“Technically and scientifically, it has certainly met our expectations,” said Alfred S. McEwen, a planetary geologist at the University of Arizona and principal investigator for the orbiter’s high-resolution camera.
Images taken by the camera, able to see features down to about a yard in size, have revealed details like rippled textures in what had looked like bland dusty regions, and researchers can now count tiny craters, enabling them to better estimate the age of terrains.
A sensitive spectrometer discovered rocks made of carbonate minerals, which may have formed when young Mars possessed a more benign environment: wet and maybe warm.
“That’s telling us something about the early history of Mars,” said Scott L. Murchie of the Johns Hopkins Applied Physics Laboratory and principal investigator for the spectrometer.
Most of the carbonates were washed away by acidic waters in later epochs.
The orbiter will continue its observations, which will allow places to be photographed more than once to capture changes in the landscape.
Meanwhile, the two Martian rovers, Spirit and Opportunity, mark their fifth anniversary this month, far outliving their original three-month mission. Spirit has recently begun moving again after sitting still through the winter while Opportunity is crossing the plains en route to a 13.7-mile-wide crater named Endeavour, a journey that could take at least another two years.
Steven W. Squyres, the principal investigator of the rovers, said it struck him as an odd milestone for people to mark. “It’s kind of like celebrating your birthday in Mars years,” he said. “Of course, I’d be younger that way.” (In Mars years, Dr. Squyres is 28.)