Near Earth Asteroid

What is considered too close for comfort?

An asteroid measuring roughly 3 miles across passed near the Earth last week at a distance of about 4.3 million miles away.  So what is considered too close for comfort?  To give an idea of the scale of this asteroid at its closest distance to the Earth, Toutartis 4179 passed at 4.3 million miles away.  Our own moon is just 238,900 miles from us and Mars varies in distance because of the Earth and Mars have unrelated orbits around the Sun.  Mars at is closest distance is 34 million miles and at the farthest could be 250 million miles out.  Scientists state that even though Asteroid (Toutatis 4179) passed safely away from the Earth that it will return in the year 2069 and that time it will pass even closer to the Earth at 1.8 million miles.  To give an idea how much damage this asteroid could do if it collided with the Earth,  scientists state that the asteroid that would have killed off the dinosaurs would have been 6 miles across so if in one of its future runs it could cause catastrophic damage.
I for one would wish that NASA would have in place an early warning system for large objects like this so that we could have enough time to do something to protect the Earth.

Below is a video from multiple space radar images.

 

Article sources are from NASA and space.com