Is there Life in Mars?

The existence of extra-terrestrial life mimars-bkg-300-dpi-finalght just be the most far reaching question that science (and yes, even geology) can ask. It goes to the heart of ideas which seem to border on the philosophical: big concepts like our place in the universe – and even the origins of life itself.

And, few would argue, our best chance of an answer currently lies on a small, barren world at the edge of the asteroid belt; when you think of Mars, after all, the words “life” and “on” are rarely far behind. But impressive as they are, our forays onto its rusty surface have not turned up the one discovery we all crave. The Red Planet, it seems, might also be rather … well it rhymes with red.

But as Mars begins to give up its geological secrets, the search for life is taking an intriguing new turn. It seems that, deep down, our solar neighbour could be hiding a different, much more Earth-like side.

In Deep Water?

When your probe is finally looking down onto its alien target – amazingly, somehow, the surface of another planet – the seemingly mind boggling task of looking for life in fact boils down to a single goal: the search for liquid water. When it comes to Mars, this search has traditionally been focused above ground – on the rocky landscape, with its suggestive channel formations. Recently, though, a rare glimpse beneath the dust could be about to bring the hunt for Martian microbes into a surprising new arena.

One of the most important discoveries to have come from Mars in the last few years, was the discovery, in 2009, that rocks within impact craters, brought up from thousands of meters below the surface, contained traces of hydrothermal minerals [1]; that is, these deep rocks had once been in contact with hot water.

On Earth, water-filled pores within the crust provide an ideal habitat for countless varieties of microorganism – in fact, almost half of life “on” our planet actually occurs below the surface, sustained not by the sun, but deep geothermal heat. In light of this, it soon became clear that the possibility that similar conditions might have existed on Mars had extremely exciting implications in the search for life: while the surface may have been hostile for billions of years, an underground reservoir – warmed by the planet’s core, and sheltered from the violence of the early solar system – could potentially have provided a safe haven for life to flourish.

The big question, of course, is how to find out; surely all traces of organic matter in the crater rocks would have been destroyed by any collision powerful enough to rip them from the crust! Excitingly, though, it is now emerging that the deep, potentially life-bearing fluids in Mars’ interior could have reached the surface in another way – and might, therefore, be within our reach. New research, published last month in the journal Nature Geoscience [2], has identified an area of the Martian surface which could, quite simply, be hiding the greatest discovery of all time…

All eyes are now on McLaughlin crater: a huge, two-kilometer dent in Mars’ northern hemisphere. Among the thousands of similar craters which dot Mars’ surface, McLaughlin is unique: as well as being exceptionally deep, it also occurs at a topographic low, making it in effect a natural borehole into the crust. The authors of the study argue that if the deep, hot fluids ever made it to the surface, it would probably have been here.

And thrillingly, their work has revealed not only signs of water but, astonishingly, that an entire lake existed within the crater floor. Furthermore, the discovery of rare clays and carbonate minerals suggest that this water had a particularly deep source. And which, taken together – the authors conclude – suggests that deep hydrothermal fluids did indeed reach the surface, leaking out into McLaughlin crater and feeding its lake.

And also, perhaps, leaving signs of life? With the potential for a “vast microbial biosphere” [2], Mars’ deep water might be about to become our next great hope – and McLaughlin crater, quite possibly, our next target.

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References:

1. Ehlmann, B. L. et al. Identification of hydrated silicate minerals on Mars using MRO-CRISM: Geologic context near Nili Fossae and implications for aqueous alteration. J. Geophys. Res.114, E00D08 (2009).

2. Michalski, J.R. et al. Groundwater activity on Mars and implications for a deep biosphere. Nature Geoscience 6 (2013).

The volcanic threat of climate change

Intriguing new evidence is emerging which suggests the dangers of climate change might go deeper than our rising seas. As if we didn’t have enough on our plate, could the vanishing polar ice caps also be about to unleash a long dormant volcanic force?

Mt. Erebus, Antarctica  ___________________________________________________________

It’s easy to get lost in the complexity of the climate change debate, but one thing, at least, is unfortunately clear: our planet is losing its cool. Whether or not you understand the finer details of a radiative forcing model, when you read that an area of ice the size of a country has melted, it hits home; with each passing year we are witnessing, with startling clarity, that the frozen expanses at our planet’s poles are undergoing a rapid and uncomfortable transformation.

