The Moon

Between 1969 and 1972, NASA’s Apollo program brought 12 astronauts to the Moon’s surface. Since then, the Moon has been untouched by human feet, standing as the only celestial body aside from Earth that we’ve set foot on.

We call Earth’s natural satellite simply “the Moon” because, before Galileo Galilei’s discovery of Jupiter’s moons in 1610, no one was aware of other satellites. The Romans called it Luna, inspiring the term “lunar” for all moon-related matters.

Born from destruction, the Moon’s formation theories agree on a cataclysmic event around 4.5 billion years ago when the solar system was just forming. The young Earth was struck by a Mars-sized object—or possibly multiple objects—that sent molten rocks and dust into space, eventually merging into the Moon.

One of the Moon’s most fascinating characteristics is its synchronous rotation; it takes 27 days to both spin on its axis and orbit Earth. This means we always see the same side of the Moon, commonly referred to as the “near side,” while the “far side” remains somewhat mysterious even after the space age allowed us to glimpse it from orbit.

The Moon’s surface is a testament to its tumultuous past. Craters, some spanning hundreds of miles, tell stories of cosmic impacts. The dark, flat plains known as “maria,” Latin for “seas,” were once believed to be filled with water. In truth, they are basins created by ancient volcanic activity, filled with solidified lava.

Unlike Earth, the Moon’s surface remains largely unaltered over time due to its lack of erosive elements like water and wind. Its craters, cliffs, and even the legacy of Apollo astronauts’ footsteps endure for ages.

Temperatures on the Moon are extreme and fluctuate swiftly, lacking an atmospheric shield to protect it from the space environment. These temperature shifts, along with meteor impacts and solar radiation, all contribute to its harsh climate.

The seismometers left by Apollo missions have taught us that the Moon is seismically active, with quakes originating from both tidal interactions with Earth and the contraction of the Moon as it still cools after its formation. This gradual cooling has caused the Moon to shrink by roughly 150 feet (50 meters) over hundreds of millions of years.

The Moon orbits our planet at an average distance of about 238,860 miles (382,500 km), which means a jet would take more than 17 days to reach the Moon. This proximity allows it to exert a significant influence on Earth, shaping the tides. Additionally, the Moon’s gravity is ever so slightly slowing our planet’s rotation—a phenomenon known as tidal braking. This interaction has been gently increasing the length of our days while incrementally distancing the Moon from Earth by 1.5 inches (3.8 centimeters) per year.

The Moon’s influence extends beyond tides to stabilizing Earth’s tilt, fostering a climate where life thrives.

The Moon boasts an impressive size, spanning about 2,159 miles (3,475 kilometers) in diameter, outclassing Pluto. It’s not alone in its grandeur—four other moons in our solar system are even more massive. At 1/4 of the size of Earth, the Moon’s substantial proportion relative to our planet is unmatched by any other moon-planet duo. 

Following Apollo 11’s historic 1969 landing with Neil Armstrong and Buzz Aldrin, six missions until 1972 brought a dozen astronauts to the Moon. There, they gathered samples, conducted experiments, traversed the terrain, and even played extraterrestrial golf.

Awaiting our return since those pioneering missions, the Moon will once again host human footsteps with NASA’s Artemis III mission, slated for a 2025 lunar landing.