Watch: this is what Mars looked like 3.7 billion years ago

While it seems to be a dead planet today, in the past the Red Planet would have felt very much like home to us - with clouds, oceans and blue sky.

We are nearly as certain as it is scientifically possible to be that there isn't any life on Mars. There is still every chance that there was life at some point, and we might still find it. The landscape is clearly marked with signs of water erosions, and Curiosity and Opportunity (the two rovers currently trundling around up there) have taught us a huge deal about its geology - including the discovery of "abundant" traces of water in Martian soil. Mars clearly had a lot of liquid water on its surface at some point.

The question, though, is why it doesn't have lakes, rivers, oceans, and streams any more - and what it looked like when it did. Nasa's Goddard Space Flight Center has taken a stab at visualising the Martian world of 3.7 billion years ago ahead of its Mars Atmosphere and Volatile Evolution (or Maven) mission which takes off on 18 November, producing a quite lovely animation:

It looks just like Earth because back then Mars had two Earth-like things going for it that it doesn't any more. Firstly, the habitable zone around the younger, larger Sun - that's the range of orbits around any star within which is neither too hot nor too cold for a planet to have liquid water on its surface - was further out, and secondly Mars also had a thick atmosphere. Without the pressure that comes with an atmosphere, liquid water will either freeze solid or evaporate instantly, as happens currently on Mars.

The habitable zone moving inwards had the happy side effect of making the Earth habitable, and eventually - as the Sun enters its final few billion years and swells in size, becoming a red giant - that zone may well move out further again and give Mars a chance at hosting liquid water again. That is, if it gets an atmosphere too, and that's the mystery. We know it must have been there once, but it isn't there now, and we can't be sure why that it. We're not even totally sure if the atmosphere's disappearance is wholly responsible for the transformation of Mars from wet, blue globe like you see above to dusty, red ball that looks like this:

That's a picture taken by the Curiosity rover.
Credit: NASA/JPL-Caltech/MSSS

One possibility for what happened to the atmosphere is that Mars' core cooled down and stopped generating both plate tectonics and a magnetic field, which would have formed a barrier that would have stopped too many atmospheric particles being stripped away into space by the solar wind. Without active volcanoes to generate gases to replace the lost particles, you end up with the situation today where the surface pressure on Mars is, on average, 0.6 percent that of what you'll find on Earth. That's equivalent to being 35km up in the sky on Earth, nearly twice as high as where commercial aeroliners fly.

Maven is an orbiting probe that will launch on 18 November and try to uncover more data about Mars' atmospheric past. Here's Joseph Grebowsky, the mission's project scientist:

Studies of the remnant magnetic field distributions measured by Nasa's Mars Global Surveyor mission set the disappearance of the planet's convection-produced global magnetic field at about 3.7 billion years ago, leaving the Red Planet vulnerable to the solar wind. 

Maven has been designed to measure the escape rates for all the applicable processes and will be able to single out the most prominent. Previous remote Mars observations from orbiting spacecraft have observed the geological features that have been used to estimate the amount of water that did exist and have analysed the global distribution of water ice and surface chemistry to infer that water was lost through time. Mars Curiosity rover has the ability to analyse the chemical composition of the solid surface, which contains information of the atmospheric composition during the formation of the planet, in particular the isotope ratios, the lower atmosphere composition, and the current gas exchange with surface reservoirs. MAVEN is going to measure the current rates of loss to space and the controlling processes. Given the lower-atmosphere information and the nature of the escaping processes, one can extrapolate from current conditions into the climate of the past.

The probe will reach Mars in September 2014, and is scheduled to work for one Earth year on its mission of uncovering more Martian secrets.

Not Earth, but Mars before it lost its atmosphere. (Image: Nasa)

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

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Meet the evangelical Christian persuading believers that climate change is real

Katharine Hayhoe's Canadian missionary parents told her science and God were compatible. Then she moved to Texas. 

During Donald Trump’s presidential campaign, alarm rose with each mention of climate change. Denial, dismissal and repeated chants of “hoax” left no doubt as to his position.

Now President Trump’s withdrawal from the Paris Agreement has been seen as a seminal moment in the fight against climate change - one which many fear could lose the battle ahead of humanity.

But one scientist has been fighting a war of her own on the ground, against those who typically doubt the facts about global warming more than most - the evangelical Christian population of America.

And to make matters even more unusual, Katharine Hayhoe herself is an evangelical Christian who lives in the indisputably "bible belt" of Lubbock, Texas.

