Summary: 'Survivability of 1-chloronapthalene during simulated early diagenesis...' (more exciting than the title suggests, honest!)

The shiny full open access version of our latest paper about organic molecules on Mars is now published online at JGR Planets. While we'd like you to read the whole thing to justify the ridiculous cost of publishing open access, if you can't be bothered then here's a summary, which should be relatively understandable.

When missions to Mars are looking for past or even present life, the evidence they are searching for is in the form of organic molecules. While not all organic molecules are formed by biological activity, some compounds, like certain fatty acids, are what we term ‘biomarkers’ and the detection of those would be very exciting as they would be a strong indication of Martian life.

Even detecting non-life-related (abiological) organic molecules on Mars would be exciting, we are sure that they should be present on Mars as the universe is full of them. Meteorites and comets are rich in organic matter, sourced from the primordial material of the early universe, and Mars must have been ‘seeded’ with these ingredients for life in much the same way as Earth.

Most attempts (bar one) to detect organic molecules on Mars, however, have only found simple chlorinated organic compounds – those with one or more chlorine molecules attached. These are not what we would expect from any of the proposed sources of organic matter on the Martian surface, they are too small and simplistic, and the chlorination is a bit weird,  and so something must have altered Martian organic matter to create them.

But when? and how? This is what we have tried to figure out....

Simple chlorinated molecules found on Mars

2 competing hypothesise for the source of these chlorinated molecules have been put forward by previous work:

1) It has been suggested that they may have formed on the Martian surface via reactions between chlorine-bearing salts (especially the perchlorates that I work with) and those organic compounds delivered by meteorites. In this case, the chlorinated organics discovered by the Curiosity Rover would be as 4.5 billion years old, the same age as the rocks they were extracted from. They would have had to survive the increased heat and pressure of being buried to about 3 km depth on a warmer ancient Mars.

The Sheepbed Mudstone, Gale Crater, Mars, where Curiosity has found most of the chlorinated compounds (from Sutter et al., 2017)

2) It has also been suggested that they are formed inside the analysis instrument of the Rover when organic carbon (either from the analysed Martian rocks or just contamination from Earth) is heated along with chlorine-bearing salts that are also known to be in the samples. The salts break down when heated to produce both oxygen and hydrochloric acid which reacts with any organic matter present. In this scenario, anything interesting is mostly burned away to carbon dioxide and carbon monoxide and lost to detection with the few surviving fragments of organic molecules becoming chlorinated. In this case the detected molecules would be formed just before detection and so survivability is not an issue.

To test if the first hypothesis was even possible we examined the ability of simple chlorinated organic molecules to survive the high pressures and temperatures associated with burial over geological timescales. We did this by subjecting these molecules to geologically-relevant pressures in a small reaction vessel, known as a bomblet, which is basically a glorified pressure cooker. Obviously we didn’t have a few billion years to wait around so we had to speed up the process. By increasing the temperature to speed up the reaction rate (remember high school chemistry?) we squeezed most of the history of Mars into a weekend.

How to squeeze 4.5 billion years on Martian geological history into a weekend. Clockwise from top left: Freshly made bomblets ready to be filled with the test chlorinated compounds. Sat inside the larger bomb - the whole thing can be filled with larger volume of sample if necessary. Making sure everything is tight so it doesn't explode when pressurised. Heating up in the reaction vessel to cook for the weekend.

By repeating this experiment at various temperatures and pressures, it was possible for Jonny Tan, one of the PhD students in the research group, to do some fancy maths and computer simulations stability of the molecule under conditions it would be subjected to on Mars. This bit was all over my head, but if you want to play around with his model, its all open source and available on github.

It was found that the bond between the chlorine atom and the rest of the hydrocarbon molecule is quite weak and breaks easily. This means that, on a warmer ancient Mars, when the sediments the chlorinated molecules were detected in were deposited, the increased surface temperatures would have promoted the loss of chlorine relatively rapidly. Intact chlorinated organic molecules would have been unlikely to even survive the first 1 billion years, never mind the 4 billion needed to get to the present day in detectable concentrations. This makes the first hypothesis (that these molecules formed on the Martian surface and are ancient) rather unlikely.

