On 8 December, Chang’e-4 will set off to become the first spacecraft to touch down on the Moon’s far side, the latest in a series of recent missions by China, a relative newcomer to lunar exploration.
And the country isn't alone. Half a century after the original space race, there has been a resurgence of interest in Earth’s satellite, with some scientists saying we are entering a renaissance of Moon exploration and science.
Race to the Moon
Human exploration of the Moon began in the mid-twentieth century, when the United States and the Soviet Union conducted a large number of lunar missions — many unsuccessful — in a race to dominate space exploration (see ‘Reaching for the Moon’). These culminated with the Apollo missions that put humans on the lunar surface in 1969.
Although these early missions had geopolitical rather than scientific motivations, they have had “an extraordinary scientific legacy”, says James Carpenter, strategy officer for human and robotic exploration at the European Space Agency in Noordwijk, the Netherlands. The samples collected during the Apollo missions taught scientists not only about the Moon, but also about planet formation and the history of the inner solar system — and they continue to be studied today.
A renaissance of lunar exploration
But, after the excitement of the space race, things went quiet. The Soviet Union sent their final mission to the Moon in 1976, while budgetary issues and a lack of political will in the United States around that time led to the cancellation of further planned missions. “A little bit of the awe and wonder was starting to wear off,” says Ryan Watkins, a lunar scientist at the Planetary Science Institute, who works in St Louis, Missouri. Instead, newly-developed space technology was applied to missions elsewhere in the solar system.
But the past two decades have seen a gradual return of lunar missions, mainly in the form of spacecraft sent to orbit the Moon. A dozen of these orbiters have been launched since 1990 by the United States, as well as by new players including Japan, China, India and Europe.
Together these craft have mapped out the Moon using state-of-the-art imaging and a variety of scientific instruments. These data have transformed scientists’ understanding of the Moon, conclusively showing that there is water ice at the poles, for example, and demonstrating that our satellite may have been geologically active until very recently.
These discoveries have set the scene for a return to the surface, says Carpenter. With many missions in the works, he says, we are heading for “a renaissance of lunar exploration”. Some scientists are even contemplating building a Moon base. (See 'When?')
Location, location, location
One landing has already taken place: in 2013, Chang’e-3 became the first mission to land on the Moon since the 1970s. Chang’e- 4 will soon follow, and landers from other countries including the US, India, Japan and Russia are also planned.
Landing locations are an important consideration for these missions. The landings of the mid-twentieth century were restricted to very similar areas on the near side of the Moon, says Watkins, so the samples they obtained were not representative of the Moon as a whole. “There’s a big push to get more diverse samples,” she says.
Chang’e-4, for example, will study the geology of the pockmarked far side of the Moon for the first time. And Carpenter is working on PROSPECT, a European contribution to a 2022 Russian lander, which will drill into the South Pole region and look at the potential for resource extraction.
Carpenter says he is excited by the collaborative nature of modern lunar exploration. Space agencies are increasingly recognizing the importance of international partnerships and co-ordination — a contrast to the early days of Moon exploration, which was borne out of intense rivalries. “I think space exploration can be something that we do as a species rather than something we do as individual nations,” he says.