The atmospheric scientist has been named one of Time magazine's 100 most influential people and one of Politico’s 50 thinkers transforming American politics. Now she is using her considerable heft to speak to those who are hardest to convince that there is a manmade problem that threatens the Earth’s future.

I meet her at the science and music festival Starmus in Trondheim, Norway, where she is to address the attendees on Thursday in a talk entitled "Climate Change: Facts and Fictions".

Hayhoe was born in Canada, to missionary parents. Her father, a former science educator, showed her that there was no conflict between the ideas of God and science. However, it was something of a surprise to her when she discovered her pastor husband, whom she married in 2000, did not feel the same about climate change. It took her two years to convince him.

What started as a conversation became an organised project when she moved to America's South in the mid 2000s. 

“Moving to Lubbock was a culture shock," she tells me. "When I moved there I wasn’t doing much outreach, but it moved me in that direction.

“Lubbock is very conservative. It’s small and isolated.

“I would say the majority of people in Lubbock are either dismissive or doubtful about climate change. I was surrounded by people - neighbours, parents of friends, people at church, colleagues down the hall in the university - who weren’t convinced.”

So Hayhoe, who works as an associate professor and director of the Climate Science Centre at Texas Tech University, set to work. She began to collect the responses she was seeing to the climate change discussion and prepare her counter-argument.

“When I talk to people who are doubtful, I try to connect with the values they already have," she says. “The greatest myth is the myth of complacency - that ‘it doesn’t really matter to me’.

"But I would say that the second most insidious myth is that you only care about this issue if you’re a certain type of person. If you’re a green person, or a liberal person, or a granola person."

The stereotypes mean that people outside that demographic feel "I can't be that kind of person because that's not who I am", as she puts it.

Hayhoe convinced her husband using data, but rather than repeating a formula, she tries to find out what will resonate with different people: "For many groups, faith is a core value that people share.”

Whether she’s speaking to city planners, water company managers, school kids or Bible believers, Hayhoe says her hook is not the facts, but the feelings.

“I recently talked to arborists," she says. "For them, trees and plants are important, so I connect with them on that, and say ‘because we care about trees, or because we care about water or what the Bible says then let me share with you from the heart why I can about these issues because it affects something that you already care about’.

“My angle is to show people that they don’t need to be a different person at all - exactly who they already are is the kind of person who can care about climate change.”

Hayhoe came to public attention in the United States after appearing in a Showtime series on climate change. She has appeared on panels with Barack Obama and Leonardo DiCaprio, and launched a web series. As well as plaudits, this level of fame has also earned her daily threats and online abuse. 

“My critics think they’re coming from a position of religion, but they aren’t," she says. "They’re actually coming from a very specific political ideology which believes that the government should not have control over people’s lives in any way shape or form - very libertarian, free market, free economy, Tea Party."

She believes that in the United States, faith and politics has been conflated to the point "people can no longer tell the difference". 

“Now it’s conservatism that informs religion," she elaborates. "If the two are in conflict - like the Bible says God has given us responsibility over everything on this earth - then people say ‘oh, we can’t affect something as big as this Earth, God will take care of it anyway’."

Around half of those who attack her on social media identify themselves as Christians, she notes, but almost all call themselves conservatives. 

As a scientist, she’s been preparing data herself - naturally - on her online attackers, with depressingly familiar results.

“As soon as you stick your head out of the trench, you get it. There have been papers published showing that white men disproportionately form up that small group of dismissives. They’re almost all men. When I track my social media comments, I would say that 99.5 per cent of them are white men.

“Out of 1,000 negative comments, I have maybe five from women.”

After the climate change argument moved up a gear - following the Paris withdrawal - Hayhoe admits that she and her fellow scientists are concerned, although she pays tribute to the businesses, cities and states from the US that have committed to following the Paris agreement themselves.

On the subject of the chief white male denier, Trump himself, Hayhoe says she has a discussion point which she feels may convince him to think carefully about his role in the fight against global warming’s impact on humanity.

“I would attempt to connect with the values that he has and show him how acting on this would be in his best interests," she says.

“One guess would be ‘what do you want your legacy to be? What do you want to be known as, the man who destroyed the world, or the man who saved it?’”

Katharine Hayhoe is speaking at Starmus on Thursday June 22. For more details, visit Starmus.

Kirstie McCrum is a freelance journalist. Follow her @kirstiemccrum.

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