Most of us have stopped to gaze at the moon at some point – but have you ever wondered what time it is there?
For those who already know, their questions may soon have answers, as space organizations are considering giving the moon its own time zone.
The European Space Agency (ESA) has said it plans dozens of lunar missions over the next decade, including missions to build bases and other habitats on the moon.
In November 2022, space organizations began discussing lunar timing at ESA’s ESTEC technology center in the Netherlands.
Pietro Giordano, Navigation Systems Engineer at ESA, said: “We agree on the importance and urgency of defining a common lunar reference time, internationally recognized, to which all lunar systems and users can refer.
“A joint international effort is now being launched to achieve this goal.”
So far, each new moon landing mission has been conducted on its own time scale, with deep-space antennas used to keep the onboard timers synchronized with Earth time.
In addition to astronauts and ground controllers being able to tell time on the Moon, the need for standard timekeeping in space is also essential for guidance and navigation.
Just as the GPS system on Earth requires precise coordination and timing, so does any infrastructure built and operated on the Moon.
NASA’s Gateway will serve as a multipurpose outpost orbiting the moon when it becomes operational sometime after November 2024.
It will open accommodations to astronauts and support the return of humans to the lunar surface.
Meanwhile, the European Space Agency will drop its own Argonaut lander on the moon.
Not only will these missions be orbiting on or around the Moon simultaneously—they will also interact and potentially relay communications with each other and make joint observations.
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One of the topics of debate is whether one organization should be responsible for setting and maintaining lunar time, and whether it should be set independently or synchronized with Earth, ESA said.
The ESA said the international team working on the topic would face “considerable technical problems”.
Why do clocks work differently on the Moon?
One challenge is that the clocks on the Moon run faster than those on Earth because the clocks go slower in the stronger gravitational field, thus gaining about 56 microseconds, or millionths of a second, per day.
Their exact rate depends on where they are on the Moon, ticking at a different rate on the lunar surface than when they are in orbit.
Bernhard Hufenbach, member of the Moonlight Management Team at ESA’s Human and Robotic Exploration Directorate, said: “Of course, the agreed time system must also be practical for astronauts.
“This will be quite a challenge on the planet’s surface, where at the equator, for 29.5 days, including two weeks of icy lunar nights, the entire Earth is just a small blue circle in a dark sky.
“But after establishing a working time system for the Moon, we can go on to do the same for other planetary destinations.”