7

Certainly among the first colonists on Mars there will be a few people interested in Astronomy enough to enjoy the night sky.

For them, familliar Mars will be missing and there will be a new, unfamiliar planet instead.

Planet by planet, how will their appearance and especially their behavior as seen from Mars differ from the way they behave in the night sky as seen from Earth?

uhoh
  • 31,151
  • 9
  • 89
  • 293
  • 1
    Companion question in Space Exploration SE: What will shooting stars look like on Mars? – uhoh May 04 '18 at 06:55
  • 1
    You're only going one planet further out so broadly, Earth would 'behave' like Venus but apart from that, what are you asking about? Their motions across the sky? Phases? If they'd be easier / harder to observe? –  May 04 '18 at 07:36
  • 2
    @Kozaky I've written over 1,000 SE questions and I've found that in some cases it's best not to over-constrain a question or spell out exactly the form of the answer ahead of time. You are welcome to post your comment as an answer, but if you just give this a day or two I think you'll find that someone will post an excellent and informative answer to the question in its current form. I think this will be a fun question to answer as-is. – uhoh May 04 '18 at 07:56
  • @Kozaky but to address your comment more directly, yes, those would indeed be important parts of an answer. – uhoh May 04 '18 at 08:09
  • 1
    Currently I would only think of answering with "They'd 'behave' more-or-less the same as they do from Earth", which reads as a broad answer to a broad question. That's just why I was asking if there was anything more specific. –  May 04 '18 at 08:49
  • 1
    Martian analemma is odd: https://apod.nasa.gov/apod/ap030626.html So planets might move a bit different than as seen from earth as well. – Wayfaring Stranger May 04 '18 at 17:19
  • 1
    Ask Jean Meeus. ;) FWIW, there's a classic old sci-fi story titled Transit of Earth by Clarke about observing such a transit from Mars on 11 May 1984. – PM 2Ring May 04 '18 at 21:55
  • @WayfaringStranger that's extremely interesting! I hope that link and it's image finds its way into an answer here! – uhoh May 05 '18 at 03:49
  • @PM2Ring Thank you for that! it turns out there's a YouTube video with a recording of Sir Clarke himself reading Transit of Earth. It's quite a thrill hearing the master narrate the event. Thank you very much for your comment! https://www.youtube.com/watch?v=csxT8Y9MaSs Also see When will the next transit of Earth be visible from Mars? Was the last one really on May 11, 1984? – uhoh May 05 '18 at 07:43
  • No worries. By sheer coincidence I re-read Transit of Earth only a few weeks back. I have a whole bunch of old scifi books and mags that were in storage at my parents' place for several decades that I "rediscovered" last year. – PM 2Ring May 05 '18 at 08:34
  • @WayfaringStranger I suppose the funny analemma is due to the Martian orbit being much more eccentric than ours. Its axial tilt is only a degree or so more than ours, so that shouldn't make a noticeable difference, but on a related note there's the solstices vs perihelion / aphelion issue to consider. – PM 2Ring May 05 '18 at 08:41
  • 1
    If you just need positions/"orbits", a planetarium program like Stellarium will work. Stellarium aims to be photorealistic, but I'm not sure how accurate it is for a Martian atmosphere. –  May 05 '18 at 16:43
  • @barrycarter I try to ask questions for which the answer will be interesting to (at least some) other readers. Sitting in a dark room running Stellarium all by myself isn't fun. However, that's a great recommendation for someone interested in posting an answer! – uhoh May 05 '18 at 17:02
  • Jupiter would be a little brighter, but probably not as bright as Earth. Earth, I think, would be visibly blue and follow a pattern similarity to Venus, never moving very far from the sun, so it would be a morning or evening planet. Venus, even more so and it would be visible quite briefly depending on sunsets of-course. Almost no atmosphere and stars are visible even when the sun is out. Ultimately I think this question is too probably too broad, each planet would need it's own description if you want details. – userLTK May 05 '18 at 18:52
  • 1
    @userLTK I've just left this comment. I'll still answer myself if nobody else bites. – uhoh May 06 '18 at 02:33
  • 1
    "Sitting in a dark room running Stellarium all by myself isn't fun". We lead very different lifestyles. –  May 06 '18 at 16:30
  • @barrycarter why not take advantage of our "heavenly symmetry" then? If you enjoy running Stellarium and it can view the planets from Mars, a few screen shots might be an excellent and accepted answer! – uhoh May 07 '18 at 03:20
  • Is Celestia unable to do what you want? I've just parked my viewpoint on 10 km over Lat 0, Long 0 on Mars, followed and centered the Sun and watched the inner planets mill around for a few hundred million seconds – Eric Towers Apr 28 '20 at 21:20
  • @EricTowers if you'd like to write up what you saw as it addresses "...Planet by planet, how will their appearance and especially their behavior as seen from Mars differ from the way they behave in the night sky as seen from Earth?" then that would be a good answer to this question and of great interest to future readers, thanks! (e.g. planet W's motion was similar to what we see on Earth except that it moves faster/slower, Earth goes retrograde every X years, planet Y is Z magnitudes brighter/dimmer, etc.) – uhoh Apr 28 '20 at 21:23
  • 1
    Related to this question: Is there an online planetarium where the observer is on another celestial body? – Fred Apr 29 '20 at 01:31

2 Answers2

3

Celestia may do what you want.

