NASA’s long-lived Mars Exploration Rover Opportunity completed its investigation of the Endeavour Crater site. The Opportunity’s goal is to learn about the history of the one-time wet environments of ancient Mars.
Observations from orbiting spacecraft have detected traces of clay minerals, which form under wet, non-acidic conditions that can be favorable for life.
“If you are a geologist studying a site like this, one of the first things you do is walk the outcrop, and that’s what we’ve done with Opportunity,” said Steve Squyres, the mission’s principal investigator at Cornell University.
Opportunity is coming up on her ninth anniversary, and the rover team chose this site as a driving destination years earlier. The site is named Matijevic Hill in honor of the late Jacob Matijevic, who led the engineering team for the twin Mars exploration rovers Spirit and Opportunity for several years.
Opportunity drove about 1,160 feet in a counterclockwise circuit around Matijevic Hill in October and November of this year, bringing the total miles driven on the mission to 22. Researchers used the rover to survey the extent of Matijevic Hill’s outcrops, as well as identify the best places to investigate further.
“We’ve got a list of questions posed by the observations so far,” Squyres said. “We did this walkabout to determine the most efficient use of time to answer the questions. Now we have a good idea what we’re dealing with, and we’re ready to start the detailed work.”
The hill is located on the western rim of Endeavour Crater, a depression some 14 miles in diameter. An impact from a celestial object, probably an asteroid, dug this crater more than 3 billion years ago, pushing rocks onto the rim from a greater depth than Opportunity reached during its first several years on Mars.
Since the impact, those rocks may have been altered by environmental conditions. Sorting out the relative ages of local outcrops is a key to understanding the area’s environmental history.
“Almost nine years into a mission planned to last for three months, Opportunity is fit and ready for driving, robotic-arm operations, and communication with Earth,” said the mission’s deputy project scientist, Diana Blaney, of NASA’s Jet Propulsion Laboratory (JPL).
Two outcrops of high interest at Matijevic are “Whitewater Lake” and “Kirkwood.” Whitewater Lake is comprised of a light-toned material that science team members believe may contain clay. Kirkwood contains small spheres with composition, structure, and distribution that differ from other iron-rich spherules that Opportunity found at its landing site and throughout the Meridiani Planum region.
Squyres calls the Kirkwood spheres “newberries.” “We don’t know yet whether Whitewood Lake and Kirkland are from before or after the crater formed,” he said. “One of the most important things to work out is the order and position of the rock layers to tell us the relative ages. We also need more work on the composition of Whitewater and debris shed by Whitewater to understand the clay signature seen from orbit, and on the composition of the newberries to understand how they formed.”
NASA launched Spirit and Opportunity in 2003 using two of the venerable United Launch Alliance Delta II rockets to send them on their way. Both completed their three-month prime missions in April 2004. Opportunity’s sister rover, Spirit, ceased operations in 2010. However, Opportunity is not alone on the surface of the Red Planet. The Mini Cooper-sized Mars Science Laboratory rover Curiosity is there also, which touched down on Mars’ dusty plains this past August.