Sheldon and Amy find themselves taking giant relationship leaps, while Raj gets in trouble on The Big Bang Theory season 8, episode 17.

The episode, titled “The Colonization Application,” will apparently focus on Sheldon and Amy as they struggle with mutual decisions. The preview for tonight’s episode tells us one of those decisions, which is enormous on the Shamy Relationship Scale… though it doesn’t register as high on anyone else’s.

But before anyone makes plans for a turtle-shower, note that CBS hints tougher decisions may loom ahead for the odd couple.

“Trouble arises when Amy learns Sheldon has applied for a one-way mission to colonize Mars,” CBS says. “Also, a trip to the pet store ends in a fight for Sheldon and Amy, Leonard surprises Penny with a very “adult” purchase, and, Raj is caught snooping in Emily’s apartment.”

Raj’s girlfriend Emily also played a small role in the zombie-portion of last week’s episode of The Big Bang Theory; ironically, that was the least interesting segment. Meanwhile, Howard had a crisis in the airport when Mrs. Wolowitz’s ashes went missing, and Penny and Sheldon took a test to make them fall in love.

It didn’t work, but good times were had all around.

Two sneak peeks from “The Colonization Application” suggest not such great times in tonight’s episode. In the first clip, Bernadette does the taxes while Howard plays video games.

The answer you’re looking for is, “Yes,” Raj.

And Sheldon and Amy begin their journey toward turtle-parenthood in the pet store of puppies.

Oh, Amy. You have no idea.

Meanwhile, the still photos from The Big Bang Theory season 8, episode 17 offer further hints that Emily will get a chance to shine in tonight’s episode. And what could be in that tube Leonard is holding?

The Big Bang Theory season 8, episode 17, “The Colonization Application,” airs tonight at 8:00 p.m. on CBS.

What are your hypotheses for ‘The Big Bang Theory’ season 8, episode 17?