Evidence for Liquid Water on Mars?

There’s been a lot of excitement this afternoon about possible evidence for water on Mars from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on board the Mars Reconaissance Orbiter (MRO). Unfortunately, but I suppose inevitably, some of the media coverage has been a bit over the top, presenting the results as if they were proof of liquid water flowing on the Red Planet’s surface; NASA itself has pushed this interpretation. I think the results are indeed very interesting – but not altogether surprising, and by no means proof of the existence of flows of liquid water. And although they may indeed provide evidence confirming that there is water on Mars,  we knew that already (at least in the form of ice and water vapour).

The full results are reported in a paper in Nature Geoscience. The abstract reads:

Determining whether liquid water exists on the Martian surface is central to understanding the hydrologic cycle and potential for extant life on Mars. Recurring slope lineae, narrow streaks of low reflectance compared to the surrounding terrain, appear and grow incrementally in the downslope direction during warm seasons when temperatures reach about 250–300 K, a pattern consistent with the transient flow of a volatile species^{1, 2, 3}. Brine flows (or seeps) have been proposed to explain the formation of recurring slope lineae^{1, 2, 3}, yet no direct evidence for either liquid water or hydrated salts has been found⁴. Here we analyse spectral data from the Compact Reconnaissance Imaging Spectrometer for Mars instrument onboard the Mars Reconnaissance Orbiter from four different locations where recurring slope lineae are present. We find evidence for hydrated salts at all four locations in the seasons when recurring slope lineae are most extensive, which suggests that the source of hydration is recurring slope lineae activity. The hydrated salts most consistent with the spectral absorption features we detect are magnesium perchlorate, magnesium chlorate and sodium perchlorate. Our findings strongly support the hypothesis that recurring slope lineae form as a result of contemporary water activity on Mars.

Here’s a picture taken with the High Resolution Imaging Science Experiment (HIRISE) on MRO showing some of the recurring slope lineae (RSL):

You can see a wonderful gallery of other HIRISE images of other such features here.

The dark streaky stains in this and other examples are visually very suggestive of the possibility they were produced by flowing liquid. They also come and go with the Martian seasons, which suggests that they might involve something that melts in the summer and freezes in the winter. Putting these two facts together raises the quite reasonable question of whether, if that is indeed how they’re made, that liquid might be water.

What is new about the latest results that adds to the superb detail revealed by the HIRISE images – is that there is spectroscopic information that yields clues about the chemical composition of the stuff in the RSLs:

 

The black lines denote spectra that are taken at two different locations; the upper one has been interpreted as indicating the presence of some mixture of hydrated Calcium, Magnesium and Sodium Perchlorates (i.e. salts). I’m not a chemical spectroscopist so I don’t know whether other interpretations are possible, though I can’t say that I’m overwhelmingly convinced by the match between the data from laboratory specimens and that from Mars…

Anyway, if that is indeed what the spectroscopy indicates then the obvious conclusion is that there is water present, for without water there can be no hydrated salts. This water could have been absorbed from the atmospheric vapour or from the ice below the surface. The presence of salts would lowers the melting point of water ice, so this could explain how there could be some form of liquid flow at the sub-zero temperatures prevalent even in a Martian summer. It would not be pure running water, however, but an extremely concentrated salt solution, much saltier than sea water, probably in the form of a rather sticky brine. This brine might flow – or perhaps creep – down the sloping terrain (briefly) in the summer and then freeze. But nothing has actually been observed to flow in such a way. It seems to me – as a non-expert – that the features could be caused not by a flow of liquid, but by the disruption of the Martian surface, caused by melting and freezing, involving  movement of solid material, or perhaps localized seeping. I’m not saying that it’s impossible that a flow of briny liquid is responsible for the features, just that I think it’s far from proven. But there’s no doubt that whatever is going on is fascinatingly complicated!

The last sentence of the abstract quoted above reads:

Our findings strongly support the hypothesis that recurring slope lineae form as a result of contemporary water activity on Mars.

I’m not sure about the “strongly support” but “contemporary water activity” is probably fair as it includes the possibilities I discussed above, but it does seem to have led quite a few people to jump to the conclusion that it means “flowing water”, which I don’t think it does. Am I wrong to be so sceptical? Let me know through the comments box!

