LtE in CMO #246,247,248,249
From Thomas A DOBBINS
@. . . . . Date:
From: "Tom & Karen Dobbins"
<kmdobbins@coshocton.com>
To: "Masatsugu MINAMI"
<VZV03210@nifty.ne.jp>
Cc: "Walter Haas" <haasw@zianet.com>
Subject: Fw: REVISED ephemerides for specular
reflections at
Dear Masatsugu:
As
Professor Gaskell has pointed out in a recent communication: “Assuming that reflecting
ice crystals are suspended horizontally, the condition for specular reflection
around local
Here
is my best effort at generating ephemerides, based on the following
presumptions: Edom Promintorium stretches from
-7 to 4 degrees in latitude and 345 to 353 degrees in longitude. These
values are based on Gérard de Vaucouleurs' analysis of Shiro Ebisawa's map (see
Gérard de Vaucouleurs “Charting the Martian Surface” S&T,
October 1965, pp. 196-201). According to the Batson, Bridges, Inge “Atlas of Mars”
(NASA, 1979), the Schiaparelli crater is centered at 343 degrees longitude, -3
degrees latitude. I have used a value of 345 degrees for Edom Promontorium for
calculating the times of possible future events.
It would appear that Japanese observers may yet have
an opportunity to witness these events without leaving their native soil!
Tom Dobbins
----- Original Message -----
From: Tom & Karen Dobbins
To: C Martin Gaskell
Cc: rfienberg@skypub.com
Sent:
Subject: REVISED ephemerides for specular
reflections at
I.) LATITUDES
De = Declination of Earth from Mars
Ds = Declination of Sun from Mars
(De + Ds)/2 = Martian latitude of possible specular
reflection
July 11 De
= 7.0 Ds = -5.7 (De+Ds)/2 = 0.65
July 12 De
= 7.0 Ds = -5.9 (De+Ds)/2 = 0.55
July 13 De
= 7.1 Ds = -6.2 (De+Ds)/2 = 0.45
July 14 De
= 7.1 Ds = -6.4 (De+Ds)/2 = 0.30
July 15 De
= 7.2 Ds = -6.7 (De+Ds)/2 = 0.25
July 16 De
= 7.2 Ds = -6.9 (De+Ds)/2 = 0.15
July 17 De
= 7.2 Ds = -7.1 (De+Ds)/2 = 0.05
July 18 De
= 7.2 Ds = -7.4 (De+Ds)/2 = -0.10
July 19 De
= 7.2 Ds = -7.6 (De+Ds)/2 = -0.20
July 20 De
= 7.2 Ds = -7.8 (De+Ds)/2 = -0.30
July 21 De
= 7.2 Ds = -8.1 (De+Ds)/2 = -0.45
July 22 De
= 7.2 Ds = -8.3 (De+Ds)/2 = -0.55
July 23 De
= 7.2 Ds = -8.5 (De+Ds)/2 = -0.65
July 24 De
= 7.2 Ds = -8.8 (De+Ds)/2 = -0.80
July 25 De
= 7.1 Ds = -9.0 (De+Ds)/2 = -1.05
July 26 De
= 7.1 Ds = -9.3 (De+Ds)/2 = -1.10
July 27 De
= 7.0 Ds = -9.5 (De+Ds)/2 = -1.25
July 28 De
= 7.0 Ds = -9.7 (De+Ds)/2 = -1.35
July 29 De
= 6.9 Ds = -10.0 (De+Ds)/2 = -1.55
July 30 De
= 6.8 Ds = -10.2 (De+Ds)/2 = -1.70
July 31 De
= 6.7 Ds = -10.5 (De+Ds)/2 = -1.90
Aug 01 De
= 6.7 Ds = -10.7 (De+Ds)/2 = -2.00
Aug 02 De
= 6.6 Ds = -10.9 (De+Ds)/2 = -2.15
Aug 03 De
= 6.5 Ds = -11.0 (De+Ds)/2 = -2.25
Aug 04 De
= 6.4 Ds = -11.2 (De+Ds)/2 = -2.40
Aug 05 De = 6.3
Ds = -11.5 (De+Ds)/2 = -2.60
Aug 06 De
= 6.2 Ds = -11.7 (De+Ds)/2 = -2.75
Aug 07 De
= 6.1 Ds = -11.9 (De+Ds)/2 = -2.90
Aug 08 De
= 6.0 Ds = -12.1 (De+Ds)/2 = -3.05
Aug 09 De
= 5.9 Ds = -12.4 (De+Ds)/2 = -3.25
Aug 10 De
= 5.7 Ds = -12.6 (De+Ds)/2 = -3.45
II.) LONGITUDES & TIMES
Phase i =
Planetocentric elongation of Mars with respect to Earth and Sun in degrees
(Phase i)/2 = Distance in degrees of
