Further evidence has emerged that Mars still has some liquid water

Scientists analysing images of Mars have found even more signs that, in rare circumstances, Mars may have water flowing across its surface.

Mars is supposed to be a dead, dry planet. There are clear signs that liquid water used to flow across its surface - remember Nasa mocking up that video of the Mars of 3.7 billion years ago? - but one of the Curiosity rover’s jobs right now is to investigate what we take to be ancient river bed.

This makes it very surprising indeed that scientists saw dark, water-like streaks in the red dust, in 2011. This should not be happening on a planet with no atmosphere.

To be clear, this isn’t proof that there’s liquid water on Mars - it’s just that we’ve seen something that looks a heck of a lot like liquid water. Here’s a slideshow of eight images showing what we’re talking about, provided by Nature:

Those black lines, as spotted by the Mars Reconnaissance Orbiter, are known as “recurring slope lineae”, and they darken the Martian soil just as water darkens soil on Earth. They were originally found two years ago at seven sites in the highlands of southern Mars, at middle latitudes which warm up in the summer and freeze again in the winter.

This latest study, by the same team of planetary scientists led by Alfred McEwen of the University of Arizona in Tucson, has found a further 12 sites with streaks, all on or near the equator. The equator has roughly the same temperatures year-round, and that means that - if there’s liquid water flowing on the surface - there must be a mechanism in place to replenish it. Mars’ low atmospheric pressure means that liquid water on the surface should sublimate into a gas almost immediately.

We now know that there’s quite a lot of water on Mars, be it frozen on the surface at the poles, under the surface elsewhere on the planet, or bound up with the soil itself. The implication of a flowing water source is that it might be the most likely location of life that still exists on Mars - but, conversely, that also makes it more crucial that we don’t send improperly sterilised probes there. If those Earth microbes are to survive anywhere on Mars - and scientists recently discovered a whole new species of microbe that could survive in even the most sterile of spaceship construction labs - then they’ll survive on these slopes.

It's also exciting for future colonists, who will save on energy if they don't have to heat up ice for drinking water. Our best chance of figuring out the exact nature of these lines on Mars is from afar, with the Mars Reconnaissance Orbiter, until we can decide what further action to take. Perhaps even the first colonisers, whoever they be (maybe it'll be Mars One, who want to send people there on a one-way mission starting from 2024) will be able to take advantage of that water source.

Dark streaks on Mars that may be water. (Image: NASA/JPL-Caltech/U. of Arizona)

Ian Steadman is a staff science and technology writer at the New Statesman. He is on Twitter as @iansteadman.

John Moore
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The man who created the fake Tube sign explains why he did it

"We need to consider the fact that fake news isn't always fake news at the source," says John Moore.

"I wrote that at 8 o'clock on the evening and before midday the next day it had been read out in the Houses of Parliament."

John Moore, a 44-year-old doctor from Windsor, is describing the whirlwind process by which his social media response to Wednesday's Westminster attack became national news.

Moore used a Tube-sign generator on the evening after the attack to create a sign on a TfL Service Announcement board that read: "All terrorists are politely reminded that THIS IS LONDON and whatever you do to us we will drink tea and jolly well carry on thank you." Within three hours, it had just fifty shares. By the morning, it had accumulated 200. Yet by the afternoon, over 30,000 people had shared Moore's post, which was then read aloud on BBC Radio 4 and called a "wonderful tribute" by prime minister Theresa May, who at the time believed it was a genuine Underground sign. 

"I think you have to be very mindful of how powerful the internet is," says Moore, whose viral post was quickly debunked by social media users and then national newspapers such as the Guardian and the Sun. On Thursday, the online world split into two camps: those spreading the word that the sign was "fake news" and urging people not to share it, and those who said that it didn't matter that it was fake - the sentiment was what was important. 

Moore agrees with the latter camp. "I never claimed it was a real tube sign, I never claimed that at all," he says. "In my opinion the only fake news about that sign is that it has been reported as fake news. It was literally just how I was feeling at the time."

Moore was motivated to create and post the sign when he was struck by the "very British response" to the Westminster attack. "There was no sort of knee-jerk Islamaphobia, there was no dramatisation, it was all pretty much, I thought, very calm reporting," he says. "So my initial thought at the time was just a bit of pride in how London had reacted really." Though he saw other, real Tube signs online, he wanted to create his own in order to create a tribute that specifically epitomised the "very London" response. 

Yet though Moore insists he never claimed the sign was real, his caption on the image - which now has 100,800 shares - is arguably misleading. "Quintessentially British..." Moore wrote on his Facebook post, and agrees now that this was ambiguous. "It was meant to relate to the reaction that I saw in London in that day which I just thought was very calm and measured. What the sign was trying to do was capture the spirit I'd seen, so that's what I was actually talking about."

Not only did Moore not mean to mislead, he is actually shocked that anyone thought the sign was real. 

"I'm reasonably digitally savvy and I was extremely shocked that anyone thought it was real," he says, explaining that he thought everyone would be able to spot a fake after a "You ain't no muslim bruv" sign went viral after the Leytonstone Tube attack in 2015. "I thought this is an internet meme that people know isn't true and it's fine to do because this is a digital thing in a digital world."

Yet despite his intentions, Moore's sign has become the centre of debate about whether "nice" fake news is as problematic as that which was notoriously spread during the 2016 United States Presidential elections. Though Moore can understand this perspective, he ultimately feels as though the sentiment behind the sign makes it acceptable. 

"I use the word fake in inverted commas because I think fake implies the intention to deceive and there wasn't [any]... I think if the sentiment is ok then I think it is ok. I think if you were trying to be divisive and you were trying to stir up controversy or influence people's behaviour then perhaps I wouldn't have chosen that forum but I think when you're only expressing your own emotion, I think it's ok.

"The fact that it became so-called fake news was down to other people's interpretation and not down to the actual intention... So in many interesting ways you can see that fake news doesn't even have to originate from the source of the news."

Though Moore was initially "extremely shocked" at the reponse to his post, he says that on reflection he is "pretty proud". 

"I'm glad that other people, even the powers that be, found it an appropriate phrase to use," he says. "I also think social media is often denigrated as a source of evil and bad things in the world, but on occasion I think it can be used for very positive things. I think the vast majority of people who shared my post and liked my post have actually found the phrase and the sentiment useful to them, so I think we have to give social media a fair judgement at times and respect the fact it can be a source for good."

Amelia Tait is a technology and digital culture writer at the New Statesman.