Year of the Comet
Comet C/2011 L4 (PANSTARRS)

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Comet C/2012 S1 (ISON)

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Web Extras

Worlds on fire

From icy bodies to Sun-drenched planets, volcanic activity seethes throughout the solar system.
By Richard Talcott
Published: December 21, 2012
Kilauea-still
The early solar system was a crowded place. Unfathomable numbers of small particles jostled with one another in the dusty disk that surrounded the nascent Sun. Collisions among these particles gradually built larger objects, and eventually planets formed. Every one of these collisions produced heat, so objects in our solar system were born hot. The rocky planets grew even warmer when heavy elements sank to form their cores, releasing gravitational energy in the process.

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