At 8:57 p.m. ET time the Rosetta space probe will be entering a critical phase in its epic journey to land on Comet Churyumov- Gerasimenko. The probe will attempt a flyby of Mars using the planets gravity to reduce its speed and adjust its course back to earth. The probe will need to pass Earth three times and Mars once before reaching the comet in 2014.
Like the planets, comets are thought to have spun out of the sun during the formation of the solar system 4½ billion years ago. But unlike planets, comets have remained largely unchanged in composition, making them a unique time capsule of the process and elements at work during the formation of the planets.
