Has DRINKABLE water been found on Mars?Expedition rover Opportunity finds first signs it once flowed there

• Clay mineral formed in a reaction with water is detected by spectrometer
• Previous evidence has pointed to water on Mars being extremely acidic
• NASA scientist describes finding as 'powerful evidence' of neutral ph water

Powerful evidence that water good enough to drink once flowed on Mars has been found by one of Nasa’s aging rover vehicles.

Evidence of water of Mars has been indicated by a succession of discoveries on Mars but until now they have all suggested flows of sulphuric acid. This is the first time water has been found in a form that is likely to be drinkable.

The discovery boosts the chances that one of life’s most important building blocks was once present  on the planet, and might even still be there.

It was hailed by a leading NASA scientist as one of the most important yet made by the Mars Opportunity rover, which is approaching the tenth anniversary of its launch.

The find that has so excited the team behind the Opportunity mission is chemical analysis of a small rock which included a clay mineral, montmorillonite, that is likely to have been formed by water with a neutral ph.

‘This is powerful evidence the water interacted with this rock and changed its chemistry,’ said Professor Steve Squyres, of NASA’s Jet Propulsion Laboratory and Cornell University.

 ‘Clay minerals only tend to form at a more neutral pH. This is water you could drink. This is water that was much more favourable for things like pre-biotic chemistry - the kind of chemistry that could lead to the origin of life.
Montmorillonite exists on Earth where it is known to be formed from a reaction with igneous rocks.
The rock that was analysed by Opportunity by its alpha particle X-ray spectrometer and microscopic imager once the rock abrasion tool had obtained a clean sample inside a square meter test area called Esperance within a region known as Cape York on the rim of a 14-mile wide crater, Endeavour.

 Signals beamed back to earth revealed to waiting scientists that it was a rock like no other yet tested by Opportunity.
‘We’ve been discovering evidence of water on Mars since we landed in 2004,’ said Professor Squyres.
‘The vast majority of them point to water that was at a very low ph – it was acid. We run around talking ‘water on Mars, water on Mars’. In fact, what Opportunity has mostly found evidence for is sulphuric acid on Mars.
‘What we have here has a very different chemistry. Clay minerals like montmorillonite only tend to form at a more neutral ph.

 'This is the most powerful evidence for neutral chemisty water that has been found by Opportunity.’
He added: ‘To me right now I would say what we have found with Esperance has sort of vaulted into my personal top five for the whole nine-and-a-half year mission. This is a good one.
'Esperance was so important, we committed several weeks to getting this one measurement of it, even though we knew the clock was ticking.
‘What's so special about Esperance is that there was enough water not only for reactions that produced clay minerals, but also enough to flush out ions set loose by those reactions, so that Opportunity can clearly see the alteration.’

Scientists are confident the spectrometer has revealed signs of water with a neutral ph because of the high proportion of aluminium detected by the spectrometer compared to other chemicals including iron, magnesium and calcium.

The rover has now been instructed by its controllers to head towards Solander Point, another part of the rim of Endeavour, having spent two years exploring Cape York.

Opportunity was launched on July 7, 2003 and landed on January 25, 2004 for what was originally expected to be a three-month mission.

It has travelled more than 36km and its motor has made 70 million revolutions, seven time more than were guaranteed by the manufacturer.
Its performance, however, exceeded all expectations and while the rover is today described as ‘arthritic’, with a ‘gimpy shoulder’ and a memory that is showing the first signs of failing, it is still operational and making amazing findings.
John Callas, the project manager for the Mars rover expeditions, said Opportunity is in ‘remarkably good health’ but added: ‘We’ve been on borrowed time for a while.’
One of the rover’s flash memories is showing signs of ‘amnesia’ he said but while it is proving an ‘occasional annoyance’ it is not yet a serious threat to the mission.
He emphasised that the rover is operating in a ‘very hostile environment’ with extreme temperature fluctuation.
‘The Rover could have a catastrophic failure at any moment,’ he added. ‘Every day is a gift.’