2/21/2023 0 Comments Mars24 time clock![]() ![]() It replaced Mars24's previous use of the term "Airy Mean Time" (AMT), which was a direct parallel of Greenwich Mean Time (GMT). Use of the term "MTC" as the name of a planetary standard time for Mars first appeared in the Mars24 sunclock coded by the NASA Goddard Institute for Space Studies. The name "MTC" is intended to parallel the Terran Coordinated Universal Time (UTC), but this is somewhat misleading: what distinguishes UTC from other forms of UT is its leap seconds, but MTC does not use any such scheme. The definition of the Martian prime meridian has since been refined on the basis of spacecraft imagery as the center of the crater Airy-0 in Terra Meridiani. This convention was readily adopted by the astronomical community, the result being that Mars had a universally accepted prime meridian half a century before the International Meridian Conference of 1880 established one for Earth. The prime meridian was first proposed by German astronomers Wilhelm Beer and Johann Heinrich Mädler in 1830 as marked by the fork in the albedo feature later named Sinus Meridiani by Italian astronomer Giovanni Schiaparelli. It is defined as the mean solar time at Mars's prime meridian. MTC is a proposed Mars analog to Universal Time ( UT1) on Earth. The older "planetographic longitude" was measured from 0°–360° West and used coordinates mapped onto the surface. 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 two Mars Exploration Rovers happen to be approximately 12 hours and one minute apart.) Each lander so far has used an approximation of local solar time as its frame of reference, as cities did on Earth before the introduction of standard time in the 19th century. However, Mars does not have time zones defined at regular intervals from the prime meridian, as on Earth. Mars has a prime meridian, defined as passing through the small crater Airy-0. Because its orbital eccentricity is greater than that of Earth, the length of day varies from the average by a greater amount than that of Earth, and hence its equation of time shows greater variation than that of Earth: on Mars, the Sun can run 50 minutes slower or 40 minutes faster than a Martian clock (on Earth, the corresponding figures are 14min 22sec slower and 16min 23sec faster). Because of orbital eccentricity, the length of the solar day is not quite constant. ![]() The equation of time is illustrated by an analemma. These include a metric time schema, with "millidays" and "centidays", and an extended day which uses standard units but which counts to 24hr 39m 35s before ticking over to the next day.Īs on Earth, on Mars there is also an equation of time that represents the difference between sundial time and uniform (clock) time. Its temperature rises and falls rapidly at sunrise and sunset because Mars does not have the Earth's thick atmosphere and oceans that buffer such fluctuations.Īlternative clocks for Mars have been proposed, but no mission has chosen to use such. Daylight is needed for the solar panels of landed spacecraft. Local solar time has a significant impact on planning the daily activities of Mars landers. Wristwatches calibrated in Martian time, rather than Earth time, were used by many of the MER team members. This results in the crew's schedule sliding approximately 40 minutes later in Earth time each day. For the Mars Pathfinder, Mars Exploration Rover, Phoenix, and Mars Science Laboratory missions, the operations team has worked on "Mars time", with a work schedule synchronized to the local time at the landing site on Mars, rather than the Earth day. Thus Mars' solar day is only about 2.7% longer than Earth's.Ī convention used by spacecraft lander projects to date has been to keep track of local solar time using a 24-hour "Mars clock" on which the hours, minutes and seconds are 2.7% longer than their standard (Earth) durations. This yields a conversion factor of 1.0274912510 days/sol. The corresponding values for Earth are 23h 56m 4.0916s and 24h 00m 00.002s, respectively. ![]() The average length of a Martian sidereal day is 24h 37m 22.663s (88,642.66300 seconds based on SI units), and the length of its solar day (often called a sol) is 88,775.24409 seconds or 24h 39m 35.24409s. ![]()
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