Talk:Timekeeping on Mars

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Simple Mars Clock[edit]

I don't think it's appropriate to place computer code in encyclopedia articles. A better idea is to describe the algorithm such that anyone can implement it in any language they choose. It would look better and take up less space. --  B.d.mills  (T, C)

Could someone verify if this formula correct, I copy-paste the code to Excel and it gives me a result different from Mars24 from NASA. - Yaohua2000 21:05, 22 November 2005 (UTC)
The formula is correct, and I have verified it against the display in Mars24. However, the result that it generates is the MSD, Mars Sol Date, and not MTC as it is labeled. To convert the value to MTC on the current sol, paste
=MOD(A1,1)*24
into cell A2 of your spreadsheet (assuming you have pasted the original formula into cell A1). The result will be MTC in hours, which you'll have to munge appropriately to extract the minutes and seconds values. - 208.59.133.14 09:16, 2 December 2005 (UTC)

Kim Stanley Robinson[edit]

Not a great fan of this writer, but didn't he steal this idea from Phillip K. Dicks' Martian Timeslip? --MacRusgail 19:07, 2 June 2007 (UTC)

Preferences aside, I think "stole" is a harsh way to put it. PKD used it first, but there are only so many ways to deal with the different day - make the day longer or use the timeslip. Regardless, Martian Time-Slip presents time in a much more fluid sense, and isn't necessarily specific to the extra 37 minutes in the day, unlike Robinson's trilogy. Both are mentioned, although admittedly the language in the section leaves one wanting. ~ Amory (talk) 23:56, 20 April 2009 (UTC)

year ratio[edit]

Using the numbers shown I get these rational approximations to the ratio of year-lengths: 2:1, 15:8, 32:17, 47:25, 79:42, 679:361. How did the last editor also get 62:33 and 94:50? While I'm up, does the article really need that section? —Tamfang (talk) 06:19, 3 November 2008 (UTC)

Would the article lose important information if the section was removed? No. It is little more than a series of numbers that can be obtained as successive approximations of a continuing fraction. Of what use is it to the article as a whole? I don't see any. I'm inclined to delete this section. -- B.D.Mills  (T, C) 11:42, 10 February 2009 (UTC)
I've deleted the section because it didn't add anything particularly useful to the article. -- B.D.Mills  (T, C) 11:00, 12 February 2009 (UTC)
I actually disagree. Much like the UTC/MTC conversion, it provides relevant numbers to the understanding of Martian time from a terran perspective, which we clearly all have. The numbers presented in the deleted box are far more taxing to derive than the largely trivial UTC/MTC conversions. There was no citation on the original box, but should one be found, I find it appropriate to place within the article. Perhaps the two sections could be merged into a larger section detailing the relationship between Earth and Mars times. ~Amory (talk) 23:57, 20 April 2009 (UTC)

Pathfinder local time[edit]

Of the five successful Mars landers to date, four employed variants of local mean solar time (LMST) for the lander site while the fifth (Mars Pathfinder) used local true solar time (LTST).
Mars Pathfinder used local apparent solar time at the landing location. Its timezone was AAT-02:13:01 ....

If Pathfinder was not on mean solar time, its "timezone" should vary by 90 minutes. Perhaps this means to say that its clock was set to LTST on the day of landing, and then used mean time with respect to that origin? —Tamfang (talk) 20:52, 16 February 2009 (UTC)

Oops, no, Airy Apparent Time would likewise vary from mean time. —Tamfang (talk) 19:25, 16 November 2009 (UTC)

Calendar[edit]

"For similar reasons, if it is ever necessary to schedule and co-ordinate activities on a large scale across the surface of Mars it would be necessary to agree on a calendar."

Says who? -Sanddef

MTC[edit]

  • MTC = (seconds since 2000-01-06 00:00:00 UTC)×(86400/88775.244)) + (44795.9998 * 86400)

I wonder why it's given in that form rather than with one operation fewer: 86400×(44795.9998 + (seconds since 2000-01-06 00:00:00 UTC)/88775.244). —Tamfang (talk) 04:40, 1 March 2009 (UTC)

Formula to convert MJD/UTC to MSD/MTC[edit]

  • Universal Time Coordinated
    • UTC = (MJD mod 86400) * 24

MJD is a count of (Earth) days. How does MJD mod 86400 (the number of seconds in a day) make any sense at all? —Tamfang (talk) 22:04, 22 March 2009 (UTC)

"planetocentric longitude"[edit]

The article states: Note that the modern standard for measuring longitude on Mars is "planetocentric longitude", which is measured from 0°–360° East and measures angles from the center of Mars. The older "planetographic longitude" was measured from 0°–360° West and used coordinates mapped onto the surface.[2]

I can't see a real difference between longitude measured on the surface (which should mean: along the equator) and longitude measured as angles from the center because I suppose that also on mars the equator is very near to a circle whose center coincides with the center of mass of the planet. However, since (like earth) Mars is not a sphere but nearly spheroid, - like on earh - there is a real difference between planetographic and planetocentric latitude . I think this is also what the source cited tells us:

Originally, a system with ‘planetographic’ latitude and longitude increasing to the west was developed to be used with the Viking observations. The US Geological Survey and other organisations then adopted a system with ‘planetocentric’ latitude and longitude increasing to the east for making future Mars maps and imagery. Both systems were approved for use on Mars by the International Astronomical Union in 2000.

(The ‘planetocentric’ system uses co-ordinates derived from the angle measured from the equator to a point on the surface at the centre of the planet, whereas the ‘planetographic’ system uses co-ordinates which are mapped on the surface.)

Concerning latitude, this text distinguishes between "planetographic" and "planetocentric", whereas for longitude, it distinguishes between "increasing to the west" and "increasing to the east".--Trigamma (talk) 18:39, 15 January 2010 (UTC)

Either way, what does "coordinates mapped onto the surface" mean? Wouldn't an assignment of planetocentric coords to a surface feature constitute a mapping to the surface? The obvious alternative to the planetocentric vector is the local gravity vector, but this would be a strange way to say that. —Tamfang (talk) 18:32, 17 January 2010 (UTC)