A study by two physicists at the U.S. National Institute of Standards and Technology (NIST) found that, on average, clocks on Mars run about 477 microseconds faster per day than those on Earth.
Although this time difference remains extremely small, it can significantly impact efforts to synchronize clocks precisely between Earth, the Moon, and Mars.
Gravitational Time Dilation
Einstein’s theory of general relativity shows that gravity affects the flow of time, a phenomenon called gravitational time dilation. From an external perspective, clocks in stronger gravitational fields tick more slowly than clocks in weaker ones.
Similarly, a second lasts slightly less time in a weaker gravitational field than it does for observers who are under stronger gravitational influence.
For instance, atomic clocks aboard GPS satellites tick faster than those on Earth because the slightly weaker gravity at medium-Earth orbit, along with time-dilation effects from their motion, results in a combined offset of about 38 microseconds per day.
Building on this understanding, NIST researchers Neil Ashby and Bijunath Patla have now developed an accurate timekeeping framework specifically for Mars.
Establishing a Lunar Time Standard
The researchers had earlier created a lunar time standard similar to Earth’s Coordinated Universal Time (UTC), the worldwide benchmark used by scientists and the Deep Space Network (DSN). UTC maintains accuracy to within about 100 picoseconds per day, with a picosecond equaling one trillionth of a second.
On the Moon’s surface, clocks advance about 56 microseconds faster per day than those on Earth, mainly due to the Moon’s mass and the combined gravitational effects of the Sun, Earth, and Moon.
However, Patla points out that tracking time on Mars involves more complexity than on the Moon: “A three-body problem is already extremely complicated. Now we’re dealing with four—the Sun, Earth, the Moon, and Mars.”
Mars’ Weaker Gravity and Reduced Solar Influence
Mars has far weaker surface gravity than Earth because its mass is only about one-tenth of Earth’s. Based on measurements from Mars missions, Ashby and Patla calculate that gravity on Mars’s surface is roughly five times weaker than Earth’s.
Moreover, Mars orbits the Sun at a distance of about 1.5 astronomical units (AU), whereas Earth is 1 AU away. Because gravitational force decreases with distance according to the inverse-square law, Mars experiences a weaker gravitational influence from the Sun.
Mars’s highly eccentric orbit compared to Earth’s further complicates the situation, causing larger variations in the gravitational forces it experiences.
As a result, although clocks on Mars run about 477 microseconds faster per day than those on Earth on average, this offset fluctuates by roughly 266 microseconds per day over the course of a Martian year.
Martian Time
A year on Mars is also significantly longer than one on Earth, since the planet takes 687 days to complete a single orbit around the Sun. In addition, a Martian day lasts longer, with Mars needing about 40 extra minutes to rotate once on its axis compared to Earth.
Developing accurate and scalable timekeeping systems is essential for future Mars missions, including the landmark moment when humans first set foot on the planet.
Ashby notes, “It may take decades for rovers to leave tracks on Mars, but we gain valuable insight by addressing the challenges of establishing navigation systems on other planets and moons now.”
In the meantime, precise off-Earth timekeeping will be critical for supporting communication, positioning, and navigation for upcoming lunar missions by both commercial companies and national space agencies.
Creating a robust timekeeping infrastructure beyond the Earth-Moon system and establishing a framework for “autonomous interplanetary time synchronization” is therefore a key objective, making this research an important milestone in space exploration.
Read the original article on: Sciencealert
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