New research fuels idea that Mars was once struck by a massive asteroid

The dramatic differences between the northern and southern hemispheres of Mars have puzzled scientists for decades. One of the proposed explanations--a massive asteroid impact--now has strong support from computer simulations. [More]

Thank you to all 387 of you who replied to last issue's poll on commencement speakers. Last issue's poll results are available here.

This Issue's Poll

Feel free to wax poetic. We'll publish a few of your responses in our next Letters section.