Harvard-Smithsonian Scientists Identify Key Sign of Habitable Worlds

"It would be hard to believe that the continuous movement of tectonic plates has no effect on the development of life on Earth."

James Trefil, physicist and author of Other Worlds: The Solar System and Beyond?

According to Harvard scientists, habitable worlds are most likely found on large, rocky planets that are up to ten times the size of Earth and contain plate tectonics.

Plate tectonics play a critical role in determining the rate of cooling of a potentially habitable planet by creating the optimum temperature ranges for the development of intelligent animal life -as continents grow, planets cool.

The researchers found that super-Earths, or planets up to ten times the size of the Earth are the best places to find extraterrestrial life. These planets contain a solid inner core that is surrounded by a liquid mantle, and on top a crust. What is seen as critical to life on one of these large extra-solar planets (exoplanets)—or planets circling a star other then the Sun—is the presence of plate tectonics.

Plate tectonics helps to explain large motions of the Earth’s lithosphere -the solid, outermost layer of the Earth which is made up of the rocky crust that form the tectonic plates. The next layer is the asthenosphere, the softer layer of the upper mantle, which steadily but very slowly flows like a liquid over millions of years. The lower layer of the mantle, which is below the asthenosphere, is a fairly rigid section because of extreme pressures around it.

There are eight to twelve major tectonic plates on our planet and twenty or so smaller ones all moving at speeds and in different directions. The constant turmoil prevents the plates from fusing into a single immobile plate.These plates move together at about 0.75 centimeters each year, some moving apart and some moving together, causing earthquakes, volcanoes, and other physical events within the Earth.

The researchers contend that such geological activity is essential for finding life on super-Earths. They have found that activities associated with plate tectonics help to enhance the chance for life, add to the diversity of life forms, and constantly move minerals, chemicals, and other life-giving substances throughout the soil.

Earth has a solid/liquid metal core that includes radioactive material giving off heat. The metal core produces a magnetic field that protects the surface of the planet from radiation from space, and the radioactive heat from the core, mantel and crust fuels plate tectonics. Why the Earth is alone among rocky planets in our Solar System in having plate tectonics is a mystery. Venus, our twin in size and density, has no tectonic activity.

In addition to plate tectonics and the Earth's location in the Milky Way with its relative abundance of elements heavier than helium, the Earth is also fortunate to exist in a spiral galaxy rather than elliptical galaxies, which are nearly as old as the universe and have a low abundance of heavy elements.

Posted by Casey Kazan.

Comments

The geological activity would free up gases / chemicals neccesary for habitability & life. I still don't think we should look for palm trees, pine forests, savannas or wheat fields on worlds like this, though. ( If we ever travel there in person )

Posted by: EvilCosmicMonkey from Knoxville | October 22, 2008 at 10:38 AM