Mars at Its All-Time Finest
- Mars at Its All-Time Finest
"Page where the story of Mars started,with pictures at site:
Martian Flare Watch
By Thomas A. Dobbins
"Story can be found at this address,with pictures at site:
Tan Wei Leong of Singapore obtained this superb CCD image of Mars
using an 11-inch telescope. Edom Promontorium, where numerous bright
flares were seen in early June 2001, is near the central meridian in
its normal non-flare state. South is up.
Will Martian flares like those observed in 2001 appear again in 2003?
Amateur and professional astronomers will be watching the red planet
closely to find out.
In the May 2001 issue of Sky & Telescope, my colleague William
Sheehan and I discussed rare historical observations of bright, star-
like flares from certain regions on the planet Mars. We suggested
that the brightenings might be caused by specular (mirror-like)
reflections of sunlight off water-ice crystals in surface frosts or
thin clouds. Many of these glints were reported when the sub-Sun and
sub-Earth points (where the Sun and Earth, respectively, are directly
overhead as seen from Mars) were nearly coincident and close to the
planet's central meridian, the imaginary line running down the center
of the visible disk from pole to pole. Based on our analysis, we
predicted that flares like those reported only four times between
1894 and 1958 might erupt in the region known as Edom Promontorium,
near the Martian equator at longitude 345°, in early June 2001.
I organized an expedition to the Florida Keys, where the red planet
would climb high in the south under exceptionally steady skies. Team
members from Sky & Telescope and the Association of Lunar and
Planetary Observers (ALPO) scrutinized the planet using a variety of
telescopes nightly beginning June 5th. No flares were seen for the
first two nights. But on June 7th, beginning around 06:35 Universal
Time (2:35 a.m. Eastern Daylight Time), about 85 minutes before Edom
crossed the central meridian, we saw a series of brightenings. Each
lasted 3 to 5 seconds; they occurred once or twice a minute over the
next hour and a half, until clouds ended the observations. The flares
were seen visually at magnifications of 300x to 366x through two 6-
inch (15-centimeter) Newtonian reflectors and were recorded on
videotape at 1,400x through a Meade 12-inch (30-cm) Schmidt-
Cassegrain telescope. Visually, the flares seemed to cut the dark
linear feature Sinus Sabaeus nearly in two. More brightenings of Edom
were observed on June 8th; these were as brilliant as the ones the
night before but not as frequent. For details see IAU Circular 7642.
One of several flares seen on June 7, 2001, peaks in brightness
(left) and fades considerably less than a minute later (right). Both
images are identically processed 9-frame composites from an SVHS
video recording made through a 12-inch telescope. South is up.
Courtesy David Moore.
Our June 2001 observations support the idea that the flares came from
sunlight glinting off patches of frost or ice on the Martian surface.
Because the flashes occurred before Edom crossed the center of the
planet's disk, the reflectors must have been tilted as much as 19°
east-west; perhaps they rested on inclined surfaces on the ground,
for example, the slopes of dunes. Intriguingly, the light-colored
oval of Edom Promontorium corresponds to the large, flat crater
Schiaparelli, and in May 2002 NASA's Mars Odyssey spacecraft found
indications that this region is anomalously rich in water ice for a
site near the Martian equator. The historical tendency of flares to
occur when the sub-Sun and sub-Earth points are nearly coincident
suggests to Masatsugu Minami, director of the Oriental Astronomy
Association's Mars section, that the sources of the reflections lie
at the bottoms of narrow fissures or trenches on the planet's
Mars observers and planetary scientists hope to learn more about the
flare phenomenon during the red planet's 2003 apparition, now
building toward a record-breaking closest approach in late August.
Because Mars's southern hemisphere is tipped our way this year, the
geometry precludes seeing any flares from Edom or other equatorial
regions. Instead, specular reflections are likely from sites at more
southerly Martian latitudes.
In late July and early August this year, the sub-Sun and sub-Earth
points will converge at a Martian latitude of 20°. By then the
apparent diameter of Mars's gibbous disk will exceed 20 arc seconds.
From July 24th through August 10th, observers should keep an eye on
northern Thaumasia, northern Solis Lacus, southern Tithonius Lacus,
Deucalonius Regio, Iapygia, and northern Hellas all at or near
latitude 20°. It will be interesting to see if specular reflections
like those observed at Edom in 2001 are rare events that suggest
something special about that site, or if they can be seen at many
locations whenever the Mars-Sun-Earth geometry is favorable.
Observations, both positive and negative, are welcomed by the Mars
sections of both ALPO and the British Astronomical Association, as
well as by the International Mars Watch. Of course, we also welcome
your observing reports at Sky & Telescope!
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Tom Dobbins is a contributing editor of Sky & Telescope magazine and
the author of several acclaimed books on observing and imaging the
solar system. S&T editors Rick Fienberg and Gary Seronik, who
accompanied Dobbins to Florida in June 2001 and saw the Martian
flares themselves, contributed to this article.
Mars Odyssey Support for Visual Ice Flashes?
A Mars Record for the Ages
©2003 Sky Publishing Corp.
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R. Tresch Fienberg, Sky and Telescope (S&T), reports that he
and a team of observers representing S&T and the Association of
Lunar and Planetary Observers (T. Dobbins, G. Seronik, D. Parker,
T. D'Auria, D. Moore, P. D'Auria, D. Troiani, S. Ireland, L.
Ireland, C. Petersen, M. Petersen, and B. Itzenthaler), succeeded
in detecting a brightening of Edom Promontorium during June 7 and
8, both visually with two 0.15-m Newtonian reflectors and via
monochrome videotape recorded with a 0.30-m Schmidt-Cassegrain
reflector located in the Florida Keys, following predictions by
Dobbins and Sheehan [2001, S&T 101(5), 115]. Observing conditions
were good, with partly cloudy skies and excellent seeing. No
brightenings were detected under good observing conditions on June
5 and 6. A perceptible brightening of Edom was first detected
around June 7.274 UT, about 85 min before the feature transited
Mars' central meridian. By June 7.278, sporadic pulsations in
brightness were evident, occurring once or twice a minute with
brightness maxima of about 3-5 s duration that were not correlated
with atmospheric turbulence; these brightness variations, which
appeared along the north margin of Sinus Sabaeus, were seen
simultaneously by visual observers and by those viewing the video
monitor until June 7.312. Brightening around Edom also occurred
on June 8, having intensity like that of June 7, with a series of
short-lived (3- to 5-s) brightenings observed during June 8.292-
8.306 and another series of frequent variations seen during June
8.328-8.350. These specular reflections may continue for the next
few nights, as detailed by Dobbins and Sheehan (op.cit.).