What Time Is It on Mars? Physicists Finally Have an Exact Answer

Summary: Time doesn’t flow uniformly across the solar system, and new research reveals just how differently it unfolds on Mars compared with Earth. By tracing subtle gravitational and orbital influences, scientists have uncovered variations in the pace of Martian time that could become crucial for future navigation and communication far from home.

NIST physicists have precisely calculated how Martian time subtly speeds up and slows down, revealing a daily drift that changes with the planet’s shifting orbit.

Ask someone on Earth for the time and you will get an exact answer, largely because our planet relies on a sophisticated network of atomic clocks, GPS satellites, and rapid communication systems.

Einstein’s work revealed that time does not pass uniformly throughout the universe. The rate at which a clock ticks changes with the strength of local gravity, which complicates efforts to keep clocks synchronized on Earth and makes coordination across the solar system even more challenging. For any long-term human activity on Mars, researchers first need a reliable answer to a basic question: What time is it on the red planet?

Physicists at the National Institute of Standards and Technology (NIST) have now produced the first detailed calculation. They determined that a clock on Mars would run 477 microseconds (millionths of a second) faster each day compared with a clock on Earth. This difference is not fixed, since Mars’ elongated orbit and the gravitational pull from nearby planets can adjust this daily offset by as much as 226 microseconds over the course of a Martian year. The results appear in The Astronomical Journal and build on a 2024 study in which NIST researchers proposed a method for precise timekeeping on the Moon.

Understanding how time progresses on Mars provides an essential foundation for future missions, explained NIST physicist Bijunath Patla. As NASA prepares upcoming Mars expeditions, having accurate knowledge of Martian time will be crucial for coordinating navigation and communication throughout the solar system.

“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

Martian days and years are longer than those on Earth. The planet’s day, or full rotation on its axis, is 40 minutes longer than Earth’s, and it takes 687 days to complete its orbit around the Sun, compared with Earth’s 365 days. But scientists needed to know how fast or slow each second passes on Mars compared with Earth.

If you were to land on the surface of Mars with an atomic clock, it would still tick the same way it would on Earth. But if you compare the Mars clock with one on Earth, they will be out of sync. The challenge is to determine how much Mars’ time is offset from Earth’s, almost like calculating a time-zone difference.

That was much trickier than NIST physicists had expected. Einstein’s theory of relativity states that the strength of gravity affects the passage of time. Clocks tick slower where gravity is stronger, and faster where gravity is weaker. The velocity of a planet’s orbit will also cause clocks to tick slower or faster.

NIST chose a point on the Martian surface to act as a reference, sort of like sea level at the equator on Earth. Thanks to years of data collected from Mars missions, Patla and fellow NIST physicist Neil Ashby could estimate gravity on the surface of the planet, which is five times weaker than Earth’s.

But they needed to figure in more than just Mars’ gravity. Our solar system has other massive bodies that pull on each other. The Sun alone accounts for more than 99% of the mass in our solar system. Mars’ position in the solar system — its distance from the Sun, its neighbors like Earth, the Moon, Jupiter, and Saturn — pulls it into a more eccentric, elongated orbit. The Earth’s and Moon’s orbits are relatively constant; time on the Moon is consistently 56 microseconds faster 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 taking all these effects into consideration — Martian surface gravity, Mars’ eccentric orbit, the effect of the Sun, the Earth, and the Moon on Mars — Patla and Ashby arrived at their answer.

Paving the Way for Solar System Internet

Maybe 477 millionths of a second doesn’t sound like a lot — it’s about a thousandth of the time it takes to blink. But accounting for tiny time differences is key to developing communications networks. 5G networks, for example, need to be accurate to within a tenth of a microsecond.

Right now, communications between Earth and Mars are delayed anywhere from four to 24 minutes (sometimes more). It’s almost like pre-telegram communications, Patla explained: People delivered handwritten letters to a ship, which crossed the ocean, and then waited weeks or months for another ship to deliver the reply.

Having a framework for timing between planets paves the way toward creating synchronized networks across vast distances.

“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.

Those networks are a long way from reality; so are long-term human and robotic Mars missions, Ashby pointed out. Studying these issues helps scientists prepare for all the variables they will encounter.

“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.”

There is also scientific value to this knowledge, Patla added. Understanding how clocks will tick on far-flung planets is new information and builds on Einstein’s theories of special and general relativity.

“It’s good to know for the first time what is happening on Mars time-wise. 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.”

Reference: “A Comparative Study of Time on Mars with Lunar and Terrestrial Clocks” by Neil Ashby and Bijunath R. Patla, 1 December 2025, The Astronomical Journal.
DOI: 10.3847/1538-3881/ae0c16

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