Life originated on earth and did not come from an extraterrestrial source. Three billion years ago, the young sun would have been 30% less luminous and the earth's atmosphere was thinner. this would mean that approximately the top 300 meters of the ocean would be frozen, blocking ultraviolet light from destroying the organic molecules. The geothermal ocean vents spewed the organic materials needed to make the first genetic material, or amino acid proteins. These then formed RNA. and from then on, unless there was climate change involved, the atmosphere or anything else outside of the water did not affect the process of life forming. Soon, the first prokaryotic cells had been formed from RNA and other proteins combining. The prokaryotic cells eventually evolved into eukaryotic cells and they evolved into multicellular organisms, which moved onto earth and evolved from there.
The origin of life is UNDENIABLY extraterrestrial. The first piece of clear evidence is the chemical composition of the human body. Oxygen, Hydrogen, and Nitrogen all have their origins elsewhere in the universe. My second argument deals mainly from the fact that life and Earth developed at two different times. Leading scientists believe that "life" (your simple prokaryotic organisms) was, in fact, brought by a meteor or other chunk of space rock. While this rock may not have been carrying life, it carried the heat and chemicals needed to synthesize life and, without it, life would not have developed.
There is enough hydrogen and oxygen in the water and nitrogen from the geothermal vents in the bottom of the ocean to form life. Not only could life have formed undersea, the nucleotides needed to form RNA could have formed in the atmosphere, which had the necessary elements, though they may not have been very abundant. Nevertheless, the nucleotides formed a chain to form what is now known as RNA, which replicated and eventually formed a cell membrane. These cells evolved to have DNA and multicellularity evolved.
As you mentioned in round one, a meteorite may have come without life, but with the necessary chemicals. This would still mean that life formed on earth. Another theory scientists have come up with is exactly that! Meteorites carried the organic molecules, the heat and the water needed for the process of life to begin. This theory suggests that life originated almost 4 billion years ago. Scientists have found fossil evidence that leads them to believe that algae-like microorganisms were firmly rooted on earth 3.7 billion years ago.