# What would it take for a Martian to see The Moon? **URL:** \ **Category:** Factual Questions\ **Created:** [July 3, 2002, 8:42pm UTC](https://boards.straightdope.com/t/what-would-it-take-for-a-martian-to-see-the-moon/117248 "2002-07-03T20:42:23Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Earl\_Snake-Hips\_Tucker](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/earl_snake-hips_tucker/32/3269_2.png) [@Earl\_Snake-Hips\_Tucker](https://boards.straightdope.com/u/Earl_Snake-Hips_Tucker)\ **Post date:** [July 3, 2002, 8:42pm UTC](https://boards.straightdope.com/t/what-would-it-take-for-a-martian-to-see-the-moon/117248/1 "2002-07-03T20:42:23Z")
Would a good pair of binoculars be enough to see it, or would he have to fire up the Illudium Q-36 Space Modulator? Could it be seen in some fashion with just a naked eye from the Martian surface? ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [July 3, 2002, 9:19pm UTC](https://boards.straightdope.com/t/what-would-it-take-for-a-martian-to-see-the-moon/117248/2 "2002-07-03T21:19:27Z")
I would wag here that he could see it unaided. Mars and the moon are fairly simular in size and me thinks the moon is more reflective then mars. Also due to mars being farther from the sun and mars is generally dimmer then the earth I would expect a martain to have a keen sense of sight adapted to low light conditions. There would also be less light scattering effect due to the thin martian atmosphere. ---
**Author:** ![Boyo\_Jim](https://avatars.discourse-cdn.com/v4/letter/b/87869e/32.png) [@Boyo\_Jim](https://boards.straightdope.com/u/Boyo_Jim)\ **Post date:** [July 3, 2002, 10:21pm UTC](https://boards.straightdope.com/t/what-would-it-take-for-a-martian-to-see-the-moon/117248/3 "2002-07-03T22:21:48Z")
There are times when the moon would be all the way over on the far side of the sun from Mars. I doubt you could see it then without something pretty powerful. But maybe Martions have 200x eyesight. Anybody know how close Earth and Mars are at closest approach? ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [July 3, 2002, 10:41pm UTC](https://boards.straightdope.com/t/what-would-it-take-for-a-martian-to-see-the-moon/117248/4 "2002-07-03T22:41:28Z")
> [@](#): > > \*Originally posted by Mjollnir \* > \*\*Would a good pair of binoculars be enough to see it, or would he have to fire up the Illudium Q-36 Space Modulator? Could it be seen in some fashion with just a naked eye from the Martian surface? \*\* I agree with **k2dave**. The moon and Mars would be separated by about 17 min. of arc at Mars’ closest approach and with two bright objects against a dark background the eye’s resolution is better than that. According to the site [eye’s resolving power](http://www.stardustgallery.com/page9.htm), the human eye can resolve down to about 6 min. of arc. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [July 3, 2002, 11:06pm UTC](https://boards.straightdope.com/t/what-would-it-take-for-a-martian-to-see-the-moon/117248/5 "2002-07-03T23:06:46Z")
```auto Diameter (km) Albedo (fraction of light reflected) Moon 3476 0.07 Mars 6788 0.16 Earth 12756 0.3-0.5 ``` The moon is much dimmer than earth. See the[picture on this page](http://space.jpl.nasa.gov/samples.html). This [Solar System Simulator](http://space.jpl.nasa.gov/) will let you see what Earth and the Moon would look like from Mars. Unfortunately it doesn’t say how bright things would be. ---
**Author:** ![Triskadecamus](https://avatars.discourse-cdn.com/v4/letter/t/b19c9b/32.png) [@Triskadecamus](https://boards.straightdope.com/u/Triskadecamus)\ **Post date:** [July 3, 2002, 11:18pm UTC](https://boards.straightdope.com/t/what-would-it-take-for-a-martian-to-see-the-moon/117248/6 "2002-07-03T23:18:56Z")
The Moon would be in it’s dark phase, with respect to Mars, at the time when they were closest, (conjunction) and full at the time when they were farthest (opposition). It would also be in the daylight sky, or the very early evening, or late pre dawn hours for most of the period of closest approach. Earth would have an essentially identical phase to the Moon, as well. The answer is a bit more complicated than it at first appears. We better wait for a real astronomer, or a real Martian. ## Tris “Reserve your right to think, for even to think wrongly is better than not to think at all.” ~ Hypatia of Alexandria ~ ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [July 4, 2002, 1:37am UTC](https://boards.straightdope.com/t/what-would-it-take-for-a-martian-to-see-the-moon/117248/7 "2002-07-04T01:37:59Z")
