APOD: Opportunity's Mars Analemma (2014 May 16)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 4038
Joined: Fri Dec 04, 2009 3:27 am

APOD: Opportunity's Mars Analemma (2014 May 16)

Post by APOD Robot » Fri May 16, 2014 4:09 am

Image Opportunity's Mars Analemma

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.

<< Previous APOD This Day in APOD Next APOD >>
[/b]

User avatar
Nitpicker
Inverse Square
Posts: 2690
Joined: Fri Sep 20, 2013 2:39 am
Location: S27 E153

Re: APOD: Opportunity's Mars Analemma (2014 May 16)

Post by Nitpicker » Fri May 16, 2014 6:31 am

Very, very cool.

I was trying to make some measurements directly from the image, before I realized that the zenith is not at the image dead-centre, but closer to the centre of the "sky dome". Opportunity is about 39 Mars-minutes (2.7% longer than minutes) ahead of the longitude from which its local mean time is measured, so the analemma appears a bit further West (to the right) than 11:02AM would otherwise suggest, making it appear to be almost time for lunch.

Boomer12k
:---[===] *
Posts: 2691
Joined: Sun Apr 22, 2007 12:07 am

Re: APOD: Opportunity's Mars Analemma (2014 May 16)

Post by Boomer12k » Fri May 16, 2014 10:25 am

Fascinating.....who'd a thunk?

I wonder if you can do this with an astronomy program, and make an Analemma for each planet....would be interesting to find out.

:---[===] *

User avatar
neufer
Vacationer at Tralfamadore
Posts: 17423
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Opportunity's Mars Analemma (2014 May 16)

Post by neufer » Fri May 16, 2014 10:45 am

Boomer12k wrote:
I wonder if you can do this with an astronomy program, and make an Analemma for each planet....would be interesting to find out.
http://asterisk.apod.com/viewtopic.php? ... 89#p184089
http://www.analemma.com/
Art Neuendorffer

User avatar
Nitpicker
Inverse Square
Posts: 2690
Joined: Fri Sep 20, 2013 2:39 am
Location: S27 E153

Re: APOD: Opportunity's Mars Analemma (2014 May 16)

Post by Nitpicker » Fri May 16, 2014 12:00 pm

Simulating or modelling an analemma is a fine thing to do. But it is somehow more beautiful to record one directly.

And to see one recorded authentically from Mars ... well, it's a good time to be alive.

User avatar
neufer
Vacationer at Tralfamadore
Posts: 17423
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Opportunity's Mars Analemma (2014 May 16)

Post by neufer » Fri May 16, 2014 12:30 pm

Nitpicker wrote:
Simulating or modelling an analemma is a fine thing to do. But it is somehow more beautiful to record one directly.

And to see one recorded authentically from Mars ... well, it's a good time to be alive.
We now have the means, motive, and Opportunity.
Art Neuendorffer

User avatar
Nitpicker
Inverse Square
Posts: 2690
Joined: Fri Sep 20, 2013 2:39 am
Location: S27 E153

Re: APOD: Opportunity's Mars Analemma (2014 May 16)

Post by Nitpicker » Fri May 16, 2014 12:46 pm

neufer wrote:
Nitpicker wrote:
Simulating or modelling an analemma is a fine thing to do. But it is somehow more beautiful to record one directly.

And to see one recorded authentically from Mars ... well, it's a good time to be alive.
We now have the means, motive, and Opportunity.
And the all important evidence. Good to see you back, Your Honor.

BDanielMayfield
Don't bring me down
Posts: 2478
Joined: Thu Aug 02, 2012 11:24 am
AKA: Bruce
Location: East Idaho

Re: APOD: Opportunity's Mars Analemma (2014 May 16)

Post by BDanielMayfield » Fri May 16, 2014 1:27 pm

neufer wrote:We now have the means, motive, and Opportunity.
Which would make us guilty your honor, of what, interplanetary trespass?

P.S. Not a crime, I would argue.
Last edited by BDanielMayfield on Fri May 16, 2014 1:43 pm, edited 1 time in total.
Just as zero is not equal to infinity, everything coming from nothing is illogical.

User avatar
Chris Peterson
Abominable Snowman
Posts: 15248
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Opportunity's Mars Analemma (2014 May 16)

Post by Chris Peterson » Fri May 16, 2014 1:39 pm

neufer wrote:We now have the means, motive, and Opportunity.
And of course, we have Curiosity. Although sadly, we are now lacking Spirit.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

User avatar
Beyond
500 Gigaderps
Posts: 6889
Joined: Tue Aug 04, 2009 11:09 am
Location: BEYONDER LAND

Re: APOD: Opportunity's Mars Analemma (2014 May 16)

Post by Beyond » Fri May 16, 2014 2:47 pm

Red rover, red rover, send your Analemma over.
To find the Truth, you must go Beyond.

