Mars has received a one-two exploration punch as the second Rover — Opportunity — achieved a successful landing tonight on the red planet. Engineers and scientists broke out in cheers and tears here at the Jet Propulsion Laboratory (JPL), mission control for the Mars Exploration Rover (MER) program. Opportunity landed in the Meridiani Planum region of Mars. The spacecraft’s exact whereabouts are not precisely known, but appears to have touched down within a pre-determined ellipse within Meridiani Planum.