319 lines
17 KiB
Plaintext
319 lines
17 KiB
Plaintext
******************************************************************************
|
||
T h e M a r t i a n C h r o n i c l e
|
||
April 1990 No. 2
|
||
******************************************************************************
|
||
The electronic newsletter by the International Mars Patrol (I.M.P.),
|
||
an observing program of the Association of Lunar and Planetary Observers
|
||
(A.L.P.O.)
|
||
Edited by: J.D. Beish
|
||
------------------------------------------------------------------------------
|
||
INTRODUCTION
|
||
|
||
The International Mars Patrol (IMP) is a cooperative program by planetary
|
||
observers located around the Earth, that makes possible a 24-hour surveillance
|
||
of all Martian longitudes. The IMP was organized during the early 1960's by
|
||
the late Charles F. Capen and cataloged nearly 20,000 visual observations,
|
||
more than 3,000 black & white and color photographs, and thousands of Martian
|
||
surface measurements contributed by amateur and professional planetary astro-
|
||
nomers.
|
||
|
||
The Association of Lunar and Planetary Observers (A.L.P.O.) is an international
|
||
group of students of the Sun, the Moon, the major planets, minor planets, me-
|
||
teors, and comets. Our goals are to stimulate, coordinate, and generally pro-
|
||
mote the study of these bodies using methods and instruments that are available
|
||
to amateur astronomers. Observations carried out by professionals or with pro-
|
||
fessional equipment are also welcome. We provide a service for the advanced
|
||
amateur specializing in particular investigations, for the novice who wishes to
|
||
develop techniques and general knowledge, and for the professional scientist
|
||
interested in group studies and systematic patrols of our Solar System neigh-
|
||
bors. All interested persons are welcome as members. Our activities are on a
|
||
volunteer basis and each member can do as much or as little as she or he wish-
|
||
es. Of course, the A.L.P.O. gains in stature in proportion to how much and
|
||
also how well each member contributes.
|
||
|
||
The Mars Section Recorders coordinate and instruct the cooperating observers
|
||
in using similar visual, photographic, photometric,and micrometric techniques
|
||
employing color filters and standard methods for reporting their observations
|
||
which results in homogeneous sets of observing data that have good analytic
|
||
value. Each apparition the Mars Section receives thousands of individual
|
||
observations of visual drawings made with the aid of color filters, black-&-
|
||
white and color photographs, intensity estimates of light and dark albedo
|
||
features, color contrast estimates, and micrometer measurements of polar caps,
|
||
cloud boundaries, and variable surface features during the 10 to 12 month obs-
|
||
erving period. The chronological filing of this large quantity of data requires
|
||
the observation information obtained for each night Universal Date be recorded
|
||
on one or two standard observing report forms!
|
||
|
||
It is with this regard that a simple, efficient and standard Mars Observing
|
||
Report Form has been prepared by the Mars Recorders. This Standard Form can be
|
||
used for reporting all types of observations such as; micrometry, transit tim-
|
||
ings, intensity estimates, etc. Photographs may also be attached to the top
|
||
or back of the forms and the relevant information blanks to be filled in at the
|
||
telescope. Planetary aspects blanks can be filled in at other times than while
|
||
observing.
|
||
|
||
|
||
The A.L.P.O. was founded in 1947, by Walter H. Haas, and now enrolls over 700
|
||
members, of which about 160 live in foreign countries on six continents. Our
|
||
group is organized into Observing Sections that study each Solar System body or
|
||
type of body.
|
||
|
||
We have held conventions every year beginning in 1956, usually together with
|
||
the meetings of the Astronomical League or of the Western Amateur Astronomers.
|
||
Our chief means of communication is our quarterly Journal ("The Strolling As-
|
||
tronomer"), although several of our Observing Sections also publish their own
|
||
newsletters and handouts.
|
||
|
||
Membership dues in the A.L.P.O. include a subscription to our Journal and are
|
||
$14.00 per year for members in the United States, Canada, and Mexico; and
|
||
$16.00 per year for other countries. (2-year rates are $24.00 and $29.00 re-
|
||
spectively.) Payment should be by check or money order payable to "A.L.P.O."
