Ask anyone on Earth what the current time is, and they can tell you in a jiffy. Across the planet, highly accurate clocks help maintain a common standard for measuring time. Mars, however, is a different story.
As conditions differ between the two planets, clocks on Mars do not keep time at the same rate as clocks on Earth. Scientists have now examined this difference in detail, comparing the passage of time on Mars with that on Earth.
Authors Neil Ashby and Bijunath Patla calculated that a clock on Mars ticks an average of 477 microseconds faster per day than a clock on Earth. The study also found that the difference between the Mars-Earth and Mars-Moon clock-rate offsets is about 56 microseconds per day. Messages between Earth and Mars currently take anywhere from four to 24 minutes to arrive depending on where the two planets sit in their orbits, so any future system built to synchronize communication between the worlds will need to build in these timing differences from day one. A Martian day, known as a sol, lasts about 24 hours, 39 minutes and 35 seconds, making it roughly 39.5 minutes longer than an Earth day. The review notes that during NASA ‘s Phoenix Mars Lander mission, personnel worked on a Mars-day schedule for 78 days, with additional artificial illumination used as a countermeasure. Their average daily sleep duration was about 5.98 hours among those whose sleep-wake cycles synchronized with the Martian day, compared with about 4.91 hours among those who did not synchronize.
Because mars follows a more eccentric orbit and its distance from the Sun changes, the researchers also found that this difference varies by 226 microseconds per day over a Martian year, in part. Because its surface gravity is about five times weaker than Earth’s and partly because its longer, 687-day year brings sharper swings in distance from the Sun, mars proved far trickier to model, partly. A team of physicists at the US National Institute of Standards and Technology set out to answer a deceptively simple question: what time is it on Mars? Their findings, detailed in a paper titled A Comparative Study of Time on Mars with Lunar and Terrestrial Clocks in The Astronomical Journal, provide a precise comparison of clocks on Mars, Earth and the Moon. Those combined factors pushed the calculations well past a simple two-body problem into far messier territory. This precision is not just an academic exercise. Accurate timekeeping is already important for modern telecommunications, navigation and other technologies, and future missions between Earth and Mars will face even more demanding timing challenges. Beyond the physics of relativity, Mars presents a more everyday timekeeping problem. A separate review in Frontiers in Astronomy and Space Sciences examined how this small difference can affect the human circadian rhythm.
