Mars
Telling the time on Mars
A Martian day, or Sol, consists of 24 Martian hours, each divided into 60 Martian minutes, which in turn are each divided into 60 Martian seconds. However, as a Martian Sol is longer than an Earth day, each Martian hour (and minute, and second) is roughly 3 percent longer than its Earth equivalent.
Terminology
Airy-0. A crater roughly 500 meters in diameter that sits inside the larger Airy crater. The centre of Airy-0 is used to define the Mars Prime Meridian.
Curiosity Rover - the Mars Science Laboratory (MSL). A currently active Rover that landed on Mars in August 2012.
LMST - Local Mean Solar Time. The time based on a mean sun position - akin to using something like GMT on Earth.
LMZT - Local Mean Zonal Time. The local mean solar time for a given time zone.
Ls - Areocentric longitude. A Mars year lasts just under 687 Earth days. Rather than describe the time of the Mars year by the use of month names, or seasons, the areocentric longitude is used instead. An areocentric longitude of 0 degrees relates to the Mars Northern hemisphere vernal equinox (on Earth in the Northern latitudes we would refer to the Earth equivalent of this as the spring equinox).
LTST - Local True Solar Time. The time based on the true position of the Sun for a given longitude.
Martian Prime Meridian. The point by which all other Mars longitudes are measured. It is defined as the centre of the Airy-0 crater.
Martian Time Zones - Each Martian time zone covers 15 degrees of longitude, and is referred by an offset to MTC, e.g. MTC+1, MTC-7, etc.
Mission Clock - The mission clock relates to each specific Martian Rover or Lander mission. Instead of using a standard time zone to measure time at each landing site, each mission so far has used its own unique mission time. The majority of these have been based on offsets of LMST for a given longitude on Mars. For various reasons these longitudes do not tend to map directly onto specific mission landing coordinates, but instead the offsets are from MTC. That\’s why, for each rover for example, the mission clock does not exactly match the LMST for the landing coordinates. The mission clock is what is used by the Rover\’s handlers back here on Earth to plan mission events. When mission clock is selected in this application for a given rover the Sol count is shown - this is a reflection of the number of days that the rover has been on Mars (oddly, some missions count Sol 1 as the landing day, while others count Sol 0 as the landing day).
MJD - Modified Julian Date. The count of Earth days since 1st January, 1970. This is simply a cumulative day count, often used by astronomers, etc.
MSD - Mars Sol Date. This is a count of the number of Sols since the Earth date of 29th December, 1873. It is effectively the Mars equivalent of the MJD.
MTC - the time zone based on the Local Mean Solar Time at the Mars Prime Meridian (previously referred to as Airy Mean Time).
Opportunity Rover - Mars Exploration Rover B (MER-B). A currently active Rover that landed on Mars in January 2004.
Sol - a Sol is a Martian day. This equates to just under 24 hours and 40 minutes in Earth time (so a Martian sol is just under 3 percent longer than an Earth day).
Spirit Rover - Mars Exploration Rover A (MER-A). A now defunct Rover that landed on Mars in January 2004.
Further information
http://www.giss.nasa.gov/tools/mars24 - the definitive Mars clock, as produced by NASA. This application is based on the calculations explained within the worked examples from this site
http://en.wikipedia.org/wiki/Mars_time - A thorough explanation of how to tell the time on Mars
http://jtauber.github.com/mars-clock - An excellent JAVAscript implementation of the MARS24 calculations
http://mars.jpl.nasa.gov - The Mars Exploration Program website
Changelog
0.9 - Initial public release to Google Play.