The Artemis programme has considered the possibility of creating a digital archive of humanity's accumulated information on the Moon. A lunar archive would have many advantages over terrestrial ones.
With the advent of the third decade of the 21st century, the world has become a tumultuous and unpredictable place. First, the coronavirus pandemic "migrated" us into virtual spaces, but now they themselves - together with the "real world" - have become the scene of geopolitical confrontation.
Many people and companies store their data - photos, videos and documents - in the cloud, but now wonder how to keep it safe when 'nothing lasts forever' on the internet. Cyberattacks, physical damage, plots by IT corporations, actions by governments seeking to protect their own sectors of the Internet - each of these can render data on remote servers inaccessible, or even destroy it altogether.
Scientists led by Carson Ezell of Harvard University have proposed a radical solution to protect data from all earthly vicissitudes: create a digital archive on the moon. Their idea is publicly available at arXiv.org, and its implementation would have many advantages over existing archives on Earth.
Access to a digital lunar archive is, oddly enough, technically capable of being much easier than access to terrestrial ones. The path from the user to any global, terrestrial data repository would inevitably traverse thousands of kilometres of fibre and wire, dozens of relay devices and multiple national boundaries. No matter how reliable the archive itself is, any break in the chain would render it inaccessible.
In contrast, the lunar repository can be contacted directly by laser. Such communication is a true p2p connection: just a receiver and a transmitter, nothing else. Its speed can be very high: the laser transponder on board the LADEE research mission has demonstrated a bandwidth of 20 megabits per second with a beam power of 500 milliwatts.
At any given time, the Moon is directly visible from half the Earth's surface (at least from a balloon above the clouds), and everywhere but the polar regions, it is above the horizon at least once every 25 hours.
The minimum signal delay is determined by the distance to the moon and the speed of light, and is just under three seconds "round trip" - you can't retransmit video calls over our planet's satellite. But in data retrieval, such a delay is perfectly acceptable.
Another challenge is the need for very precise laser aiming. The better it is, the smaller the spot size that is guaranteed to "cover" the receiver and the less power the laser needs to produce enough signal intensity on it.
An optical system similar to an amateur telescope with a clockwork drive is sufficient to focus and aim the beam from Earth to the Moon. In the future, laser-based lunar communication repeaters may provide quite modern data transmission speeds at a cost comparable to Starlink terminals.
Conditions on the Moon are much more stable than at any sheltered location on Earth. The lunar surface is exposed to radiation from solar flares and its temperature ranges from minus 170 degrees Celsius at night to plus 130 degrees during the day. But beneath the layer of lunar regolith, the temperature remains constant and radiation is reduced to Earth-like levels. Tectonic activity on the satellite is vanishingly weak: there is no atmospheric erosion at all and the regolith buffers well against meteorite impacts.
If the archive is buried a few meters deep, it can be retrieved in its physical integrity, in the same place and at approximately the same depth, tens or even hundreds of millions of years later. Repeaters and solar panels (or reactor heat exchangers) will have to be left on the surface, but even these, with sufficient design thought, will be able to function longer than any above-ground mechanisms.
Scientists propose to archive primary information - the human genome, descriptions of technology, artwork, images and movies - during the first planned lunar missions of the Artemis programme and estimate the amount at 10 petabytes. That seems like a lot of data, but it could be recorded on, say, five pounds of 512 gigabyte microSD cards. Of course, the archive would require high-capacity storage media, but at current recording densities, a lot of data could indeed be delivered to the Moon in just one launch.
The first attempt to send an archive to a satellite has already taken place. The Israeli lunar expedition's Beresheet lander was launched in 2019 and carried a memory module with a Wikipedia upload as well as some 30 million pages of digitised books on board. Unfortunately, the vehicle crashed on landing on the moon at the time.
