After two failed attempts to launch its Artemis 1 mission to the moon, NASA engineers are now performing maintenance work on the Space Launch System rocket while it is still at Launch Pad 39B at Kennedy Space Center. As the US space agency works on its mission that will pave the way for putting humans back on the Moon after 50 years, here are 5 interesting facts you may not have known about Earth’s only natural satellite.
The Moon has an “atmosphere”
While conventional wisdom would tell you that the Moon has no atmosphere and therefore no gas on its surface, that’s not quite true. NASA deployed the Lunar Atmospheric Composition Experiment (LACE) instrument to the Moon during the Apollo 17 mission. LACE helped scientists discover that there are a small number of atoms and molecules on the planet, including l helium, argon, neon, ammonia, methane and carbon dioxide.
However, it is a very thin layer of gas that can’t quite be called an atmosphere, but the more accurate term would be “exosphere”. Unlike Earth’s dense atmosphere where the movement of gas molecules is dominated by collisions with each other, the moon’s exosphere is so thin that atoms and molecules almost never collide. Instead, gas molecules on the moon freely follow arcing paths determined by the moon’s gravity and the processes that created the molecules.
There are many possible origins for the gases on the satellite, including chemical reactions between the solar wind and lunar surface materials, the release of materials from comet and meteoroid impacts, and the “outgassing” of the interior of the Moon. These processes could also provide the energy that determines the movement of gas molecules.
The moon is shrinking and it causes moonquakes
As its interior cools, the Moon continues to shrink. In fact, according to NASA, its diameter has shrunk by more than 50 meters over the past hundreds of millions of years. And just like how a grape begins to have wrinkles when it shrinks in a lift, the Moon has such wrinkles too. But unlike a grape, the Moon’s surface is not flexible and quite brittle. This means that the shrinkage causes “thrust faults” where one section of the crust is pushed up over a neighboring part.
NASA analysis showed that these faults are active and likely producing moonquakes, some of them quite strong, registering around five on the Richter scale. These fault lines sometimes look like small stair-like cliffs when viewed from the lunar surface. These can reach several tens of meters high and extend over several kilometres.
The twelve moon walkers
Between 1969 and 1972, 12 astronauts walked on the lunar surface. This includes Neil Armstrong, Buzz Aldrin, Charles Conrad, Alan Bean, Alan Shepard, Edgar Mitchell, David Scott, James Irwin, John Young, Charles Duke, Eugene Cernan and Harrison Schmitt. Apollo astronauts brought back a total of 382 kilograms of lunar rock and soil and scientists are still studying these samples.
While the lunar landscape may be that of an empty desert, scientists believe it contains many important resources that can be harvested for “in situ” use during space missions. These include hydrogen, which can be used to propel rockets; water ice, which can be split into hydrogen and oxygen for fuel and helium-3, a non-radioactive isotope of helium that could potentially be used to provide nuclear power in the future.
These resources are one of the reasons China and the United States are racing to dominate the Moon and space. In fact, after discovering a mineral called Changesite-(Y), China’s National Space Administration approved plans for three future unmanned missions to the Moon. Changesite-(Y) is believed to contain helium-3.
The only natural satellite of our planet takes as long to revolve around the Earth as it does to revolve on its axis. For this reason, we only see one side of the Moon, called the near side. The dark side remains forever turned away from us. In 2019, China became the first country to land a spacecraft on the far side of the Moon.
This “two-sided” nature of the Moon also results in wildly variable temperatures on its surface. While the moon’s sunny side can get hotter than boiling water, up to 123 degrees Celsius, the temperature sometimes drops to minus 233 degrees Celsius in the permanently shadowed polar craters.