Darian calendar

The Darian calendar is a proposed system of timekeeping designed to serve the needs of any possible future human settlers on the planet Mars. It was created by aerospace engineer, political scientist, and space jurist Thomas Gangale in 1985 and named by him after his son Darius. It was first published in June 1986.[1] In 1998 at the founding convention of the Mars Society the calendar was presented as one of two calendar options to be considered along with eighteen other factors to consider for the colonization of Mars.[2]

Year length and intercalation

The basic time periods from which the calendar is constructed are the Martian solar day (sometimes called a sol) and the Martian vernal equinox year. The sol is 39 minutes 35.244 seconds longer than the Terrestrial solar day and the Martian vernal equinox year is 668.5907 sols in length (which corresponds to 686.86 days on Earth). The basic intercalation formula therefore allocates six 669-sol years and four 668-sol years to each Martian decade. The former (still called leap years even though they are more common than non-leap years) are years that are either odd (not evenly divisible by 2) or else are evenly divisible by 10, producing 6,686 sols per ten years (668.6 sols per year).

A 1998 iteration of the Darian calendar made years divisible by 100 common years, but years divisible by 500 stay leap years.[3] However, this static intercalation scheme did not take into account the slowly increasing length of the Martian vernal equinox year. In 2006 Gangale devised a series of intercalation formulas, all of which have in common the basic decennial cycle, as shown in the following table:

Range of years Formula Mean length of calendar year
0–2000 (Y − 1)\2 + Y\10 − Y\100 + Y\1000 668.5910 sols
2001–4800 (Y − 1)\2 + Y\10 − Y\150 668.5933 sols
4801–6800 (Y − 1)\2 + Y\10 − Y\200 668.5950 sols
6801–8400 (Y − 1)\2 + Y\10 − Y\300 668.5967 sols
8401–10000 (Y − 1)\2 + Y\10 − Y\600 668.5983 sols

This extended intercalation scheme results in an error of only about one sol at the end of 12,000 Martian years, or about the year 24,180 of the Common Era.[4]

Calendar layout

The year is divided into 24 months. The first 5 months in each quarter have 28 sols. The final month has only 27 sols unless it is the final month of a leap year when it contains the leap sol as its final sol.

The calendar maintains a seven-sol week, but the week is restarted from its first sol at the start of each month. If a month has 27 sols, this causes the final sol of the week to be omitted. This is partly for tidiness. It can also be rationalised as making the average length of the Martian week close to the average length of the Terrestrial week, although it must be remembered that 28 Earth days is roughly equal to 27 14 Martian sols and not 27 56 Martian sols.

In the table, the days of the week are Sol Solis, Sol Lunae, Sol Martis, Sol Mercurii, Sol Jovis, Sol Veneris, Sol Saturni.

Sagittarius   Dhanus   Capricornus
So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa
1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7
8 9 10 11 12 13 14 8 9 10 11 12 13 14 8 9 10 11 12 13 14
15 16 17 18 19 20 21 15 16 17 18 19 20 21 15 16 17 18 19 20 21
22 23 24 25 26 27 28 22 23 24 25 26 27 28 22 23 24 25 26 27 28
         
Makara   Aquarius   Kumbha
So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa
1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7
8 9 10 11 12 13 14 8 9 10 11 12 13 14 8 9 10 11 12 13 14
15 16 17 18 19 20 21 15 16 17 18 19 20 21 15 16 17 18 19 20 21
22 23 24 25 26 27 28 22 23 24 25 26 27 28 22 23 24 25 26 27  
         
Pisces   Mina   Aries
So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa
1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7
8 9 10 11 12 13 14 8 9 10 11 12 13 14 8 9 10 11 12 13 14
15 16 17 18 19 20 21 15 16 17 18 19 20 21 15 16 17 18 19 20 21
22 23 24 25 26 27 28 22 23 24 25 26 27 28 22 23 24 25 26 27 28
         
