The man in the moon never seems to look away from the Earth. During its different phases, the Earth’s only natural satellite changes shape, but the sentinel never seems to disappear from his heavenly seat. The first human-made object to touch down on the moon, the Luna-2 of the erstwhile Soviet Union, landed in his territory in 1959. Ten years later, Neil Armstrong became the first human to step on this side of the moon. And till last week, all lunar missions would descend on the same realm. 2019 has begun with a Chinese spacecraft, the Chang’e4, landing on an unexplored part of the Earth’s satellite, popularly called the Dark Side of the Moon.
The appellation is a misnomer. All sides of the moon receive sunlight at different points during the moon’s orbit around the Earth. But the moon points only one hemisphere towards the Earth. Astronomers use the terms, the “near side” and “far side,” to refer to the two parts of the satellite. The far side was so far only known from orbital images. But its unexplored surface is believed to contain a treasure trove of information that could advance our understanding of the history of the solar system. Space scientists believe that lava from ancient asteroids has washed away a lot of the records of the moon’s formation on the side that has been the subject of research so far. The realm of the moon on which the Chang’e4 landed, in contrast, is much more heavily cratered and far more pristine, though it too was pounded by asteroids. The success of the Chinese mission opens the door to understanding such resilience.
Chang’e4 landed on the Von Kramer crater within the South Pole-Aitken basin, known to be the biggest depression in the solar system. Studying the composition of ancient craters such as the Von Kramer can help scientists gain an insight into the asteroids that rained down on the Earth during the planet’s youth. Understanding the history of contact with these heavenly bodies could yield important clues to the origins of life on the planet. Moreover, Chang’e4’s success could help realise the long-held astronomers’ dream of an observatory on the moon. The side facing the Earth is not suitable for such a project because noises from GPS satellites, Wi-fi, TV stations and many other human interferences hamper the transmission of low-frequency messages. But the Earth’s satellite protects its far side from such noise. The Chinese mission’s success could lead to telescopes beaming observations from the Dark Side of the Moon. The popular appellation could then be consigned to history books.