Physicists Finally Figured Out How Time Really Works on Mars
Ask someone on Earth what time it is, and the answer feels simple. Behind the scenes, though, that simplicity depends on atomic clocks, GPS satellites, and incredibly precise global networks. Now imagine trying to answer the same question for another planet. That challenge has just taken a major step forward, as physicists have calculated, with unprecedented precision, how fast time passes on Mars compared to Earth.
Scientists at the National Institute of Standards and Technology (NIST) have published the most accurate comparison yet of Martian time versus Earth time. Their conclusion is both subtle and important: clocks on Mars tick faster than clocks on Earth, by an average of 477 microseconds per Earth day. While that difference is tiny, it has major implications for future Mars missions, navigation systems, and even the idea of a solar system–wide communication network.
Why Time Is Complicated Beyond Earth
On Earth, timekeeping is carefully standardized. Atomic clocks define the length of a second, GPS satellites constantly synchronize signals, and high-speed telecommunications keep everything aligned. But physics tells us that time is not universal.
Albert Einstein’s theories of special and general relativity showed that time changes depending on gravity and motion. Clocks tick slower in stronger gravity and faster in weaker gravity. Motion matters too: the faster an object moves through space, the slower time passes for it relative to a stationary observer.
These effects are extremely small in everyday life, but they become critical when comparing clocks on different planets. If humans plan to explore Mars long-term—or eventually live there—scientists need to know exactly how Martian time differs from Earth time.
The Core Result: Mars Time vs Earth Time
The NIST team calculated that Martian clocks run faster than Earth clocks by 477 microseconds per day, on average. A microsecond is one millionth of a second, so this difference is only about a thousandth of the time it takes to blink.
However, the story doesn’t stop there.
Mars does not move around the Sun in a neat, nearly circular orbit like Earth. Instead, it follows a more eccentric (elongated) orbit, which means its speed and distance from the Sun change noticeably over the Martian year. Because gravity and velocity affect time, this leads to variations in how fast time passes on Mars.
According to the study, the daily time difference between Mars and Earth can increase or decrease by as much as 226 microseconds over the course of a Martian year.
Choosing a Reference Point on Mars
To make these calculations meaningful, scientists needed a consistent reference point—similar to how sea level at Earth’s equator is often used for time and gravity measurements on our planet.
The researchers selected a specific location on the Martian surface as their reference. Using decades of data from Mars missions, they were able to estimate the planet’s surface gravity with high precision. Mars’ gravity turns out to be about five times weaker than Earth’s, which plays a major role in why clocks there tick faster.
If you physically carried an atomic clock from Earth to Mars, it would function normally. But when compared side by side with an Earth-based clock, the Martian clock would slowly drift ahead.
More Than Just Mars’ Gravity
One of the biggest challenges in this research was accounting for all the gravitational influences acting on Mars. While Mars’ own gravity matters, it’s only part of the picture.
The Sun, which contains more than 99% of the solar system’s total mass, exerts a massive influence. On top of that, Earth, the Moon, Jupiter, and Saturn also tug gravitationally on Mars, subtly altering its orbit and velocity.
This turns the problem into a complex multi-body system. Earth and the Moon have relatively stable orbits, which is why time on the Moon consistently runs about 56 microseconds faster per day than on Earth. Mars, by contrast, experiences much larger fluctuations because of its orbital shape and gravitational environment.
Accounting for all of these effects required advanced relativistic modeling and careful numerical analysis.
Mars Days and Mars Years Are Longer Too
Time on Mars isn’t just different because of relativity. The basic structure of the Martian day and year also differs from Earth’s.
A single Martian day, known as a sol, is about 40 minutes longer than an Earth day. Meanwhile, a Martian year lasts 687 Earth days, nearly twice as long as a year here.
These differences already complicate mission planning, rover operations, and communication schedules. Adding relativistic time offsets makes precise synchronization even more important.
Why Microseconds Matter So Much
At first glance, hundreds of microseconds per day might sound trivial. In modern technology, however, tiny timing errors can cause major problems.
For example, 5G communication networks require synchronization accuracy of about one-tenth of a microsecond. Satellite navigation systems like GPS depend on extremely precise clock alignment to calculate positions accurately.
Right now, communication between Earth and Mars suffers from delays of four to 24 minutes, depending on the planets’ positions. Messages are essentially sent like letters across space, with long waits for replies. Precise planetary timekeeping won’t eliminate these delays, but it lays the groundwork for more reliable, synchronized interplanetary networks.
In the long term, such systems could make space communication feel far less disconnected and more continuous.
Preparing for Future Mars Missions
NASA and other space agencies are already planning future robotic and human missions to Mars. Understanding how time behaves on the planet is a critical part of that preparation.
Future Mars navigation systems may eventually resemble Earth’s GPS, relying on networks of satellites and surface-based clocks. For these systems to work, scientists must know exactly how relativistic effects alter clock rates on Mars.
Even if large-scale Mars exploration is still decades away, studying these issues now helps engineers anticipate challenges before they become mission-critical problems.
What This Means for Physics
Beyond its practical uses, the study has scientific value of its own. Measuring how time behaves on Mars provides a real-world test of Einstein’s theories in a new gravitational environment.
Every new planetary time comparison strengthens our understanding of how relativity operates across the solar system. Mars adds complexity that Earth and the Moon do not, making it an especially valuable case study.
Time, after all, is one of the most fundamental concepts in physics. Understanding how it flows under different conditions deepens our grasp of the universe itself.
Looking Ahead
This research builds on earlier work by the same NIST team, including a 2024 study focused on precise timekeeping on the Moon. Together, these efforts represent a broader push toward extending Earth’s timing infrastructure beyond our planet.
As humans continue to explore space, knowing exactly what time it is—everywhere—will matter more than ever.
Research paper:
Neil Ashby et al., A Comparative Study of Time on Mars with Lunar and Terrestrial Clocks, The Astronomical Journal (2025)
https://doi.org/10.3847/1538-3881/ae0c16
