Why scientists want to put a laser on the Moon

Scientists have suggested building a powerful, ultra-precise laser on the Moon to help spacecraft land more safely.

The idea comes from researchers at JILA (formerly Joint Institute for Laboratory Astrophysics) in the United States. They believe putting a special kind of laser inside one of the Moon's coldest craters could make lunar navigation much more accurate.

Accurate timing and navigation are extremely important for spacecraft. Even tiny mistakes can cause big problems when landing on the Moon. That's where this laser could help.

Some craters near the Moon's north and south poles never receive direct sunlight. Because the Moon hardly tilts as it orbits Earth, parts of these craters stay in permanent shadow. Scientists think temperatures there can drop to around –253°C, which is 20 kelvin.

Kelvin is a temperature scale used by scientists. Zero kelvin is the coldest temperature possible.

These permanently shadowed craters are not just cold - they are also very stable. There is almost no atmosphere on the Moon and Jun Ye from JILA explains why that matters:

"The whole environment is stable, that's the key," says Ye. "Even as you go through summers and winters on the moon, the temperature still varies between just 20 to 50 kelvin. That's an incredibly stable environment."

The laser would work by bouncing a beam between two mirrors inside a crater.

The distance between the mirrors must stay almost exactly the same. If it changes even slightly, the laser becomes less precise.

In laboratories on Earth, scientists keep these mirrors inside a vacuum (an airless space) and cool them to very low temperatures to stop them expanding, shrinking or vibrating. And the Moon's cold, airless craters could naturally provide those same conditions.

A super-stable laser could help spacecraft measure distances more precisely and guide landers safely to the surface.

This could be especially useful near the Moon's poles, where lighting conditions can make landings difficult.

Simeon Barber from The Open University says the idea could improve safety:

"We have seen various recent lunar polar landers have suboptimal landing events because of illumination conditions, which hinder the use of vision-based landing systems," says Barber explaining it could make successful landings more frequent and reliable.

In simple terms, poor lighting can confuse camera-based landing systems. A stable laser could give spacecraft another way to check exactly where they are.

So far, only one country has landed people on the Moon: the United States. Between 1969 and 1972, NASA sent 12 astronauts to walk on the lunar surface during the Apollo missions.

The first Moon landing happened on 20 July 1969 during Apollo 11, when Neil Armstrong became the first human to step onto the Moon.

The most recent crewed landing was in 1972 during Apollo 17, more than 50 years ago.

American space agency Nasa, has a new series of missions called the Artemis programme. It aims to send astronauts back to the Moon for the first time since the final Apollo mission.

Artemis II is planned to be the first crewed mission around the Moon since Apollo 17. It will fly astronauts close to the Moon and back to Earth, but won't land on the surface. This mission is expected in March this year ans will last about ten days.

Artemis III is planned to land astronauts on the Moon again. The current target date is around 2027–2028.

The China National Space Administration (CNSA) also wants to send astronauts to the Moon by the year 2030.