Today in Weird Invertebrates: Lawn Crayfish

Since I live in the Great White North, which is not generally known for its peculiar fauna, I had never heard of burrowing crayfish. I owe my newfound knowledge to Ursula of Kevin and Ursula Eat Cheap, who also hadn’t heard of such a thing until she found one hanging out in her lawn. (link goes to the episode of their hilarious, if occasionally surreal, podcast where she scolds the state of North Carolina for not putting “We have lawn crayfish!” on their roadsigns.) So, since one of my missions in life is to learn all there is to know about weird invertebrates, I did some digging about the burrowing crayfish.

There’s not an awful lot of information about burrowing crayfish online, and much of the google hits are people going “I think there’s a crayfish… in my lawn?!” (To be fair, that is precisely what I’d do were I in that situation.) Interestingly, most of the papers I found about them make a comment about their life cycle or ecological existance being poorly understood. Perhaps this says more about me than about wetland biologists, but were I a field biologist, burrowing crayfish’d be near the top of my list of research subjects.

Crayfish anatomy

The cray(on)fish. Roughly but not rigourously to scale.

Here’s what I’ve found about them. There are several species of burrowing crayfish, in both the Cambaridae and Parastacidae families. The former live in the southern US, while the later live in the Tasmania and the damper parts of Australia. Their life cycles seem to be similar to most crayfish, hatching from eggs stuck to their mother’s underside, and as they grow they molt. Like all crayfish, they have two large claws, four pairs of walking legs, and several pairs of swimming legs. They range in size from a few centimeters to a few inches (Ursula estimated the one in her yard was about five inches long), and their colour varies between species from bright red to bright blue. Ursula also said something about them glowing under ultraviolet light, but I can’t find anything confirming that. If you have a lawn crayfish and a black light, please investigate and report back!

Like all crayfish, burrowing crayfish eat anything they can get their claws on, including roots and dead plant matter in and around their burrows. Some species stick around in their burrows for food, while others are more likely to go foraging outside.

The burrowing crayfish live where there is a high water table, and often near sources of surface water. They dig complex burrows with branching paths and multiple sections, and usually at least part of the burrow sits below the water table. As they excavate the burrow, they drag mud and dirt up to the surface, and sometimes form a chimney at the mouth of their burrow. What’s not clear to me is how, exactly, they dig out their burrows. Their claws are well adapted for nabbing dinner, warding off predators, and defending territory, but they don’t look like very efficient shovels. On top of that, I’ve no idea how they’d transport the dirt up from the bottom of their burrow up to the top, let alone make a chimney out of it — maybe they shove it along with their tails? Or maybe the claws are shaped to be at least semi-efficient shovels? I’ve found no satisfactory answers, so if you’ve got an idea, please, leave it in the comments.

Crayfish with backpack

Perhaps they’ve developed backpacks to haul the dirt to the surface.

While the numbers are far from clear, since many burrowing crayfish species are poorly studied, it seems like burrowing crayfish are more threatened ecologically than other species of crayfish, and several are critically endangered. Unfortunately, many of the google hits for burrowing crayfish pertain to how best to get rid of lawn crayfish, because they can do a lot of aesthetic damage to a lawn. As water use shifts and water tables lower, however, their available habitat may shrink significantly. Hopefully, researchers will get some more concrete numbers and answers about burrowing crayfish before they suffer more habitat and population loss.

Crayfish, master of simple machines

Or maybe they use a pulley system!

New Ideas in Academic Presentations: PICO at the EGU

I’ve been deliberately vague about the research I do, since I’m trying to remain at least somewhat anonymous for now, but it’s in the realm of geosciences, and after a side trip, I’ve come back from the European Geosciences Union meeting in Vienna. This year, the EGU introduced a new type of presentation: along with the traditional oral and poster presentation styles, they added the PICO (Presenting Interactive Content) as an attempt to bridge the gap between the two. Here’s the official EGU video explaining the format:

PICO presentations have two parts: first there is a rapid-fire string of two minute/two slide talks by all the presenters in a session, and then there is a block of time where presenters can give a longer, more in-depth and informal presentation on one of the large touch screens in the area. Audience members can scan through the full presentations on the screens themselves, and presenters can circulate and solicit feedback on their work.

The first part serves as an elevator pitch: ideally, it gives a quick sketch of the presenter’s work, and entices the audience to listen to the full presentation. The second part allows for the presenter to get direct feedback from the audience, gives the presenters a focussed audience (since they can seek out the presentations that interested them, rather than milling through hundreds of posters), and increases the range of visual aids available. In many ways, it combines the best parts of oral and poster presentations, and I think it’s got a lot of potential.

