[fideloper]

Or it's unique properties + earth's in combination are the only reason why life exists.

[SoftwareMaven]

There are theories putting Mars in that position: that early on, Mars was more hospitable due to less water, and microbes eventually caught a ride on something ejected from Mars via volcano or meteor impact.

[ChuckMcM]

"Theia, baseball of God" sounds like a good title :-)