Questions About Mars

February 17, 2005 9:24 AM

I'm looking for really any information on Mars and Mars colonization, but in particular two questions: Would the sun rise in the east and set in the west? and What would the night sky look like? What would the prominant objects be?
posted by dagnyscott to Science & Nature (14 answers total)

The night sky would look almost just like ours.

Mars rotates in the same direction as Earth and so the Sun would rise and set in exactly the same way.

The biggest differences would be the lack of light pollution, thinner atmosphere, and greater amounts of dust in the atmosphere.

Jupiter might look a little bigger, but since it's basically a point-source to your naked eye, you'd only see it as marginally brighter than on Earth. Oh, also, no huge Moon, but two dinky little captured asteroids (Phobos and Deimos) that you'd be hard-pressed to actually notice.
posted by bshort at 9:31 AM on February 17, 2005

Also, the Earth would be a relatively bright, bluish object in the sky.
[planetary images from mars]
posted by cardboard at 9:49 AM on February 17, 2005

I would guess meteorites would last a bit longer due to the thin atmosphere. There would be no (ok, maybe three or four) unnatural satellites.

The Earth would be a morning or evening star.
posted by bondcliff at 9:51 AM on February 17, 2005

Don't forget that the horizon would be much closer on Mars than on Earth due to the smaller size. And bshort, they are fines, not dust - haven't you read the Mars Trilogy (;>) - which is one of the best series on Mars I have read. If you wanted to find out more about Mars, read Red Mars, because there is much discussion about areology and native martian landforms - from the canyon systems to the giant shield volcanoes to the Tharsis Bulge. It is science fiction, but very much "hard science fiction" in which Robinson goes into detail about technology, society and the like.
posted by plemeljr at 10:06 AM on February 17, 2005

Oh, also, no huge Moon, but two dinky little captured asteroids (Phobos and Deimos) that you'd be hard-pressed to actually notice.

Not that hard-pressed. Phobos and Deimos are much smaller than our moon, but they're also much closer to Mars than the moon is to the earth. The angular (apparent) sizes of Phobos and Deimos from Mars are still smaller than our moon, but large enough that they would be visible as more than just points of light. (0.16° and 0.036°, compared to our moon's 0.52°).

However, since they're much closer to the planet, that also means they orbit much faster; Phobos takes under 8 hours to orbit Mars. Probably not quite fast enough to be visibly moving (compare artificial satellites in low earth orbit, which take only 90 minutes and are visibly moving to the naked eye), but getting close. Deimos takes about 30 hours.
posted by DevilsAdvocate at 10:08 AM on February 17, 2005

Oh i just love this thread. please tell me more, i am being enchanted.
posted by svenskjenta at 10:17 AM on February 17, 2005

"East" and "west" would be far more arbitrary concepts on Mars. The planet's magnetic field is exceedingly weak and non-homogenous. It's likely that any inhabitants would use the sunrise and sunset as their direction guideposts, and infer a north and south from there.

Second, Mars' axis tilt of 25 degrees (close to Earth's 23.5) means that the length of a day would vary there for the same reason it does here.
posted by Plutor at 10:26 AM on February 17, 2005

For the same reason as it being a morning or evening star (the Earth being an inferior planet relative to Mars), Earth would have phases, like the Moon.

The sun rises in the east and sets in the west for all the planets except Venus (and maybe Uranus, which is tilted about 90 degrees to the ecliptic, making it hard to define east and west.)

If my math doesn't fail me, Phobos should look about a quarter as big in the Mars sky as Luna does in the Earth's sky. Deimos is much smaller and further away and would be kind of dinky. (on preview, what DevilsAdvocate said.)

Read Kim Stanley Robinson's and Ben Bova's and Greg Bear's recent Mars books.

It's not clear to me that the thin atmosphere would make meteors last longer -- it might take much longer for their exteriors to get hot enough to see.

Also on preview, the meaning and utility of east and west on Mars don't have anything to do with the planet's spotty magnetic field. But Martians wouldn't use magnetic compasses.
posted by Zed_Lopez at 10:32 AM on February 17, 2005

I have no idea how realistic these movies were, but both Mission to Mars and Red Planet [sci fi movies that came out in 2000] have parts that take place on the planet. Mission to Mars specifically talks a lot about the atmosphere [heat, moisture, airlessness, etc] and has a lot of sky shots. Neither movie is awesome but both are watchable. I can remember very few details of either.
posted by jessamyn at 10:34 AM on February 17, 2005

Not relevant to your two main questions, but one other interesting thing about Mars I heard recently (and I forget where, so I can't cite a source). Not only is Mars' atmosphere much thinner than the earth's, but the day-to-day and hour-to-hour variations in atmospheric pressure are much greater, as a percentage of the total. While atmospheric pressure at a given point on the earth's surface varies by no more than a few percent (barring extraordinary events like being inside a hurricane, and even then you're only talking around 10%), apparently the pressure on Mars often varies by 25% of the total pressure.
posted by DevilsAdvocate at 11:14 AM on February 17, 2005

Not sure if it can help but this website is a pretty good overview of what a Mars mission might look like.
posted by bondcliff at 11:19 AM on February 17, 2005

I've failed to recommend Kim Stanley Robinson's 'Red Mars' on numerous occasions, because as a novel it's really terrible. (I may be old fashioned, but I always thought a novel should be an interesting story about people.)

But as a thinly-veiled scientifically-minded explanation of what Mars colonization might be like, it's really first rate and I bet you'd enjoy it.
posted by ikkyu2 at 1:42 PM on February 17, 2005

During sunset, the horizon turns a deep blue, almost like our daytime sky.
posted by fatbobsmith at 5:05 PM on February 17, 2005

I do think the Kim Stanley Robinson books are rewarding, but they aren't for all tastes.

Three facts I haven't noticed above: the Martian day is about forty minutes longer than a day on Earth, the surface gravity is only 40% of Earth's, and the Martian year is approximately twice as long.

bshort is half right about Jupiter. At its closest approach to Mars Jupiter is closer than it ever gets to Earth, but at its farther approach it is farther than it ever gets from Earth. So for half of the [Martian] year it would look slightly larger than we're used to but for the other half it would look slightly smaller. I want to say that it would be appreciably brighter all the time because of the thinner atmosphere and obvious lack of light pollution but I'm not sure how much the atmospheric transparency is reduced by dust, all factors that bshort addressed.

Jupiter is closer and appears larger for half of the Martian year, but for the other half it is actually farther from Mars than
posted by Songdog at 5:06 PM on February 17, 2005