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Rolling Boulders…

I’m a bit slow to get started this morning, since I didn’t get home until the wee small hours after a trip to the Royal Astronomical Society yesterday, followed by a pleasantly tipsy dinner at the Athenaeum with the RAS Club. Anyhow, one of the highlights of the meeting was a presentation by Prof. Gerald Roberts from Birkbeck on Marsquakes: evidence from rolled boulder populations, Cerberus Fossae, Mars.  The talk was based on a recent paper of his (unfortunately behind a paywall), which is about trying to reconstruct the origin and behaviour of “Marsquakes” using evidence from the trails made by rolling boulders, dislodged by seismic activity or vulcanism.  Here is a sample picture showing the kind of trails he’s using – the resolution is such that one pixel is only 20cm!

There are enough trails to allow a statistical analysis of their distribution in space and in terms of size (which can be inferred from the width of the trail). I had some questions about the analysis, but I haven’t been able to read the paper in detail yet so I won’t comment on that until I’ve done so, but the thing I remember most from the talk were these remarkable pictures of what a rolling boulder can do on Earth. They were taken after the earthquake in Christchurch, New Zealand, in 2011.

A large boulder was dislodged from the top of the hill behind the house in the second picture. It didn’t just roll, but bounced down the slope (see the large furrow in the first picture; similar bouncing trajectories can be seen in the picture from Mars), smashed straight through the house, exited the other side and came to rest on a road. Yikes.

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Best Evidence Yet for Flowing Water on Mars (via Well-Bred Insolence)

A nice blog on the evidence (such as it is) for water on Mars, which is good because it means I don’t have to try writing about it!

I’m not sure it is water. That dark colour suggests to me it might be Guinness…

NASA's Mars Reconnaissance Orbiter has discovered what amounts to the best evidence yet for liquid water on Mars.  Let's be clear though, it's not exactly a flowing spring, and you're unlikely to be drinking this stuff fresh out of the ground, but the odds are now much better for extremophilic bacteria surviving on the Red Planet. The results were reported in Science today (I was able to access through University subscriptions, but I am afraid th … Read More

via Well-Bred Insolence

A Martian Oz?

I noticed a news item last week about research which points out that the remarkable fact that parts of Mars look a bit like Australia. Take this image, for example, of the region called Nili Fossae in which the Sydney Opera House can be seen clearly in the upper left…

Apparently the rocks in this region “resemble” those in an area of Australia called the Pilbara. Scientists believe that microbes formed some distinctive features in the Pilbara rocks – features called “stromatolites” that can be seen and studied today. According to  Adrian Brown, who works for the SETI Institute,

“Life made these features. We can tell that by the fact that only life could make those shapes; no geological process could.”

Unfortunately however, all that has really been established is that the Martian rocks have a similar mineral composition to those found in Australia – there’s no evidence (yet) that the “features” made by living creatures are present. Nevertheless, the newspapers have got very excited about this and today’s Guardian even ran an editorial on this item, from which I quote

Sceptics may think the comparison tenuous. They may also note that yesterday’s news reports either framed the possibility as a question – could there be life? – or put it in inverted commas. There is no proof. There is quite likely no life either.

Quite.

I always find it very interesting how everyone gets so worked up about the possibility of there being, or having been, life on Mars when we’re such careless custodians of the flora and fauna of our own planet. I suppose behind it all there’s a hope that there might be sentient beings out there in space who can tell us how to look after ourselves a bit better than we’re able to figure out for ourselves.

Unfortunately, the recent “discovery” provides very strong evidence against there being any form of intelligent life whatsoever on Mars. After all, it’s just like Australia.

Life, the Universe, and Coloured Pencils

Yesterday’s post got me thinking about what it is that makes scientists decide on their own speciality. It’s got to have something to do with the intersection between interest and aptitude, in that I think we learn gradually through our time at School that there are some things we can do well and others that we can’t but the things we can do well aren’t always things we find sufficiently interesting to make a career doing.

I suspect luck also plays a big part, in that the choices one gets to make must be taken from the options at a very particular time. I ended up doing research in cosmology after my first degree, but it wasn’t any kind of a grand plan that got me to Sussex in 1985 to do that but it just seemed the best choice to me out of all the half-a-dozen other places I visited.

