NASA’s prolific Mars Reconnaissance Orbiter has completed five years of circling the Red Planet.

The orbiter has opened up a treasure trove of information about ancient environments, ice-age-scale climate cycles and present-day changes on Mars.

The spacecraft’s large solar panels and dish antenna have enabled it to transmit more data to Earth - 131 terabits and counting, including more than 70,000 images - than all other interplanetary missions combined.

The craft encountered several hiccups after a seven-month journey from Earth when it fired its six main engines for nearly 27 minutes as it approached Mars on March 10, 2006. Mars could not capture it into orbit without this critically timed manoeuvre to slow the spacecraft.

"That was tense, waiting until the spacecraft came back out from behind Mars and we had contact,” recalled Dan Johnston, now the mission’s deputy project manager at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

The mission has illuminated three very different periods of Mars history. Its observations of the heavily cratered terrains of Mars, the oldest on the planet, show that different types of ancient watery environments formed water-related minerals.

With observations of new craters, avalanches and dust storms, the orbiter has shown a partially frozen world, but not frozen in time, as change continues today.

Apart from the observations, the mission provides support for other spacecraft as they land and operate on the surface. Its cameras captured the Phoenix Mars Lander as it parachuted to the surface in 2008 and monitored the atmosphere for dust storms that would affect Phoenix and the Mars Exploration Rovers Spirit and Opportunity.

JPL’s Phil Varghese, project manager for the Mars Reconnaissance Orbiter, said, “The spacecraft is still in excellent health. After five years at Mars, it continues with dual capabilities for conducting science observations, monitoring the Mars environment and serving as a relay.” The orbiter has examined potential landing sites for NASA’s Mars Science Laboratory mission, which will land a rover named Curiosity at one of those sites in August 2012.

Its Mars Color Imager has produced more than four Earth years of daily global weather maps.

The Compact Reconnaissance Spectrometer for Mars has mapped minerals on more than three- fourths of the planet’s surface. The Mars Climate Sounder has monitored atmospheric temperature and aerosols with more than 59 million soundings. The Shallow Radar has checked for underground layers in more than 8,600 swaths of ground-penetrating observations.

"We have already learned that Mars is a more dynamic and diverse planet than what we knew five years ago. We continue to see new things,” concluded JPL’s Rich Zurek, project scientist for the Mars Reconnaissance Orbiter.

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