User avatar
neufer
Vacationer at Tralfamadore
Posts: 17423
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Opportunity's Mars Analemma (2014 May 16)

Post by neufer » Fri May 16, 2014 3:08 pm

Click to play embedded YouTube video.
BDanielMayfield wrote:
neufer wrote:
We now have the means, motive, and Opportunity.
Which would make us guilty your honor, of what, interplanetary trespass?

P.S. Not a crime, I would argue.
https://www.youtube.com/watch?v=wxIHV-R0YVE
https://www.youtube.com/watch?v=4q6k4KdpMUg
Art Neuendorffer

User avatar
neufer
Vacationer at Tralfamadore
Posts: 17423
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Opportunity's Mars Analemma (2014 May 16)

Post by neufer » Fri May 16, 2014 3:09 pm

:roll:
Last edited by neufer on Fri May 16, 2014 4:29 pm, edited 1 time in total.
Art Neuendorffer

starsurfer
Stellar Cartographer
Posts: 4102
Joined: Thu Mar 15, 2012 7:25 pm

Re: APOD: Opportunity's Mars Analemma (2014 May 16)

Post by starsurfer » Fri May 16, 2014 3:15 pm

neufer wrote:
Nitpicker wrote:
Simulating or modelling an analemma is a fine thing to do. But it is somehow more beautiful to record one directly.

And to see one recorded authentically from Mars ... well, it's a good time to be alive.
We now have the means, motive, and Opportunity.
Opportunity rover:
"If it wasn't for those pesky dust storms, I would have gotten all the frames. Drat and double drat!"

walker1001

Re: APOD: Opportunity's Mars Analemma (2014 May 16)

Post by walker1001 » Fri May 16, 2014 4:02 pm

neufer wrote:
Nitpicker wrote:
Simulating or modelling an analemma is a fine thing to do. But it is somehow more beautiful to record one directly.

And to see one recorded authentically from Mars ... well, it's a good time to be alive.
We now have the means, motive, and Opportunity.
But sadly no canals, no Martians, no War of the Worlds. :D

User avatar
Beyond
500 Gigaderps
Posts: 6889
Joined: Tue Aug 04, 2009 11:09 am
Location: BEYONDER LAND

Re: APOD: Opportunity's Mars Analemma (2014 May 16)

Post by Beyond » Fri May 16, 2014 4:32 pm

YEA :!:
To find the Truth, you must go Beyond.

geoffrey.landis
Ensign
Posts: 50
Joined: Thu Aug 20, 2009 3:49 pm

Black sky

Post by geoffrey.landis » Fri May 16, 2014 9:21 pm

The caption is a little misleading. It's not that the martian sky is "blacked out" around the solar images; what you're seeing is that when we're pointing the camera directly at the sun, we use a neutral density solar filter, which is so dark that the sky comes out black.

User avatar
Nitpicker
Inverse Square
Posts: 2690
Joined: Fri Sep 20, 2013 2:39 am
Location: S27 E153

Re: APOD: Opportunity's Mars Analemma (2014 May 16)

Post by Nitpicker » Fri May 16, 2014 11:05 pm

geoffrey.landis wrote:The caption is a little misleading. It's not that the martian sky is "blacked out" around the solar images; what you're seeing is that when we're pointing the camera directly at the sun, we use a neutral density solar filter, which is so dark that the sky comes out black.
I would not have called that misleading. "Blacked out" and "underexposed" are more or less synonymous in this context.

JEH1138
Asternaut
Posts: 1
Joined: Fri May 16, 2014 11:57 pm

Re: APOD: Opportunity's Mars Analemma (2014 May 16)

Post by JEH1138 » Fri May 16, 2014 11:59 pm

So forgive me fore being dense, but does the sun in a Martian analemma cross back on itself at all? Is it just too hard to see from greater distances? Probably my lack of understanding about what actually causes the shape over time.

--j

User avatar
Chris Peterson
Abominable Snowman
Posts: 15248
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Opportunity's Mars Analemma (2014 May 16)

Post by Chris Peterson » Sat May 17, 2014 12:06 am

JEH1138 wrote:So forgive me fore being dense, but does the sun in a Martian analemma cross back on itself at all?
No.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

User avatar
Nitpicker
Inverse Square
Posts: 2690
Joined: Fri Sep 20, 2013 2:39 am
Location: S27 E153

Re: APOD: Opportunity's Mars Analemma (2014 May 16)

Post by Nitpicker » Sat May 17, 2014 12:21 am

No, it does not cross itself. This is because the higher eccentricity of Mars's orbit has a much more dominant effect on the analemma, than the inclination of Mar's polar axis to the Ecliptic. These two components of the more circular Earth orbit, are much more closely matched in magnitude (but the effect of the inclination has twice the frequency).

