At 10:31 p.m. PDT today, April 27, (1:31 p.m. EDT), NASA’s Mars Science Laboratory, carrying the one-ton Curiosity rover, will be within 100 days from its appointment with the Martian surface. At that moment, the mission has about 119 million miles (191 million kilometers) to go and is closing at a speed of 13,000 mph (21,000 kilometers per hour).