2023-08-26 11:55:53
It was comparable to the race between Roald Amundsen and Robert F. Scott 112 years ago in Antarctica. Both wanted to be the first to reach the point on Earth’s southern hemisphere where the planet’s axis of rotation intersects its surface. But now it wasn’t humans doing their utmost to reach their destination, it was two remote-controlled robots setting off for the moon’s south polar region.
The Indian lunar vehicle Chandrayaan-3 was launched in mid-July, followed almost a month later by the Russian lunar probe Luna-25. Similar to the two competing polar explorers, it was all about glory: Who would be the first to land safely and unscathed in the most inhospitable area of the Earth’s satellite? What’s more, the robots are supposed to search there for the deep-frozen water that is said to be there in large quantities.
While the Russian probe crashed uncontrollably to the lunar surface last weekend after a failure in one of the rocket motors, Indian space experts managed to land Chandrayaan-3 safely near the South Pole on Wednesday this week. Launched on July 14 from the Satish Dhawan Space Flight Center in the state of Andhra Pradesh, the probe deorbited a landing module as planned, which is now almost 600 kilometers from the lunar South Pole on the Earth’s satellite. It’s called Vikram, named after the founder of the Indian space organization ISRO. On board this module is a small, six-wheeled rover that will be remotely controlled to explore the lunar south pole over the next two weeks. Pragyaan (Sanskrit for “wisdom”) has two spectrometers on board that can be used to detect water molecules.
The landing module of the Indian lunar mission Chandrayaan-3 touches down on the South Pole on August 23, 2023 at 2:33 p.m. German time, shown here as an animation). : Image: Reuters
But why is the search for water on the moon so important that two unmanned probes were sent to this truly extreme area? The motives for this are of a much more pragmatic nature than in the search for water on Mars. While the detection of water on the red planet could give an indication of the possibility of life on other planets, the moon is about practical things: the precious water is being sought here to enable people to survive. After all, astronauts who are to spend time in a permanently manned lunar base in the future are spared the fate of the crews of the International Space Station (ISS) of having to quench their thirst with – albeit fully cleaned and disinfected – urine. Water is also needed to make fuel for rockets, which humans can use in a second step to set off from such a possible outpost on the moon to the other planets in the solar system.
First indications of moon water
The fact that there can be water at all at the south pole of the moon is related to the laws of celestial mechanics. When Amundsen and Scott were on their expeditions to Antarctica in the winter of 1911-12, there was no darkness there. It was midsummer, and the sun shone on the frozen continent twenty-four hours a day. There are no such seasons on the moon, because the axis around which the moon rotates once in 27.3 earth days is only inclined by 1.5 degrees to the ecliptic – and not by 23 degrees like the earth’s axis. Therefore, the Sun is never more than a few degrees above the South Pole horizon. As a result, parts of the landscape are bathed in constant light. However, since there are also many impact craters and mountains with steep flanks, large parts of this landscape lie in perpetual shadow.
The temperature differences between sunlit slopes and the zones of permanent shade could not be more extreme. Temperatures of 50 degrees were measured in the sun by orbiting satellites. In contrast, the shadow zones have some of the coldest temperatures in the solar system, namely down to minus 248 degrees. Water molecules are frozen solid in these harsh conditions and, if there are enough of them, could be thawed and used by future ‘lunanauts’.
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