The chlorinated organics detected on Mars in ancient sediments are therefore likely to have been formed very recently, most probably when heating in the Rover's analysis oven promoted reactions between Martian organic matter and chlorine-bearing salts.

Whilst this conclusion isn't going to blow anyone's mind, as most studies had assumed this anyway, it's good to have some actual experimental evidence to back these things up.

Latest (catchy titled) paper summary: Perchlorate‐Driven Combustion of Organic Matter During Pyrolysis‐Gas Chromatography‐Mass Spectrometry: Implications for Organic Matter Detection on Earth and Mars

Credit: JGR: Planets

Our latest paper is now out and openly accessible to read here. I’d rather like you to read the full version so we can justify the £2500 it cost to remove the subscriber-only paywall and make it open access. However if you CBA to plough through all the technical jargon (there’s not too much I hope) here’s a little (hopefully) more accessible (and shorter) summary of what we found out.

As you probably know if you’ve read any of my other posts, my research is mostly on the interactions between organic matter and minerals on Mars, with the overall aim of trying to figure out why we’re having such a hard time detecting organic matter on the Martian surface. If you’re new here then what you need to know first is that organic matter, in this sense, does not necessarily have anything to do with life (whatever recent headlines have said). Organic molecules are just molecules that contain carbon, they are the building blocks of life BUT can also be produced from non-biological processes – even in deep space.

We know that organic matter should be widespread on the Martian surface as it will be delivered there by meteorites, comets and interplanetary dust particles. There may also have occurred processes in Martian history that created organic molecules on Mars itself (although this is less certain), and if there is, or has, ever been life on Mars then that would also leave behind molecular traces of itself. Even if the only source of organic matter to the Martian surface is from outer space, and the high radiation environment of the Martian surface (there’s very little atmosphere for protection) breaks that down somewhat, the constant delivery of organic matter over billions of years should have left something behind we can detect.

Oddly, though, despite trying since the Viking life detection mission back in the mid ‘70s, we have failed to detect any evidence of complex organic matter until very recently (more on that later). All attempts to look for organic matter in the Martian rocks and soil have used thermal decomposition – heating up the sample in an oven so that anything in there breaks down into small enough molecules to be identified by the on-board instruments. However, mostly, they only detected (at best) very simple, small, chlorinated organic molecules along with carbon dioxide and carbon monoxide gases. Not as interesting as we’d hoped.

Simple, chlorinated organic molecules found on Mars previously

The discovery of perchlorate in the Martian soil by the Phoenix lander in 2008 gave an answer to this puzzle of the missing organic matter. Perchlorate is an ion made up of 1 chlorine and 4 oxygen atoms, when you heat this up it breaks down to produce lots of oxygen – it basically explodes! This makes it useful for rocket fuel (ammonium perchlorate was used as the propellant for the space shuttle rocket boosters) but not so useful when you’re looking for tiny amounts of organic matter which are in the same soil/rock sample. When you heat up a sample that contains both perchlorate and organic matter the oxygen release causes the organic matter to combust (burn away) and be lost as carbon dioxide and carbon monoxide – not helpful for analysis.

We therefore wanted to find out the true potential of this reaction for destroying evidence of organic matter to answer the question: How much organic matter, relative to perchlorate, do we need in a sample to be able to detect it? If we could answer this, maybe we could figure out where, if anywhere, on Mars could have a ratio more favourable for detection.

To do this I made up lots of different mixtures of magnesium perchlorate and charcoal, (charcoal is superficially similar to the organic matter in meteorites, but much more accessible) and flash heated these samples to see what gases they gave off. By analysing the relative proportions of carbon dioxide and carbon monoxide given off it was possible to rapidly see the extent of combustion. If there was too much perchlorate/too little organic matter in a sample then all of the organic matter’s carbon would be saturated by oxygen - complete combustion - and only carbon dioxide would be given off. If there was too little perchlorate/too much organic matter for this to occur then it would be the oxygen that would saturate and not all of the carbon would be combusted, this incomplete combustion would produce carbon monoxide as well as carbon dioxide and there would, in theory, also be surviving organic molecules that were not burned away. The point at which we started producing carbon dioxide was termed the critical ratio.

