I just realized that it's not quite true that Earth doesn't know what happened to Grace after he went back for Rocky.
I mean, NASA keeps tracks of what's happening on the other planets. They know which planets are infected with the astrophage.
So they probably know that Erid is NOT infected with it anymore, which means they can come to the conclusion that Grace must have suceeded in finding Rocky.
And now there's a wikipedia page for Rocky and Grace respectively that specifically describe them as the saviours of two planets.
They don't know that the Eridians pulled food out of their collective asses, though.
I mean, shoot, Grace didn't even think the Eridians would pull it off. His last message was, "totally going to starve for this, bye."
(And to be fair -- the Eridians almost didn't pull it off in time.)
The presumption on Earth is probably that Grace starved saving Erid in addition to starving to save Earth like he was supposed to.
That being said, if Yao and Ilukhina hadn't died in a coma, the three of them alive wouldn't have had enough food to be sent back to Earth. Grace is only able to make it that long on the food he has because it's three people's worth. Which means the three of them either would have been not given the astrophage that Grace used to save Rocky; or else the three of them would have been packed up on Rocky's ship and waiting for Grace to magic Eridiian food into edibility (no pressure) when the whole taumoeba escape went down. Earth would have been fine, they still would have sent the beetles, but Erid would have been fucked.
Yao and Ilukhina didn't die to save Earth, but they explicitly died and saved Erid.
















