Mars The Opposition of Mars
14 October 2020

Image created from http://space.jpl.nasa.gov/
For animation (0.4 Meg) click here


Mars, the red planet, holds a great fascination for humans. Associated with the God of War, this fascinating world has been the subject of endless speculation on whether life once inhabited it. Currently a bevy of spacecraft are circling its frigid and arid surface taking detailed images and probing Mars's atmospheric composition. They will be joined by three new spacecraft which will investigate Mars's atmosphere further as well as subsurface composition and look for past life. The robot explorer Opportunity which ranging over Mars's surface for for 14 years was lost in the 2018 global dust storm. The Mars rover Curiosity now has 8 years of exploring the red planet. Curiosity will be joined by the Perseverance rover and its helicopter and the Tianwen-1 Lander and rover. The search for evidence of life on Mars and a possible sample return makes this oppositions missions very exciting.

Mars Facts:
Diameter: 6794 km
Moons: 2, Phobos and Demios (Fear and Terror)
Year: 687 days
Day: 1.026 Earth days
Mass: 0.107 Earth Mass (0.64 x1024 Kg)

This year is a good opposition of Mars. Not as good as the opposition of 2018, or the Great Opposition of Mars in 2003, But there won't be a better one one until 2033. This year is a great opportunity for people to observe this fascinating world. What is an opposition? Opposition refers to when a planet is opposite the Sun in the sky. This can only happen to outer planets, as Earth must pass between the Sun and the planet. The Earth passes Mars in its orbit every 26 months, and at this time we get a good view of the Red Planet.

When Mars is also making its closest approach to the Sun, our view is very good indeed. While Mars is on average 228 million km from the sun, due to Mars's elliptical orbit this varies by 42 million kilometers. If Mars is at its furthest from the Sun at opposition, Mars is also around 99 million km from Earth, while if Mars is at its closest to the Sun during opposition, this value narrows to only 57 million km. Favorable oppositions occur only once in every 15 to 17 years. During the Great Opposition of 2003, Mars and Earth were a mere 55.8 million km apart. This degree of closeness will not be achieved again until 2287. This year, Mars and Earth will be a decent 63 million km (0.42 AU) apart.

Oppositions in the early months of the year, when Mars is furthest from the Sun, are always poor. The best oppositions occur around August. This is very good for Southern observers, as Mars is high in the sky, and the winter sky is usually still and transparent, ideal conditions for watching Mars. This years opposition occurs during October. Mid-Spring is not as ideal as winter, nonetheless the conditions are still good for Southern Observers. The cool nights makes warm clothes a must, but atmospheric turbulence is low and skies are likely to be very clear, making Mars's markings easier to distinguish. The visible disk of Mars increases in diameter, from 5 arc seconds, to 22.3 arc seconds (an arc second is approximately 1/3600th of your finger-width). While this sounds astoundingly small, 22.33 arc seconds will give a significant disk in most amateur telescopes, even the small ones from Tasco. Mars will be 1/76 th of the diameter of the Moon, about 2/3 the diameter of Jupiter and about the 1/3 rd bigger than the diameter of Saturn (Saturn itself, not the ring system, which is larger) This year, the Opposition (October 14) is later than the closest approach of Mars to Earth (October 7), so the best views will actually be on the days around October 7th.

What you can expect to see

Unaided eye. The best observing will be from mid September to late October. At opposition Mars rises around sunset, so Mars is best observed from around two hours after Sunset or roughly 7:30 pm daylight saving time (6:30 pm standard) time for most of this period. Mars is the brightest object in the sky aside from the Sun, Moon or Venus (visible Only in The morning sky). Mercury, Jupiter Saturn and Mars are visible in the early evening sky from late September to mid-October, but Mars's distinctive red colour and north-easterly makes it easy to identify. Bright Mercury is low in the west, Bright yellow Jupiter is only a bit dimmer than Mars and Saturn are together in the north west, so spotting Mars is quite easy. If you are still having trouble locating Mars, on October 2 and 3 The Full Moon is close to Mars. From the 15th September to early October Mars is in the east at 10 pm local time. At opposition Mars is a bit over three hand-spans above the eastern horizon at astronomical twilight (and hour and a half after sunset)as seen from Melbourne (when your hand is held out flat, thumb in, with your arm outstretched, your hand covers 6 degrees of sky, see diagram at right, people in the rest of Australia will see Mars at a roughly similar height at astronomical twilight.

