Ask HN: SPARK2014 or Rust for high-integrity, secure, distributed application?

I have a job opportunity to develop a secure, high-integrity, high-reliability, very low fault distributed communications application where I will have the option of choosing the PL/platform. SPARK2014 has an edge over Rust due to its more venerable Ada relationship, verification toolset, and use in government contracts. I know Rust has gained a lot of traction, but the arena for this opportunity is slow to adopt new technologies. I didn't put Erlang/Elixir in the title, although the fault-tolerance and distributed nature of them has me interested especially NIFs in Rust. Any advice or tips are very much appreciated. Thanks!