Mars theory cites episodes of wet asteroids By Paul Recer The Associated Press WASHINGTON — Mars never had oceans as some researchers claim, but instead is a cold, dry planet that was pounded by water-bearing asteroids and showered with scalding rain that carved vast gullies and valleys, a new study claims. The study, reported this week in the journal Science, sheds new light on a continuing debate by Mars researchers about how much water was on Mars, where it went and how it formed the planet's intricate pattern of canyons, riverbeds and deltas. Using Mars photos and computer simulations, researchers...