The propagation speed of gravitational waves remains the speed of light; if the receiving end is too far away, it is essentially meaningless. A mere 100 Earth years could bring about a revolutionary change to a civilization in the scientific era. If aliens were to take action, the receiving end should not be set too far away.
These four conjectures primarily serve to tell others that there is no need to worry about an alien civilization suddenly appearing within the next 10 years; humanity still has plenty of time to make decisions.
Technically, there are established procedures for the exploration of Mars and Titan. It's simply a matter of sooner or later; the base can turn those places upside down in the coming years.
The trouble lies in dealing with the situations on Earth.
If astronauts are sent to dig extensively on Mars, there's a high probability that the existence of an alien civilization will become public knowledge.
