Talk:Timekeeping on Mars

Simple Mars Clock
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
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)


 * Robinson wrote his PhD thesis on the novels of PKD, so it would be very harsh to say he stole any ideas. Any such references would almost certainly be an homage. SelfCorrection (talk) 05:56, 18 March 2021 (UTC)

year ratio
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

 * 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
"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

 * 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

 * 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"
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)

Conversion factor of 1.0274912510?
The first paragraph of the Time of day section includes "This yields a conversion factor of 1.0274912510 days/sol."

I can't replicate this using the numbers stated in the same paragraph.
 * For a sidereal day the numbers are 88,642.663 seconds for Mars and 86,164.0916 seconds for Earth resulting in a ratio of 1.0287657115...
 * For a solar day the numbers are 88,775.24409 seconds for Mars and 86,400.002 seconds for Earth resulting in a ratio of 1.0274912273...

The math using the solar day is closer to what the article reports and so here they are side by side:
 * 1.0274912510 number reported in the article's Time of day section
 * 1.0274912273 calculated from 88,775.24409 divided by 86,400.002
 * 1.02749125 from later in the article in the Sols section

I have set up a Google Sheet at https://docs.google.com/spreadsheets/d/1YncLGxJWq2rLDT0w62FNKY4zW5MCVENIJBHK101eTSY/edit?usp=sharing that shows my math.

Why am I getting 1.0274912273 when the article shows 1.0274912510? --Marc Kupper&#124;talk 19:16, 2 August 2015 (UTC)


 * The figure $86,400.002$ is an average over the last 50 years. The actual value right now is closer to $86,400.001$ and continuously fluctuating. According to the article Day, "A day of exactly $86,400$ SI seconds is the base unit of time in astronomy". And indeed, the number reported in the article is $88,775.244$/$86,400$ rounded to 10 decimals.
 * BTW, the NASA page Mars24 Algorithm and Worked Examples uses the slightly larger conversion factor 1.0274912517, which implies.
 * — Edgar.bonet (talk) 16:01, 7 January 2016 (UTC)

Mars Time /Earth time conversion
I'm not good enough to do this myself, so I don't, but reading over Mars Exploration articles that hop around with ambiguous time frames (Example: The rover has been on Mars for four years at this point - is that Earth years or Martian years?), we really could use a converter template that can take Earth time and convert it into Mars time and state that it's mars time. Like something where you can put in Earth notation   and get it to spit out "2 Martian years and 78 sols" on the page.

Yes, I know it's like going to the auto industry and saying "Hey, let's make a car that gets 200 miles to the gallon" - it's easy to say, and sounds simple; but it isn't - but I'm just putting the idea out there in case it tickles the right person's brain.--Varkman (talk) 10:23, 7 January 2016 (UTC)
 * That's actually a really good idea. (I wish I'd thought of it. :(p ) It could also apply to other planets. Why don't you post the suggestion at template talk? (TBH, IDK where you find that... : Maybe somebody can whip something up.  TREKphiler   any time you're ready, Uhura  03:01, 8 January 2016 (UTC)
 * It's at WT:WPT, should you want to cross-post. Primefac (talk) 03:14, 8 January 2016 (UTC)
 * Thx, Primefac. (You've just made my posts at the Mars & Solar System projects moot, curse you. ;p )  TREKphiler   any time you're ready, Uhura  06:05, 8 January 2016 (UTC)


 * Not so sure that's a good idea. Up to now, there are few instances where a Martian year or a Venusian year are stipulated, and when they are used, the term "year(s)" is disambiguated with the planetary adjective.  In planetary articles where the term "year(s)" is used, it is understood to mean "Earth years" unless otherwise stipulated/described. Happy New Year!  Paine   06:36, 8 January 2016 (UTC)


 * Sounds like a good idea for general template that takes two planets, and converts years and days. Though if it converts both years and days together, it'd probably need to be written in LUA. You can always try to request that convert be adjusted to add such capabilities to its suite. -- 70.51.44.60 (talk) 09:53, 8 January 2016 (UTC)