|
||
|
||
If our organization sounds of possible interest to you, write to:
|
||
Harry D. Jamieson, A.L.P.O. Membership Secretary,
|
||
P.O. Box 143, Heber Springs, Arkansas 72543.
|
||
-----------------------------------------------------------------------------
|
||
***IDENTIFYING A MARTIAN DUST STORM***
|
||
|
||
Although immense global dust storms are firmly entrenched in Martian lore,
|
||
they may be rare. Lowell Observatory's Leonard Martin has written 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 dis-
|
||
covered by Viking Spacecraft). However, smaller dust storms or dust clouds
|
||
are observed on Mars. These dust clouds are very difficult to identify in
|
||
their beginning stages and, in some cases, go undetected even after they have
|
||
fully developed.
|
||
|
||
Numerous reports of yellowish hazes have appeared in the literature and in the
|
||
International Mars Patrol 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. 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 sen-
|
||
sitometric calibration is usually lacking.
|
||
|
||
While working with Leonard Martin (Planetary Research Center, Lowell Observa-
|
||
tory, Flagstaff, Arizona) 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 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).
|
||
|
||
|
||
Table I (con't)
|
||
|
||
II. Martian dust clouds.
|
||
|
||
1. Obscuration -- 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.
|
||
|
||
|
||
Confusion over the colors of Mars is nothing new. When the bright planet Mars
|
||
is observed against a nighttime sky, the planet's predominantly orange colored
|
||
surface becomes highly saturated to the eye. The darker albedo features, when
|
||
observed against this saturated background are perceived as complementary hues.
|
||
This effect is known as "simultaneous contrast" and is explained the May 1989
|
||
Sky and Telescope Magazine, Vol. 77, No. 5, page 474, inset "Mars from Mauna
|
||
Kea" in an article by W.K. Hartmann, "What's New on Mars?".
|
||
|
||
COLOR FILTERS
|
||
|
||
A full set of photo-visual color filters is a most important observing aid the
|
||
planetary astronomer can have in his or her arsenal of telescopic accessories.
|
||
Color filters help overcome image deterioration caused by atmospheric scatter-
|
||
ing of light, permit separation of light from different levels in a planetary
|
||
atmosphere, increase hue contrast between areas of differing color, and reduce
|
||
irradiation within the observer's eye. All of these factors increase the
|
||
sharpness of surface and cloud details that are seen on the planet Mars.
|
||
|
||
Using color filters at the telescope can be a most challenging an rewarding ex-
|
||
perience, although several weeks of practice may be necessary to condition the
|
||
observer to detect those subtle wisps of clouds and hazes often observed in the
|
||
Martian atmosphere. Without the aid of these filters, many interesting phenom-
|
||
ena may go undetected.
|
||
|
||
Table I. Eastman Kodak Wratten Color Filters used for visual and
|
||
photographic observations of Mars. Transmission Characteristics
|
||
are given.
|
||
|
||
RED (W25,29) -- Gives maximum contrast of surface features, polar
|
||
cap edges, enhances fine surface details, and dust cloud bound-
|
||
aries.
|
||
|
||
ORANGE (W21,23A) -- Further increases contrast between light and
|
||
dark features, penetrates hazes and most clouds, and brightens
|
||
dust clouds.
|
||
|
||
Table I (con't)
|
||
|
||
YELLOW (W8,12,15) -- Brightens desert regions, darkens blue and
|
||
brown features.
|
||
|
||
GREEN (W56,57) -- Darkens red and blue features, enhances frost
|
||
patches, surface fogs, polar projections,and polar cap boundaries.
|
||
|
||
BLUE-GREEN (W64) -- Enhances ground fogs, limb and polar hazes.
|
||
|
||
BLUE (W80A,38A)-- Shows atmospheric clouds, discrete white clouds,
|
||
and limb hazes, and darkens reddish features, which probably con-
|
||
tributes to the illusion of blue or violet haze.
|
||
|
||
VIOLET (W47) -- Shows blue and blue-white clouds,limb hazes,equa-
|
||
torial cloud bands, polar cloud hoods, and dark dust clouds,and
|
||
aids in the detection of the Violet Clearing phenomenon.
