The word hidden in this sudoku-style puzzle solution is simply out of this world!

Solve this wordoku in the same way as a sudoku with letters instead of numbers (each of the nine letters in each row, column and nine-square cell). Once solved, one of the overall diagonals can be rearranged into the name of a gas present in Titan’s atmosphere.

This week’s letters are: A C E L N S T U Y