Mars made its closest approach since 2003 on Dec. 18, 2007 at 6:46 p.m. EST. Scientists now report there is a one in 75 chance of an asteroid impacting the planet within 30 days. Credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA), J. Bell (Cornell University), and M. Wolff (Space Science Institute, Boulder)