Why the Sun and the Earth in the lunar sky decide where we land.
Landing on the Moon is only the first problem. A lander then has to stay powered, stay warm and stay in touch, and all three depend on one thing: where the Sun and the Earth sit above the horizon at that spot, on that day.
Mission planners weigh many things. These three are the ones MOONbound helps you compare.
Power and heat
A lunar day lasts about 29.5 Earth days: roughly two weeks of sunlight, then two of night. Surfaces swing from about 127 °C in sunlight to −173 °C in the dark, so a lander must finish its work in daylight or survive the cold.
The Moon’s axis is tilted only about 1.5°, so near the poles the Sun skims the horizon. Some ridges there stay lit for most of the year, while the floors of deep craters never see the Sun.
Radio contact
The Moon always shows Earth the same face, so from the near side Earth hangs in almost the same spot in the sky and a lander has a direct radio line home, about 1.3 seconds away.
It is not perfectly still: the Moon’s slow wobble, called libration, shifts Earth by several degrees. Near the poles Earth sits low and hills can hide it, and on the far side it never rises, so a relay satellite is needed.
Slopes, rocks and craters
Gentle slopes and few boulders decide where a lander can stand. Orbiters such as NASA’s LRO map the ground to within metres, and the Apollo sites were picked from such images and from earlier robotic scouts.
The terrain also draws the skyline. A ridge a few kilometres away can shade the Sun or block Earth, which is why MOONbound scans the horizon around every site.
The same Sun behaves very differently depending on where you stand. Watch one lunar day, sped up, at two places.
The Sun climbs high, crosses the sky and sets, then stays gone for about two weeks. Earth, on the near side, hardly moves.
Time is sped up: each loop is one lunar day.
The Sun never climbs much more than a degree or so above the horizon. It circles slowly, hills hide it for a while, and every shadow is very long.
Same time scale. This is why the exact site and date matter so much.
From the first robot to the first footprints, and on to a crowded south pole.
The Soviet Union’s probe made the first soft landing on the Moon and sent back the first pictures from the surface.
Five NASA landers scouted the ground and tested how firm it was, so Apollo knew a spacecraft would not sink.
Neil Armstrong and Buzz Aldrin landed in the Sea of Tranquility, the first people on the Moon. LRO has since photographed the site from orbit, and the lander’s descent stage is easy to spot.
The crew landed within walking distance of Surveyor 3, about 180 metres away, proving a pinpoint landing was possible. They brought back parts of the old probe.
The last crewed landing, in the Taurus-Littrow valley. Harrison Schmitt, the only professional geologist to walk on the Moon, studied this split boulder. In all, twelve people walked on the Moon and brought back about 382 kg of rock and soil.
Chang’e 3 made the first soft landing in almost four decades. In January 2019 Chang’e 4 became the first to land on the far side, talking to Earth through a relay satellite.
India’s Chandrayaan-3 landed near the south pole in August 2023, and Japan’s SLIM made a precision landing in January 2024. Commercial landers followed: Intuitive Machines’ Odysseus in February 2024 and Firefly’s Blue Ghost in March 2025. Next come the Artemis landings, aimed at the south pole.
MOONbound compares sites and dates by the sunlight and Earth views they get. See the NASA data behind it.