Mars is in the undistinguished constellation of Pisces the Fish. At opposition Mars is not near anything particularly interesting except the variable star Mira, which may be still bright then. It will head towards the beautiful cluster the Pleiades in February 2021, then on to Taurus. Mars is in retrograde motion at the moment, and occurs due to Earth overtaking Mars in its orbit. A map showing this motion is here.

Mars_Opposition _14-10-20_2057.png
Evening sky on Wednesday 14 October (the night of opposition) looking east as seen from Adelaide at astronomical twilight, 90 minutes after sunset (20:57 ACDST). Mars is close to The variable star Mira, which should be still bright enough to see with the unaided eye. The inset shows the telescopic view of Mars. Similar views will be seen elsewhere in Australia at the equivalent local time (90 minutes after sunset). (click to embiggen).

Binoculars Mars is a barely visible disk on the days around closest approach with 10 x 50 binoculars and larger (although markings will not be seen with standard binoculars).

Telescopes The best time to observe Mars is when it is highest in the sky, unfortunately this occurs well after midnight for a large proportion of best viewing times, and not long after midnight for the rest. Be prepared for some late nights if you want the best telescopic views (see the Ephemeris below, Transit times are when Mars is highest).

Mars shows clearly visible markings in a 50 mm refractor telescope, and significant detail can be seen in a 4" reflector, while 6" and 8" instruments will give better detail still. However, be aware that large dust storms may erup, and for the 2018 Opposition Mars was afeatureless ball for a lot of the time. No current Earth-bound telescope can reveal the huge volcano, Mons Olympus (other than a faintish darker spot on the surface), or the huge valley of Vale Marensus, which are seen in many of the spacecraft images. However, significant features such as Syrtis major (featured in the Masthead graphic) will be visible in even a small telescope. The Martian day is about 40 minutes longer than the Earth day, so if you observe at the same time each night, you can see the surface features rotating into and out of view. Dust storms can also occur, sometimes lasting days (as I mentioned above). Wind removal and deposition of the reddish, iron rich dust can also reveal or obscure features, so Mars's appearance can be somewhat different between each opposition. Seasonal winds alternately covering and uncovering darker features with lighter dust were once interpreted as seasonal plant growth. Studying the Martian storms and the changing surface features is a valuable amateur activity.

In the May 2001 issue of SKY & TELESCOPE (pages 115 to 123), Thomas Dobbins and William Sheehan discussed rare historical observations of bright, star-like flares from certain regions on the planet Mars. They suggested that the flares might be caused by specular reflections of sunlight off water-ice crystals in surface frosts or atmospheric clouds, specifically at times when the sub-Sun and sub-Earth points were nearly coincident and near the planet's central meridian (the imaginary line running down the center of the visible disk from pole to pole). In 2001 flashes were seen by observers in the US in Edom Promontorium, near the Martian equator.

So mid September to late October is an excellent time to dust off that old telescope lying around in the garage, or to beg a view from a friend or neighbour with a telescope. Better yet, many astronomical clubs hold open nights, and this is an excellent opportunity to see this fascinating world in a decent telescope. Also, some of the local planetariums may be showing off Mars if they have telescopes (See the Links section for addresses).