longitude from CM (in direction of evening limb post opposition) of possible
specular reflection Longitude Offset = 345 + (Phase i)/2 = longitude of Martian CM for specular reflection at Edom
Promontorium Time = Nominal UT time of possible specular reflection at Edom
Promontorium
July 11
Phase i = 22.9 degrees (Phase i)/2 = 11.4 Longitude Offset =356.4 Time =
July 12
Phase i = 23.6 degrees (Phase i)/2 = 11.8 Longitude Offset =356.8 Time =
July 13
Phase i = 24.3 degrees (Phase i)/2 = 12.2 Longitude Offset =357.2 Time =
July 14
Phase i = 24.9 degrees (Phase i)/2 = 12.4 Longitude Offset =357.4 Time =
July 15
Phase i = 25.6 degrees (Phase i)/2 = 12.8 Longitude Offset =357.8 Time =
July 16
Phase i = 26.2 degrees (Phase i)/2 = 13.1 Longitude Offset =358.1 Time =
July 17
Phase i = 26.9 degrees (Phase i)/2 = 13.5 Longitude Offset =358.5 Time =
July 18
Phase i = 27.5 degrees (Phase i)/2 = 13.8 Longitude Offset =358.8 Time =
July 19
Phase i = 28.1 degrees (Phase i)/2 = 14.0 Longitude Offset =359.0 Time =
July 20
Phase i = 28.7 degrees (Phase i)/2 = 14.4 Longitude Offset =359.4 Time =
July 21
Phase i = 29.3 degrees (Phase i)/2 = 14.6 Longitude Offset =359.6 Time =
July 22
Phase i = 29.8 degrees (Phase i)/2 = 14.9 Longitude Offset =359.9 Time =
July 23
Phase i = 30.4 degrees (Phase i)/2 = 15.2 Longitude Offset =000.2 Time =
July 24 Phase i = 30.9 degrees (Phase i)/2 = 15.5 Longitude Offset =000.5 Time =
July 25
Phase i = 31.5 degrees (Phase i)/2 = 15.8 Longitude Offset =000.8 Time =
July 26
Phase i = 32.0 degrees (Phase i)/2 = 16.0 Longitude Offset =001.0 Time =
July 27
Phase i = 32.5 degrees (Phase i)/2 = 16.3 Longitude Offset =001.3 Time =
July 28
Phase i = 33.0 degrees (Phase i)/2 = 16.5 Longitude Offset =001.5 Time =
July 29
Phase i = 33.4 degrees (Phase i)/2 = 16.7 Longitude Offset =001.7 Time =
July 30
Phase i = 33.9 degrees (Phase i)/2 = 17.0 Longitude Offset =002.0 Time =
July 31
Phase i = 34.4 degrees (Phase i)/2 = 17.2 Longitude Offset =002.2 Time =
Aug 01
Phase i = 34.8 degrees (Phase i)/2 = 17.4 Longitude Offset =002.4 Time =
Aug 02
Phase i = 35.2 degrees (Phase i)/2 = 17.6 Longitude Offset =002.6 Time =
Aug 03
Phase i = 35.7 degrees (Phase i)/2 = 17.8 Longitude Offset =002.8 Time =
Aug 04
Phase i = 36.1 degrees (Phase i)/2 = 18.0 Longitude Offset =003.0 Time =
Aug 05
Phase i = 36.5 degrees (Phase i)/2 = 18.3 Longitude Offset =003.3 Time =
Aug 06
Phase i = 36.8 degrees (Phase i)/2 = 18.4 Longitude Offset =003.4 Time =
Aug 07
Phase i = 37.2 degrees (Phase i)/2 = 18.6 Longitude Offset =003.6 Time =
Aug 08
Phase i = 37.6 degrees (Phase i)/2 = 18.8 Longitude Offset =003.8 Time =
Aug 09
Phase i = 37.9 degrees (Phase i)/2 = 19.0 Longitude Offset =004.0 Time =
Aug 10 Phase i
= 38.3 degrees (Phase i)/2 = 19.2 Longitude Offset =004.2 Time = 23.53
@. . . . . . . . . . . Date:
From: "Tom & Karen Dobbins"
<kmdobbins@coshocton.com>
To: "Masatsugu MINAMI" <VZV03210@nifty.ne.jp>
Cc: "Bill Sheehan"
<sheehans@tds.net>, <73737.1102@compuserve.com>
Subject: Analysis of June 7 and June 8 Martian
flares
The
anomalous brightenings at Edom Promintorium witnessed from the
1.)
