Skip to comments.Astronomy Picture of the Day -- Opportunity's Mars Analemma
Posted on 05/15/2014 9:34:33 PM PDT by SunkenCiv
Explanation: Staring up into the martian sky, the Opportunity rover captured an image at 11:02 AM local mean time nearly every 3rd sol, or martian day, for 1 martian year. Of course, the result is this martian analemma, a curve tracing the Sun's motion through the sky in the course of a year (668 sols) on the Red Planet. Spanning Earth dates from July, 16, 2006 to June 2, 2008 the images are shown composited in this zenith-centered, fisheye projection. North is at the top surrounded by a panoramic sky and landscape made in late 2007 from inside Victoria crater. The tinted martian sky is blacked out around the analemma images to clearly show the Sun's positions. Unlike Earth's figure-8-shaped analemma, Mars' analemma is pear-shaped, because of its similar axial tilt but more elliptical orbit. When Mars is farther from the Sun, the Sun progresses slowly in the martian sky creating the pointy top of the curve. When close to the Sun and moving quickly, the apparent solar motion is stretched into the rounded bottom. For several sols some of the frames are missing due to rover operations and dust storms.
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I’ve heard of a dilemma before, and now this analemma, but where’s the bilemma and trilemma?
The trouble with Mars is that there are no seas for the analemma’s to dive into and drown themselves.
I got this one! You’re talking to Mr. Analemma here, inter alia. The analemma is a composite of two effects, the dynamical variation of the planets motion in its orbit, and seasonal variation of the apparent diurnal motion of the sun due to the inclination of the ecliptic, a geometrical effect.
I had this all figured out one time, where the relative significance of the two effects could be accounted for by rotating a 3-d wire figure, which when “closed” would give the figure 8 we see on earth, or when “opened” by axial rotation to “uncross” the wire figure, would give the ovate form of the Martian analemma. So ... use your imagination.
BTW, that analemma scene with Tom Hanks in CASTAWAY ? Complete crap! Don’t even talk to me about it!
My grandparents had a globe in their front room which had an analemma in the Pacific Ocean west of Chile. Never knew what it was all about.