The Perseverance rover of the US space agency is preparing to take its first sample of Martian rock.
The nucleus, the size of a finger, will be packed in a sealed tube for possible return to Earth.
Scientists say their best chance of determining whether Mars has ever harbored life is to study its surface materials in sophisticated home laboratories.
Perseverance landed on the Red Planet in February, in a 45 km (30 mile) wide crater called Jezero.
Satellite images indicate that this deep depression once housed a lake, fed by a deltaic river.
As such, it is considered an excellent candidate for the preservation of ancient microbial organisms – if they ever existed.
The NASA robot traveled about 1 km (3,000 feet) south of where it dramatically landed five months ago.
He is now arrested at a place that has been nicknamed the “Paver Stones” or “Fractured Rough”.
This is a collection of pale colored rocks that the mission team believe represents the base, or ground, of Jezero.
Scientists want to determine if these pavers are of sedimentary or volcanic origin. Either is interesting, but the special quality of volcanic rocks is that they can be dated with great precision and accuracy in a laboratory, says chief scientist Ken Farley.
“It would really determine the timing of a lot of the things we are looking at on Mars,” he told reporters.
Perseverance will first abrade the surface of a selected section of Paver Stone, to remove the obscuring dust from Mars, then examine the site with its powerful instruments.
These are held at the end of his robotic arm. They are able to determine the chemical composition, mineralogy and texture within a rock – to definitively identify it.
Finally, in early August, the robot will secure a drilled core.
The rover will cache something like 40 of these little sample tubes during its mission. Subsequent projects from NASA and the European Space Agency (ESA) will arrive on Mars to appropriate them and bring them home.
Professor Farley said he expects four unique samples to be cached in the crater area currently under investigation. This includes an attractive rock outcrop, called Artuby. This is about 600 meters away and appears to contain very finely layered sediment, potentially deposited by the lake and river delta system that once occupied Jezero.
“This is exactly the type of rock that we are most interested in studying for potential bio-signatures in this ancient rock record,” said the California Institute of Technology researcher.
NASA is delighted with the performance of Perseverance.
A particular success has been its driving style, which now achieves a high level of autonomy.
While older vehicles needed a lot of direction from controllers on Earth, or could only navigate slowly, Perseverance can image terrain at high speed and plot a route with great efficiency. The robot can do this for trips of 100m or more, avoiding difficult obstacles, such as large boulders or cracks in the ground, along the way.
The rover is helped by the reconnaissance carried out through the mini-helicopter that it brought to Mars.
Called Ingenuity, this little helicopter flew past Perseverance to survey the terrain.
“We just completed Flight Nine (of Ingenuity),” said Jennifer Trosper, NASA project manager.
“He broke all of our records. The duration was two minutes and 46 seconds, the speed was 5m / s, and we quadrupled the distance we had ever traveled, and we flew about 625m.”