|
||
|
||
MAGENTA (W30,32) -- Enhances red and blue features, darkens green
|
||
features.
|
||
|
||
|
||
THE MARS RECORDERS
|
||
|
||
To participate in our Mars observing program, receive the Martian Chronicle, an
|
||
observing form (to copy as many times as required) -- please send 8 Self Ad-
|
||
dressed Stamped Envelopes to the individual listed below that corresponds to
|
||
your local area. Each of the following ALPO Mars Recorders will be responsible
|
||
for receiving and corresponding with observers in a specific geographic area:
|
||
|
||
Jeff D. Beish, 9460 Toni Drive, Miami, Florida 33157 (CompuServe 72317,3306)
|
||
-- Alabama, Arkansas, Florida, Georgia, Hawaii, Kentucky, Mississippi, North
|
||
Carolina, South Carolina, Tennessee, and Virginia.
|
||
|
||
Harry Cralle, 3902 E. 29th Street (J-4), Bryan, Texas 77802
|
||
-- Arizona, California, Colorado, Kansas, Louisiana, Missouri, Nevada, New
|
||
Mexico, Oklahoma, Texas, Utah, and Wyoming.
|
||
|
||
Carlos Hernandez, 2714 Plaza Drive, Woodbridge, New Jersey 07095
|
||
-- Alaska, Connecticut, D.C., Delaware, Massachusetts, Maryland, Maine, New
|
||
Hampshire, New York, New Jersey, Pennsylvanian, Road Island, and Vermont.
|
||
|
||
Don C. Parker, Coral Gables, Florida 33156 (CompuServe 72317,3157)
|
||
-- Overseas and U.S. Territories.
|
||
|
||
Dan Troiani, 629 Verona Ct., Schaumburg, Illinois 60193
|
||
-- Idaho, Illinois, Indiana,Iowa, Michigan, Minnesota, Montana, Nebraska, North
|
||
Dakota, Ohio, Oregon, South Dakota, Washington, West Virginia, and Wisconsin.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
CALENDAR OF EVENTS -- MARS, 1990-91
|
||
|
||
03/06/90 -- Martian Southern Spring Equinox. South Polar Cap (SPC) should be
|
||
near maximum diameter. Is South Polar Hood (SPH) present? Look for North Polar
|
||
Hood. Disk diameter only 4.9 arcseconds ("). Mars rises approx. 2.5 hours
|
||
before Sun.
|
||
|
||
04/01/90 -- Disk diameter 5.4". Mars rises over 3 hours before Sun. Can the
|
||
major albedo features be seen? SPC large and bright. Is the eastern border of
|
||
Syrtis Major withdrawing? In violet light are orographic clouds present over
|
||
Tharsis-Amazonis? April Fool's Day!
|
||
|
||
04/27/90 -- Disk diameter 6". SPC rifts developing. Watch for those Martian
|
||
dust clouds (red filter), orographics clouds (violet filter).
|
||
|
||
05/12/90 -- Novissima Thyle appears as a bright SPC projection. However disk
|
||
diameter still small.
|
||
|
||
05/21/90 -- Southern hemisphere mid-spring. Any dust clouds yet? Orographics
|
||
over the Tharsis volcanoes -- W-Cloud? Maximum earthward tilt of Martian South
|
||
pole for this apparition, affording good views of SPC. Has Novissima Thyle sep-
|
||
arated from SPC to become Mountains of Mitchel? At disk diameter of 6.6" are
|
||
the Rima Australis and Magna Depressio visible in SPC?
|
||
|
||
06/05/90 -- Disk diameter is now 7". Rapid SPC retreat. Quality micrometer me-
|
||
asurements of SPC possible.
|
||
|
||
06/29/90 -- Mars at perihelion (closest to Sun). Disk diameter now 7.8". Views
|
||
of surface details better. Rapid SPC retreat. W-clouds possible. Dust clouds?
|
||
Is Novus Mons (Mts. of Mitchel) detached from SPC?
|
||
|
||
07/15/90 -- Late Southern spring. SPC now more than 20 degrees diameter. Watch
|
||
for dust clouds (red filter!). Numerous white patches possible on surface.
