New Delhi: Last week, NASA's senior rover – Opportunity – which has been on Mars since 2004, reached its 5,000th Martian day, or sol and has once again unveiled a surprise feature of the Red Planet.
Its most recent observations are of possible 'rock stripes' that could suggest actions of water, wind or other processes on the Red Planet.
The ground texture seen in the image released by the space agency resemble those on some mountain slopes on Earth that result from repeated cycles of freezing and thawing of wet soil. But, according to NASA, it might also be due to the wind, downhill transport, other processes or a combination.
"It's mysterious. It's exciting. I think the set of observations we'll get will enable us to understand it," said Opportunity Deputy Principal Investigator Ray Arvidson of Washington University in St. Louis.
Opportunity, which landed on Mars in January 2004, is currently investigating a channel called "Perseverance Valley," which descends the inboard slope of the western rim of Endeavour Crater.
"Perseverance Valley is a special place, like having a new mission again after all these years," Arvidson said.
"We already knew it was unlike any place any Mars rover has seen before, even if we don't yet know how it formed, and now we're seeing surfaces that look like stone stripes," Arvidson added.
On some slopes within the valley, the soil and gravel particles appear to have become organized into narrow rows or corrugations, parallel to the slope, alternating between rows with more gravel and rows with less.
While the origin of the whole valley is uncertain, rover-team scientists are analyzing various clues that suggest actions of water, wind or ice.
Opportunity was planned as a 90-sol mission as NASA did not expect the rover to survive through a Martian winter.
But the rover surpassed expectations and reached its 5000th sol on February 16. It is investigating a channel called "Perseverance Valley," which descends the inboard slope of the western rim of Endeavour Crater.
A Martian "sol" lasts about 40 minutes longer than an Earth day, and a Martian year lasts nearly two Earth years.
Opportunity has driven over 45 kilometers from its landing site to its current location and it has returned about 225,000 images so far, NASA said.
(With IANS inputs)