Although friction and a parachute helped reduce its speed, Phoenix was designed to separate from the chute at about 0.6 mile (a kilometer) above Mars, relying on pulsing thrusters to smooth its final descent. During its 422-million-mile flight from Earth to Mars after launching on August 4, 2007, Phoenix relied on electricity from solar panels during the spacecraft"s cruise stage.
The cruise stage was jettisoned seven minutes before the lander, encased in a protective shell, entered the Martian atmosphere. Batteries provide electricity until the lander"s own pair of solar arrays spread open. “We"ve passed the hardest part and we"re breathing again, but we still need to see that Phoenix has opened its solar arrays and begun generating power," said JPL"s (Jet Propulsion Laboratory"s) Barry Goldstein, the Phoenix project manager.
The 12-foot-wide (3.6-meter-wide) solar arrays will bring Phoenix back up to full power after it had switched to battery power upon separation from the cruise module. The success is a critical step for possible future human missions to Mars, because people would not survive the high-velocities associated with airbag landings.
“The way we"re going to land humans on Mars is with propulsion systems and landing legs," said Ed Weiler, associate administrator for NASA"s Science Mission Directorate. Mars is about 171 million miles (275 million kilometers) away, so data transmissions take just over 15 minutes to reach Earth.
The craft is able to send UHF radio signals directly to Earth-based telescopes, but most of its engineering data and images will be sent via relays through Mars-orbiting probes. “The hardest part is over, but there"s still a lot of drama waiting for us," said Goldstein.
Over the next few days, scientists will study the probe"s surroundings and conduct a full health check on the lander and its payload of scientific instruments. Once Phoenix gets its bearings, it can begin its 90-day mission to dig deep into the Martian permafrost and analyze soil and ice samples, in part to determine whether Mars ever had the right conditions to support life.