NASA’s old Opportunity rover on Mars has just made what may be one of its most significant discoveries to date.
Nine-year-old Opportunity rover has identified rock laden with what scientists believe to be clay minerals.
Their presence is an indication that the rock, dubbed Esperance, has been altered at some point in the past through prolonged contact with water.
Opportunity has seen a clay-bearing outcrop before but scientists say this is by far the best example to date.
“It’s very rich,” said Steve Squyres, the rover’s principal investigator.
“We’ve been discovering evidence for water on Mars since we first landed back in 2004. What’s different here?
“If you look at all of the water-related discoveries that have been made by Opportunity, the vast majority of them point to water that was a very low pH – it was acid.
“We run around talking about water on Mars. In fact, what Opportunity has mostly discovered, or found evidence for, was sulphuric acid.
“Clay minerals only tend to form at a more neutral pH. This is water you could drink. This is water that was much more favorable for things like pre-biotic chemistry – the kind of chemistry that could lead to the origin of life.”
Opportunity Mars rover discovers Esperance rock with signs of water
Prof. Steve Squyres, who is affiliated to Cornell University, Ithaca, New York, said he was inclined to put Esperance in his personal top five discoveries made on Mars by Opportunity and her twin rover, Spirit, which stopped working in 2011.
The clays are aluminium-rich, possibly of the type montmorillonite. However, because Opportunity’s X-ray spectrometer can only discern the atomic elements in a rock, and not their mineralogical arrangement, no-one can say for sure.
Nonetheless, the mere occurrence of clays is further proof that the Red Planet was much warmer and wetter billions of years ago; a very different place to the cold, desiccated world it has become.
And these results complement nicely those of NASA’s newer rover Curiosity, which has also identified clays at its landing site almost half-way around the planet’s equator.
The old robot made its find at a location called Cape York, which is sited on the rim of a 22 km-wide crater known as Endurance.
Mission managers have now commanded it to start moving along the ridge to a destination dubbed Solander Point.
There is an expectation that Opportunity will find a deeper stack of rocks at the new location to follow up the Esperance water story.
“Maybe [we can] try to reconstruct the actual depositional environment of these materials and whether they were lacustrine – that is, formed by a lake – or fluvial (river) or an alluvial fan (network of streams), or whatever,” said deputy principal investigator Ray Arvidson, of Washington University, St Louis.
Opportunity is now operating well beyond its expected lifetime.
When it landed at Eagle Crater in January 2004, NASA hoped to get at least 90 working Martian days (sols) from the machine. Remarkably, it continues to roll beyond 3,300 sols.
It has an “arthritic” robotic arm, its solar panels are losing efficiency, and it drives backwards to save wear on its locomotion system.
Opportunity is also now having to contend with glitchy flash memory. But NASA is determined to keep pushing the vehicle for as long as possible.
“Remember, the rover continues in a very hostile environment on Mars,” said John Callas, NASA’s Opportunity project manager.
“The rover could have a catastrophic failure at any moment. So, each day is a gift.”
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NASA has reported that its Curiosity rover has made another significant discovery on Mars.
Curiosity has drilled into a rock that contains clay minerals – an indication of formation in, or substantial alteration by, neutral water.
Scientists say the find is one more step towards showing conditions on Mars in the distant past could have supported life.
Many rocks studied previously were probably deposited in acidic water.
While this would not have precluded the possibility of micro-organisms taking hold on Mars, it would have been more challenging, scientists believe.
Identifying clays shows there were at least some locations on the planet billions of years ago where environments would have been much more favorable.
“We have found a habitable environment that is so benign and supportive of life that probably if this water was around and you had been there, you would have been able to drink it,” said John Grotzinger, Curiosity’s project scientist.
Curiosity rover drilled a powdered sample from a mudstone at its exploration site in Gale Crater, a deep impact bowl on Mars’ equator.
This was delivered to the two big onboard laboratories, Sam and Chemin, for analysis.
The rock sample was found to contain 20-30% smectite – a particular group of clay minerals.
Their high abundance and the relative lack of salt are strongly suggestive of a fresh-water environment for the mudstone’s formation.
The presence of calcium sulphates, rather than the magnesium or iron sulphates seen in previous rock analyses at other locations on the planet, adds to the evidence that the sampled rock in Gale was deposited in a neutral to mildly alkaline pH environment.
Mars Curiosity rover has drilled into a rock that contains clay minerals, an indication of formation in, or substantial alteration by, neutral water
Scientists think Curiosity probably drilled into an ancient lakebed.
The analysis also identified sulphur, nitrogen, hydrogen, oxygen, phosphorus and carbon – some of the key chemical elements for life.
Additionally, it found compounds in a range of oxidized states, meaning there were electrons moving through the environment. Those could have been co-opted as an energy source by simple life-forms, if they ever existed in Gale.
“What we’ve learned in the last 20 years of modern microbiology is that very primitive organisms – they can derive energy just by feeding on rocks,” explained Prof. John Grotzinger.
“Just like on [a] battery – you hook up the wires and it goes to a lightbulb and the lightbulb turns on. That’s kind of what a micro-organism would have done in this environment, if life had ever evolved on Mars and it was present here.”
Curiosity rover is assembling quite a catalogue of water evidence in the crater.
Already, it has seen the remains of an ancient riverbed system, where water once flowed perhaps a metre deep and quite vigorously.
The picture that seems to be emerging is one where sediments were transported downhill from the eroding crater rim into a network of streams that then flowed into the lake environment represented by the mudstone.
Curiosity is currently working in a small depression known as Yellowknife Bay, about half a kilometre from the location where it touched down last August.
NASA’s original mission plan was to head towards the big mountain that dominates the centre of Gale Crater, but the fascinating science at Yellowknife Bay has delayed this journey somewhat.
In recent days, operations have been slowed by a software glitch, requiring the vehicle to be run off its reserve computer.
There is also the imminent issue of solar conjunction, which will see Mars move behind the Sun as viewed from Earth, blocking communications.
All this means that Curiosity will be at Yellowknife Bay for a while yet.
“Basically, we can’t talk to the rover and the rover [can’t] talk to us for most of the month of April,” said Michael Meyer, the lead scientist on NASA’s Mars exploration programme.
“We’ll do some more science activities though the end of this month, [provided] the engineers confirm it’s safe for us to do those operations. But we will not do a second drill hole until after solar conjunction.”
When the rover does finally get to the mountain, known as Mount Sharp, the expectation, based on satellite imagery, is that it will again find clay minerals.
This will enable the robot to compare and contrast past environments.
The US space agency’s Opportunity rover, which continues to work nine years on from its landing, is also believed to be sitting on top of clay-bearing rocks at its exploration site far to the west of Gale. Opportunity, however, does not have Curiosity’s capability to assess those rocks.
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