Phase i
(planetocentric elongation of Mars with respect to Earth and Sun) = 5.9 degrees
(Phase i)/2
= distance in degrees of longitude from CM (in the direction of the morning
limb prior to the date of opposition) of the source of specular reflection = ~3
degrees
CM at
De = 1.7 degrees
Ds = 2.5 degrees Assuming a
horizontal reflecting surface, the nominal position of the source of the
reflection should be at (1.7 + 2.5)/2 = 2.1 degrees.
2.)
Phase i
(planet centric elongation of Mars with respect to Earth and Sun) = 5.1 degrees
(Phase i)/2
= distance in degrees of longitude from CM (in the direction of the morning
limb prior to the date of opposition) of the source of specular reflection =
~2.5 degrees
CM at
CM at
De = 1.9 degrees
Ds = 2.2 degrees Assuming a
horizontal reflecting surface, the nominal position of the source of the
reflection should be at (1.9 + 2.2)/2 = 2.05 degrees.
It is noteworthy that despite a source latitude of
2.1 to 2.5 degrees suggested by the values of De and Ds, the apparent location
of the center of the activity appeared to be several degrees to the south.
@. . . . . .
. . . Date:
From: "Tom & Karen Dobbins"
<kmdobbins@coshocton.com>
Reply-To: "Tom & Karen Dobbins"
<kmdobbins@coshocton.com>
To: "Masatsugu MINAMI"
<VZV03210@nifty.ne.jp>
Subject: Comments on
Dear Masatsugu:
Here is an Interesting exchange of ideas between two
planetary scientists from NASA JPL, Tim Parker and Albert Haldemann, regarding
the nature of the
Tom
-------------------------------
Date:
From: Albert
Haldemann <albert@shannon.jpl.nasa.gov>
To: Tim Parker
<tparker@mail1.jpl.nasa.gov>
Subject: Re: Fwd:
Fw:
Tim,
I've looked at
the Blue Book (Mars ephemeris) for this year; I think that if nothing is
observed in July (and I predict it won't be) then the particular hypothesis
about the scattering mechanism (horizontally suspended ice crystals) can be
discarded (assuming Gaskill has got his prediction right based on the theory,
which is not entirely clear, as I don't have the S&T article to look at).
I think in the end
it will prove to be an opposition effect related to the surface. In the blue
book the ephemeris is:
0h UT:
Date Sub-Earth Sub-Solar Separation
Long Lat
Long Lat (deg.estim)
4 Jun
259.8 +1.17 268.1
+3.31 8.6
8 Jun 224.3
+1.91 229.6 +2.36
5.3
12 Jun 188.9
+2.69 191.2 +1.41
2.6
16 Jun 153.5
+3.48 152.8 +0.44
3.1
20 Jun 118.1
+4.25 114.3 - 0.53
6.4
while in July the
Earth-Sun separations are much greater (i.e. NO opposition effect):
14 Jul 264.0
+7.28 243.0 - 6.44
25.1
I note that the
minimum phase angle as far as longitude cross-over occured on or around Jun 7,
which is when the brightenings were reported.
So I also then
note that you should probably keep looking this week as the Earth-Mars-Sun
phase angle hasn't changed a whole lot since last week, and there is another
longitude cross-over this week on or around Jun 14 when the latitude difference
is only 3 degrees!
I think however
that the crossing will occur at UT times that would require Australian
observers...so find some and get them video cameras!
I further note
that there is no longitude crossing of the sub-Earth and sub-solar points until
the very end of July or beginning of August when the difference in latitudes of
those points is about 19 degrees...so I'm skeptical that the July observations
will pan out...but look this week!
All this based on
MY suspicion that this is a surface-slope-mediated specular opposition-effect.
