The most fascinating aspect of the discussion was that both of the scientists are convinced that aliens exist. They never doubted this for a second. The entire conversation was based on the assumption that they do exist, even though, as they admitted, there is no evidence for this at the present time. One of the scientists briefly discussed Darwinian evolution, saying that we "know how life evolved." However, he also admitted that they do not know how life began (a fairly important thing I would say).
While talking about earth, alien life, space, communication, etc., there was something significant missing. What was missing? God was missing.
Although these scientists (who are clearly secularists) do not know how life began and have no evidence that aliens exist, they still believe they exist. Meanwhile, they refuse to believe that God exists despite obvious evidence in creation for His existence. Throughout the conversation, it was clear that existence of God is not even considered in their worldview. They have ruled Him out.
What is so interesting is the scientists' lack of consistency when it comes to belief and evidence. They believe in alien life despite no evidence for it. At the same time, they do not believe in God despite evidence for Him.
This is a classic case of believing what we want to believe. These scientists want to believe in alien life because it will make their jobs much more interesting. Also, aliens will place no moral/ethical/ spiritual demands upon their lives.
They don't believe in God because they don't want to surrender to His sovereign rule as King. They do not want the constraints that someone else will place upon their lives.
This is just another example of secular scientists do not looking at actual evidence/data to come up with their worldviews. Instead, they believe what they want to believe about the world and then set out to prove it under than name of "science."
Unless we get prideful in looking at this, let us remember that but for the grace of God, we would be just like these secular scientists. So, how do we reach them with the gospel? It won't be from arguments from scripture (at least not at first). The first thing to do is to love them unconditionally and sacrificially in a way the world won't. That will get their attention. Once our love for them piques their curiosity, then we will have an open door for the gospel.