Aliens on Mars

Many have speculated, are there aliens on Mars? The anwser is yes, there are aliens on Mars. Alien lifeforms in microbial form apparently do live there, but did sentinent alien beings ever live there? The question comes from the fact that Mars used to apparently have flowing rivers and a temperate climate that may have had oxygen in it. Could there perhaps be the ruins of an alien society under the vast red dirt of mars, AND JUST WHY HAVENT WE GONE THERE YET?