For recording the appearance of Mars, all you need is a sheet of paper on a sturdy background, a pencil (or coloured pencils if you want to try recording the colors you see), a small torch covered in red cellophane and a watch. Make sure you and your telescope are located in a relatively dark place, and have modest circles pre-drawn on your paper (I use a 20 cent piece or my telescope eyepiece cap). Have your telescope out for a while beforehand so that it is at ambient temperature, to prevent air currents in the telescope from ruining the image. Record the date and time, and the weather (if it is windy, how much cloud, how much moonlight, what is the dimmest star you can see, etc.). Make sure you are wearing warm clothing, then make yourself comfortable at the eyepiece, preferably with a chair that allows you to sit and view comfortably, and, well, start drawing. It may take a few tries before you get the hang of recording what you see by red light, but you will feel a warm glow of accomplishment when you can. The Ephemeris below gives the time Mars rises, its magnitude, and its altitude at midnight (5 degrees is equivalent to the distance covered by an outstretched hand), and its apparent diameter in arc seconds. For comparison the Moon is 1921.59 arc seconds across and Jupiter is currently 38.9 arc seconds across.

If you have a mobile phone, and a decent sized telescope, you may be able to snap images of Mars with your phone, there are now a variety of mobile phone attachments for holding phones to a telescopes eyepiece. Setting the phones camera app so that you see something other than a tiny overbright dot will require some experimentation.


Ephemeris of Mars
 	
Date      Altitude		Mag	Diam " Distance		Rise Time 	Transit    
             at Midnight                	(AU)      	(ACST)    	(ACST)