Mesha   Taurus   Rishabha
So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa
1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7
8 9 10 11 12 13 14 8 9 10 11 12 13 14 8 9 10 11 12 13 14
15 16 17 18 19 20 21 15 16 17 18 19 20 21 15 16 17 18 19 20 21
22 23 24 25 26 27 28 22 23 24 25 26 27 28 22 23 24 25 26 27  
         
Gemini   Mithuna   Cancer
So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa
1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7
8 9 10 11 12 13 14 8 9 10 11 12 13 14 8 9 10 11 12 13 14
15 16 17 18 19 20 21 15 16 17 18 19 20 21 15 16 17 18 19 20 21
22 23 24 25 26 27 28 22 23 24 25 26 27 28 22 23 24 25 26 27 28
         
Karka   Leo   Simha
So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa
1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7
8 9 10 11 12 13 14 8 9 10 11 12 13 14 8 9 10 11 12 13 14
15 16 17 18 19 20 21 15 16 17 18 19 20 21 15 16 17 18 19 20 21
22 23 24 25 26 27 28 22 23 24 25 26 27 28 22 23 24 25 26 27  
         
Virgo   Kanya   Libra
So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa
1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7
8 9 10 11 12 13 14 8 9 10 11 12 13 14 8 9 10 11 12 13 14
15 16 17 18 19 20 21 15 16 17 18 19 20 21 15 16 17 18 19 20 21
22 23 24 25 26 27 28 22 23 24 25 26 27 28 22 23 24 25 26 27 28
         
Tula   Scorpius   Vrishika
So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa
1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7
8 9 10 11 12 13 14 8 9 10 11 12 13 14 8 9 10 11 12 13 14
15 16 17 18 19 20 21 15 16 17 18 19 20 21 15 16 17 18 19 20 21
22 23 24 25 26 27 28 22 23 24 25 26 27 28 22 23 24 25 26 27 28

The last day of Vrishika is an intercalary day that only occurs on leap years, much like February 29 in the Gregorian calendar.

Start of year

The Martian year is treated as beginning near the equinox marking spring in the northern hemisphere of the planet. Mars currently has an axial inclination similar to that of the Earth, so the Martian seasons are perceptible, though the greater eccentricity of Mars' orbit about the Sun compared with that of the Earth means that their significance is strongly amplified in the southern hemisphere and masked in the northern hemisphere.

Epoch

Gangale originally chose late 1975 as the epoch of the calendar in recognition of the American Viking program as the first fully successful (American) soft landing mission to Mars (the earlier 1971 Soviet Mars 3 Landing having delivered only 15 seconds of data from the planet's surface). In 2002 he adopted the Telescopic Epoch, first suggested by Peter Kokh in 1999 and adopted by Shaun Moss in 2001 for his Utopian Calendar, which is in 1609 in recognition of Johannes Kepler's use of Tycho Brahe's observations of Mars to elucidate the laws of planetary motion, and also Galileo Galilei's first observations of Mars with a telescope. Selection of the Telescopic Epoch thus unified the structures of the Darian and Utopian calendars, their remaining differences being nomenclatural. It also avoids the problem of the many telescopic observations of Mars over the past 400 years being relegated to negative dates.

Nomenclature

The Darian calendar has been widely imitated.[5] Suggested variations abound on the World Wide Web that use different nomenclature schemata for the days of the week and the months of the year. In the original Darian calendar, the names of the 24 months were provisionally chosen by Gangale as the Latin names of constellations of the zodiac and their Sanskrit equivalents in alternation. The 7 sols of the week, similarly, were provisionally named after the Sun, the largest Martian moon Phobos (Sol Phobotis) and the 5 brightest planets as seen from Mars including Earth (Sol Terrae). These were later modified to follow the familiar convention of the Romance languages, replacing Sol Phobotis with Sol Lunae and Sol Terrae with Sol Martis.[6] The Darian Defrost Calendar, however, creates new names for the Martian months out of patterns relating letter choice and name length to month order and season. The Utopian Calendar, devised by the Mars Time Group in 2001, also has additional suggestions for nomenclature modification.[7]

Mars Julian sol

The Mars Julian sol count is analogous to the Julian Day count on Earth, in that it is a continuous numerical counting of days from an epoch. The Mars Julian sol epoch is the same as for the Darian calendar, thus Mars Julian sol 0 is 1 Sagittarius 0.

