Many people marvel at all the special things that make life possible on earth, and wonder if there could be any other "just right" planets like this Goldilocks planet of ours -- a term used by Clara Moskowitz in "What Makes Earth Special Compared to Other Planets?" She discusses several unique aspects about earth. The importance of tectonic plates and the role water plays with that mechanism is something I hadn't really considered before. Here's what she says:
Goldilocks planet

Earth's water is also special in that it has remained liquid for so long. How has Earth been able to hold on to its oceans while those on other planets freeze or fry?

"Many details as to why Earth is the only planet with liquid water in our solar system need to be worked out," said Diana Valencia, a graduate student in Earth and Planetary Sciences at Harvard University. "Certainly the distance to the sun has made it possible. A planet much farther in would receive too much energy from the sun, and a planet too far out would quickly freeze."

Our planet's Goldilocks-like "just right" location in the solar system has helped, as has its system of plate tectonics — the slip-sliding movements of Earth's crust that are thought to have created the planet's towering mountain ranges and plummeting ocean depths.

"The fact that Earth has plate tectonics allows for the carbon-silicate cycle to operate over geological timescales," Valencia said. "With the carbon-silicate cycle, the levels of carbon in the atmosphere get regulated to keep the surface temperature around that of liquid water."

Plate tectonics and water are inextricably linked. Not only does plate tectonics enable liquid water to exist by way of regulating the temperature, but many scientists have argued water enables plate tectonics to happen.

"Without water the planet would be geologically dead," said Caltech's Mike Brown, discoverer of the newly reclassified "plutoid" object named Eris, which lies beyond Pluto in our solar system. "Water is what lubricates plate tectonics, which is what leads to the extreme difference between continents and seafloors, the large amount of earthquakes and volcanoes, fresh mountain-building. Venus has no water, no plate tectonics, no deep sea floor, no steep mountains, no continents, probably few earthquakes or volcanoes. A much less geologically interesting place!"

Another "just-right" aspect of Earth is its size: If it was much smaller, it wouldn't be able to hold on to our precious atmosphere, but much larger and it might be a gas giant too hot for life.

The presence of our big brother planet, Jupiter, farther out in the solar system blocking Earth from much of the incoming debris, has also helped Earth become a safe haven for life. Jupiter acts like a giant broom, sweeping the solar system of debris — rocks as small as cars and as huge as moons — that could snuff out life in one fatal blow. This protective effect was particularly helpful in the solar system's early years, when Earth still got pummeled but, scientists say, not nearly as bad as would have been the case without Jupiter.
Yes, earth is an incredible and amazing place. How did we get so lucky? Various forms of the anthropic principle can be invoked to take the worshipful edge away from our contemplation of earth's majestic match to the improbable requirements for life ("Don't marvel that everything has worked out just right for life - if those coincidence hadn't occurred, we wouldn't be here to ask why"). However, I prefer gratitude to a kind and brilliant God who crafted this place for us. Latter-day Saints go a step further by believing that the universe has millions upon millions of earths similar to this one where other sons and daughters of God dwell. We know almost nothing about that, so don't press me for answers! But the wonder of all those galaxies and marvelous creations across the cosmos is not there just for us and our telescopes. There may even be intelligent life on hundreds of other places like this right here in our own galaxy, not to mention the Andromeda Galaxy (M31), Bode's Galaxy (M81), the Black Eye Galaxy (M64), the Sombrero Galaxy (M104), and even the Los Angeles Galaxy (MLS).
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