15-Sep-20	+35 22' 27"	-2.1	20.86	0.4486003	20:42:17	2:29:07
16-Sep-20	+36 01' 22"	-2.2	21.0	0.4457861	20:37:57	2:24:52
17-Sep-20	+36 40' 19"	-2.2	21.13	0.4430752	20:33:33	2:20:34
18-Sep-20	+37 19' 16"	-2.2	21.25	0.4404709	20:29:05	2:16:12
19-Sep-20	+37 58' 08"	-2.2	21.37	0.4379764	20:24:33	2:11:48
20-Sep-20	+38 36' 52"	-2.3	21.49	0.4355949	20:19:58	2:07:19
21-Sep-20	+39 15' 23"	-2.3	21.6	0.4333293	20:15:19	2:02:48
22-Sep-20	+39 53' 38"	-2.3	21.71	0.4311826	20:10:36	1:58:14
23-Sep-20	+40 31' 30"	-2.3	21.81	0.4291574	20:05:49	1:53:36
24-Sep-20	+41 08' 55"	-2.3	21.91	0.4272564	20:01:00	1:48:56
25-Sep-20	+41 45' 49"	-2.4	22.0	0.4254819	19:56:07	1:44:12
26-Sep-20	+42 22' 05"	-2.4	22.08	0.4238366	19:51:10	1:39:26
27-Sep-20	+42 57' 38"	-2.4	22.16	0.4223227	19:46:11	1:34:37
28-Sep-20	+43 32' 22"	-2.4	22.24	0.4209427	19:41:09	1:29:46
29-Sep-20	+44 06' 12"	-2.4	22.3	0.4196988	19:36:05	1:24:52
30-Sep-20	+44 39' 01"	-2.5	22.36	0.4185934	19:30:57	1:19:55
01-Oct-20	+45 10' 42"	-2.5	22.41	0.4176287	19:25:48	1:14:57
02-Oct-20	+45 41' 11"	-2.5	22.46	0.4168069	19:20:36	1:09:56
03-Oct-20	+46 10' 19"	-2.5	22.49	0.4161302	19:15:22	1:04:54
04-Oct-20	+46 38' 01"	-2.5	22.52	0.4156007	19:10:06	0:59:50
05-Oct-20	+47 04' 11"	-2.5	22.54	0.4152205	19:04:49	0:54:44
06-Oct-20	+47 28' 42"	-2.5	22.55	0.4149915	18:59:30	0:49:37
07-Oct-20	+47 51' 29"	-2.6	22.56	0.4149156	18:54:10	0:44:28
08-Oct-20	+48 12' 25"	-2.6	22.55	0.4149947	18:48:49	0:39:18
09-Oct-20	+48 31' 24"	-2.6	22.54	0.4152304	18:43:28	0:34:08
10-Oct-20	+48 48' 23"	-2.6	22.52	0.4156244	18:38:05	0:28:56
11-Oct-20	+49 03' 16"	-2.6	22.49	0.4161782	18:32:42	0:23:44
12-Oct-20	+49 15' 58"	-2.6	22.45	0.4168930	18:27:20	0:18:32
13-Oct-20	+49 26' 28"	-2.6	22.4	0.4177701	18:21:57	0:13:19
14-Oct-20	+49 34' 40"	-2.6	22.35	0.4188106	18:16:35	0:08:07
15-Oct-20	+49 40' 34"	-2.6	22.28	0.4200152	18:11:13	0:02:54
16-Oct-20	+49 44' 08"	-2.6	22.21	0.4213846	18:05:52	23:52:31
17-Oct-20	+49 45' 21"	-2.6	22.13	0.4229191	18:00:32	23:47:20
18-Oct-20	+49 44' 12"	-2.5	22.04	0.4246187	17:55:14	23:42:11
19-Oct-20	+49 40' 43"	-2.5	21.95	0.4264830	17:49:57	23:37:03
20-Oct-20	+49 34' 55"	-2.5	21.84	0.4285113	17:44:42	23:31:56
21-Oct-20	+49 26' 51"	-2.5	21.73	0.4307027	17:39:29	23:26:50
22-Oct-20	+49 16' 33"	-2.5	21.61	0.4330561	17:34:18	23:21:47
23-Oct-20	+49 04' 05"	-2.4	21.49	0.4355700	17:29:09	23:16:45
24-Oct-20	+48 49' 31"	-2.4	21.36	0.4382429	17:24:04	23:11:45
25-Oct-20	+48 32' 56"	-2.4	21.22	0.4410733	17:19:00	23:06:47
26-Oct-20	+48 14' 24"	-2.3	21.08	0.4440595	17:14:00	23:01:52
27-Oct-20	+47 54' 01"	-2.3	20.93	0.4471997	17:09:02	22:56:59
28-Oct-20	+47 31' 52"	-2.3	20.78	0.4504922	17:04:08	22:52:08
29-Oct-20	+47 08' 04"	-2.3	20.62	0.4539351	16:59:17	22:47:20
30-Oct-20	+46 42' 41"	-2.2	20.46	0.4575265	16:54:29	22:42:34
31-Oct-20	+46 15' 50"	-2.2	20.29	0.4612646	16:49:44	22:37:52
01-Nov-20	+45 47' 36"	-2.1	20.12	0.4651474	16:45:03	22:33:12
02-Nov-20	+45 18' 05"	-2.1	19.95	0.4691730	16:40:25	22:28:34
03-Nov-20	+44 47' 23"	-2.1	19.77	0.4733395	16:35:51	22:24:00
04-Nov-20	+44 15' 35"	-2.0	19.6	0.4776449	16:31:20	22:19:28
05-Nov-20	+43 42' 46"	-2.0	19.42	0.4820873	16:26:53	22:15:00
06-Nov-20	+43 09' 02"	-2.0	19.23	0.4866647	16:22:30	22:10:34
07-Nov-20	+42 34' 27"	-2.0	19.05	0.4913753	16:18:11	22:06:11
08-Nov-20	+41 59' 07"	-1.9	18.86	0.4962171	16:13:55	22:01:51
09-Nov-20	+41 23' 06"	-1.9	18.68	0.5011881	16:09:43	21:57:35
10-Nov-20	+40 46' 27"	-1.9	18.49	0.5062864	16:05:34	21:53:21
11-Nov-20	+40 09' 15"	-1.8	18.30	0.51151		16:01:30	21:49:11
12-Nov-20	+39 31' 34"	-1.8	18.11	0.5168569	15:57:29	21:45:03
13-Nov-20	+38 53' 28"	-1.8	17.92	0.5223249	15:53:32	21:40:59


These values are for Adelaide, not corrected for daylight saving time. Rise and transit times will be similar in other cites at the same local time. Transit times are when Mars transits the meridian, and is at its highest point in the sky. At transit, Mars will be almost at the zenith (the highest point above the horizon)in the north (well, basically almost straight up).



Here are some links to Mars sites of interest:


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Created: Saturday, 21 May 2016, 11:22:32
Last Updated: Saturday, 12 September 2020, 11:22:32