Impact may have transformed Mars
From Times Staff and Wire Reports
Astronomers have long puzzled over Mars’ landscape. The southern hemisphere is pockmarked and filled with rugged highlands, whereas the northern hemisphere is smoother and covered by low-lying plains. Three papers in Thursday’s journal Nature argue that an asteroid or comet whacked Mars about 4 billion years ago, blasting away much of its northern crust and creating a hole over 40% of the surface -- perhaps the largest gash on any object in the solar system.
Scientists who had no role in the studies said the research strengthened the case for a colossal impact but did not rule out the other theory: that molten rock from inside the planet might have formed the different crusts.