 * Agree with Paine. And even if a conversion is desired for some reason, something like “about 2.1 Martian years” would likely be more useful than “2 Martian years and 78 sols”. — Edgar.bonet (talk) 10:53, 8 January 2016 (UTC)

Arean Time Zone System
I googled "Central Oxian Time" and got exactly one result, this article. I don't think this section is properly sourced, and may be invented out of whole cloth. — Preceding unsigned comment added by Dthomas218 (talk • contribs) 20:10, 1 March 2016 (UTC)


 * Confirmed. I removed the section. — Edgar.bonet (talk) 10:54, 2 March 2016 (UTC)

Meaning of sol
The following was left on my talk page by 5.228.254.248. I am moving it here, as it is more appropriate:


 * A: The term sol is used by planetary astronomers to refer to the duration of a solar day
 * B: The term sol is used by planetary astronomers to refer to the duration of a solar day on Mars
 * The text above is a comparison of two contested edits on the page Timekeeping on Mars.
 * B causes confusion, and is inaccurate, as solar day or Sol will be used for other planets and not just the first that we visit.
 * A is concise clear, and links to an intermediary article for further reading.

By writing A, you are basically claiming that the term sol is commonly used for the duration of a solar day on any planet. If you have reliable sources substantiating this claim, then it's fine to keep it. However, currently, the sentence has only a reference to a page on NASA's web site showing a picture by Opportunity with the following caption (emphasis mine):


 * NASA's Mars Exploration Rover Opportunity used its navigation camera to take the images combined into this stereo view of the rover's surroundings on the 959th sol, or Martian day, of its surface mission (Oct. 5, 2006).

Here NASA is writing quite clearly that by sol they mean Martian day. Whether or not the term can be applied to other planets is not apparent in this source and, I would say, is not really relevant to the current article.

In your comment above, you added a wikilink to Sol. This is a disambiguation page. Among the many other definitions, it gives “the duration of a solar day on Mars”. No mention about sol meaning solar day in general.

Thus, either you provide a reliable source to be quoted as a reference for A (sol = solar day in general), or we keep B (sol = solar day on Mars), which is consistent with the source. — Preceding unsigned comment added by Edgar.bonet (talk • contribs) 13:11, 4 May 2016 (UTC)


 * I have another question regarding how one defines a "sol."


 * Namely, is it a measure a sidereal Mars day (the time lapse between two consecutive transits of the Sun through the first point of Aries—from the Martian frame-of-reference)?


 * Or is it a (slightly longer) tropical Mars day—the time lapse between two consecutive Martian sunrises?


 * Pine (talk) 11:39, 13 August 2017 (UTC)

Duration of hours, minutes, and seconds
The article states that hours and minutes are 2.7% longer on mars, but id does not extend this to seconds, although I believe that a longer second is also used in "Mars Time". Now the second is a SI unit that should not really be hampered with - it has a clear and precise definition, while hour and minute are not SI units. So while one could define a "Mars hour", a "Mars second" is in conflict with the SI. I am pretty sure that longer seconds are used in mars mission (since the Mars24 algorithm of NASA computes it this way), and I undertand that it is close to trivial to make a mechanical clock run 2.7% slower, as a realization of a Mars Clock on Earth. However, I believe that it should at least be mentioned, if not discussed, that Mars time conflicts with the SI definition of the second.129.247.247.239 (talk) 14:11, 11 June 2019 (UTC)
 * There is no standard, only proposals, for timekeeping on Mars, something the article makes this pretty clear. Discussions of units of time greater than seconds are clearly relative to the rotational period and dates and seasons relative to the orbital period (specifically the solar longitude). I read the 2.7% figure as an innocent approximation which nicely summarizes the longer sidereal period.  It's also referencing a convention used by spacecraft lander projects", makes no claim to be standard so I'm not seeing a conflict with SI.  --MadeYourReadThis (talk) 15:25, 11 June 2019 (UTC)

Local Mean Solar time
The raw images of Perseverance are given with Local Mean Solar time. I assume that midnight is at 0:00. Is noon at 12:19:48 or at 12:00 with a stretched second, minute or hour length? I asked Nasa but they did not answer. Schrauber5 (talk) 09:17, 12 July 2021 (UTC)