But do we fully understand the dangers of an ice-free planet? The impacts of rising sea levels are clear enough, but recently there has been growing unease among Earth Scientists that the melting ice could be hiding a different kind of threat. Clues have begun to emerge in the rock record which hint that, at the end of the last ice age, as the land emerged from its long hibernation, something within the Earth itself began to stir.

Analysis of ancient lavas from Iceland have shown that around 12,000 years ago, volcanic activity there began to increase at an astonishing rate – with eruptions becoming up to fifty times more frequent [1]. And now, after similar patterns were discovered at volcanoes from Western Europe to the Americas, geologists are being forced to confront uncomfortable possibility: could climate change, while it was lifting our planet out of the ice-age, also have triggered this increase in volcanic activity?

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Until now, the response from Earth Scientists has been a unanimous “maybe” on the subject. But now new evidence has emerged, deep beneath Antarctica, which seems to strengthen the case for this unsettling theory. A new study [2], published this month in the Journal of Volcanology and Geothermal Research, not only suggests that climate change and volcanic activity might be linked, but that their relationship could go back much further than was previously thought.

The huge glaciers which smother the Antarctic continent are a treasure trove for climatologists; beneath its barren surface, layers of ice a mile thick have preserved an unmatched record of our planet’s climatic history. Yet as tough and imposing as this great southern wilderness might seem, deep down, it has a fragile heart. The climatic history of Antarctica itself is one of constant change: temperatures here have been rising and falling, and the great ice sheets growing and shrinking, for millions of years.

But there is another force at work beneath the frozen surface – one which makes this an ideal location to study the effect that ice can have on our planet’s deep interior. Antarctica may be the coldest place on Earth, but a vein of fire cuts up from below; the great lava lake of Mount Erebus is the modern-day remnant of volcanic activity which, alongside glacial forces, has shaped this enigmatic landscape over geological time.

And it was here that a team of Earth Scientists – led by Dr. Rosie Nyland of Bowling Green State University – headed for answers. In their study, Nyland and her co-workers analysed rocks from the volcanic heartland of Western Antarctica, extracted from more than a kilometer below the surface by the ambitious Antarctic Drilling Project (ANDRILL). On the shores of the Ross Sea, thick layers of marine sediment extend deep beneath the permafrost – the product of continuous glacial activity. Within the ANDRILL rock core, the researchers observed the telltale geological fingerprints of the rise and fall of ice sheets; and by accurately dating each sediment layer, it was possible for them to reconstruct how ice levels had changed over time – providing an amazing record of climate change stretching back more than twenty million years.

But something else had been preserved in the rocks. Littered throughout the sediments were layers of volcanic ash – unmistakable evidence that the area had been volcanically active while the rocks were being deposited. And the fortunate occurrence of this ash gave the team a unique opportunity: by measuring how the amount of volcanic material varied across different sediment layers, they were able to estimate how the strength of volcanic activity had changed over time. (Because larger eruptions tend to give off more ash, a particularly ashy layer indicates that volcanic activity was higher when those sediments were deposited – and the opposite true for layers with less ash).

And it was this crucial step which led to their breakthrough: when Nyland and her team compared the volcanic and glacial records, they they discovered a clear pattern – up to ten times more ash was deposited when ice cover was low than when ice was more widespread. Over a period of three million years, the strength of volcanic activity mimicked the amount of ice cover with remarkable consistency; in other words, here was clear evidence that climate change might have been the driving force for an increase in volcanic activity – not just once, but repeatedly.

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These new findings are the latest in a small but growing chain of evidence which suggests that, through the process of deglaciation, climate change could be able to trigger volcanic eruptions. If it was happening millions of years ago in Antarctica, and as recently as a few thousand years ago in Iceland, could it be that increased volcanic activity is an inevitable consequence of a warming climate?

In light of our current situation, this would certainly be a cause for concern. As we slide irreversibly into a man-made deglaciation, we are seeing the disappearance of ice which, throughout recorded history, has covered some of the world’s most volcanically active regions; the Antarctic ice sheet is among the most rapidly melting regions on Earth, and the glaciers which cap some tropical volcanoes are already vanishing completely. This raises the disturbing possibility that human actions might be about to remove a natural shield from our planet – one which has, until now, been keeping its destructive power at bay.

