Scientists probing Mercury's surface with radio waves now believe that the closest planet to the sun has a hot equator but no internal heat source, as previously thought. They have no clues as to what makes up the interior of Mercury.
Last year, the astronomers, from the University of New Mexico and the Los Alamos National Laboratory, probed Mercury with radio wave-emitting equipment.
They found that Mercury's erratic orbit, which swings it from 28.5 million miles to 43.5 million miles from the sun every 88 days, creates eccentric heating patterns. As a result, the planet has a hot spot on its equator that has been known to reach temperatures above 600 degrees Kelvin (620 degrees Fahrenheit). Some previous studies have suggested that Mercury had internal heat sources, but the new findings rule out this possibility, the scientists said.