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Red Planet Regale

by Perry Pezzolanella

A beautiful tiger-hued star will make 2018 be remembered as the year of Mars. It will blaze long into the balmy summer nights and deep into the frosty autumn evenings while drawing the attention of even the casual sky watcher. Mars will be at its best since the historic opposition of August 2003 with opposition on July 28, which means it will be up all night, but it will never appear as big as the Earth’s Moon, which was an internet hoax circulating for years after the 2003 opposition. Due to its highly elliptical orbit, it will be at its closest, largest, and brightest on July 31. On that date, Mars will be 35.79 million miles from Earth and 24.3 arcseconds across, burning fiercely at magnitude -2.8.

Mars is the only planet that clearly displays a solid surface. It is a rusty desert world of windswept sand dunes, towering volcanoes, gaping canyons, craters, and two polar ice caps. These polar ice caps are the easiest to see and are composed of frozen water and carbon dioxide. During this opposition, the south pole will be pointed at Earth as it will be summer in the southern hemisphere. The huge Martian southern polar ice cap will be rapidly shrinking as summer progresses there, and here on Earth also. It will be fascinating to watch the changes as the ice cap slowly sublimates and recedes as summer progresses. Mars has several dark and bright features that will be visible, provided there are no dust storms raging across the planet at the time. The darker, brownish areas are primarily dust-free rock outcrops with the largest and darkest being a wedge called Syrtis Major. Sinus Meridiani (Meridiani Planum) is where the Opportunity Rover landed in January 2004 and continues to explore. Solis Lacus is another prominent dark feature that looks like an eye and is often nicknamed the Eye of Mars. Hellas is a deep impact basin over 1000 miles across that is filled with very fine, highly reflective dust that can be confused for clouds, or the south polar ice cap. Mars demands extreme patience when it comes to observing; several nights of observing will train the eye to focus on detail. Larger telescopes will improve the view along with the use of orange or red filters. Mars will be low during this apparition as it will be in Capricornus and could be bothered by air turbulence and summer haze, but should improve as autumn approaches here on Earth. On the plus side, any haze could also act as a filter and provide a night of steady seeing.

The first row of diagrams that follow show a complete surface map of Mars with the most prominent features visible as well as the polar ice caps. Three different global views follow with the darkest and most prominent surface features shown. The dates in the third row indicate when these features will be nearly centered on Mars at 11PM EDT (10 PM EST). These provide views for a few hours either way or a few days around the given dates. Since Mars rotates on its axis in 24 hours and 37 minutes, these features will shift throughout the night. The rotation rate from Syrtis Major to Sinus Meridiani is six hours. From Sinus Meridiani to Solis Lacus is another six hours. If Solis Lacus is visible, then it will be another twelve hours before Syrtis Major returns to view. The fourth row indicates the change in size and brightness for Mars during this apparition.

The best time to observe Mars is when it is larger than 10 arcseconds across. This will occur from April 19 through November 22, which is nearly the longest possible for any apparition and will provide ample time to train the eye enough to make sketches or to take photos and video. The retrograde path of Mars among the stars from June 26 until August 27 can also be observed and plotted. Take note of the changing phases of Mars as it becomes noticeably gibbous by October with only 86% of its disc being lit by the Sun as seen from Earth.

Due to its very elliptical orbit, not all oppositions of Mars are good, but this one is the best we will get until 2035 as future oppositions will be increasingly further away. The next opposition on October 13, 2020 will also be an impressive 22.6 arcseconds across and should not be missed. So, make the best of every clear night this year and see what Mars has to offer for the amateur, professional, and public alike.