IAAA (I am an astronomer) and I agree with **k2dave** et al. Of course, as **Triskadecamus** said, you can’t see the earth when it’s closest to Mars because it’d be lost in the glare of the sun. But even when the two planets are 90 degrees away in their orbits, the earth/moon pair appears 5 arcminute apart. With a 7x magnification on a typical pair of binoculars, you can bring them 0.5 degrees apart, or about the diameter of the moon as seen from the earth. I’m sure the moon is bright enough to see - it would only be a couple of magnitudes dimmer than Mars looks from Earth. ---
**Author:** ![Bryan\_Ekers](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bryan_ekers/32/183_2.png) [@Bryan\_Ekers](https://boards.straightdope.com/u/Bryan_Ekers)\ **Post date:** [July 4, 2002, 3:05am UTC](https://boards.straightdope.com/t/what-would-it-take-for-a-martian-to-see-the-moon/117248/8 "2002-07-04T03:05:55Z")
You could defintely see the moon as a small dark spot near a large dark spot (the Earth) when the Earth/Moon system passed between the sun and Mars. You’d have to apply a filter to dampen most of the sun’s light, though it wouldn’t have to be nearly as thick, since the sun is considerably dimmer from Mars than from Earth. Similar technique was used to prove the existance of Pluto’s moon, Charon. Pluto appeared to pass near a distant star. Pluto “missed” but the star briefly blinked out, giving evidence for a satellite. ---
**Author:** ![Tars\_Tarkas](https://avatars.discourse-cdn.com/v4/letter/t/6a8cbe/32.png) [@Tars\_Tarkas](https://boards.straightdope.com/u/Tars_Tarkas)\ **Post date:** [July 4, 2002, 3:19am UTC](https://boards.straightdope.com/t/what-would-it-take-for-a-martian-to-see-the-moon/117248/9 "2002-07-04T03:19:29Z")
Why would i want to see your moon? We got two of our own!!! ---
**Author:** ![Duck\_Duck\_Goose](https://avatars.discourse-cdn.com/v4/letter/d/50afbb/32.png) [@Duck\_Duck\_Goose](https://boards.straightdope.com/u/Duck_Duck_Goose)\ **Post date:** [July 4, 2002, 3:21am UTC](https://boards.straightdope.com/t/what-would-it-take-for-a-martian-to-see-the-moon/117248/10 "2002-07-04T03:21:10Z")
😕 So, what’s the Straight Dope, then? Could a Martian see Earth’s moon with his grandma’s birdwatching binoculars without having to fire up the Space Modulator, or not? **Scr4** doesn’t sound too sure, is the thing… ---
**Author:** ![Boyo\_Jim](https://avatars.discourse-cdn.com/v4/letter/b/87869e/32.png) [@Boyo\_Jim](https://boards.straightdope.com/u/Boyo_Jim)\ **Post date:** [July 4, 2002, 3:28am UTC](https://boards.straightdope.com/t/what-would-it-take-for-a-martian-to-see-the-moon/117248/11 "2002-07-04T03:28:28Z")
I stand by my WAG, that at oppostion (thanks to Triskadecamus for providing the correct terminology) the moon wouldn’t be visible. I’ll join with the other WAGers that binocs WOULD be enough at conjunction. ---
**Author:** ![Ssarl\_the\_happy\_Martian](https://avatars.discourse-cdn.com/v4/letter/s/6a8cbe/32.png) [@Ssarl\_the\_happy\_Martian](https://boards.straightdope.com/u/Ssarl_the_happy_Martian)\ **Post date:** [July 4, 2002, 3:29am UTC](https://boards.straightdope.com/t/what-would-it-take-for-a-martian-to-see-the-moon/117248/12 "2002-07-04T03:29:07Z")
> [@](#): > > \*Originally posted by Triskadecamus \* > **We better wait for a real astronomer, or a real Martian.** Well… I’m not telling 🙂 ---
**Author:** ![Victory\_Candescence](https://avatars.discourse-cdn.com/v4/letter/v/e5b9ba/32.png) [@Victory\_Candescence](https://boards.straightdope.com/u/Victory_Candescence)\ **Post date:** [July 4, 2002, 3:49am UTC](https://boards.straightdope.com/t/what-would-it-take-for-a-martian-to-see-the-moon/117248/13 "2002-07-04T03:49:06Z")
**Squink** : That Solar System Simulator you linked to was absolutely fantastic! I don’t think I’ll be getting any work done for the next few days. ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [July 4, 2002, 7:47am UTC](https://boards.straightdope.com/t/what-would-it-take-for-a-martian-to-see-the-moon/117248/14 "2002-07-04T07:47:34Z")
> [@](#): > > \*Originally posted by scr4 \* > \*\*IAAA (I am an astronomer) and I agree with **k2dave** et al. Of course, as **Triskadecamus** said, you can’t see the earth when it’s closest to Mars because it’d be lost in the glare of the sun. But even when the two planets are 90 degrees away in their orbits, the earth/moon pair appears 5 arcminute apart. With a 7x magnification on a typical pair of binoculars, you can bring them 0.5 degrees apart, or about the diameter of the moon as seen from the earth. I’m sure the moon is bright enough to see - it would only be a couple of magnitudes dimmer than Mars looks from Earth. \*\* Well, the Martian atmosphere on the surface has about the same pressure as the earth atmosphere at 65000 ft (19800 m) so the scattering wouldn’t cause than much glare would it? We can see planets within 15[sup]o[/sup] (one hour after sunset) of the sun so my WAG would be that Martians could see the earth-moon system within 5[sup]o[/sup] of conjunction. At the Mars-Earth distance at that angle from conjunction the earth-moon separation would be over 16 min. of arc. Martians certainly could see us at 30[sup]o[/sup] from conjunction when the separation would be over 13 min. which is more than twice the limiting resolution of the eye. ---
