Most of the material in that disk was then pulled toward the center to form the sun. Other particles within the disk collided and stuck together to form ever-larger bodies, including Earth. Scientists think Earth started off as a waterless mass of rock. However, analyses of minerals trapped within ancient microscopic crystals suggest that there was liquid water already present on Earth during its first million years, Marchi said. Radioactive materials in the rock and increasing pressure deep within the Earth generated enough heat to melt the planet's interior, causing some chemicals to rise to the surface and form water, while others became the gases of the atmosphere.
Recent evidence suggests that Earth's crust and oceans may have formed within about million years after the planet took shape. Earth's core is about 4, miles 7, km wide, slightly larger than half the Earth's diameter and about the same size as Mars. The outermost 1, miles 2, km of the core are liquid, while the inner core is solid. That solid core is about four-fifths as big as Earth's moon, at some 1, miles 2, km in diameter. The core is responsible for the planet's magnetic field, which helps to deflect harmful charged particles shot from the sun.
Above the core is Earth's mantle, which is about 1, miles 2, km thick. The mantle is not completely stiff but can flow slowly. Earth's crust floats on the mantle much as a piece of wood floats on water. The slow motion of rock in the mantle shuffles continents around and causes earthquakes, volcanoes and the formation of mountain ranges. Above the mantle, Earth has two kinds of crust. The dry land of the continents consists mostly of granite and other light silicate minerals, while the ocean floors are made up mostly of a dark, dense volcanic rock called basalt.
Continental crust averages some 25 miles 40 km thick, although it can be thinner or thicker in some areas. Oceanic crust is usually only about 5 miles 8 km thick.
Water fills in low areas of the basalt crust to form the world's oceans. Earth gets warmer toward its core. At the bottom of the continental crust, temperatures reach about 1, degrees Fahrenheit 1, degrees Celsius , increasing about 3 degrees F per mile 1 degree C per km below the crust.
We do know that life as we understand it requires very special conditions to exist. In fact, many scientists believe that these conditions exist elsewhere and offer the possibility for life beyond just our Earth. These may be very simple organisms such as bacteria or even more complex life such as plants and animals.
All living things need some sort of food, water, the right atmosphere and temperature. Even the strength of gravity determines the form of our bodies such as our bones and muscle strength. All living things on earth have adapted to our atmosphere, which means all living things need our mix of atmospheric gases.
Life elsewhere would be specifically adapted to their own conditions. Water is a really important ingredient to sustain the kind of life we know on Earth. Both plants and animals require water for survival. Planet Earth is very special because it contains so much water in liquid form. One of things that the Mars Rover, Curiosity, is looking for is the presence of water now or evidence that it existed in the past on Mars.
It appears that Mars did have lots of liquid water at one time. Conditions might have been right on Mars to support life. For living things the correct temperature is really important.
Most life on earth lives in warm to moderate temperatures. So, there still might be life on other planets, or even the moons of other planets, but it would probably be very different than life on Earth! These other possible forms of life would be very far away so they are not something to worry about.
Looking for more Never Stop Asking "Why? Catch up on all of the past "Why's" on the blog. Plate tectonics helps ensure this rock gets dragged downward, where it melts, and this molten rock eventually releases this carbon dioxide gas back into the atmosphere through volcanoes. Seager agreed, saying that "volcanism might very well provide enough fresh supplies of whatever life might need. Other factors researchers have trotted out for why life succeeded on Earth include how little variation there is in our sun's radiation compared with more volatile stars, or how our planet has a magnetic field that protects us from any storms of charged particles from the sun.
Violent bursts of radiation could have scoured life from Earth in its early, fragile stages. Still, "people are constantly rethinking each of these things and how important they are," Seager said. We want to learn about what gray areas might exist for possible life.
Earth remains the only known planet to host life, due to a unique combination of factors. However, continued monitoring of alien worlds might one day change that, by finding other planets that share these attributes or by discovering other ways that life has found to blossom in the universe. Live Science. Charles Q. Planetary Defense Coordination Office. Planetary Science Mission Posters. Planetary Science Mission Fleet.
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