Before I meander off the point again I’ll just pass on something that one of my teachers at school told me, and which probably had a big effect on an impressionable teenager. It was my chemistry teacher, Geoff (“Doc”) Swinden, that probably had more influence than anyone in making me decide to become a physicist.

By the way he was called “Doc” because he had a PhD (or perhaps a DPhil, as I think  he got his doctorate, in organic chemistry, from Oxford University). I didn’t go into Organic Chemistry, of course, but that was mainly because I hated the practical aspects of chemistry and pose a considerable threat to the safety of others when placed in any kind of laboratory environment.

Anyway, I remember very well a comment of Doc Swinden’s to the effect that anyone wanting to be called a proper scientist should avoid any subject that required the use of coloured pencils. That ruled out biology, geology and a host of others and left me firmly in the domain of physical science. I ended up going to Cambridge to do a degree in Natural Sciences, which allowed me to do chemistry and physics for a year and then decide which to continue. Obviously I went the way of physics.

I don’t regret going into physics at all, but I don’t think this bit of advice was all good. When I went to Cambridge to study Natural Sciences, I had to pick an extra subject to do in the first year to do alongside my main choices, chemistry, physics and mathematics. Among the options were geology, biology of organisms, and biology of cells but, mindful of the possibility that all of these might require the dreaded coloured pencil, I went for a course called Crystalline Materials. It’s true that I didn’t have to colour anything in, but it was the most mind-numbingly awful course I’ve ever taken. I very nearly failed it at the end of the first year, in fact, but still managed to get  a First-class mark overall.

Going back to yesterday’s post, I realise that one of the reasons I’m less gung ho for Mars exploration than some of my colleagues might be that it’s a bit too much like geology or even biology. It seems the ghost of the coloured pencil is still haunting me.

To Mars or not to Mars?

Amongst  the news this week was President Obama’s announcement of a new space exploration policy for NASA. Out goes the Constellation program, including the Orion crewship, its Ares launch rocket, and the rest of the project’s Moon-bound architecture. Obama says NASA were on an unsustainable path, costing too much money and taking too long to develop. Instead he’s given them extra funds ($6 billion, modest by the standards of space exploration) and told them to find new ways of putting people into space. Obama’s particular goal is to send someone to Mars by the mid 2030s and return them safely to Earth. I think Obama’s plans have ruffled a few feathers, especially among those longing for a return to the Moon, but it seems to me to be both bold and intelligent. 

The European Space Agency also has a programme – called Aurora – which includes components involved with both robotic and human exploration. This programme is a kind of optional extra within the ESA budget and countries that wanted to join in were asked to pay an extra contribution. The UK opted in so now we pay a top-up on our subscription to ESA in order to participate. This will be one of the things that transfers to the new UK Space Agency, when it’s up and running properly, from the Science and Technology Facilities Council (STFC).

Thus far the UK policy has been not to get involved in human space exploration. There are a lot of reasons behind that, but one of the most important is sheer cost. Space exploration is expensive by its very nature, but involving human beings creates enormous extra costs connected with keeping them alive and keeping them safe while they are in space. Since our national expenditure on space exploration has largely been channelled through STFC (or its predecessor PPARC) where it has had to compete for funds with “pure” science activities in the areas of particle physics and astronomy (and, more recently, nuclear physics).

I think the scientific argument against funding human exploration has always been as follows. There aren’t many things that people could do on Mars that a robot couldn’t – here I’m talking just about scientific experiments and the like. Human space exploration is much more expensive than the robotic variety. The scientific value for money is consequently much higher for robotic missions ergo, since money is tight, we don’t do human space exploration. Plus, we couldn’t afford it anyway…

The other factor is that there aren’t many feasible targets for manned spaceflight in the first place. The Moon and Mars are basically it. Other objects in the solar system are either too distant or too inhospitable (or both) to be considered. Unmanned probes haven’t all been successful, but some certainly have paid off enormously in scientific terms. I give the Cassini-Huygens mission to Saturn (and its extraordinary moon Titan) as an example that has turned out, in my opinion, to be nothing short of sensational. The images of Titan’s surface sent back by Huygens were gobsmackingly amazing, for instance.