If we have too much perchlorate and not enough organic matter (subcritical ratio) then there is enough oxygen produced to saturate all the carbon so the organic matter is fully combusted to carbon dioxide. If we have enough organic matter and less perchlorate (supercritical ratio) then we run out of oxygen, not all of the carbon can be saturated so we have partial combustion, producing carbon monoxide as well and organic molecules can survive to be detected. 

It turned out that this critical ratio was about 11 times as much charcoal as magnesium perchlorate. And by doing some maths we figured out that this meant (as the charcoal is a little over 50 % carbon) that on Mars you’d need about 6 times as much organic carbon than magnesium perchlorate in a sample to be able to detect it.

While this paper was out in review, there was a big NASA announcement (link to paper and summary). They’d finally found evidence of complex organic matter on Mars, but only in two samples. This suggested to us that for some reason these ‘new’ (they were analysed in 2015, it just took a long time to get the work published) samples must have an organic carbon/perchlorate mixture above our critical ratio and all the other samples previously analysed must have one below the critical ratio. Thankfully for us, someone had made and published those measurements of perchlorate levels in all of the analysed samples. It turned out that, yes, the samples that showed evidence of complex organic matter had about a tenth of the perchlorate content as the samples that only simple chlorinated molecules were detected in – kind of nicely proving our point for us, thanks NASA!

More complicated organic molecules that have recently been detected on Mars

This demonstrated that the perchlorate levels on Mars are variable and that this is important. If we want to find any more organic matter to increase our knowledge of extra-terrestrial organic chemistry, or even for life detection, we must look where the perchlorate levels are reduced. Perchlorates are highly soluble, this is why they are rare on Earth except in hyper-arid regions such as the Atacama Desert, so we should be looking for areas of recent water activity where they may have been washed away.

Where should Curiosity look next? (Credit: NASA)

My first conference talks, two very different experiences

I flew all the way out to California last week to present work at the COSPAR (Committee of Outer Space Research) conference in Pasadena. 

I had been accepted to give two talks which was both pretty exciting and terrifying as I had somehow avoided ever giving a talk at a conference until now. Poster presentations, which I have done many of, are way more chilled (in my experience). You stand by your poster for a few hours and if anyone is interested they come and find you for a one-on-one chat, and there’s usually free beer to help the science flow. A talk on the other hand is (for me) a much more stressful proposition. Standing up in front of your peers, which may include eminent scientists who may ask horrifically complicated questions at the end, or may even just stand up and denounce your work to the whole audience (this dick-move is unfortunately quite a common occurrence). As such, I was quite nervous about the whole thing.

Both of my talks were about very different subjects. One for a project that is only a minor part of my job and I am in no way an expert on the subject matter – I was just the compiler of a large group’s work; the other on my latest research, which I’m pretty psyched to tell people about. So I felt somewhat worried about screwing up the first and not doing justice to the work of actual experts, but pretty good and excited about the latter.

What went down, however, was the complete opposite of my expectations.

In first talk, which was the one I was panicking about, went surprisingly well. I was presenting the chapter we have been writing for the Planetary Protection of the Outer Solar System (PPOSS) project. This is a report on how we can improve future organic contamination control for missions to the icy moons of Jupiter and Saturn.

I was basically arguing that organic molecules (from plastics, oils, grease, etc.) on spaceflight hardware pose as great a threat to our attempts to detect life in the outer solar system as microbial hitchhikers (the current main target for planetary protection efforts). This is because, if we have a ‘dirty’ instrument we may only detect the ‘dirt’. In a normal environment this is often not such an issue as we can usually recognise contaminants. However, we do not understand much about the environments of the icy moons, especially the radiation levels, and how that will affect the contamination molecules, the molecules which could be evidence of extra-terrestrial life (what we call ‘biomarkers’), and any other non-biological organic molecules that are present on the surface. Basically we’re looking for a needle in a haystack, except we don’t know what the needle is made out of, nor what the haystack is made out of, if we don’t have a clean instrument we’ll never figure this out.

