Omnilingual - H. Beam Piper

Omnilingual (novella) by H. Beam Piper
To translate writings, you need a key to the code-and if the last writer of Martian died forty thousand years before the first writer of Earth was born... how could the Martian be translated?
A team of archeologists attempt to discern the nature of a lost civilization from the ruins they left behind.
Published February 1957 ~ Astounding Science Fiction