Behold Mars! Red Planet Closest and Brightest Until 2035

Mars leaves a bright glitter path on Lake Superior near Duluth, Minn. on a recent night. Bob King

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.

When the faster Earth laps Mars every couple years, the two planets come closest and Mars is said to be at opposition. It lies directly opposite the sun in the sky — rising at sunset and setting at sunrise — and remains visible all night. Due to Mars's more strongly elliptical orbit (see below) some oppositions, like the current one, are closer than others. The closest are called perihelic while distant ones are aphelic. NASA

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. 

A planet's (black dot) distance and speed constantly changes as it orbits the sun in an ellipse. Earth's elliptical orbit brings it about 3 million miles closer to the sun in January compared to July. Wikimedia Commons / CC BY-SA 4.0

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. 

This amazing image of Mars, made on Sept. 30, reveals much detail. Most obvious are the South Polar Cap and the dark, Africa-shaped surface feature called Syrtis Major. Syrtis Major is an extinct shield volcano rich in dark-colored basalt rock. The pale orange, vaguely circular feature above Syrtis is Hellas, the largest impact basin on the planet with a diameter of 1,400 miles (2,300 km). South is up. Damian Peach

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.

The residual, water-ice South Polar Cap photographed from orbit on Feb. 25, 2015 by the Mars Express space probe. ESA / DLR / FU Berlin / CC BY-SA 3.0 IGO

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. 

I've labeled some of the most prominent telescopic features to look for on Mars. CM stands for central meridian and is explained below. Damian Peach (top left, right); Mark Schmidt (top middle); Chris Go (bottom left) and Anthony Wesley (bottom middle and right).

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.

This map of Mars will help telescopic observers identify features on the planet. South is up. The numbers across the top are longitudes. The best time to see a particular region is when its longitude crosses the central meridian (CM), an imaginary line that runs from pole to pole across the center of the disk. We view anything on the CM square on. ALPO / Daniel Troiani

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 the 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. 

As the faster Earth overtakes Mars around opposition the Red Planet appears to slow down and then move in reverse (westward) across the sky before resuming its normal or prograde motion on November 15. If you note the position of Mars in relation to stars near it and observe it once a week, you'll see this loop — over time — with you own eyes. Socrates Linardos CC SA 4.0 International with additions by the author

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.  


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