Titan, one of the Icy Moons of Saturn has a very complicated organic chemistry. To have any chance of understanding it we need to not contaminate our analyses with organic molecules from Earth as they may be greatly altered by the complex radiation environment and unrecognizable for what they are by the time they get there (image credit: NASA)

This becomes a planetary protection issue as if we detect our own contamination and mistake it for evidence of extra-terrestrial life everybody will get really excited and future missions will waste a lot of time and money trying to find out more about these imaginary aliens. Conversely, the contamination levels could be so high that they mask a real life signal – in this scenario we would lose our interest in looking for life on the moon, maybe never checking again and instead only sending ‘dirty’ non-life detection missions to look at other aspects of the moon. This could permanently contaminate the moon and destroy any chances of detecting that life there in the future. Both of these scenarios are pretty bad for planetary protection whose main goal is to avoid jeopardizing the search for extra-terrestrial life.

Despite the fact that I was delivering this talk first thing in the morning, telling a room packed full of real planetary protection experts (I’m just a confused geologist remember) how to do their job it went down pretty well. It triggered questions and discussion on whether organic contamination control is a planetary protection issue, exactly what we were trying to achieve.

Me doing science (credit ESF-Science Connect)

After the success of the first talk I was feeling pretty confident for my second where I was going to be presenting what I actually know about – my own research on the interactions between organic matter and minerals on Mars. This was mid-afternoon on the Thursday, what you’d expect to be the perfect slot: not too early or late so people haven’t woken up or have shut down, not right at the start or end of the week so people haven’t arrived yet or already left and not just before or just after lunch so that people aren’t too hungry or in their post-lunch daze.

In this talk I was presenting the findings in our latest paper, this will shortly be available open access but is currently behind a paywall here. I talked about how we’d calculated the minimum about of organic matter there would need to be in a Martian sample for a rover to be able to detect it despite the presence of problematic minerals (using current techniques). I then showed how this worked with samples from the closest environment we have to Mars on Earth, the Atacama Desert, and then applied this new knowledge to explain why organic matter has suddenly been found on Mars after 40 years of trying.

Nobody cared.

The end of my talk and the customary ‘I’d be happy to answer any questions’ was met with glazed expressions and silence. I half expected a tumbleweed to blow down the central aisle of the conference hall. Normally in these situations the chair of the session will have a question prepared, but even they were unable to hide their disinterest.

As an early career researcher, giving my second ever conference talk, on something I spent months working on, this was pretty crushing. I could only scurry back to my seat and, somewhat shell-shocked, watch the rest of the afternoon’s session.

What had I done wrong, it had all seemed to go smoothly from my end?

As the rest of the session unfolded it all became clear. It was not that I had delivered bad science, I had delivered the wrong science for the crowd’s interest. While I am primarily a lab rat, doing experiments to try to understand the results coming back from the Mars rovers, everybody else in the session worked on the satellites orbiting Mars. They were all interested in atmospheric gas measurements or photographs of surface landforms which is what all the other talks were about. This was, for once, not my fault. I should never have been given a talk in this session. While it was titled, ‘Mars Science Results’ and so should have been suitable, because of the dominance of orbital data it was not a diverse enough audience. This was on the session organisers.

Despite this realisation this pretty much ruined the rest of the conference for me, it was just too much of a downer after the way I’d built it all up in my head beforehand – I am NOT a confident public speaker in the slightest so had really had to psyche myself up.

This dependence on the right audience being present seems to be the major crucial thing to get something good out of a conference presentation of any sort. I’ve also had this with poster sessions in the past. I stood around for hours with no one interested enough to come up for a chat next to a poster at the European Geophysical Union conference a few years ago. I was presenting some my PhD research on high resolution palaeoclimate reconstruction based on the chemistry of coral skeletons. Everybody else in the session was doing things with water or plant chemistry – but we were all using ‘isotopes for novel environmental studies’ or whatever the title of the session was. Dead sessions like this are excruciating, you’re almost praying for the crazy ‘scientist’ who’s had a few too many at the free bar to come up and discuss his latest theory with you – there’s often one. Other poster sessions I’ve had great discussions which have led to ideas to improve the work I’m presenting or have created ideas for new projects. Although sometimes I just make a tit of myself, while intimidated and slightly star struck, in front of the top scientists in my field (although as long as they leave with a copy of my latest paper its all good…right?).

The issue seems to be that you can’t really gauge what it’s going to be like when you submit your abstract – the session titles and descriptions are always so vague. I guess if this happens you just have to shrug it off and just take it as a good practice run for the next time you have a more interested crowd. It’s not put me off anyway, now I really need to pull my finger out and write that AGU abstract, hopefully the crowd there will be better…

The System Works....Occasionally

I've said some pretty nasty things about Reviewer 2 in the past, they always seem intent on screwing us over in some way or another. However, we've just had a paper accepted for publication and this manuscript's journey through the system has finally (after 3 prior publications) shown me how the system is supposed to work.

