You are the President of Earth, and a mysterious planet from another galaxy is hurdling towards our planet.
Transmissions from the mysterious planet have been sent directly to you by those who live there. It has life with sentient intelligent beings. They have double the population of our world's. Their technological tier is unclear, but it's at least roughly equivalent to ours, if not superior. Just when they were about to state if they were friendly, hostile, or otherwise, a solar storm flares and blocked their communications from us. Their intentions are unknown.
The scientists have calculated a 70/30 percentage chance of one-of-two outcomes of where this planet will go. There's a 70% chance this planet will shrimply be caught by the suns gravity and will orbit harmlessly between Earth and Mars, giving us a new neighbor (for better or worse). But, there's also 30% chance this planet will collide with Earth, mutually destroying their world and our own.
The planet is closing in and will be here quite soon, and the solar storms are keeping communications of the otherworldly beings blocked. As President of Earth, you exclusively have the activation code for a planet destroying super weapon. It is charged ready to fire on your command. If it is not fired now it will have to be deactivated to prevent a massive overload, and will take 2 years for it to charge and be ready again.
You can either destroy their planet and kill all the otherworldly beings, or you can do nothing and take your and eberryone's chances for our potentially new but mysterious neighbors.
Make your choice, President of Earth.