Albert
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To:
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kmdobbins@coshocton.co
From: Tim Parker
<tparker@mail1.jpl.nasa.gov>
Subject: Fwd: Re:
Fwd: Fw:
Albert:
Thanks for the
suggestions. yes, this week Schiaparelli
will not be on the central meridian from So.
planetarily,
-Tim.
DISCLAIMER: All opinions herein are MY OWN, not JPL's.
Dr. Albert
Haldemann t:818-354-1723 f:818-354-6825
e:albert@shannon.jpl.nasa.gov pg(e):1717964@skytel.com
JPL 238-420,
@. . . . . . . . . . .Date:
From: "Tom & Karen Dobbins"
<kmdobbins@coshocton.com>
Reply-To: "Tom & Karen Dobbins"
<kmdobbins@coshocton.com>
To: "Masatsugu MINAMI"
<VZV03210@nifty.ne.jp>
Subject: Fw: Not the opposition surge effect
Dear Masatsugu:
I believe that Professor Gaskell has very convince
refuted the notion of an opposition effect advanced by Albert Haldemann of
NASA/JPL.
Warmest regards,
Tom
----- Original Message -----
From: "C Martin Gaskell" <gaskell@unlserve.unl.edu>
To: <albert.f.haldemann@jpl.nasa.gov>
Cc: <kmdobbins@coshocton.com>; <73737.1102@compuserve.com>;
<rfienberg@skypub.com>; <gseronik@skypub.com>;
<tparker@mail1.jpl.nasa.gov>;
<dcpmiami@mail.earthlink.net>
Sent:
Subject: Not the opposition surge effect
> Dear Albert,
>
> A copy of your e-mail to Tim Parker got forwarded on to me. The Martian glints are not the well-known
opposition surge
> effect because some of the glints (e.g., the impressive
> quite far from opposition.
I hope you've had time now to look up the Dobbin & Sheehan (2001)
article where these are
> listed.
>
> The back-scattering of the opposition surge is also over much too
broad angle an angle to explain the transient brightenings.
> Back-scattering can be atmospheric (as seen on the earth) or due
to properties of the surface (as seen on the moon). If the aerosols
>are optically thick the atmospheric effect dominates, but on Mars
the clouds are usually optically thin.
The surface effect is best
>studied for the moon. From
low moon orbit one sees a bright point on the surface in the anti-solar
direction (this is very obvious in
>Apollo movies). However it covers quite a wide angle - bigger
than the moon subtends from the earth. From the earth we do NOT
>see a bright spot appearing in the center of the moon at full moon;
we see the total brightness of the moon increasing (the opposition
>surge). Mars subtends a much smaller angle than the
moon so this is true a fortiori for Mars.
>
> The picture on p. 115 of Dobbins & Sheehan is actually of the
opposition effect, not specular reflection.
The full picture can be seen
>at
Ĝ http://www.msss.com/mars_images/moc/5_24_98_glint_release/index.html
> where the caption (wisely) hedges on whether the effect is a
surface one or an atmospheric one.
Incidentally, the picture on the MSS
>web site is upside down
compared with the one in Dobbins & Sheehan.
The Mars Orbiter Camera picture was, of course, taken from
>Mars orbit so, as with
pictures taken from lunar orbit, the angle the glow in the anti-sun direction
subtends is quite substantial. As
>seen from the earth, the
size of the spot will be vastly greater than the angle Mars subtends in the sky
so an observer would not see a
>small bright spot on
Mars. This is again analogous to what we
see from the earth at full moon.
>
> If the
> relative rarity of the glints strongly implies that they are
weather related - either only appearing on days when clouds are in the
>atmosphere, or when there is
a frost on the ground.
> Best wishes,
>
> Martin Gaskell
> Dept. Physics & Astronomy
>
>
@. . . . . . . . . . . Date:
From: "Tom & Karen Dobbins"
<kmdobbins@coshocton.com>
Reply-To: "Tom & Karen Dobbins" <kmdobbins@coshocton.com>
To: "Masatsugu MINAMI"
<VZV03210@nifty.ne.jp>
Cc: <rfienberg@skypub.com>
Subject: Saheki, McClelland, and Tasaka versus 2001
observations -- FINAL CORRECTED VERSION
Here are the parameters that prevailed at the time
of Saheki and McClelland's 1954 sightings and Tasaka's 1958 sighting of flares
at Edom Promintorium, generated by Jeff Beish's WIMP program:
1.) Saheki
De = 0.5 degrees Ds = -5.1 degrees (De + Ds)/2 = -2.3 degrees = nominal Martian
latitude of source of specular reflection, assuming horizontal orientation.