My previous manuscript had a rather rocky journey to publication, with numerous rejections from editors (too specialist interest) and having to appeal the decision of a particularly arsey Reviewer 2 who suggested rejection even after we'd done all they'd asked - months of extra experimentation.

This time, the reviewers - especially Reviewer 2 - picked apart the gaps and weaknesses in the manuscript that were mostly in there as we forget that outside our tiny lab other people have other ways of thinking about things so we need to explain everything:

'please elaborate...'

'how do you justify using this technique/sample...?'

'why did you not do it this way rather than the way I'd do it...?',

They also found a (rather glaring) omission, we'd been using carbon monoxide/carbon dioxide ratios detected by the GC-MS as a quick proxy for the survival of excess organic carbon on combustion - but had offered no proof that this actually worked other than theoretically, oops!

And they used their expertise to suggest how we could fix these problems to make the study better, all written in the sort of way that suggested they were genuinely interested in our findings and wanted to help.

Yes, this resulted in extra lab time to do a few more experiments (and the odd bit of swearing at the mass spectrometer), but the extra work gathered greatly strengthened the manuscript - and I made a real pretty new figure with the new data. 

When it came back from its second round of review Reviewer 1 was happy and Reviewer 2 had a few very minor comments, the worst of which just needed me to delete a sentence where I'd slipped into what could be construed as somewhat wild over speculation about some of the Mars data.

I genuinely mean the thanks to the two (anonymous) reviewers in the acknowledgements this time, they really did make the science better.

This is how the peer review system is supposed to work.

Don't be a dick.

Scientifically accurate, non clickbait title: NASA finds organic matter on Mars which is probably not evidence of life but there's a very slim chance it could be

Warning – angry rant, lots of swears

So after the weeks of hype build-up NASA released their latest big findings from the Curiosity Rover last night. Sensationalist clickbait tweets and headlines from the scientific media seem to tell us that we’ve finally got direct evidence of life on Mars:

‘Scientists for the first time have confidently identified on Mars a collection of carbon molecules used and produced by living organisms’ @nytimes

‘Mars has complex organic material that may be from ancient life’ @newscientist

 ‘NASA finds ‘building blocks of life’ in 3 billion-year-old lakebed on Mars….is there finally proof of alien life on the red planet’ The Sun

 And that bastion of great science reporting The Express goes full on with ‘Life on Mars: NASA finds ‘HOLY GRAIL’ in rover search for ALIEN LIFE’  and ‘Nasa UNCOVERS evidence of LIFE on Mars in latest SHOCK revelations’- actually fucking capitalising the bollocks bits, seriously?!?!?

Really,?!? FUCKING REALLY?!?!?

Now, there’s nothing wrong with the articles themselves but as has been shown time and time again plenty of people don’t actually read past the headlines and a quick check of the comments show that we now have people believing NASA has announced finding life on Mars (although if you can be bothered to comment why not read the full article)… Unfortunately rather than being interested in good science communication it appears, yet again, that the media is only interested in getting website traffic so more people see some fucking annoying pop-up of a new Volvo or something.

If you’ve actually read this far you won't be surprised to learn that the truth is nowhere near as exciting as the headlines suggest. Basically NASA has found exactly what it has expected, but failed, to find since the Viking missions in the 1970’s, organic macromolecular material. While this could have a biological origin, there is NO evidence for this! Organic material just like this is produced abiotically (without life) throughout the universe. We find very similar molecules in meteorites that have fallen to Earth and the impact of meteorites along with comets and interplanetary dust particles will have delivered organic matter to the Martian surface. It has been calculated that 100-300 metric tons of organic matter is delivered to the Martian surface in this way EACH YEAR. There are also ways in which the organic matter could have been produced on Mars itself through hydrothermal or igneous processes. While we cannot rule out the possibility that these molecules are evidence of ancient life that lived in the lake these sediments were deposited in this is the least likely source, we KNOW the other processes would have happened, we have NO EVIDENCE of life.

