Why hasn't Mark saved Robot and Monster Girl?

I am a show watcher not a comic reader so I'll say that outright, but one thing has pissed me off since Nolan returned to earth and met mark.

Nolan flew through a flaxan portal and decimated their planet, we kind of all know this. Most importantly, without the use of portals, Nolan returned to earth. It's reasonable to say that Nolan has an idea how to get back to the flaxans planet.

Why wasn't Mark's first mission in space, to save 2 earth heroes that can watch the planet while he's away? He was a part of / getting fucked up in the 3rd flaxan fight. He saw Rudy and monster girl go through and is fully aware they're missing. Is this too 1+1=2 ...

Rudy saved mark after Cecil put the chip in his head, he saved mark from being stranded through angstroms portal, and just generally I believed they were close. Why doesn't he save his friend with his dad? He owes robot a few favours if you ask me...

Mark's not being a good friend, I dunno.