Phase = 6.9 degrees (post date of opposition) CM = 319 degrees 319 - (6.9/2) = ~315 degrees = nominal
Martian longitude of source of specular reflection, assuming horizontal orientation.
Based on Saheki's large-scale drawings, it is
possible to determine the site of the presumed reflection that he witnessed
with considerable precision (conservatively +/- 3 degrees of latitude and
longitude). The latitude does indeed appear to be at about the nominal position
of -2 or -3 degrees, but the longitude of the flare appears to be at 356
degrees. 356 - 315 = 41 degrees. This corresponds to a surface inclined by
about 41 degrees from the horizontal (wow!) on an east-west axis.
2.) McClelland
De = -2.9 degrees Ds = -10.6 degrees (De + Ds)/2 = -6.7 degrees = nominal Martian
latitude of source of specular reflection, assuming horizontal orientation.
Phase = 24.9 degrees (post date of opposition) CM = 346 degrees 346 - (24.9/2) = ~ 333.5 degrees = nominal
Martian longitude of source of specular reflection, assuming horizontal
orientation.
McClelland's sketch also permits the site of the
reflection to be determined with considerable precision (conservatively +/- 3
degrees of latitude and longitude). The latitude appears to be at about -2
degrees, tolerably close to the -6.7 degrees predicted, suggesting a
north-south inclination of 6.7-2 = <5 degrees, but the longitude appears to
be located at 356 degrees or thereabouts.
356 - 333.5 = 22.5 degrees. This
corresponds to a surface inclined about 22.5 degrees from the horizontal on an
east-west axis, and in the same direction as in the case of Saheki's
observation.
3.) Tasaka
De = -13.6 degrees Ds = -11.4 degrees (De + Ds)/2 = -12.5 degrees = nominal Martian
latitude of the source of specular reflection, assuming horizontal orientation.
Phase = 4.5 degrees (post date of opposition) CM = 331.5 degrees 331.5 - (4.5/2) = ~ 329 degrees = nominal
Martian longitude of source of specular reflection, assuming horizontal
orientation.
Based
on Tasaka's beautiful drawing, the latitude of the source (about -2 degrees)
differs from the nominal -12.5 degrees by about 10 degrees. The longitude of the flare lies at about 355
degrees. 355 - 329 = 26 degrees. This
corresponds to a surface inclined by 26 degrees from the horizontal on an
east-west axis.
These
phenomena seem to be rather insensitive to geometry, causing me to wonder why
they are not seen far more frequently. Or are they routinely written off to
effects of atmospheric turbulence and tricks of the eye, and hence go
unreported? It may emerge that last week's success in
@. . . . . . . . .Date:
From: "Tom & Karen Dobbins"
<kmdobbins@coshocton.com>
To: "Masatsugu MINAMI"
<VZV03210@nifty.ne.jp>
Subject: Fw:
----- Original Message -----
From: "Tim Parker" <timothy.j.parker@jpl.nasa.gov>
To: "Tom Dobbins" <r&d@organictech.com>;
<kmdobbins@coshocton.com>
Sent:
Subject:
> Tom:
>
> I've started to look at the MOC Wide Angle images for possible evidence
of specular reflections in the
>images show an opposition effect, and this bright spot doesn't look
especially different when it's over
>task, and I've got to get ready for a planetary geologic mappers
meeting that I'm hosting next week in
>point you and interested
others to Malin Space Science Systems' website, specifically the page with the
archived wide angle images
>that could be used for such a search. It's
http://www.msss.com/moc_gallery/index.html, specifically the "Daily Global
map Data"
>and more specifically the Red images (the blue ones are lower in
resolution by quite a bit, but might be useful if the angle of the glint
>relative to nadir places it outside the narrower red frames). Clearly, some calculations will be needed to
determine whether a glint
>could be observed from a
>(presumably a specular reflection off horizontal ice crystals in
clouds or surface materials would be west=sunward of the nadir point
>on the ground). Have you
thought about the timing of the flashes from the Keys relative to the subsun
and subearth and what they
>might say about the actual angle of the "reflector(s)"
responsible? Schiaparelli's floor is
largely horizontal, but there are regional
>slopes in the surrounding terrain (and along the crater rim), and
if the reflections come from the
surface, they might not be horizontal.
