Destroy life on earth. I phrased it as a tautology to be humorous, but very large impacts are possible. I doubt life would survive an impact such as the one w

Destroy life on earth. I phrased it as a tautology to be humorous, but very large impacts are possible. I doubt life would survive an impact such as the one we hypothesized to have created the moon. http://en.wikipedia.org/wiki/Giant_impact_hypothesis http://en.wikipedia.org/wiki/Giant_impact_hypothesis "collision between the Earth and an astronomical body the size of Mars"