Set design was great, with proper sound effects.
Earth look good as well.
From a plot perspective, I don't know why they just didn't send down the algae without them going along, since 2 of them didn't want to go.
It WAS an option - they didn't need to pilot it.
They said to the survivors - 'we're sending IKARUS, but we're coming too' so that shows the didn't need to go with it.
Spoiler...
From memory, the toxic fog had stopped spreading further and had not covered a large area where there were survivors. This inspired the young guy to return to Earth and he pleaded with the woman (his partner and future mother of their unborn child) to go too so the child could have a natural life on a planet and not be stuck on the space station, but she flat refused. She then pretended to agree so she could sabotage the controls and stop them.
I was surprised the young guy had forced the older man to come too, as the man's hands were bound and she had to release them.
Overall, it was an interesting movie with an impressive production design. Seeing the fog moving across Earth for the first time from the woman's POV during the space walk was horrifying but it's not a movie I'll watch again. It didn't captivate me enough.