>
> If the angle is too large to offer a glint during nadir
observations, another possibility that could be tried based on calculations
similar
>to your and perhaps Gaskell's predictions for terrestrial viewing
but with Mars Global Surveyor orbit parameters considered, would
> be to rotate the MGS spacecraft off-nadir to acquire a wide angle
swath (similar to the "context images, perhaps, in size and
> 250m/pixel resolution) of the Edom/Schiaparelli area (though
Shciaparelli is probably too large for a single image at 250m/pixel, the
> camera can sum pixels for lower resolution and broader coverage,
though). MGS is currently in its
extended mission, so they are
>able to roll the spacecraft for off-nadir observations of
scientifically interesting targets and landing site imaging activities (with
>obvious considerations for their relative scientific value, as they
sacrifice normal nadir observations and complicate operations when
>they roll the spacecraft). I
think that, with some careful thought given to whether MGS could see flashes,
Mike Malin (MOC Principal
>investigator) might be willing to try to image a specular
reflection (their recent posting of the opposition surge image shows that
>they're paying attention to
the amateur observations - oh yeah, and I forwarded Don's announcement to them
8^)). Mike may already
>be thinking about something like this, though there is a crunch
coming up with pressure from MER about getting off-nadir images of
>landing sites and from the Odyssey orbiter wanting continuous
atmospheric monitoring by the Thermal Emission Spectrometer on
>MGS during their aerobraking period, coming up in about 2
months. If you think this might be worth
pursuing, and need someone
>that Mike might at least listen to (he's got a reputation for
ignoring people, deserved or otherwise), I work with him on occasion and
>would be happy to pass the request on to him.
> planetarily,
> -Tim.
@. . . . . . . . . . Date: Sat,
From: "Tom & Karen Dobbins"
<kmdobbins@coshocton.com>
To: <vzv03210@nifty.com>
Subject:
Dear Masatsugu:
I
just returned to the
Warmest regards,
Tom
@. . . . . . . . . . Date:
From: "Tom & Karen Dobbins"
<kmdobbins@coshocton.com>
To: "Masatsugu MINAMI"
<VZV03210@nifty.ne.jp>
Cc: "C Martin Gaskell"
<gaskell@unlserve.unl.edu>
Subject:
Dear Masatsugu:
Attached
please find a sequence of four composite images (composed of 9 frames each)
from
We
are all indebted to astrovideographer David Moore
of 
many
hours examining the videotapes, tediously registering and stacking individual
frames, and skillfully processing the resulting composite images. He was an
invaluable member of the Florida Keys Mars expedition.
Accompanying
verbal descriptions:
06h:45m:42s
Intensely bright, almost stellar flare.
06h:46m:15s
Brightness waning.
06h:46m:49s
Brightness increasing again.
When time permits we will attempt to make an AVI or
MPEG animation in the hope of showing the pulsations in brightness that we
observed.
By
the way, I believe that the discrepancies between the 1954 Japanese ephemeris
values for De and Ds and those
produced by Jeff Beish's WIMP program can be attributed to the refinement of
Martian cartographic coordinates circa 1973 that resulted from Mariner 9 data.
Warmest
regards,
Tom
@ . . . . . . . It is my understanding -- admittedly
perhaps quite imperfect -- that the Mars maps based on Mariner 9 images
resulted in a modest revision of the values of Martian cartographic
coordinates, principally and systematically in latitude. I base this on remarks
found on pages 323 to 326 in the chapter "Geodesy and Cartography" by
Davies, Batson, and Wu of the US Geological Survey in Kieffer et al's massive
book "Mars" (Univ. of Arizona Press,1992). Could this account for the
discrepancies between the values of De and Ds in the older almanacs --
American, British, etc... -- and current ephemeredes, or the difference between
areocentric and areographic latitudes? I will ask Jeff Beish, author of the
WIMP software, for an explanation.
(
@. . . .
