The six-member crew of the International Space Station is tasked with studying a sample from Mars that may be the first proof of extra-terrestrial life, which proves more intelligent than ever expected.
This movie contains 43 potentially triggering events.
I found the rat being killed extremely upsetting. However it's clear its about to happen before it actually does, so you have time to look away/cover your screen.
Alien goes inside a person to kill them but not to possess and another to feed on them. Another person helps the alien in his obsession but is not implied that he is possessed by the alien.
Just to add to the above, this scene starts at 38.18 and ends at 40.30. It happens after he goes into the lab with the new life form and it goes into his mouth. Since they are weightless the blood floats out of his mouth, it is graphic for what it is but doesn't look for act like normal v*. At about 41.00 the creature comes out his mouth bringing a lot of blood with it.
The creature crawls into the mouth of a character. There is a very long and vivid choking scene before he begins to cough up blood, and eventually the creature crawls back out of him after he has died.