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. sk yandtele scope.com • JA N UA RY 2 019 53