I love the story concept, it has an ironic hook and it’s clear to see the character’s goal and what’s at stake if he fails. Not sure how it would play on screen though, as you don’t see many action films with a 60 year-old protagonist. Regardless, you have nailed the fundamentals of a great logline…

After an explosion, a marine wakes up in a place with other people from different times, his mission is to lead the group to recover artifacts spread in different times in history and avoid an alien invasion in the future.

After a marine awakes with people from different ages, he must lead the group to recover the three parts of the spear of destiny spread throughout history to repel an alien invasion in the future.?

The hook of your logline is the marine waking up with characters who have all been transported there from different eras of time. That’s an interesting hook and you need to milk that element dry.

The big question, of course (apart from why they must retrieve artifacts from different historical times) is who has put this bunch of people together and why? It can’t just happen for no reason, and all I can do with your logline is assume that the aliens have transported them through time and put them together (my reasoning being that aliens in your story would more than likely have the ability to time-travel than the humans). So why would the aliens (or whoever is responsible) do that?

About the artifacts – you need a time lock. The marine and his group must find these artifacts before the aliens find them. The aliens need them to complete their invasion (you decide why and how), but the marine somehow discovers that if he can find them and destroy them first, then the aliens can’t invade. Maybe the artifacts make up some kind of time-travel device or it creates wormholes or whatever, so their main armada can’t get to Earth without it. This brings me to my next point:

You have to personalise the story. You have the marine as the central character, which is good, but the main antagonistic force is the ‘alien invasion’, which is not specific enough. You need one antagonist that represents the aliens and this is the person that the marine will be fighting – they’re both racing each other to retrieve the artifacts.

For me, the explosion and the marine waking up are not important enough elements that they should be in the logline. You take them out, you’ve got more room to get in the important stuff, like so:

“A marine must lead a group of time-travellers to retrieve the four sections of ?????? before an alien soldier can use them to lead his invasion armada to Earth.”

Hope this helps 😉