The Spark Ada safety critical subset is memory safe, but Ada isn't. It's possible to write a kernel in Spark, but hard to believe that you'd get buy-in from other kernel developers. Ada doesn't eliminate use after free, race conditions, or dereferencing null pointers[0]. Rust addresses these, so it's hard to see Ada as an improvement.

[0] https://www.reddit.com/r/ada/comments/mme3jk/is_ada_memory_s...