It should be noted, though, that this most recent study suggests that, in Antarctica at least, any increase in volcanic activity might not happen until several thousand years after deglaciation occurs. But that is not to suggest that we can afford to relax completely. With research at such an early stage, there is still significant uncertainty, and as more evidence accumulates, we could learn that other volcanoes respond to deglaciation in different ways. As an example of this, we need look no further than Iceland – our volatile northern neighbour – where the interval between deglaciation and the onset of volcanic activity seems to be alarmingly fast. If Europe can be brought to its knees by a single eruption from this island – and a particularly small one, at that – what could be in store for us if activity there increases in the future?

So while the volcanic effects of climate change might not be comparable with more immediate dangers – catastrophic flooding or soaring heatwaves, say – they should still remind us that our actions can affect the Earth in more subtle ways than immediately meet the eye. And that, while we are distracted by goings on at the surface, it helps to remember that we sit perched on a thin shell above a still-mysterious expanse below: the other 99% of our planet.

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References

1. Tuffen (2010): How will melting of ice affect volcanic hazards in the twenty-first century? Philosophical Transactions of the Royal Society; vol 368, no. 1919.

2. Nyland et al. (2013): Volcanic activity and its link to glaciation cycles: Single-grain age and geochemistry of Early to Middle Miocene volcanic glass from ANDRILL AND-2A core, Antarctica. J. Volcanol. Geotherm. Res. Vol. 250.

3. http://www.nature.com/news/greenland-defied-ancient-warming-1.12265

 

The human side of earthquakes?

In the sphere of natural disasters, earthquakes in particular stand out for their ability to wreak random devastation. Hurricanes can be tracked – even volcanic eruptions might give the occasional rumble of warning – yet well into the 21st century when and where an earthquake will strike still seems as unpredictable as ever. However evidence has recently emerged which could challenge this long-standing view – and possibly even change the way we think about earthquakes altogether. In October 2012, just as six seismologists were about to be convicted by an Italian court in the “earthquake prediction” debacle, a study emerged which grabbed headlines for an altogether stranger reason: could human actions actually be causing earthquakes?

Published in the journal Nature Geoscience, the article focused on a very unusual earthquake which in May 2011, hit the town of Lorca in Southern Spain. It was the deadliest quake that the country had seen for half a century – killing nine people and injuring hundreds more. But this tragic event also attracted the attention of Earth Scientists for another reason altogether: geologically speaking, this earthquake should simply not have been there …

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It was clear from the offset that something about the Lorca event didn’t quite fit. For starters, there was the matter of its size. One thing that immediately stood out was that despite being so destructive, this was, in fact, a rather small earthquake; a magnitude 5.1 – earthquakes of this size happen almost every day somewhere on Earth, and cause so little fuss they are not usually even reported.

It was uncomfortably clear, though, that something was seriously different about this particular earthquake – why had it caused so much damage? The answer to this question introduces the really strange thing about the Lorca quake – because while it may have been profound in many ways, one thing that it was not was deep. Earthquakes of this size usually occur quite far within the crust, typically below 10 kilometers. In contrast, the Lorca earthquake occurred at an almost ridiculously shallow depth – possibly as little as a thousand meters below the surface. Put simply, traditional scientific wisdom dictated that it should not have been able to occur.

The fact that it did is what made it so unusually powerful; the seismic waves released by the unusually shallow rupture retained much more of their original energy, during their short journey to the surface, than a normal, deeper earthquake would have. It was abundantly clear, then, that understanding this disaster was vital – both to solve a scientific enigma, and explain a serious humanitarian tragedy. This was the task that fell to the Nature Geoscience authors: a team of Earth Scientists led by researchers from The University of Western Ontario.

Using new developments in satellite observation, they set out by studying the ground motion that the earthquake had caused (how much and in what direction the Earth’s surface had shifted after faulting had occurred). This led to an early breakthrough: the pattern of deformation from the earthquake allowed the researchers to pinpoint the precise location of its epicentre. The culprit was the Alhama de Murcia fault: a thin, shallow fissure in the crust south of Lorca.