What I think is the most interesting thing here, and one that is not really touched on in the paper (presumably because it’s in Science so they didn’t have the page space) is WHY we have detected these molecules now? There have been hints of organic matter in previous samples from the Sheepbed mudstone further up the formation, but these were low responses and all simple chlorinated molecules, these more complex molecules have been found in the older Murray mudstones. It is suggested that these, being buried deeper, have been less exposed to the destructive effects of cosmic radiation, but over the time periods involved could a little bit less exposure really have saved them? One of the reasons we hadn’t found complex organic material up until this point was because it was destroyed during analysis. Minerals in the Martian soil (such as perchlorates) were releasing oxygen when heated and this caused the organic material to combust and be lost to analysis (this is what I work on). For these molecules to be detected now, there must either be more of them in the sediment or less of the oxidising minerals and it is interesting to think what processes could have concentrated the organic matter or removed the minerals in these units…

I’m not going to go into any more detail on the science side of things, everything I want to say revolves around some unpublished work we’ve currently got in review and I’m not supposed to discuss that kind of stuff till it’s out. Needless to say we’ll be getting it back to update it with these latest findings before it can be published.

Here’s a link to the actual paper in Science

And a nicely put together write up by someone who’s much better at these things than I am

The closest I will ever get to Mars - Atacama fieldwork

I've just got back from a week's fieldwork in the Atacama Desert, Chile. The part of this massive, over 100,000 square kilometer area, desert we were in is one of the driest places on Earth - only the Antarctic Dry Valleys have a lower annual precipitation.

I was participating in a field campaign organised by the HOME (Habitability of Martian Environments) project with a German-based team of astrobiologists, microbiologists and astronomers. This project focuses on the Atacama as it is the most Mars-like environment we can study first hand. Here, they test theories of how microbial life may adapt and survive to the harshest hyper-arid, high-UV and high-salinity environments, as they may have on Mars. This group has just published, to a massive media reception, a study showing that microbial life can exist in a dormant state, underground, possibly for 1000's of years, even in the driest part of the desert - blooming after rare rainfall events. Maybe this is how life adapted to the gradually drying climate on Mars billions of years ago.

The desert was amazing, the landscape really was Martian. No signs or sounds of life (except for the occasional long-distance travelling vulture) and just reddish dry, dusty rocks and sands as far as the eye could see. It really did look just like the images coming back from Gale Crater on Mars - except for the bright blue sky.

The Atacama or Mars?

We were in the desert to collect more samples to further this research and other work on hyper-arid soils and Martian analogs carried out by the many collaborators of the group. Unfortunately, it appeared as though the hyper-arid core of the desert had been a bit wet recently... Evidence of heavy rainfall and past standing bodies of water were everywhere. Even the pits, dug in previous years, that we had planned to sample from had been half infilled by water-transported debris - shifting this was to prove hard work and very time consuming.

We did think early on in the week that we had found a breakthrough to this problem of reaching the, now reburied, ancient sediments as a massively deep (45 m) hole was found, purely by accident by a team member looking for a quiet toilet spot. This looked to have been drilled as some part of recent mining activity which is all over the place in the area. As the only climber in the group I was tasked with figuring out how we could safely descend into the hole and collect samples from previously unexplored depths. Luckily there was a climbing shop in Antagofasta, the nearest town, and after a bit of language-barrier related fun (what is screwgate in Spanish anyone?) we managed to purchase everything necessary for 2 people to go down at a time - including over 250 m of various ropes and cord.

The hole, laser measurements showed it was 45 m down to the water

Practicing at camp

After a fun evening teaching the rest of the group how to put on harnesses and use a gri-gri (autoblocking belay device) to descend and self-belay I rigged up a complex system of anchors (hammered in stakes), safety lines and knotted hand lines to re-ascend with. Then descended down the hole to test the system while everyone else watched. Desert dust clogged the ropes and belay device which made abseiling down difficult and jerky, dust and small rocks fell from the poorly consolidated side walls of the narrow hole. As I got deeper it got cold quickly. I stopped at 10 m to test how easily it was to get out again and pulled myself onto the 'rope ladder' hand line I'd made to climb back up on.

