All eyes are on Mars this week. On Oct. 6 it will reach it's minimum distance from Earth of 38.6 million miles (62.1 million km) and shine incredibly bright, besting even mighty Jupiter. The two planets won't be this close again nor will Mars be as brilliant until September 2035. A week later on Oct. 13 Earth and Mars will be at opposition, precisely lined up together on the same side of the sun and only slightly less close.
Earth is the faster orbiting planet because it's closer to the sun, but Mars is also moving along its orbit, too. That's why it takes about two years for Earth to catch up to the Red Planet and pass it. The same way you enter the left lane of the freeway to pass a slower car, Earth pulls up alongside slower Mars this week and then passes it on the 13th.
All planets orbit the sun in slightly squished circles called ellipses, with the sun slightly off to one side of the ellipse. As the planet goes around its orbit, its distance and speed are constantly changing — faster when closer, slower when farther. If the orbit were a perfect circle distance and speed would never change. Earth's orbit is close to circular but not quite. Its distance from the sun varies by about 3 million miles. But Mars's orbit is considerably more eccentric (squished) with a distance that varies by almost 27 million miles.
When Earth passes Mars at opposition when the planet is farthest from the sun, Mars is bright but not overwhelming. However, when we lap the planet when it's closest to the sun, Mars is also much closer to the Earth and VERY bright. This special circumstance happens just once every 15 or 17 years. 2020 is one of those special years and the reason Mars is so prominent in the sky.
This is also the best time to observe the Red Planet in a telescope. Mars is the only planet in the solar system with readily visible surface features. Every other planet is either covered in clouds or, in the case of Mercury, too small and far away to make out anything.
Mars is different. With a 6-inch telescope you can see the most prominent dark markings like Syrtis Major (which just happens to be in view during evening hours this week for observers across the Americas), Mare Cimmerium, Sinus Sabeus, Sinus Meridiani and the South Polar Cap (SPC). The cap has a core of water ice topped by a layer of frozen carbon dioxide (dry ice). With summer underway in the Martian southern hemisphere much of that dry ice has vaporized, exposing the water ice cap to view. You'll be able to watch it shrink further in the coming weeks.
Meanwhile, it's winter in the northern hemisphere. Although the North Polar Cap is tipped out of view, the North Polar Hood, a great blanket of clouds that cover the polar region in winter, extends over the northern edge of the disk and looks like a bluish-white haze.
While Mars will show a disk the color of pink fire even in a small telescope you'll need to magnify it at least 100x (200x is better) to clearly see the markings I mentioned. Fortunately, the planet is much higher in the sky than the last time it was closest in 2018 and less affected by "bad seeing" caused by air turbulence. When it comes to increasing the contrast and visibility of dark surface markings a red filter such as a Wratten 23A or 25 is an excellent choice. You can buy eyepiece filters here.
For atmospheric details like occasional clouds or hazes along the eastern and western edges of the Martian disk use a blue filter or Wratten 80A. Given that dust storms are most common in spring and summer, there's always the chance that one will blow up in planet's southern hemisphere this month or next. Dust storms often reveal themselves by obscuring a surface marking that should otherwise be there. If you saw it one night, and it's smudged out a couple nights later, suspect a dust storm as the culprit. A yellow Wratten 8 filter will help you see them better.
Mars rotates once every 24.6 hours so it's helpful to know what side of the planet you're looking at when it's time to point your telescope. Just go to Sky & Telescope's Mars Profiler. When you open the page it will show you what part of Mars faces you at that moment, but you'll want to change the time to when you plan to be out. The profiler uses Universal Time, basically the same as Greenwich. To convert to local time subtract 4 hours for Eastern; 5 for Central; 6 for Mountain and 7 for Pacific.
For example, 3:00 UT (3:00 a.m. in the morning), Oct. 7 converts to 11 p.m. Eastern Time; Oct. 6; 10 p.m. Central Time; 9 p.m. Mountain and 8 p.m. Pacific. If you're confused or run into a problem just send me your question, and I'll be happy to help.
Whether or not you have a telescope you can still enjoy the planet's powerful presence in the night sky as well as its upcoming conjunctions with the moon on Oct. 29 and Nov. 25. If you enjoy photography consider including Mars in landscapes taken at night at dusk or in moonlight. You can also explore the planet in great detail using Google Mars or experience Mars up close in near-real time at NASA's Raw Images site, where fresh photos from the Curiosity rover are uploaded daily.
It's a shame that COVID-19 still rages or many local astronomy clubs would be sharing the planet at public observing nights.