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But locating the earthquake was only half the problem, as the presence of a shallow fault, in itself, is not unusual. The key question the team faced was just how the Lorca earthquake had been able to happen, at a seemingly impossible depth; what was different, then, about this particular corner of Spain?

Whatever the explanation, the team realised that the key would be the Alhama de Murcia fault itself; reasoning that, as the source of the earthquake, it was here that they should concentrate their efforts. And in doing so, their breakthrough came. As they probed Lorca and its surroundings for clues, something emerged which the researchers realised could be crucial. Something with a distinctly human origin.

Their search revealed that the part of the fault responsible for the earthquake, was located in an area which had been seriously affected by human industrial activity: the Alto Guadalentin aquifer. In the fifty years before the Lorca disaster this area had undergone severe water removal – so much so that the local water table had dropped by 250 meters. Perhaps more worryingly, the ground around it had begun to sink, by a few tens of centimeters per year; suggesting that a change had been triggered far below the surface, within the rocks of the aquifer itself.

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It was their next step which put the Nature Geoscience authors in the headlines – when they raised the possibility that the location of the Lorca earthquake might have been more than just geographical coincidence; Could the water removal at the Alto Guadalentin aquifer actually be linked to the disaster?

Rather than just another step, this might seem more like a leap of faith; after all – you might ask – how could something as seemingly harmless as removing water from the ground be connected to an earthquake which reduced a town to rubble?! But, as the sagging ground of the aquifer showed, far from being superficial, the water extraction had in fact caused a profound change – one which, the researchers reasoned, could have had consequences beyond water loss.

The underlying cause of most earthquakes is a build-up of pressure (or ‘stress’) in the rocks of the crust. The critical next question posed in the Nature Geoscience study was: could human activities at the aquifer have affected the local stress conditions, and increased the chance of an earthquake? The water in an aquifer, which is stored in pore space within rocks, actually has a strengthening effect –  supporting them against the extremely high pressures they are exposed to within the Earth. The authors realised that removing this pore water could therefore have the opposite effect:  increasing the pressure the rocks were exposed to, and therefore increasing the chance of an earthquake.

In order to test the plausibility of this idea, the researchers created a model which simulated the effect of the water loss, on the stress conditions within the Alto Guadalentin aquifer. The question they needed to answer was: could the physics behind their theory explain the earthquake? It was here that they made their key breakthrough: The model predicted that the most significant stress change would occur in a specific region of the aquifer, which matched extremely well the location of the Alhama de Murcia fault – precisely where the 2011 earthquake had occurred.

To look at, it might not have looked like much – just a red blob over a blue background – but what this result hinted at was nothing less than extraordinary: the Lorca earthquake, in which nine people lost their lives, might have been linked to, or even caused by, human activities.

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Understandably, these incredible findings spread like wildfire across the scientific community – not to mention the global media at large, for whom the headline “earthquake caused by humans” must have seemed irresistible. And rightly so; the implications of this study are undeniably very exciting, and could have serious implications for how we think about earthquake hazards. But for the many people left devastated by the tragic events of May 2011, this issue went far beyond scientific curiosity, of course. The thought that their ordeal might have been preventable must surely stick in the throat.

This study does not prove conclusively (nor does it claim to) that human actions were responsible for this tragedy. The south of Spain has been tectonically active for millions of years, and this tragedy could still have been an entirely natural disaster. That said, it is impossible to ignore how well these new findings agree with – though ‘predict’ would still be going to far – the location of this engimatic earthquake. What’s more, if water extraction did play a role in the disaster, this would go some way to explaining how it was able to occur at such a shallow depth – one possibility being that the increase in stress caused by water loss might have triggered an earthquake which otherwise might not have been able to occur.

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At the very least, this study should serve as a sharp reminder: that by exploiting the resources beneath our feet, we might be affecting our planet more subtly than meets the eye. And though research is still at a very early stage, the possibility that deep drilling might contribute to earthquakes is one that – as our reliance on subsurface reserves of oil, gas and water are only about to increase – must be explored very carefully.

Reference:

González et al. The 2011 Lorca earthquake slip distribution controlled by groundwater crustal unloading. Nature Geoscience, vol. 5