planetary science

Astronomers argue that there’s an undiscovered giant planet far beyond the orbit of Neptune. A newly discovered rocky body has added evidence to the circumstantial case for it.

A series of fossil finds suggests that life on Earth started earlier than anyone thought, calling into question a widely held theory of the solar system’s beginnings.

Jason Morgan developed the theory of plate tectonics in 1967 while working among a critical mass of talented geophysicists at Princeton University.

Even in the age of sun-observing satellites, astronomers like Jay Pasachoff still seek out total solar eclipses for the tales they can tell about our sun.

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.