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Solar System

Planets and Moons Suddenly Got Much Younger
October 20, 2002
A planet or moon covered with craters just looks old, doesn’t it?  Planetary geologists have long relied on crater counts to estimate the absolute ages of surfaces, such as on the moon, Mars, Europa, and every other solid body.  Lots of craters meant old.  Few craters meant young.  Presumably, impacting bodies came in like clockwork […]
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Cosmology

Questioning Earth’s Privileges
September 20, 2002
51; Two articles this week downplayed considerations that would make the Earth seem like a special place in the universe.  Both have ties to NASA.     Are life-friendly stars limited to a narrow band in the galaxy called the Galactic Habitable Zone (GHZ)?  NASA-supported Astrobiology Magazine cast doubt on the idea.  Citing a study […]
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Solar System

A “Completely Different Slant” on Solar System Formation
July 20, 2002
51; “Did great balls of fire form the planets?” New Scientist asks.  A new theory “challenges the notion that the solar system started out as a placid sea of dust motes which simply clumped together to form planets.” If accepted, it “puts a completely different slant on what happened in the early solar system in […]
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Solar System

Hiding Comets Out of Bounds
June 20, 2002
51; There’s a new theory floating around about where most of the comets came from: other stars.  For many years, astronomers hid them in an unobservable region called the Oort cloud that was assumed to be partly a remnant of the sun’s primordial disk, and material that was ejected outward.  Now, according to the BBC […]
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