Comparison with timekeeping systems in planetary science

Since the Darian calendar is designed as a civil calendar for human communities on Mars, it has no precise analog in the scientific community, which has no need to mark Martian time in terms of weeks or months. Two unrelated epochs that have gained some traction in the scientific community are the Mars sol date and the Mars year. In 1998 Michael Allison proposed the Mars sol date epoch of 29 December 1873 (Julian Day 2405521.502).[8] In 2000 R. T. Clancy et al. proposed the Mars year 1 set to the epoch 11 April 1955 (Julian Day 2435208.456).[9] The Clancy Mars year is reckoned from one Martian northward equinox to the next (Ls = 0°), and specific dates within a given year are expressed in Ls. The Clancy Mars year count is approximately equal to the Darian year count minus 183. The Allison Mars sol date epoch equates to Ls = 276.6° in a year that is undefined in the Clancy Mars year count. It converts to 25 Virgo 140 on the Darian calendar and Mars Julian sol 94128.511.

Martiana calendar

In 2002 Gangale devised a variant of the Darian calendar that reconciles the months and the sols of the week in a repeating pattern and removes the need to omit days of the week. In the Martiana variant, all the months in a given quarter begin on the same sol of the week, but the sol that begins each month shifts from one quarter to the next, based on the scheme devised by the astronomer Robert G. Aitken in 1936.[10]

The following table shows the sol of the week on which each month in the quarter begins. The first quarter corresponds to spring in the Martian northern hemisphere and autumn in the Martian southern hemisphere.

  First quarter Second quarter Third quarter Last quarter
Even-numbered years Sol Solis Sol Saturni Sol Veneris Sol Jovis
Odd-numbered years Sol Mercurii Sol Martis Sol Lunae Sol Solis

The leap sol occurs at the end of odd-numbered years as in the original Darian calendar. Since the last month of odd-numbered years contains 28 sols, the following year also begins on Sol Solis, resulting in a two-year cycle over which the relationship of the sols of the week to the months repeats. The sol that is added every tenth year is epagomenal (not counted as part of the week), thus the two-year rotation of the sols of the week is not disrupted. The Martiana scheme avoids the Darian calendar's need to shorten the week to six sols three to four times per year. The disadvantage is that the scheme results in a two-year cycle for reconciling the sols of the week and the months, whereas the Darian calendar is repeatable from month to month.

Other Darian calendars

In 1998 Gangale adapted the Darian calendar for use on the four Galilean moons of Jupiter discovered by Galileo in 1610: Io, Europa, Ganymede, and Callisto.[11] In 2003 he created a variant of the calendar for Titan.[12]

