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(What are they trying to do? Embarrass our Sun and make it feel insecure and inferior?)

Rejoice oh young star in thy youth.

Our sun went through its T-Tauri phase and blew Earth’s primordial atmosphere into space (mostly highly volatile compounds like methane and ammonia). The subsequent heating and outgassing from volcanic activity resulted in a highly reduced atmosphere of water vapor, nitrogen and carbon dioxide. When earth’s atmosphere reached saturation temperature, all of the water vapor (~100 bars) rained out to form the oceans. Oxygen came later from an explosion of algae and other plant life but that’s another story. The comet theory for our oceans is invalid because of a significant difference in the O18/O16 ratio found in comets compared with that of ocean water.

Sadly, venus most likely contained as much water as on earth initially but the atmosphere never cooled enough to reach saturation vapor pressure. All of the water eventually boiled off into space. The oceans on earth stabilized the climate along with earth’s magnetic field and the presence of a large moon to keep earth’s axis from tipping on its side. We’re ackshully very lucky to be here. Then there is the argument for intelligent design but I digress.

-Frank

"We’re ackshully very lucky to be here"

An interesting topic. Just how lucky is still open for grabs. Planets capable of life may be common, or one in a trillion, in which case we may be the only one in the whole galaxy.

But just consider the variables. The Earth is the right distance from the sun. The sun itself is unusually stable, producing no planet-killing superflares within last 3 or 4 billion years. Probably because of its low spin. The solar system itself is very stable, due to orbital resonances of all the planets, especially Jupiter. The earth has a large moon to help stabilize its axial tilt. How common is that? The earth's magnetic field protects us from atmosphere loss and solar radiation. The fractured crust brings up fresh material from the mantle in a slow, mostly non-destructive fashion. There may be a dozen other factors that make earth suitable for life, so what are the odds of it all happening in one place? With only a single statistical example, no one can say. Then again, major extinction events occur roughly every 100 million years, resetting life back to the earlier beginnings.