Humanity has always aspired to inhabit Mars. Understanding the correct time on the planet is crucial for establishing communication networks if humans intend to dwell on Mars for an extended period. Scientists have now found the answer to this seemingly complex issue.
The National Institute of Standards and Technology (NIST) in the United States stated in a press release on December 1 that, according to Albert Einstein’s General Theory of Relativity, time is not synchronized across the universe. The speed at which clocks run varies due to the gravitational strength in their surrounding environment.
Physicist Bijunath Patla from the institute mentioned that understanding how clocks work on Mars is fundamental for future space missions. With NASA planning Mars exploration missions, comprehending the time on the planet will aid in synchronizing navigation and communication across the entire solar system.
A day and year on Mars are both longer compared to Earth. Mars has a rotation period 40 minutes longer than Earth and takes 687 days to orbit the sun, whereas Earth only requires 365 days. Scientists need to determine whether each second on Mars passes faster or slower than on Earth.
If an atomic clock from Earth is brought to Mars, it would still function the same way but not in sync with clocks on Earth. Therefore, it is crucial to ascertain the time difference between Mars and Earth, akin to calculating time zone differences.
This proved to be much more challenging than anticipated by NIST scientists. General Theory of Relativity indicates that gravitational strength affects the passage of time. In areas with stronger gravity, clocks tick slower, while in weaker gravity zones, clocks tick faster. The planet’s orbital speed also impacts the clock’s speed.
Choosing a point on the Martian surface as a reference point, similar to Earth’s equatorial sea level, the scientists estimated the gravitational strength on Mars to be only one-fifth of Earth’s based on data collected from years of Mars exploration missions.
However, they must consider not only Mars’ gravity but also the gravitational influence of other massive celestial bodies in the solar system. The mass of the sun alone accounts for over 99% of the solar system’s total mass.
Additionally, Mars’s position in the solar system — its distance from neighboring celestial bodies like the sun, Earth, the moon, Jupiter, and Saturn — results in an orbit that is more elliptical. In contrast, the orbits of Earth and the moon are more stable. Time on the moon is always 56 microseconds (millionths of a second) faster than on Earth.
By considering factors such as Martian surface gravity, the planet’s eccentric orbit, the influence of the sun, Earth, and the moon on Mars, among others, Patla and Ashby calculated Mars time. On average, the clock on Mars is 477 microseconds ahead of Earth’s clock each day.
While 477 microseconds may seem insignificant, it is crucial for the development of communication networks to accurately control extremely small time differences. For example, the precision of a 5G network requires to be within one-tenth of a microsecond.
Currently, communication delays between Earth and Mars range from 4 to 24 minutes (sometimes even longer). Patla explained that this is akin to communication methods before the telegraph — where people sent handwritten letters on a ship crossing the ocean, then waited weeks or even months for a response from another ship.
By determining the time difference between Mars and Earth, scientists have laid the foundations for establishing a planetary communication time framework, paving the way for the construction of synchronized networks spanning vast distances.
Patla remarked, “It’s exciting to finally understand how time passes on Mars. This was unknown before. It enhances our knowledge of the theory itself, including the laws of clock behavior and relativity.”
He stated, “The passage of time is the basis of relativity — how we perceive it, calculate it, and what influences it. These concepts may seem simple, but they are quite complex to calculate.”
The research findings mentioned above were published on December 1 in the Astronomical Journal.