NASA's twin rovers, named Spirit and Opportunity, have been cruising through the frigid temperatures of space toward Mars for seven months, traveling about 300 million miles. Spirits of the engineers and scientists who have worked on this mission for the last three years will likely heat up around 7:04 p.m. PST when the Spirit spacecraft rotates to face its heat shield forward for final approach. The first step the rover will take in shedding more than half of the spacecraft it has been traveling in should occur at 8:14 p.m. PST, when the entry vehicle is scheduled to separate from the cruise stage. The rover should come screaming into the Martian atmosphere going 12,000 mph at 8:29 p.m. PST.

During the next six terrifying yet thrilling minutes, Spirit will jettison its heat shield, deploy its airbags, fire its retro rockets, cut loose its backshell and parachute, and bounce against the martian surface at 8:35 p.m. PST. The rover, protected by a lander structure and airbags, could bounce up to five stories high and rock and roll as far as 1 kilometer (0.6 mile) across the martian ground before it completes its grand finale stop before 8:45 p.m. PST.

Through the sequence of events this Saturday, Spirit will initially communicate with Earth through a series of simple tones -- imagine the harmonic tones in the movie Close Encounters of the Third Kind, but with a different melody and a much slower tempo. The Deep Space Network antennas on Earth could hear from Spirit Saturday night, but may not receive the first signal from a healthy spacecraft until Sunday evening. Within the first 24 hours, Spirit will have several chances to communicate with Earth both directly to the Deep Space Network and through NASA's Mars Global Surveyor orbiter and NASA's Odyssey orbiter. Both orbiters currently collect science at Mars and cruise above the martian surface at 400 km (250 miles), and they will each fly over Spirit's landing site, Gusev Crater, throughout the mission.

To watch Spirit's rover team and mission controllers live during the landing events from Jet Propulsion Laboratory in Pasadena, California, please tune into NASA TV, beginning at 6:45 p.m. PST.

View a detailed description of the Entry, Descent, and Landing Sequence of Events