|
||
|
||
07/30/90 -- Martian Southern Summer Solstice. SPC continues to retreat poleward
|
||
Disk diameter 9".
|
||
|
||
08/16/90 -- Disk diameter is now 10". Some photography now possible. Discrete
|
||
(white) clouds and white areas should be minimal. SPC small, offset from pole.
|
||
|
||
09/01/90 -- SPC retreat slowing--stable polar remnant. Is Syrtis Major narrow?
|
||
Blunted? Possibility of dust storms again increasing. Large northern winter
|
||
North Polar Hood (NPH) should be prominent. Measure latitude of NPH -- does it
|
||
retreat or disappear when dust storm present?
|
||
|
||
09/14/90 -- Disk diameter 12". Begin high resolution visual observations and
|
||
high quality photography begins.
|
||
|
||
10/17/90 -- High probability of dust storms. Disk diameter 15.4". Tilt of Mars
|
||
now affording good view of both polar regions: large NPH. Look for tiny SPC
|
||
remnant near South limb. SPC offset, so easier to see when CM near 30 degrees.
|
||
Is SPC remnant present in mid-summer?
|
||
|
||
|
||
|
||
CALENDAR OF EVENTS -- MARS, 1990-91 (con't)
|
||
|
||
11/09/90 -- Continued alert for dust storms. SPC remnant visible? Antarctic
|
||
hazes present? Is NPH variable, occasionally bright? (Use a violet filter for
|
||
NPH measurements, observations.)
|
||
|
||
11/20/90 -- Closest approach (0400 UT) to Earth. Disk diameter 18.1".
|
||
|
||
11/27/90 -- Opposition (2028 UT). Disk diameter 17.9". Late Southern summer: Is
|
||
SPC remnant still present. Photographs needed of SPC. NPH still observable.
|
||
Watch for signs of NPH thinning. Are South polar hazes present?
|
||
|
||
12/17/90 -- Disk diameter 16". NPH should be easily visible if present. Close-
|
||
ly monitor hood from now on. When does it disappear and the NPC appear? Is SPC
|
||
remnant still present? Any evidence of SPH? Watch Syrtis Major for signs of
|
||
expansion to east.
|
||
|
||
01/05/91 -- Southern hemisphere autumnal equinox. Carefully monitor antarctic
|
||
region for evidence of SPC remnant and/or hazes. Will SPH form? N. hemisphere
|
||
vernal equinox. Monitor arctic closely for date of disappearance of NPH. Watch
|
||
for possible reformation of polar hood. NPC at maximum extent with edge near 55
|
||
degrees areocentric latitude. Disk diameter 13.2". Begin micrometer/reticle NPC
|
||
measurements, using red/orange filters.
|
||
|
||
02/01/91 -- Disk diameter 10". Photography difficult but visual observations
|
||
and NPC measurements still possible. Monitor antarctic for SPC remnant, hazes.
|
||
Are Hellas, Argyre brightening?
|
||
|
||
02/24/91 -- Disk diameter rapidly shrinking--now 8". Early Northern hemisphere
|
||
spring. Continue NPC measurements. Is North Cap fairly static or entering rapid
|
||
retreat phase? South polar regions becoming difficult to observe. Any signs
|
||
of SPH?
|
||
|
||
3/14/91 -- Disk diameter 7". Limb clouds/hazes should start to increase. Look
|
||
for them in violet light. What is size, shape of Syrtis Major?
|
||
|
||
04/04/91 -- Disk diameter 6". N. hemisphere mid-spring. Is NPC beginning rapid
|
||
retreat? Are limb arcs increasing in frequency, intensity. Use filters! Ant-
|
||
arctic hazes, hood? Cloud activity increases.
|
||
|
||
|
||
For complete details for the physical and geocentric positions of Mars send for
|
||
the "A.L.P.O. Solar System Ephemeris," $6.00 in the U.S, Canada, and Mexico;
|
||
$8.50 in other countries. Write to: John E. Westfall, A.L.P.O. Director/Editor,
|
||
P.O. Box 16131, San Francisco, CA 94116. |