Needless to say, this is pretty interesting (and deep) information. Leave it to Musk to plan and allow for such a thing. It sure sounds like something out of a science fiction movie. However, if you read the context provided on the Arch Mission Foundation's website, it really does make perfect sense:

"The Arch Mission Foundation™ (pronounced ar·k) exists to help humanity preserve and spread its knowledge across vast distances of time and space.

We believe that the purpose of life is to evolve and spread intelligence across the universe.

Ancient civilizations accomplished this by preserving their data in stone, a very long lasting medium — for example, The Pyramids of Giza. But ironically, despite our higher level of technological attainment, our civilization's data is far less durable.