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On Earth, finding the exact time is effortless. Our planet relies on a sophisticated global system that combines atomic clocks, GPS satellites, and ultra-fast communication networks to keep everything in sync.
That precision does not extend naturally beyond Earth. Albert Einstein showed that time does not move at the same pace everywhere in the universe. The rate at which a clock ticks depends on gravity, meaning clocks run slightly slower in stronger gravity and faster in weaker gravity. Even coordinating time across Earth is complex. Extending that coordination across the solar system is far more challenging. For future explorers hoping to live and work on Mars, one fundamental question must be answered first: What time is it on Mars?
Scientists Calculate Mars Time for the First Time
Physicists at the National Institute of Standards and Technology (NIST) have now produced a precise answer. Their calculations show that, on average, clocks on Mars tick 477 microseconds (millionths of a second) faster per day than clocks on Earth. That difference is not constant. Because of Mars’ stretched orbit and gravitational influences from other bodies, the time difference can vary by as much as 226 microseconds per day throughout the Martian year.
The research was recently published in The Astronomical Journal and builds on a 2024 study in which NIST scientists outlined a framework for highly precise timekeeping on the Moon.
Understanding how time passes on Mars is essential for future missions, said NIST physicist Bijunath Patla. As NASA prepares for more advanced Mars exploration, accurate timing will be critical for navigation, communication, and coordination across planetary distances.
“The time is just right for the Moon and Mars,” Patla said. “This is the closest we have been to realizing the science fiction vision of expanding across the solar system.”
Mars Time Zone
Mars operates on a different schedule than Earth in more ways than one. A single Martian day lasts about 40 minutes longer than an Earth day, and a Martian year stretches across 687 Earth days compared with 365 days on Earth. Beyond those obvious differences, scientists needed to determine whether each second on Mars passes at the same rate as it does on Earth.
An atomic clock placed on the surface of Mars would function normally. The clock itself would tick just as it does on Earth. The problem appears when that Mars clock is compared with one on Earth. Over time, the two clocks drift apart. The task for scientists was to determine exactly how large that offset becomes, similar to defining a planetary time zone.
That calculation proved more complicated than expected. According to Einstein’s theory of relativity, gravity alters the flow of time. Clocks slow down in stronger gravity and speed up where gravity is weaker. A planet’s motion through space also affects how time passes, with orbital speed contributing additional changes.
Gravity, Orbits, and Relativity
To make the calculations possible, NIST researchers selected a specific reference point on the Martian surface, comparable to sea level at Earth’s equator. Using data gathered from years of Mars missions, Patla and fellow NIST physicist Neil Ashby estimated surface gravity on Mars, which is about five times weaker than Earth’s.
Gravity from Mars alone was not enough to explain the full picture. The solar system is a dynamic environment filled with massive objects that constantly pull on one another. The Sun contains more than 99% of the solar system’s total mass, and its gravitational influence dominates planetary motion.
Mars’ location in the solar system — its distance from the Sun, its neighbors like Earth, the Moon, Jupiter and Saturn — forces it into a more elongated and eccentric orbit. By contrast, Earth and the Moon follow relatively stable paths. As a result, time on the Moon consistently runs 56 microseconds faster per day than time on Earth.
“But for Mars, that’s not the case. Its distance from the Sun and its eccentric orbit make the variations in time larger. A three-body problem is extremely complicated. Now we’re dealing with four: the Sun, Earth, the Moon and Mars,” Patla explained. “The heavy lifting was more challenging than I initially thought.”
After accounting for Martian surface gravity, orbital motion, and the gravitational effects of the Sun, Earth, and Moon, Patla and Ashby arrived at their final calculation.
Paving the Way for Solar System Internet
A difference of 477 millionths of a second may seem insignificant. It is roughly one thousandth of the time it takes to blink. Yet such tiny differences matter greatly in modern technology. For example, 5G communication systems require timing accuracy within a tenth of a microsecond.
Today, messages sent between Earth and Mars take anywhere from four to 24 minutes to arrive, and sometimes even longer. Patla compared the situation to communication before the telegraph, when handwritten letters crossed oceans by ship and replies took weeks or months to return.
Developing a reliable framework for timekeeping between planets could eventually allow for synchronized communication networks across the solar system.
“The time is just right for the Moon and Mars. This is the closest we have been to realizing the science fiction vision of expanding across the solar system.” Bijunath Patla, NIST physicist
“If you get synchronization, it will be almost like real-time communication without any loss of information. You don’t have to wait to see what happens,” Patla said.
Preparing for Future Mars Exploration
Fully synchronized interplanetary networks remain far in the future, as do permanent human settlements on Mars. Still, studying these timing challenges now helps scientists anticipate the obstacles ahead, Ashby noted.
“It may be decades before the surface of Mars is covered by the tracks of wandering rovers, but it is useful now to study the issues involved in establishing navigation systems on other planets and moons,” Ashby said. “Like current global navigation systems like GPS, these systems will depend on accurate clocks, and the effects on clock rates can be analyzed with the help of Einstein’s general theory of relativity.”
Patla added that the research also advances fundamental science. Measuring how time behaves on distant worlds provides new tests of Einstein’s theories of special and general relativity.
“It’s good to know for the first time what is happening on Mars timewise. Nobody knew that before. It improves our knowledge of the theory itself, the theory of how clocks tick and relativity,” he said. “The passage of time is fundamental to the theory of relativity: how you realize it, how you calculate it, and what influences it. These may seem like simple concepts, but they can be quite complicated to calculate.”
