"Touchdown signal detected."
Riotous applause in Mission Control followed these words from primary commentator Richard Kornfeld today—confirmation that NASA's Phoenix Mars lander successfully touched down near the north pole of Mars.
"Absolutely perfect. It went right down the middle," said Barry Goldstein, Phoenix project manager at the Jet Propulsion Laboratory in Pasadena, moments after the landing.
"It was better than we could have possibly wished for."
At 7:53 p.m. ET Mission Control received the signal that the craft had survived the tricky descent through the red planet's atmosphere dubbed the seven minutes of terror.
During that time the probe had to slow itself from 12,700 miles (20,438 kilometers) an hour to 5 miles (8 kilometers) an hour before gently setting down on Martian permafrost.
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.
Now "we have to make sure the spacecraft is healthy, but by God, it's landed in a place where it's in an almost horizontal position," said Peter Smith, Phoenix principal investigator at the University of Arizona in Tucson.
Data from the craft show that it now sits on Mars with just a quarter of a degree tilt.
Phoenix is now the first probe to reach a Martian pole and the first to successfully land with powered thrusters since the Viking missions in 1976. Both Mars rovers landed using airbags to cushion the blow.
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 can take more than 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 are being sent via relays through Mars-orbiting probes.
A few minutes after landing, the orbiters moved out of range of Phoenix, so scientists had to wait for about an hour and a half to re-establish contact and start collecting information.
The first data stream includes images of both 18-foot-wide (5.5-meter-wide) solar arrays fully deployed, as well as a footpad firmly planted on the surface.
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.