Summary to "Planet by planet, how will their appearance and especially their behavior as seen from Mars differ from the way they behave in the night sky as seen from Earth?"

  • Mercury and Venus are very similar. I don't observe retrograde motion in these planets or Earth.
  • Earth: wildly different. It seems much farther away and dimmer.
  • Mars: wildly different. It seems much closer and brighter.
  • Jupiter and other outer planets: very similar. These mostly creep across the field of distant stars near the ecliptic. Periods are closer to a Martian year than a calendar year. If you track (described below) an outer planet, you can observe its retrograde motion. For instance Jupiter turns retrograde in March 2069 and does not turn prograde until October 2069.

To see that for yourself...

In Celestia 2.7, pick your viewpoint. Let's pick the center of Mars, at latitude 0, longitude 0, altitude 0 km.

(menu)Navigation | Go to Object...
Object Name:  Mars
Latitude:  0
Longitude:  0
Distance: 0
km

setting our target on Mars

Now sometimes the texture wrapped on Mars is visible and we don't want that getting in the way, so let's make Mars invisible.

hiding Mars

While we're here, let's also pick "Follow" so that Mars will not leave us behind when we speed up time.

Now we need to find the Sun.

Celestial Browser | (tab)Solar System |
(item) Solar System Barycenter | 
(subitem) Sol | (context menu) Center

center

If we speed up time now, we will be at the center of Mars, always pointed in the same direction (relative to the distant stars), so every Martian year, the Sun will roll back through our field of view. We need to track the Sun. Click on the Sun in the starfield, which will highlight it with four red arrowheads. Then type "T" (the capital letter "T"), which will set us to track Sol.

Now let some time pass. Rather a lot of time. Maybe raise the rate to between 1e+06 and 1e+08 -times faster so some of the outer planets will wander in among the inter planets.

(menubar)Time | (button) 10x faster

(repeat as needed).

It can be helpful to have visible coordinate systems. In my screenshots, the "Ecl" (ecliptic line) is shown, using the toggle on the (menubar)Guides.

You may notice that Mercury's orbit doesn't quite fit in the field of view (shown in the lower-right corner, together with out "Track Sol" and "Follow Mars" conditions). You can narrow the field of view by typing comma, ",", and widen it by typing period, ".". A FOV of 70-ish degrees seems to keep the inner planets in view at all times.

enter image description here

The easiest way to track an outer planet seems to be to wait until the one you want passes Sol, click on it to Select it (which takes focus away from the Celestial Browser, which does not happen if you use the Celestial Browser to Select the planet), then "T" to track it. Retrograde motion should be during periods when the distance to the planet is near minimal.

Eric Towers
  • 171
  • 5
  • Thanks for your tutorial! I think this is a work in progress, if you can add a tl;dr at some point specifically addressing "...Planet by planet, how will their appearance and especially their behavior as seen from Mars differ from the way they behave in the night sky as seen from Earth?" that would be great! – uhoh Apr 28 '20 at 22:27
  • 1
    @uhoh : Some comments added. Not entirely sure what would be a compact characterization of "behaviour". – Eric Towers Apr 28 '20 at 22:44
  • Well wouldn't Mercury and Venus remain a lot closer to the Sun? (also see 1, 2) Wouldn't their synodic periods and times between moving form "morning stars" to "evening stars" be substantially different (3, 4, 5)? Would we see a lot more "lunar" occultations of planets? – uhoh Apr 28 '20 at 22:53
  • 1
    @uhoh : Seems likely. I'm unlikely to measure these things... – Eric Towers Apr 28 '20 at 22:54
  • synodic period is gotten from algebra, maximum elongation from trigonometry; these don't need fancy programs and texture wrappers necessarily – uhoh Apr 28 '20 at 23:00
  • in the mean time, you might be able to post an additional answer to Is there an online planetarium where the observer is on another celestial body? oh, perhaps not; Celestia is not an "online program", rats. – uhoh Apr 28 '20 at 23:11
  • 1
    I like that you included Earth and Mars. You might like to add that you need to look down rather than up to see Mars and vice versa for Earth. – badjohn Apr 30 '20 at 08:06
2

This should be a relatively simple problem to solve - which is the Academician's way of saying "do it as a homework problem" :-) .

First thing: find some celestial mechanics calculator and determine when each outer and inner planet is visible in Mars' night sky. That gives you timings.

Next thing: compare the distance from each outer planet to Mars vs. Earth. Maybe start with closest and farthest approach as examples. That'll tell you both the angular extent of the planet as well as the relative brightness compared with Terran observations. Don't forget to add a fudge factor for the atmosphere.

In fact, probably the most obvious difference will be that stars no longer twinkle. (yeah I'm ignoring during serious dust storms). You could use a wicked large primary and have no need of adaptive optic corrections.

BTW there are photos of Earth as seen by the Mars rovers (or maybe just the surveying satellites, I forget) so you can get an idea of the color/features available.

Carl Witthoft
  • 3,813
  • 1
  • 13
  • 17
  • 1
    After thinking about userLTK's comment a while I'm beginning to think the question is indeed too broad for this site. One way to fix would be to ask only about Earth's appearance from Mars, as it would contain all of the necessary science and math to address the other planets later. Since you've already posted an answer, I'd like to ask if you would be OK with me making that change? – uhoh May 06 '18 at 02:32
  • 1
    @uhoh sure, or you could just post a new question on that specific topic. – Carl Witthoft May 07 '18 at 11:21