Fuck

The Gri-Gri was completely seized up, dust had coated the thick 10 mm rope I'd bought to be extra safe and the extra friction meant it would take both hands to haul it through the belay device, I only had one free as the other was needed to take my weight off the rope I was on and onto the handline. This made reascending, safely, by the planned means impossible, ~If I had ascended the handline I would not have been able to self-belay at the same time so if the thin handline rope had snapped I wold have fallen.

I was stuck hanging 10 m deep, with a jammed Gri-Gri in the middle of the desert....Bollocks.

After trying everything I could to free myself (short of 10 m of vertical pruscking, which might have also jammed up and left me in even more of a tangle) while the group at the top grew understandably more anxious, I had to admit I'd fucked up and shout for a pull. Tying hand and foot loops in the second rope that had been set up I held on tight as 8 of my colleagues hauled me back into the light as I self belayed up my (now-unweighted and free moving) rope in case they dropped me. As they pulled me up the ropes cut into the soft sediment sending down a hail of dirt and stones - thankfully I was wearing a helmet as some of the chunks were big enough to do some damage.

Because of these unstable side walls it was decided that, rather than modify the technique used to avoid anyone getting stuck and going again, we should abandon the (w)hole idea as it was just too unsafe. I had seen some large rocks in the side walls as I went past and if they had fallen out and hit you at depth you'd be a gonner, helmet or not. So the hole remains unexplored and the depths of the Atacama keep their secrets, for now...

The failure at the deep hole meant that the only way to sample ancient sediments would be to dig. Much of the week was therefore spent digging, with pickaxe and spade - and on the last day, through harder layers - a jackhammer, and hauling buckets. This was hard, sweaty work, especially in the heat of the midday sun and the intense afternoon winds. A far cry from my usual day-to-day activity in the climate-controlled lab. It didn't take me long to come around to the German's habit of hydrating with 'isotonic' cervezas.

Digging for Science

By the end of each day we were knackered, we worked until just before sunset so there was enough light to sort out camp and build our fire. We had earned our barbecue and passed pisco around the campfire. Camping in the middle of the desert, we slept under the stars; the Milky way was the brightest I've ever seen it, we saw Jupiter rising, shooting stars, the International Space Station and even Mars.

Our view from our sleeping bags each night

Halfway through the week we had a rest day visiting the Very Large Telescope (VLT). Located on top of a flattened mountain at around 2500 m altitude, this is one of the most powerful telescopes in the world looking at some of the clearest skies. They don't lie, it is Very Large; 4 identical telescopes (each pretty big themselves) which work together collecting light to form a 'virtual telescope' around 130 m across. Before returning to camp, we stopped off back in Antagofasta to wash away the last few days of desert dust by swimming in the Pacific. That felt amazing, but the feeling didn't last long, the dust gets everywhere, I'll be finding it for weeks.

The VLT

We only really got going with sampling in the last few days due to all of the digging and re-planning required first. Because I am interested in the organic molecules present in the sediments at minute amounts and others are interests in rare microbes, all of the sampling had to be carried out in as clean and sterile a way as possible. This is obviously not easy in the desert, especially when the afternoon winds pick up and you end up running 500 m after your face mask as it disappears into the distance... This was slow going and we were maybe not quite as productive as we had hoped. However, we sampled many interesting sediments which should have a good story to tell.

'Sterile' sampling

I nearly didn't have any samples to bring back at all. After checking my bags and making my way through security in Antagofasta airport I ('Samwell Roy-lay') was called back through security and taken into the back room by a serious looking security guy. The suspicious looking 'powders' wrapped in aluminium foil had unsurprisingly got security excited.

This is it, I thought, the latex gloves are going on....

Thankfully, we'd anticipated this and got a letter, explaining what the samples are and why I really don't want to open them in a dirty airport, translated into Spanish (thanks to the magic of Twitter), printed on official looking Imperial College London headed paper, signed and rubber stamped. This literally saved my ass.

While that is an experience I wouldn't want to repeat, working in the desert was an amazing experience. The geology is like nothing I'd ever seen before and I have a new understanding of how the subsurface may be in the hyper-arid Martian environment. It was great to be finally back in the field after so long stuck in the lab and offroading pickup trucks, sleeping under the stars and sitting late around the campfire with a great bunch of people was pretty awesome too.

Camp under the stars

Maybe they'll let me go back when I've worked my way through this bunch of samples, best get cracking...