See also:
http://en.wikipedia.org/wiki/Equation_of_time (for Earth)
and:
http://en.wikipedia.org/wiki/Timekeeping_on_Mars

User avatar
neufer
Vacationer at Tralfamadore
Posts: 17423
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Opportunity's Mars Analemma (2014 May 16)

Post by neufer » Sat May 17, 2014 3:09 am

Nitpicker wrote:
No, it does not cross itself. This is because the higher eccentricity of Mars's orbit has a much more dominant effect on the analemma, than the inclination of Mar's polar axis to the Ecliptic. These two components of the more circular Earth orbit, are much more closely matched in magnitude (but the effect of the inclination has twice the frequency).
No, it does not cross itself... because the equation of time effect due to the inclination of Mars' polar axis (i.e., the close spacing of time zones near the poles) is closely matched in magnitude with that due to the high eccentricity of Mars' orbit (such that they nearly cancel each other at aphelion).
Art Neuendorffer

User avatar
neufer
Vacationer at Tralfamadore
Posts: 17423
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Opportunity's Mars Analemma (2014 May 16)

Post by neufer » Sat May 17, 2014 3:14 am


walker1001 wrote:
But sadly no canals, no Martians, no War of the Worlds. :D
They sought it with thimbles, they sought it with care;
They pursued it with forks and hope;
They threatened its life with a railway-share;
They charmed it with smiles and soap.
Art Neuendorffer

User avatar
Nitpicker
Inverse Square
Posts: 2690
Joined: Fri Sep 20, 2013 2:39 am
Location: S27 E153

Re: APOD: Opportunity's Mars Analemma (2014 May 16)

Post by Nitpicker » Sat May 17, 2014 3:25 am

neufer wrote:
Nitpicker wrote:
No, it does not cross itself. This is because the higher eccentricity of Mars's orbit has a much more dominant effect on the analemma, than the inclination of Mar's polar axis to the Ecliptic. These two components of the more circular Earth orbit, are much more closely matched in magnitude (but the effect of the inclination has twice the frequency).
No, it does not cross itself... because the equation of time effect due to the inclination of Mars' polar axis (i.e., the close spacing of time zones near the poles) is closely matched in magnitude with that due to the high eccentricity of Mars' orbit (such that they nearly cancel each other at aphelion).
Not convinced. Show me the "equation of time" graph for Mars, including the two components from which it is formed.

A sundial on Mars would become a lot slower/faster over the course of a year, than a sundial on Earth (compared to an accurate clock). But Mars and Earth have similar inclinations, and both have the line of apsides far from the nodes. The big difference is the high eccentricity of Mars's orbit.

User avatar
alter-ego
Serendipitous Sleuthhound
Posts: 877
Joined: Mon Apr 21, 2008 4:51 am
Location: Redmond, WA

Re: APOD: Opportunity's Mars Analemma (2014 May 16)

Post by alter-ego » Sat May 17, 2014 6:18 am

Nitpicker wrote:
neufer wrote:
Nitpicker wrote:
No, it does not cross itself. This is because the higher eccentricity of Mars's orbit has a much more dominant effect on the analemma, than the inclination of Mar's polar axis to the Ecliptic. These two components of the more circular Earth orbit, are much more closely matched in magnitude (but the effect of the inclination has twice the frequency).
No, it does not cross itself... because the equation of time effect due to the inclination of Mars' polar axis (i.e., the close spacing of time zones near the poles) is closely matched in magnitude with that due to the high eccentricity of Mars' orbit (such that they nearly cancel each other at aphelion).
Not convinced. Show me the "equation of time" graph for Mars, including the two components from which it is formed.

A sundial on Mars would become a lot slower/faster over the course of a year, than a sundial on Earth (compared to an accurate clock). But Mars and Earth have similar inclinations, and both have the line of apsides far from the nodes. The big difference is the high eccentricity of Mars's orbit.
As you stated, the figure-8 shape is lost due to the dominant eccentricity component within the analemma. Per your request, I've calculated the EOT and analemma components for Mars. Instead of using Earth months on the EOT X-axis, I used orbital position angle which works the same. I personally like viewing the analemmas.

Mars Equation of Time & Components.JPG
Mars Analemma & Components.JPG
  1. Edit: At first, I mistakenly annotated the "Eccentricity Only" graph as being a 0° inclination case which is not true. The declination would remain 0° if that were the case. Just think of it as having axis tilt component removed.
Mars Analemma - Half Eccentricity.JPG
  • Edit: I decided to add the analemma for the case where the eccentricity is ½ the actual value. The figure-8 is beginning for form.

As an aside, geosynchronous satellites show the same gamut of analemmas too, and for the same reasons. From nice figure eights (circular orbits with non-zero orbital inclinations) to the pointy type (high eccentricity).
You do not have the required permissions to view the files attached to this post.
Last edited by alter-ego on Sat May 17, 2014 7:58 am, edited 1 time in total.
A pessimist is nothing more than an experienced optimist

User avatar
Nitpicker
Inverse Square
Posts: 2690
Joined: Fri Sep 20, 2013 2:39 am
Location: S27 E153

Re: APOD: Opportunity's Mars Analemma (2014 May 16)

Post by Nitpicker » Sat May 17, 2014 7:42 am

Thank you alter-ego. Nice work.