Mohawk Valley Astronomical Society

Return to Newsletter Index

Red Planet Rival

by Perry Pezzolanella

An unusual star will blaze like a burning ember during the spring nights calling attention to it to all who wonder what it is. The burning ember of the night is Mars, returning better than it has been since 2005 with opposition on May 22, which means it will be up all night. Due to its highly elliptical orbit, it will be at its closest, largest, and brightest on May 30. On that date Mars will be 46.8 million miles from Earth and 18.6 arcseconds across, burning ruddily at magnitude -2.1.

Mars is interesting to observe because it 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 neither pole will be pointed at Earth as it will be autumn in the northern hemisphere and spring in the southern hemisphere. The huge southern polar ice cap will be better seen as summer progresses here on Earth and it will be fascinating to watch the changes as the ice cap slowly sublimates and recedes as summer approaches there. 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 very low during this apparition as it will be in Scorpius and could be bothered by air turbulence and summer haze, but an excellent chance to compare its hue with its rival, Antares. The 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 11 PM EDT. 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 March 15 through September 8, which 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 April 17 until June 29 can also be observed and plotted. Take note of the changing phases of Mars as it becomes noticeably gibbous by August with only 85% 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 in over a decade and it only gets better. The next opposition on July 27, 2018 is the best since 2003 and until 2035 at 24.3 arcseconds across. The opposition of October 13, 2020 will also be an impressive 22.6 arcseconds across. Intense exploration of Mars continues as it is the only world besides the Moon where mankind can hope to settle, so make it an evening and see what Mars has to offer for the eyes, sketchpad, camera, and most of all, the imagination.