At the end of the film, Capa's heroic sacrifice restarts the sun, rescuing humanity from certain doom. However, Earth has endured a drastic drop in temperatures (suggested by the scene of Sydney buried under snow), which would have devastated ecosystems all over the planet. Even though the sun has been restored, people on Earth will still struggle to grow crops and restore the atmosphere's oxygen for years to come. These struggles mean that the planet will probably face civil unrest, wars, and hunger for years to come.
Yes, but they'll live.
Seconded. Sure, the upheaval will suck major balls, but at least there will be an Earth to rebuild.
More of Fridge Sadness, really (Fridge Tearjerker?). The friends and families of the crew members could see from Earth that the crew had succeeded, but had no way of knowing that they'd all died in the process. They wouldn't be able to contact them to find out that there was nobody there due to the dead zone around the sun, and they would just be waiting for the ship to come back not knowing that it never will, and would never have any way of knowing what happened on the it.
All the grey dust on Icarus 1 - they mention that most dust comes from human skin (incorrect) but in their case, it may actually be correct - the dust is the burned off skin of the crew, all of whom were fried.
Pinbacker's favorite biblical quote- "We are dust"? It takes on a whole new meaning when you think of Searle's "Hey Capa, we're only stardust." Remember how Pinbacker has been "Communing with God" for the last seven years? If we're stardust, and our star is God... what are we?