse over Aurorae Sinus onto Solis Lacus (The Eye
 of Mars!)  By  04 November 1990 observers reports agreed remarka-
 bly as to the size and distribution of three dust clouds  located
 over the Solis Lacus region.
    Analyzing the IMP drawings and photographs from 5 and 6  Novem
 ber suggested that there was more than one dust  storm occurring-
 on Mars. The multiple character of the storm was  verified  by  a
 CCD photo taken at the Pic-du-Midi Observatory on 5 November (see
 top right photo on cover of S&T, June 1991).   With  the  Martian
 central meridian at approximately 30 dg, this image  shows numer-
 ous foci of dust obscuring: 1) western Nilokeras and Lunae L., 2)
 Agathadaemon, Melas L., and southern Aurorae  S.,  3)  the  north
 eastern border of Solis L., and 4) southeastern Thaumasia Foelix,
 approximately 80W, 40S.  In addition, Chryse and Xanthe were much
 lighter than normal, suggesting diffuse dust in these regions.
    By 6 November the character of the dust storm complex began to
 repidly change. Detailed drawings by Rogers, Jacobson, and  Boyar
 and high resolution photographs by  Parker  and  Beish,  who  was
 employing the University of Hawaii's 24-inch Cassegrain on  Mauna
 Kea, showed three brilliant spots in the vicinity of Solis Lacus.
 All were very bright in red light. The first lay  over  northwest
 Solis Lacus, at 90W, 22S, obscuring  approximately  30%  of  this
 feature.
    European observations of regions to the east  of  Solis  Lacus
 revealed a return of visibility  of  Aurorae  Sinus  and  Ganges,
 although some dust remained in Eos, with bright fingers of  cloud
 extending northeastward into Chryse. Some dust was also  reported
 crossing Bosporus into Argyre I. Nearly all  observers  commented
 on the dullness and irregular  shape  of  the  North  Polar  Hood
 (NPH).
    By 11 November members of the OAA had taken up  the  study  of
 this southern dust cloud. It appeared as a  whitish  mist  across
 Bosporos. Superb drawings and photographs by Minami and  Miyazaki
 place its western boundary near 120W on 11 November. By 13 Novem-
 ber this boundary was still 115 dg., but the  cloud  had  thinned
 considerably. Bosporos became faintly visible on 14 November, and
 the western boundary of  the  Thaumasia  Foelix  dust  cloud  was
 estimated at 65-70 dg.W. By 15 November Bosporus was  again  well
 defined, and Mars appeared free of obscurations.  Both  U.S.  and
 Japanese observers failed to find evidence of residual dust.  The
 Martian atmosphere had cleared very rapidly indeed.

                           POLAR REGIONS

    During both the October and the November storms,  most  observ
 ers reported that the North Polar Hood  (NPH)  underwent signifi-
 cant changes, becoming dull and broken. Photographs and  drawings
 from both periods show albedo features visible beneath the  hood,
 suggesting a thinning of the  canopy  at  those  times.  The  NPH
 appeared to diminish in size and intensity between 5 and  7 Octo-
 ber. On 8 October the Martian north polar region was  again  bril
 liant, but in reviewing the observations, there is some  question
 about whether it was the hood that was seen or perhaps the  North
 Polar Cap shining  through  a  thinned  hood.  Unfortunately  not
 enough color filter work was done on the polar regions to  answer
 this question.
    The behavior of the NPH followed much the same pattern  during
 the November dust outbreaks. It became dull on 5 November and  by
 7 November albedo features in Mare Boreum could be  seen  through
 it, giving the hood a broken appearance. By 9 November  the  hood
 appeared somewhat brighter in red and integrated  light  than  in
 violet, suggesting the appearance  of  the  cap.  Over  the  next
 several days this condition persisted, but  by  18  November  the
 North Polar Hood had returned to normal.
    The South Polar Cap (SPC)  was  visible  throughout  both  the
 October and November dust storms. Although antarctic  hazes  were
 frequently sighted  during  these  periods,  observers  employing
 large apertures and color  filters  were  able  to  see  the  SPC
 through early December.

                THE 1990 - 1991 METEOROLOGY OF MARS

    Classified by the color, bright Martian atmospheric clouds and
 hazes are  best observed using a blue or violet  filter  and fre-
 quently cross-checked with those made in red light for atmospher-
 ic penetration.  Without the aid of color filters, condensates in
 the atmosphere of Mars is difficult, if  not  impossible,  to de-
 tect.
    Clouds and hazes were rare during the first ten months of  the
 apparition.  It is not unusual for Mars' atmosphere to  be  clear
 during its southern spring and summer. Cloud  activity  increases
 during Martian southern autumn.  (NOTE:  Mars  has  four  seasons
 similar to Earth, we see both hemispheres and  becomes  confusing
 if the hemisphere is  not  labeled).    The  atmosphere  of  Mars
 became dusty after two  transient  dust  storms  appeared  during
 October and November 1990 (discussed above).  As  result,  an in-
 crease in meteorology became apparent from late November onward.
      Martian  meteorological  activity  remained  minimal   until
 September 1990. Observers employing blue and violet filters  were
 able to detect a few interesting  clouds  and  hazes  in  Chryse,
 Candor, and Tharsis.
    Intermittent morning limb  hazes  recorded  by  IMP  observers
 during April, May, and June 1990.  By the  end  of  July  morning
 limb hazes began to be reported with increasing frequency. Photo-
 graphs by Isao Miyazaki, Parker, and others, and  visual  reports
 during August and September show morning limb hazes had developed
 from the south polar region to the north polar  region.   Morning
 limb hazes fell off during late Martian southern summer.
    As a result of the dust storm in October,  morning  limb  haze
 increased in extent  and  brightness  beginning  on  05  October.
 Again, the morning limb haze became bright and  prominent  on  04
 November.  Evening limb haze  only  reported  only  a  few  times
 during mid-November  1990.  By  late  summer  and  early  spring,
 evening limb became increasing hazy.
      Martian clouds were also reported after  the  November  dust
 storm.  Recurrent topographic clouds are dense whitish clouds  of
 limited extent. They occur seasonally and regionally and  persist
 for days,  showing  growth  and  displacement  within  a  region.
 Topographic clouds tend to appear in or near large, deep craters,
 and great plains and valleys.  Four areas on  Mars,  Aram,  Edom,
 Libya, and Ophir,  form white  clouds  during  most  apparitions.
 Inspection of this area with blue-green (W64),  blue  (W38A),  or
 vilot (W47) filters  will aid in their detection.
    One topographic cloud  that  appears  in  Libya  nearly  every
 apparition was reported cloudy from 08 October through 14 October
 1990  and again from 16 November though 07 December 1990.
    White areas are bright surface or near surfase  frosts  and/or
 fogs that are seen in all colors.  Bright  white  areas  were  re
 ported in Edom (345 W, 4 S) frequently from  mid-October  through
 November 1990.