The moon's south pole has for years, been a location of interest to scientists. While water has been detected across the lunar surface, the majority of water ice signals come from the poles. And its presence on the lunar south pole, was confirmed in 2020 with data from NASA's Stratospheric Observatory For Infrared Astronomy (SOFIA) telescope.
At the moon's south pole, only elevated peaks are lit by the sun since the sun is always positioned around the horizon due to the lunar planet's tilt. More low-lying areas are permanently shrouded in shadow, hence the name: permanently shadowed regions (PSRs). Temperatures can drop to as low as -418 degrees Fahrenheit (-250 degrees Celsius), colder than Pluto. This makes it an ideal spot to maintain water ice.
Water molecules are frozen and trapped on a PSR region, because it is simply too frigid for them to evaporate. This water content then gets mixed with lunar soil, resulting in the growth of large "pockets" of water and soil at the lunar south pole.
In 2008, Indian Space Research Organization, ISRO's Chandrayaan-1 spacecraft carried a NASA-provided science instrument called the Moon Mineralogical Mapper (M3) to lunar orbit. This determined the existence of water ice inside craters at the moon's south pole. And in 2009, NASA's Lunar Reconnaissance Orbiter (LRO) purposefully slammed a dark crater at the lunar south pole with the Lunar Crater Observation and Sensing Satellite (LCROSS). This created a plume of debris that LCROSS jetted through, enabling it to detect water ice that had been hidden in darkness.
Initial concern that the molecule hydroxyl (OH) was confused to be the water molecule (H2O), was later allayed with the SOFIA telescope data. And based on this data, scientists estimated there could be as much as 12 ounces of water for every one cubic meter (just over 35 cubic feet) of lunar soil at the southern pole of the moon. The two lunar poles harbor over 600 million tons of water ice, according to the Planetary Society's analysis of Chandrayaan-1 and LRO data. This is a low-end estimate according to experts, but it's enough to fill around 240,000 Olympic-sized swimming pools.
Scientists' knowledge of the presence of water on the moon comes entirely from spacecraft orbiting the lunar planet, like the LRO, which has collected precise information about the region and its terrain. Landing near the lunar south pole is not easy, making ISRO's chandrayaan-3 mission in August a historic first.
Just days before the landing of Chandrayaan-3, Russia had planned to make its glorious return to the moon's surface after 47 years with Luna-25, which launched on Aug. 10. But on Aug. 19, Roscosmos announced that it had lost contact with the mission. The spacecraft had crashed into the moon's surface during landing preparations.
Because of the shadowy nature of the moon's south pole, and obstacles such as boulders or craters, a soft landing is tricky with most lunar probes which rely on cameras to guide their final approach to the lunar surface. Even on well-lit regions of the moon, landing is risky. Just one chance encounter between a boulder big enough to tip a spacecraft and a lander would end in disaster for the mission.
Such risk is also magnified by the fact that the lunar south pole lacks large expanses of flat terrain as are found at the moon's equator, for instance. Terrain at both lunar poles is known to be heavily cratered as well as more likely to be sloped and rocky.
The south pole of the moon can't be seen from Earth, hence the use of orbiting spacecraft like LRO. Orbiters around the lunar planet are scoping out the orb's perilous polar regions for suitable landing zones to limit the risks to future missions.
Any lunar probe that seeks to land at the south pole must also be able to withstand the frigid temperatures. A lunar rover that strays into one of the many PSRs, will be out of contact with the sun, meaning it can't rely on solar power to operate and must instead have a nuclear power source.
PSRs are also out of the line of sight of Earth, meaning relaying messages to and from mission control in the shadowy regions is tricky.
Besides the fact that water is, of course, essential for life as we know it, it also has other uses. For instance, it can act as a coolant for equipment and even provide rocket fuel. The latter could be especially useful for a staging mission to Mars launched from the moon someday.
The discovery of water on the moon is a vital step in deep space exploration. This is why national space agencies and scientists are scrambling to get lunar probes exploring the moon's south pole. Future missions will take the mapping of the terrain to a whole new level, with the VIPER mission in particular hunting for resources that could be mined and exploited by the crew of the NASA's Artemis program.
Leading aerospace giants like Lockheed Martin, Boeing and Elon Musk's SpaceX, are among few global companies building spacecraft like Orion and Starship respectively, that will be used in future lunar missions.