Thanks, Debbie for your comment.

I agree. Also, it's most efficient to test for known possibilities of life when on Mars. Once they have the specimen on Earth, they can test for other possibilities.

The one issue is if the ancient life on Mars is too exotic, we may not test for it because we don't know how to. What would be interesting is if we find that it is a modification of life on earth - similar enough to recognize yet different. For eg - if the Martian DNA replaces some of the essential elements with another similar one in the periodic table (Si instead of C)?