TOUCHDOWN!: The Spirit is on Mars

On Saturday night, everything went exactly according to plan for Spirit.

At 8:27 p.m. MST, during final approach, the craft turned to point its heat shield toward the Martian atmosphere. At 9:15, the spacecraft separated from its cruise stage, which carries solar panels that provide power during the seven-month trip to Mars and thrusters that allow fine-tuning of the trajectory before atmospheric entry.

At 9:29 p.m., the Spirit probe, encased in a protective cocoon called an aeroshell, slammed into the top of the Mars atmosphere at 12,192 mph, 73 miles above the surface. Atmospheric friction heated the aeroshell, built in Jefferson County by Lockheed Martin Space Systems, to about 2,600 degrees while protecting the 384-pound rover stowed inside.

At 9:33 p.m., the parachute deployed 25,000 feet above the surface, as the spacecraft descended at 446 mph. A minute later, the aeroshell's heat shield was jettisoned. One minute later, the lander's radar system locked onto the ground.

A few seconds later, mission control announced: "At this point in time, we should be on the ground."

At 9:36 p.m., cheers erupted in the control room when engineers received radio beacons suggesting that the airbag-cushioned lander was on the ground. Hand shakes, high-fives and hugs were exchanged. But mission controllers described the signals as "intermittent," and the room went dead quiet as engineers awaited confirmation.

Tense minutes followed. Then, at 9:51 p.m., communications manager Polly Estabrook announced, "We see it. There it is," indicating that mission control was detecting Spirit's radio signal on the ground after it bounced and rolled to a stop.