**Author:** ![Snooooopy](https://avatars.discourse-cdn.com/v4/letter/s/ee7513/32.png) [@Snooooopy](https://boards.straightdope.com/u/Snooooopy)\ **Post date:** [July 4, 2002, 7:51am UTC](https://boards.straightdope.com/t/what-would-it-take-for-a-martian-to-see-the-moon/117248/15 "2002-07-04T07:51:57Z")
“Where’s the ka-boom? There’s SUPPOSED to be an Earth-shattering ka-boom!” I once knew a guy who could do a dead-on Marvin. He was cool. ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [July 4, 2002, 9:11am UTC](https://boards.straightdope.com/t/what-would-it-take-for-a-martian-to-see-the-moon/117248/16 "2002-07-04T09:11:51Z")
> [@](#): > > \*Originally posted by David Simmons \* > \*\* > > Well, the Martian atmosphere on the surface has about the same pressure as the earth atmosphere at 65000 ft (19800 m) so the scattering wouldn’t cause than much glare would it? We can see planets within 15[sup]o[/sup] (one hour after sunset) of the sun so my WAG would be that Martians could see the earth-moon system within 5[sup]o[/sup] of conjunction. At the Mars-Earth distance at that angle from conjunction the earth-moon separation would be over 16 min. of arc. Martians certainly could see us at 30[sup]o[/sup] from conjunction when the separation would be over 13 min. which is more than twice the limiting resolution of the eye. \*\* I have been reading and rereading this post trying to figure out what in hell I was doing when I wrote it. My best theory so far is that my evil twin, a sort of Mr. Hyde, who was dead drunk and suffering from a severe oxygen shortage to the gray cells at the time, is responsible. Since almost everything I posted on this thread has been wrong is it OK if I crawl over to the sidelines and watch the rest of this particular game from the bench? ---
**Author:** ![Go\_alien](https://avatars.discourse-cdn.com/v4/letter/g/9d8465/32.png) [@Go\_alien](https://boards.straightdope.com/u/Go_alien)\ **Post date:** [July 4, 2002, 10:07am UTC](https://boards.straightdope.com/t/what-would-it-take-for-a-martian-to-see-the-moon/117248/17 "2002-07-04T10:07:47Z")
> [@](#): > > \*Originally posted by David Simmons \* > \*\* > Since almost everything I posted on this thread has been wrong is it OK if I crawl over to the sidelines and watch the rest of this particular game from the bench? \*\* No, don’t, it’s very entertaining, even if meaningless!😃 ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [July 4, 2002, 2:23pm UTC](https://boards.straightdope.com/t/what-would-it-take-for-a-martian-to-see-the-moon/117248/18 "2002-07-04T14:23:55Z")
> [@](#): > > \*Originally posted by Duck Duck Goose \* > \*\ ***Scr4** doesn’t sound too sure, is the thing… \*\* I never sound sure about anything, you know. At least, I don’t think I do. If you just want a simple, definite answer, you need to talk to a politician, not a scientist. 😃 Anyway as **David Simmons** pointed out, you can probably see the earth/moon when it’s fairly close to conjunction. So there’s a good chance you can resolve the two with your naked eyes. With a pair of decent binoculars you can resolve the two even when Earth and Mars are close to opposition (distance of about 2.5 AUs, or 5 times as far as when they are in conjunction.) ---
**Author:** ![scotth](https://avatars.discourse-cdn.com/v4/letter/s/b9e5f3/32.png) [@scotth](https://boards.straightdope.com/u/scotth)\ **Post date:** [July 4, 2002, 2:40pm UTC](https://boards.straightdope.com/t/what-would-it-take-for-a-martian-to-see-the-moon/117248/19 "2002-07-04T14:40:10Z")
I would suggest it would be rather easy to see Earth’s moon with a pair of binoc from mars. I regularly demonstrate for friends that Jupiter’s moons are easily visible with a pair of regular 7x50mm binocs. IO and and Europa are both smaller than our moon (a bit), Ganymede and Callisto are about 50% larger. But, all four are easily visible with ordinary binocs. With that in mind, Jupiter is much farther away than Mars and quite a bit less sunlight falls on Jupiters moon’s. IO is also closer to Jupiter than our moon is to earth and it is still plenty far enough away to see as a seperate object. It should be easy with binocs. I would think nearly naked eye visible. ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [July 4, 2002, 4:52pm UTC](https://boards.straightdope.com/t/what-would-it-take-for-a-martian-to-see-the-moon/117248/20 "2002-07-04T16:52:55Z")
> [@](#): > > \*Originally posted by Go alien \* > \*\* > > No, don’t, it’s very entertaining, even if meaningless!😃 \*\* Your enthusiastic support is appreciated.