The Search for Planet X

In the 19th century, a wealthy astronomer named percival lowell started looking for planet x. He built an observatory on a mountain in Arizona that had the best observing conditions around. But he can't find it and so someone else is hired to carry out the search. The mission was called Asteroid belt Survey but they couldn't find anything. Now we need the moon as our only way of knowing whether or not there are planets beyond Earth.