First murder help

MEA handles quests a bit differently than some games, and you can't always finish a quest in same 'act' that you get it.  Eos is the first planet you get access too once you start exploring, to get it, you have to finish enough of main quest on the station to unlock the ship access, then go down to the docks and use the door to get on the ship.  Once you have access to the ship, you have to explore and scan Eos, land there, complete the quests there to fix the atmosphere, set up the colony there, leave, go do some more stuff up to another planet, then get the notification that the atmosphere has cleaned up.  Once the atmosphere gets cleaned up, it should open exploration of the area previously to hostile to explore(but not all of it) and then you can look for first murder locations and follow the trail to find out what happened.  So to finish this one side quest you will have to finish more than just a basic part of the game.  There are others like this as well, so don't expect on all occasions to get a quest and to be able to finish it quickly, because some require advancing the main story before you can continue them and thus get to where you need to go.