I need the bizarro Martian version of Galileo.
February 24, 2011 4:36 PM   Subscribe

Martian Astronomer Filter--when Mars moves like this in the sky from our point of view on Earth, how does the Earth appear to move from Mars' perspective?

For a visual arts project I'm doing, I want to visualize what the Earth looks like from the surface of Mars during the period of apparent retrograde motion. Basically, the other side of that image above.

My for spatial relations center seem to be lacking, cause I can't seem to figure it out and it's driving me crazy. I'm trying to account for things like position on the surface, the relation of the two planets' orbits on the z-plane, etc.

I wish I'd paid more attention in that astronomy lab I took in college instead of trying to flirt with my TA.
posted by JMB1138 to Science & Nature (3 answers total) 1 user marked this as a favorite
Best answer: someone else can come in with better explanations, but to me, it always helped to look up at Venus, imagine it was blue, and pretend I was on Mars. (since the apparent motion of the planets would be different when looking at a planet inside vs outside of your planet's orbit)

It's not quite the same, but the motions should be similar. It would be an "evening star" sometimes and a "morning star" other times.
posted by johnstein at 4:45 PM on February 24, 2011

Yes, same as Venus looks to us when were in retrograde relative to it.

Mars will begin apparent retrograde motion after Earth (from the POV of Mars) has reached it's highest point in the sky at sunset. During retrograde, the Earth will appear lower in the sky at every following sunset until it's lost in the glare of the sun. A few weeks later, it'll appear before the sun rises, a little earlier every day until it reaches maximum separation from the Sun.

Then at that point Mars' apparent retrograde motion will stop. Earth will be gaining past, around the to far side of the Sun and while Earth's angle of separation will decrease, Mars (from the POV of earth) will still appear to be advancing slowly, relative to the starry background.

It's not as simple to explain as I first though.

Forget about the "s" curve business, just think about it as two cars on a round-about, with the inside car overtaking the other.
posted by bonobothegreat at 5:10 PM on February 24, 2011

Thirding the planet transposition solution. Earth looks to Mars as Venus looks to Earth.

Note that in general, Venus is not a nighttime object for us, rather a morning or evening "star". Similarly, Earth would appear only in the Martian morning or evening, and sometimes not at all (when too close to the Sun from the Martian perspective).
posted by intermod at 8:36 PM on February 24, 2011

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