. . . . . . .Date: Sat,
From:
"Tom & Karen Dobbins" <kmdobbins@coshocton.com>
To:
"Masatsugu MINAMI" <VZV03210@nifty.ne.jp>
Cc:
"C Martin Gaskell" <gaskell@unlserve.unl.edu>
Subject:
A response to Young's remarks about the
Dear
Masatsugu:
Regarding the message from Andrew Young (a specialist in stellar photometry at
Frankly, I think Young fails to grasp a vital point essential to understanding
the flare phenomena. The rotation of Mars will displace the angle of any
reflecting surface by about 1.2 degrees of longitude every five minutes, so discrete
patches of frost don't have to "disappear" for pulsating flares to be
seen! Moreover, Young's notion that just before local
Rather than the exotic (and in my opinion highly improbable) mechanisms
proposed by Young, I believe that Martin Gaskell has provided a far more
plausible explanation.
Gaskell writes:
(1) The reflector is inclined to the horizontal at a fair bit – this
strongly rules out clouds. It's got to be on the surface.
(2) The range of inclinations is readily explained by a range of slopes on the
surface.
(3) The rapidity of the fluctuations tells us that there are regions of the
reflector with slightly different slopes (by a fraction of a degree).
(4) The size of region needed to explain the flashes of a few seconds is only a
few times bigger than a football field. There are plenty of flat regions
on this scale. I think the faces of sand dunes are an interesting possibility,
although by no means the only one.
(5) These flashes are only seen when the weather is right (not every day), so
they are fog/frost induced. It's not shiny rocks.
Here's my scenario for what happens:
In the morning the sun heats the ground and makes water evaporate. The
Martian air is always close to saturation and, unlike the earth's, is
significantly colder than the ground. Ice crystal therefore condense in
the air above the ground forming a fog (as see on the earth when the sun shines
on wet ground and as imaged on Mars). The ice crystals fall on the ground
creating a frost. Fog and frost must go hand in hand.
Ice crystals have a very high albedo so they inhibit any more heating of the
ground where they fall and they can stay there for quite a while. On
Mars, unlike on the earth, the surface temperature is ruled almost entirely by
the amount of sunlight absorbed and by the emissivity of the surface, not by
the atmosphere (on the earth, with a much denser atmosphere, heating by the air
dominates instead).
Why does fog/frost form in valleys? Answer: because the wind is calm
there and the water vapor content of the air is not reduced by turbulent mixing
with drier air (the same holds for the earth).
What governs when frost is seen in Schiaparelli? Answer: How windy it is.
Fog and frost will only be seen on the calmest days (as on Earth).
I am convinced that these ideas of Gaskell's contain the essential truth of the
matter.
Warmest regards,
Tom
@ . . . . . . . A passing thought that you may wish
to share with your colleagues during your upcoming meeting...
After
a lapse of over a century, it may be time to revive the long-abandoned 19th
century practice of calculating ephemerides for Martian specular reflections --
not for features like Syrtis Major that were once mistaken for bodies of water,
but for a select handful of locales that are known to frequently harbors
ice-fogs and frost deposits. During the extremely favorable perihelic
apparition of Mars in 2003, the values of De and Ds will be virtually
coincident at -19.4 degrees in late July and ealy August, when the apparent
diameter of the planet's disc will exceed 22 seconds of arc. I recommend that
northern
Meanwhile, I
am certain that the unfolding dust storm is occupying your attention!
Warmest regards,
(
@. . . . . . . .Dear Masatsugu: A very interesting
suggestion from the renowned French planetary astronomer Audouin Dollfus...
(
----- Original Message -----
From: <Audouin.Dollfus@obspm.fr>
To: <kmdobbins@coshocton.com>
Sent:
Subject:
> Dear mr Dobbins
> Thank hou for your very interesting message about flashing
> If the effect is due to specular reflection on shining surfaces,
> the light should be highly polarized. Could it be possible to
> observe through a polaroid, oriented to transmit the polarized
> light parallel to the direction of the lines of cusps, and then
> perpendicular to this direction, several times alternatively?
> I observed a specular
polarization effect on the Moon, see
> for example my paper in ICARUS, 140, pp 313 to 327
(1999). On the
> Moon, covered essentially by very small grains, the effect should
> be smaller than with anticipate larger elements on Mars.
> Sincerely Audouin DOLLFUS
@ . . . . . . . I hope that the CMO conference went
well. In three days Don Parker will present the Edom Promontorium flare results
to the ALPO convention in
(
(Note)
The monograph is the one entitled:
THE
MARTIAN FLARES MYSTERY - SOLVED? by
Thomas Dobbins, William Sheehan, Donald Parker, David Moore, and Tippy
D'Auria (Ed)
Tom DOBBINS (OH,