Important dates in Martian history

Event Gregorian date UTC SCET Darian date Mars Julian sol Mars Sol date Airy mean time
Mariner 4 flyby15 July 19651:00:5726 Taurus 1891266683253923:25
Mariner 6 flyby31 July 19695:19:0715 Cancer 1911281063397715:10
Mariner 7 flyby5 August 19695:00:4920 Cancer 1911281113398211:29
Mariner 9 entered orbit13 November 197118:0020 Kanya 1921289193479019:19
Mars 2 entered orbit27 November 19716 Libra 192*128933*34804*
Mars 3 contact lost 15 seconds after landing2 December 197113:5211 Libra 192128938348093:06
Mars 2 contact lost22 August 197216 Kumbha 193*129194*35065*
Mariner 9 contact lost27 October 197226 Mina 193*129259*35130*
Mars 4 failed to enter orbit10 February 197410 Sagittarius 194*129717*35588*
Mars 5 entered orbit12 February 197415:4512 Sagittarius 1941297193559017:18
Mars 5 contact lost7 March 19746 Dhanus 194*129741*35612*
Mars 7 lander missed Mars9 March 19748 Dhanus 194*129743*35614*
Mars 6 landing, contact lost after 224 seconds12 March 19749:11:0511 Dhanus 1941297463561716:56
Viking 1 entered orbit19 June 197612 Pisces 195*13055420*36425*
Viking 1 landing20 July 197611:5314 Mina 1951305843645518:40
Viking 2 entered orbit7 August 19764 Aries 195*130602*36473*
Viking 2 landing3 September 197622:583 Mesha 195130629365000:34
Viking 2 Orbiter contact lost25 July 19785 Mesha 196*131300*37171*
Viking 2 Lander contact lost11 April 19802 Mina 197*131909*37780*
Viking 1 Orbiter contact lost17 August 198014 Rishabha 197*132033*37904*
Viking 1 Lander contact lost11 November 19821 Leo 198*132828*38699*
Phobos 2 entered orbit29 January 198911 Vrishika 201*135038*40909*
Phobos 2 contact lost27 March 198910 Dhanus 202*135093*40964*
Mars Pathfinder landing4 July 199716:5726 Taurus 206138034439054:41
Mars Pathfinder rover Sojourner contact lost27 September 199710:2325 Mithuna 2061381164398715:43
Mars Global Surveyor entered orbit11 September 19971:17:009 Mithuna 2061381004397117:08
Mars Climate Orbiter destroyed entering atmosphere23 September 19999:058 Karka 207138823446944:16
Mars Polar Lander impact3 December 199920:1521 Simha 2071388924476317:32
2001 Mars Odyssey entered orbit24 October 20012:18:0024 Simha 2081395644543512:21
Nozomi failed to enter orbit14 December 20036 Tula 209*140325*46196*
Mars Express entered orbit25 December 20033:0016 Tula 209140335462068:27
Beagle 2 lander impact25 December 20033:54:0016 Tula 209140335462069:20
MER-A Spirit landing4 January 20044:3526 Tula 209140345462163:35
MER-B Opportunity landing25 January 20045:0518 Scorpius 2091403654623614:35
Mars Reconnaissance Orbiter entered orbit10 March 200621:2420 Dhanus 2111411204699112:48
Phoenix landing25 May 200823:5425 Kumbha 212141906477771:02
Phoenix contact lost28 October 20089 Rishabha 212*142057*47928*
MER-A Spirit contact lost22 March 20104 Kumbha 213*142553*48424*
MSL Curiosity landing6 August 20125:1713 Rishabha 214143398492695:50
MAVEN entered orbit22 September 201402:2418 Cancer 215144154500258:07
Mars Orbiter Mission entered orbit24 September 201402:0020 Cancer 215144156500276:27
ExoMars Trace Gas Orbiter entered orbit, Schiaparelli EDM lander impact19 October 201615:243 Simha 2161448925134814:02
MER-B Opportunity ceased communication12 June 20184 Cancer 217*145477*51348*
InSight landing, Mars Cube One flyby26 November 201819:52:5926 Kanya 2171456405151105:14:37

*Mars dates are approximate where the exact time of the event is not stated.

The Darian calendar in fiction

Gangale was inspired to create the calendar after reading Red Planet, a 1949 science fiction book by Robert A. Heinlein. In the book, Heinlein postulates a 24-month Martian calendar.[13]

The Darian calendar is mentioned in several works of fiction set on Mars:

