Scientists have discovered that time moves slightly faster on the Red Planet than on Earth. Clocks on Mars, when measured from Earth, run an average of 0.477 milliseconds (477 microseconds) faster in a 24-hour period compared to time recorded on Earth, a new study has found. Knowing this difference may help establish an “internet” throughout the solar system.
In the coming decades, humanity’s presence in the solar system will increase, and missions like NASA’s Artemis mission are expected to pave the way for permanent settlements on the moon and beyond. Developing a standard clock for each location in space would help astronauts navigate these worlds while coordinating communications with Earth.
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Time keeps slipping away
When measured from Earth, speed and gravity cause time to tick at different rates for different solar system objects. A 2024 study calculated that the moon’s clock would be on average 56 microseconds (one millionth of a second) faster than Earth’s clock. After establishing this, physicists Neil Ashby and Bijnath Patra of the National Institute of Standards and Technology in Boulder, Colorado, turned their attention to Mars.
First, they chose a reference level on Mars, called the Arade, which corresponds to Earth’s sea level. They then used physics-based formulas to calculate how the gravity and velocity of Mars and Earth affect time on Mars in Leoid. Mars’ slow orbital speed compared to Earth would slow down a Mars-based clock, but Mars’ weak surface gravity, which is one-fifth less than Earth’s sea-level gravity, would make the clock even faster.
However, the shape of the trajectory was ignored in this analysis. Mars’ orbit is distorted by the gravitational pull of Earth and the Moon, making it more egg-shaped than Earth. (The effects of Mars’ moons Deimos and Phobos are negligible, Patra told Live Science in an email. Because of their small size, they are only a few miles wide, while Earth’s moon is 2,159 miles wide, or 3,475 kilometers.) So Ashby and Patra factored Mars’ orbital shape, the sun’s gravity, and Earth’s moon’s gravity into the equation.
Setting the clock on Mars
The analysis showed that clocks on Mars tick an average of 477 microseconds per Earth day faster than clocks on Earth, as measured from Earth. But amazingly, this value changes by 226 microseconds (about half the offset value itself) every day of the Martian year. This variation is due to the egg-shaped orbit of Mars and changes in the gravity of nearby objects as they approach and move away from Mars.
Additionally, the researchers found that the clock changes by an additional 40 microseconds every seven synodal cycles on Mars. A synod cycle is the time it takes for Mars to reappear in the same position.
“The fluctuations and the fluctuations in the planetary dance (resonance period) of Earth and Mars were surprising,” Patra said. This is because the scale was larger than expected.
The findings, published Dec. 1 in the journal Astronomy, could help scientists synchronize time across the solar system and establish high-speed communication channels with an interplanetary internet in the distant future, but high variability will complicate the effort, Patra said. He added that the study “provides a baseline for future tests of general relativity and fundamental physics that explore the nature of spacetime.”
However, the calculations were still inaccurate by about 100 nanoseconds (0.1 microseconds) per day over long timescales because small changes in the planet’s motion were not taken into account. This inaccuracy is negligible, but it means resetting Mars’ clock every 100 days.
The study also did not take into account factors such as how the planet’s orbit precesses or wobbles over time, and the effects of Earth and Mars’ gravitational quadrupole moments (a measure of the arrangement of masses within the structure). Taken together, these limitations can make it more difficult to obtain more accurate time calculations, the researchers said.
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