My first Magazine Sky & Telescope - 01.2019 | Page 55

polar hood of fog and clouds in
May, became visible by the start of
July, though it too was streaked by
dust, producing a dimmed appear-
ance compared to its usual bril-
liant white. The Tharsis volcanoes,
including Olympus Mons, each
stood out as readily discernible
dark spots from the monochro-
matic surroundings below them.
By early July, most observers had
written off the planet’s 2018 oppo-
sition as a bust, steeling themselves
for disappointing views of a bright
but bland, unadorned ball. But
fortunately, things quickly began to
turn around.
In mid-July, reports of a clear-
ing atmosphere began spreading
throughout the observing commu-
nity. While the planet displayed a
distinctly reduced contrast overall,
familiar albedo features, including
Solis Lacus and the small albedo
extensions from Mare Cimme-
rium known as Gomer Sinus, were
readily visible. Planetary imager
Damian Peach noted “a dark
albedo feature across Phasis-Dae-
dalia [part of Solis Lacus] which
was not visible before the storm
(though has appeared following
dust events in the past).” Both
Peach and French amateur Chris-
tophe Pellier spotted several small
storms within Solis Lacus in the
last week of the month as opposi-
tion approached, though fortu-
nately none of these lasted more
than a day or two.
Following opposition on July
27th and closest approach a
few days later, the Red Planet’s
atmosphere slowly continued to
clear, producing detailed (though
low-contrast) views for dedicated
and casual planetary observers
alike. Additional subtle changes of
albedo features have been observed,
but none as drastic as those that
occurred following the great dust
storm of 1956, which erased the
large, dark feature known as
Thoth-Nepenthes (S&T: March
2014, p. 54).
t This image shows
a small but bright
dust storm captured
on the morning of
May 31st by New
England amateur
John Boudreau us-
ing a 14¼-inch Dall-
Kirkham rel ector.
t Dust ills the gi-
gantic canyon sys-
tem Valles Marineris
on the morning of
June 13th, enabling
Darren Ellemor to
record this enigmat-
ic feature with just
a 6-inch Schmidt-
Cassegrain.
t By the time of
opposition, the dust
was noticeably set-
tling out of the Mar-
tian atmosphere.
This produced
low-contrast but
recognizable albedo
features. This image
by Anthony Wesley
is very similar to
the view at the
eyepiece.
t In early August,
observers began to
recognize changes
in the planet’s
albedo features. The
dark marking in the
Solis Lacus region
in this image is a
feature sometimes
seen after a large
dust storm, as
noted in the text.
Some minor global changes have
been recorded following the storm.
A general reduction in contrast
implies that some light dust remains
suspended in the upper atmosphere.
Additionally, the thin white clouds
of water vapor that treated observ-
ers each apparition over the past 15
years have been completely absent so
far in the latter half of 2018.
The storm was unusual in several
respects compared to events of the
past. As mentioned earlier, it started
in a region that, while known for
producing small regional storms
throughout the past decade, had not
generated a storm of this magnitude
to date. Additionally, the storm grew
quickly and spread mostly across
the northern hemisphere but never
completely obscured the entire
planet. While classified as a global
dust storm, it didn’t become quite
as opaque as the last big storm that
scuttled the tail-end of the 2001
apparition.
And just a little more than two
months after erupting into view, it
was mostly gone. The planet seemed
to give observers a reprieve, with
good views of major albedo markings
returning just following opposition.
Mars is one of the most interest-
ing planets from an observational
standpoint. As the most Earthlike
planet, it displays weather similar
to ours. And it’s the only terrestrial
planet besides Earth on which ama-
teurs can easily see the surface and
recognize known features. For many
of us, tracking the development of
regional dust storms, for example,
or watching for water vapor clouds
along the planet’s limb and clinging
to the slopes of the Tharsis volcanoes
makes the planet particularly attrac-
tive. So from that point of view, the
2018 apparition wasn’t a complete
bust for observers — in fact, it stands
out as one of the more exciting ones
in recent memory.
¢ Associate Editor SEAN WALKER
observes the planets using a 12½-
inch f/5 Newtonian relector.
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