See also

Notes

  1. Gangale, Thomas. (1986-06-01). "Martian Standard Time". Journal of the British Interplanetary Society. Vol. 39, No. 6, p. 282–288.
  2. http://www.univelt.com/linkedfiles/MarsSocietyProc.html
  3. Gangale, Thomas. (1998-08-01). "The Darian Calendar". Mars Society. MAR 98-095. Proceedings of the Founding Convention of the Mars Society. Volume III. Ed. Robert M. Zubrin, Maggie Zubrin. San Diego, California. Univelt, Incorporated. 13-Aug-1998.
  4. Gangale, Thomas. (2006-07-01). "The Architecture of Time, Part 2: The Darian System for Mars." Society of Automotive Engineers. SAE 2006-01-2249.
  5. Gangale, Thomas. "The Darian Calendar for Mars: Children and Collateral Relatives". Martian Time. Retrieved 4 February 2015.
  6. Gangale, Thomas. "The Darian System". Retrieved 18 June 2016.
  7. Moss, Shaun. "The Utopian Calendar". Martian Time. Archived from the original on 25 May 2015. Retrieved 3 February 2015.
  8. Allison, Michael (198-08-13). "A Mars Proleptic Calendar and Sol-Date Timing Reference". Presented at the Founding Convention of the Mars Society.
  9. Clancy, R. T., B. J. Sandor, M. J. Wolff, P. R. Christensen, J. C. Pearl, B. J. Conrath, and R. J. Wilson (2000-04-25). "An intercomparison of ground-based millimeter, MGS TES, and Viking atmospheric temperature measurements: Seasonal and interannual variability of temperatures and dust loading in the global Mars atmosphere". Journal of Geophysical Research. vol. 105, no. E4, page 9564.
  10. Aitken, Robert G. (1936-12-01). "Time Measures on Mars". Astronomical Society of the Pacific Leaflets. Leaflet 95—December, 1936.
  11. Gangale, Thomas. "The Calendars of Jupiter". Martian Time. Retrieved 3 February 2015.
  12. Gangale, Thomas. "The Darian Calendar for Titan". Martian Time. Retrieved 3 February 2015.
  13. Jan Gyllenbok, Encyclopaedia of Historical Metrology, Weights, and Measures, volume 1, p. 284, Birkhäuser, 2018 ISBN 9783319575988.

References

  • Bennett, Christopher L. (2011-04-26). Star Trek: Department of Temporal Investigations: Watching the Clock, p. 352. Pocket Books/Star Trek.
  • Gangale, Thomas. (1986-06-01). "Martian Standard Time". Journal of the British Interplanetary Society. Vol. 39, No. 6, p. 282–288
  • Gangale, Thomas. (1997-02-01). "Mare Chronium: A Brief History of Martian Time". American Astronautical Society. AAS 90–287. The Case for Mars IV: The International Exploration of Mars. Ed. Thomas R. Meyer. San Diego, California. Univelt, Incorporated.
  • Gangale, Thomas. (1998-08-01). "The Darian Calendar". Mars Society. MAR 98-095. Proceedings of the Founding Convention of the Mars Society. Volume III. Ed. Robert M. Zubrin, Maggie Zubrin. San Diego, California. Univelt, Incorporated. 13-Aug-1998.
  • Gangale, Thomas, and Dudley-Rowley, Marilyn. (2004-07-01). "The Architecture of Time: Design Implications for Extended Space Missions" Society of Automotive Engineers. SAE 2004-01-2533. SAE Transactions: Journal of Aerospace.
  • Gangale, Thomas, and Dudley-Rowley, Marilyn. (2005-12-01). "Issues and Options for a Martian Calendar". Planetary and Space Science. Vol. 53, pp. 1483–1495.
  • Gangale, Thomas. (2006-07-01). "The Architecture of Time, Part 2: The Darian System for Mars." Society of Automotive Engineers. SAE 2006-01-2249.
  • Rajaniemi, Hannu. The Quantum Thief, Ch, 12. Tor Books.
  • Sakers, Don. (2004-01-01). The Sf Book of Days, pp. 7, 19, 31, 53, 81, 103, 113, 123, 135, 145–149. Speed-Of-C Productions.
  • Smith, Arthur E. (1989-01-01). Mars: The Next Step, p. 7. Taylor & Francis.

Apps

This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.