The window to life on the moon

Our Moon is today lifeless and uninhabitable. There is no significant atmosphere, no liquid water on the surface, no magnetosphere to protect against solar winds and cosmic radiation, as well as large temperature fluctuations. Linking this moon to habitability seems daring and upends previous hypotheses. Prof. Dr. Dirk Schulze-Makuch, astrobiologist at TU Berlin, and his colleague Ian A. Crawford from the University of London have compiled and compared the latest research on the investigation of soil and rock samples. They conclude that there could have been a time window more than three billion years ago when life on the lunar companion was possible. Their results and conclusions have just been published in the renowned journal "Astrobiology".

"It's not about finding 'green men'. Bacteria and microbes are also biological life, and above all: these primitive life forms are the basis for the development of higher, intelligent, and even technology-using life forms," says Dirk Schulze-Makuch from the TU Center for Astronomy and Astrophysics, who has been researching "Life on extraterrestrial planets" at TU Berlin for several years, among other things supported by an ERC grant from the European Research Council (https://www-astro.physik.tu-berlin.de/Atacama-project). He can already point to various sensational results, especially regarding probable microbial life on Mars.

"We assume that the Moon was formed as a result of a gigantic collision of the Earth with another celestial body 4.5 billion years ago," says Schulze-Makuch. Volatile substances and liquids could have survived in parts of the newly formed Moon or been deposited through meteorite impacts – the frequency of which still bears witness on the lunar surface. Other scientists had also already suspected that in this early period, crater eruptions and the release of lava, as well as large amounts of gases, could have formed a protective atmosphere that might have lasted about 70 million years. "The lunar atmosphere about 3.5 billion years ago was probably denser than today's atmosphere of Mars. Overall, this results in a remarkable time window in which not only liquid water could have existed on the Moon's surface but also life," says Schulze-Makuch.

About four billion years ago, when the first life emerged on Earth, many asteroids and meteorites collided with Earth. Bacteria could have reached the Moon from Earth, survived the impact and flight, precisely in the time window when life on the Moon was possible, when water was present in an early atmosphere on the surface, and also a magnetic field. In the rock samples from the lunar surface, which were collected during the Moon missions, there are indications of oxidation processes and hydrothermal processes.

To further substantiate these initial findings and the resulting highly speculative hypotheses, the scientists conclude, it is necessary to advance corresponding research programs worldwide. They recommend conducting these investigations in new (Moon) simulation chambers, as well as on the International Space Station ISS. Only then can we test whether there could have been an early window for life on the Moon.

The article by Dirk Schulze-Makuch and Ian A. Crawford "Was there an Early Habitability Window for Earth’s Moon?" is published open access by Mary Ann Liebert Publishing.