Mohawk Valley Astronomical Society

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Red Planet Beckons

by Perry Pezzolanella

A dazzling, tiger-hued star will beckon during the cooler late summer nights and chilly autumn evenings as Mars returns for another outstanding opposition almost as good as the one in 2018, but in many ways, even better. Opposition occurs on October 13, which means it will be up all night, rising at sunset and setting at sunrise. Due to its highly elliptical orbit, it will be at its closest, largest, and brightest on October 6. On that date, Mars will be 38.57 million miles from Earth and 22.6 arcseconds across, blazing at magnitude -2.6. 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 being composed of highly reflective 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 southern polar ice cap will have shrunk to nearly its smallest as summer will be at its peak. It is always interesting to watch the changes in the ice cap to see how small it will get. 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. Another, Meridiani Planum, was explored by the Opportunity Rover from 2004-2018, and Solis Lacus, looking like a dark eye, is often nicknamed the Eye of Mars. Bright Hellas, on the other hand, 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 higher in the sky in Pisces compared to the last apparition in 2018 and will not be bothered as much by air turbulence. The clear autumn nights may make for a truly memorable apparition if seeing is steady and sharp. 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 June 11 through January 4, which is one of 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 September 9 until November 14 can also be observed and plotted. Take note of the changing phases of Mars as it becomes noticeably gibbous by the end of the year with only 89% of its disc being lit by the Sun as seen from Earth. Due to its very elliptical orbit, not all oppositions of Mars are favorable, but this is one of the better ones we will see until 2033 as future oppositions will find Mars increasingly farther away. The next opposition on December 7, 2022 will be noticeably smaller at 17.2 arcseconds across. Therefore, answer the call of Mars and take advantage of every clear night this year to see what it has to offer.