Kenneth Chang

A rare and finely preserved skull unearthed in Argentina belonged to a dinosaur with a drooping head, far bigger eyes and keener hearing than some of its more evolved relatives, providing new clues about this group of lumbering plant-eaters.

At the end of the dinosaur age, Tyrannosaurus rex was a behemoth killer animal, up to 40 feet long and weighing several tons — the top carnivore in the food chain.

In less than a week, Scott J. Kelly will once again feel weight. On Tuesday, he is to turn over command of the International Space Station. A few hours later, he will land in Kazakhstan, ending 340 consecutive days in space — a record for a NASA astronaut.

Two astronomers reported Wednesday that they had compelling signs of something bigger and farther away than Pluto — something that would definitely satisfy the current definition of a planet.

The European Space Agency's ambitious attempt to place a spacecraft on the surface of a comet succeeded when a signal arrived at the mission control center at Darmstadt, Germany, on Wednesday.

A comet that once promised to light up the night skies -- then all but vanished but later seemed to blaze back to life -- is now fading away, astronomers say.

It looked to be uniformly bland, which is why scientists chose it as the first rock to be examined up close last year by the Mars rover Curiosity: a run-of-the-mill volcanic rock, something to test and calibrate the rover's instruments.

If you "like" this article on a site like Facebook, somebody who reads it is more likely to approve of it, even if the reporting and writing are not all that great.