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Textbooks say that the moon was formed after a Mars-size mass smashed the young Earth. But new evidence has cast doubt on that story, leaving researchers to dream up new ways to get a giant rock into orbit.
Breathless media coverage notwithstanding, the cases for and against a hypothetical Planet Nine in the outskirts of the solar system remain inconclusive.
Join David Kaplan on a virtual-reality tour showing how the sun, the Earth and the other planets came to be.
Geochemical signals from deep inside Earth are beginning to shed light on the planet’s first 50 million years, a formative period long viewed as inaccessible to science.
Searching for signs of life on faraway planets, astrobiologists must decide which telltale biosignature gases to target.
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