Before going on let me point out that I’m a cosmologist, not a planetary scientist. There’s a tendency among scientists to think that their own field is more important than the others with which it has to compete for funding. It’s perfectly natural that someone working on galaxy formation should find galaxies more interesting than planets, and vice-versa. We all pick what we want to work on, and obviously we pick what interests us most.  But any scientist worth his/her salt should have enough of a grasp of the big picture to recognize outstanding work in disciplines other than their own.  I don’t want anyone to think that the following comments are intended to suggest that there isn’t excellent work going on in the UK and rest of the world in the field of planetary exploration.

I do think, however, that there is a big difference in character between fundamental science (especially particle physics and cosmology) and planetary exploration. In fundamental physics we are attempting to uncover the nature of basic constituents of the universe and the general laws that govern the structure of matter and how it interacts and evolves – in other words, its scope is (or at least tries to be) universal. It’s certainly this aspect – trying to unravel an enormous cosmic puzzle – that drew me into cosmology. By contrast, the study of a particular planet – even a fascinating one, such as Saturn with all the beautiful orbital dynamics going on in its ring system – lacks this aspect of universality. That’s why cosmology interests me more than planetary exploration does. This is nothing more than a statement of personal interest.

Having said that – and pointing out  again that I’m no particular expert on the Solar System – I don’t find the Moon and Mars very  interesting from a scientific point of view compared with, say,  the outer planets which I find fascinating. Others – a great many others, in fact – obviously do see a lot of interest in Mars. I’m not at all convinced about the scientific merit of some other space probes either, especially the planned Mercury orbiter BepiColombo. But there we are. We can’t all expect to agree on everything. What I’m trying to say, though, is at the moment these different types of activity are funded from the same pot. In order to draw up an order of priority, STFC has to compare apples with oranges with predictably bizarre outcomes.

Moreover, space exploration – especially human space exploration – isn’t just about science. There are definite commercial opporunities in space, in both short and long term.  Space missions often  provide results that are fairly easily accessible to non-scientists, so has considerable popular appeal as well as inspiring young people to take up science and engineering subjects. It has immense cultural impact too, altering the way we think about ourselves and our place in the Universe. But these aren’t unique to space exploration. Particle physics and astronomy do this too.

 But the overriding factor is the politics. When NASA put a man on the Moon 40 years ago, it was never about science – it was a political statement made right at the height of the Cold War. We no longer have a Cold War, but nations still feel the need to show off to each other. It’s called national pride. Politicians know how this works, and how it can turn into votes…

So we shouldn’t think of the plan to put a man on Mars as being primarily a scientific thing anyway. I’m quite comfortable with that.  My worry – if the UK decides to take part in manned Mars exploration – is that the money will come from the already dwindling pot allocated to fundamental science. Particle physics and astronomy research in the UK is on the ropes after the recent devastating cuts. Any more blows like this and we’ll be on the floor. I’m deeply worried that far worse is already on the way – a combination of public spending cuts after the general election and political directives to devote more to space exploration.

The new UK Space Agency could be either a hero or a villain, and I don’t know how it will turn out. On the one hand, the creation of this organization may prevent the fundamental sciences from being squeezed further by expensive space projects. In this way it might represent a recognition of the different characteristics I talked about above. The industrial and commercial aspects of space exploration are present in the new outfit too.  On the other hand, the result of hiving off the “glamorous” space parts of STFC may lead to further cuts in what is left behind. I’m also nervous about the future relationship between UKSA and STFC, especially the extent to which the former can demand research grant funding from the latter.

I’m sorry this has been such a long and rambling post, but this has been on my mind for quite some time and I wanted at last to put something together about it. I could summarise what I’m saying as follows:

•  I’m not convinced about the scientific case for Mars exploration – particularly if it involves manned missions
• BUT it’s not my field so it’s not my decision to make
• AND there’s more to Mars than science anyway
• SO by all means do it if there’s a will
• BUT for heavens sake don’t pay for it by killing off the rest of astronomy

This is something that I’d be genuinely interested in hearing other views on. What is stated above is my opinion and is not intended to be representative of anyone, but I’d be very interested in hearing other views through the comments box.