why isn't it

[froggy]

because of all the planets we have observed, ours is the only one with conditions that would allow evolution to occur.

and the reason for that is?

42

or twice 21

 

[Jon]

i knew the answer the atmosphere sorta runs interference for us,the point was to see if it made you wonder why earth was all by itself and why the so-called evolution only happened to a single planet.

Because of all the planets we have observed, ours is the only one with conditions that would allow evolution to occur.

and the reason for that is?

Probability and statistics.

 

[American Horse]

why isn't the earth full of craters like all the other planets and moons?

Thickness of the atmosphere. The planets you see "full of craters" don't get "shooting stars" .... all of their debris hits the surface. Most of what enters our atmosphere burns up before it hits.

Perceptive of you, but that doesn't go far enough, nor include all impact events. Obviously objects the size of the ones in my "attachment image" were large enough to reach the Earth's surface in spite of the density of the atmosphere. As a matter of fact any object large enough to make a crater that would be detectable aerially even a decade later would most likely make it through the atmosphere without being "burned up." A large object like the one the produced the Tunguska event for instance was destroyed because it was composed of tenuous, icy, cometic material for instance. It exploded above the Earth's surface similar to the atomic explosion over Hiroshima or Nagasaki. It's component parts, glued together over billions of years by slow accretion, once heated by friction with the earth's atmospere blew apart from the steam produced by the heat, and all that was released was water vapor and dirty fines. But large rocky objects and especially irony objects will make it to the surface of the Earth.

I think Noose4's image was of the grand canyon, and he was showing the round crater like indentions along the main drainage channel because they are so similar to those in my image. These appear to be "hanging valleys" possibly produced by glacial action during some past ice age. Notice that they are lower than but have been fed by valleys above on the higher plateau. During an ice age they would have been filled with ice which would've broken up the valley floors creating that kind of shape.