But it’s a new format of communication in a realm where new and innovative methods of communication are few and far between, and from what I saw, this format was largely a missed opportunity. The two minute talk seemed to throw people the most: rather than editing their material severely for the pitch, many people put every detail into their slides. I saw slides with half a dozen paragraphs, half a dozen figures, and a few with both. Even on a giant projection screen, it’s unreadable, and when it’s flashed for a minute, it’s a detriment to the presentation. If I tried to focus on even one thing on the screen, I tuned out what the presenter was saying. Visual aids should be just that: aids. They should support communication, and here communication is not throwing every detail at the wall and seeing what sticks.

The longer presentations were generally better, but I thought many of them read as “powerpoint slides that accompany a oral presentation” rather than a presentation which can stand on its own (in case an audience member flips through it on their own) as well as a guide or aid for the presenter for a full, informal talk. Since this was a new format, I suspect no-one really knew what to do with it, but I think that it’s an opportunity to try something new, rather than reverting to old approaches.

One of the really powerful things with this format is that it makes it much easier to build a presentation that’s interesting and accessible to a range of audiences. I can’t be the only person who wanders in to sessions on things I know little about but sound interesting, but often I wind up confused and/or bored in those sessions because the presenter, not unreasonably, assumes that their audience is familiar with their field and adjusts their level of detail and jargon accordingly. But even for an audience of peers, a two minute talk is not the time for fussy details and specificity, so ideally the elevator pitch component would be accessible to a wide audience, encouraging people to come at least get a zeroth-order approximation to what people are doing in fields beyond their own.

But the real flexibility comes in with the longer presentation with the touch screens. Most of the people I saw at these presentations flipped through presentations on their own (maybe with two or three other people) even when they were talking with the presenter. The very small audience size and the electronic medium means that the presentation doesn’t have to flip linearly: the presenter can give an accessible, jargon free presentation, and where there are more details relevant to people who work on related topics, can put a link that says “Click here for more details” that leads to a side branch that contains details or data. This way the details are there for people who care about them, and interested audience members can ask or investigate, but they don’t clog up the presentation for people who don’t care about them.

This structure means you can reach a wider audience with a single presentation, which at a scientific conference, is obviously important. It also makes the presenter think about what’s essential information and what’s fussy details, and to think about how to effectively communicate that. To be clear, I’m not saying fussy details have no place in academic presentations — science is about details and precision, and that precision is important in communication too. But someone with no previous knowledge of your work won’t be able to understand your work effectively if the way it’s communicated is all details. I’m also not saying that I’ve cracked the code for academic presentations: while I think I’m improving, I still often use too many words and too many unnecessary details in my presentations. I think giving a PICO talk, which made me think about how to strip my work down to the bare bones for the two minute part, was a very helpful exercise.

But from what I (very informally) gathered, the reaction to the format was mixed. I’m interested to see whether the EGU uses it again next year, and if it does, what adjustments (if any) they make to it. I’m also curious to what extent the hesitance to embrace the format (or at least what I perceived as hesitance) are influenced by the wider-spread reluctance to avoid short, snappy talks for fear of them either TED-ifying or oversimplifying the material.

Somewhat relatedly, there’s a recent post on University Affairs criticizing the Three Minute Thesis competition:

For me, the 3MT [Three Minute Thesis] certainly prompted the question of whether academic researchers should be in the business of embracing an era of short attention spans, a world in which you should be able to say something succinctly or not at all.

To my mind, this isn’t an either/or sort of thing: it’s quite possible, and very useful, to be able to communicate the essential gist of an idea as well as the fully developed idea laden with nuance and detail, and both tacks are useful in different situations and for different audiences. PICO presentations are set up to highlight both tacks, which forces presenters to approach their material differently than traditional presentations. Much of the criticism of the Three Minute Thesis competition in the piece seems to be that people do it badly, and I’d argue that that’s incentive to do *more* of these sorts of talks, not less. I can’t speak for all academics, for sure, but there’s little formal emphasis put on developing communication skills, written or oral. Neither are skills that everyone naturally has, so having more venues and opportunities to learn how to be an engaging communicator are useful. (I do, however, agree with the author that grant money should not be tied to these sorts of competitions.)

To that end, the EGU’s new format has even more potential, since it’s not a complete jump to the slick world of snappy ideas. It encourages people from outside the field to sit in — my session comprised of three completely distinct topics, and I’d’ve never gone to either of the other two topics’ talks had they not been bundled with mine. But most importantly, it’s a way to get academics thinking differently about communication, and communication beyond their peers. To that end, I hope the EGU keeps the format and expands the number of sessions that use it.

Giant Squid!

Giant squid (Architeuthis dux) are rare deep-sea invertebrates, which are known mostly through dead specimens that have floated to to surface, washed up on beaches, or met an untimely end in the stomach of a sperm whale. Excitingly, the first video footage shot by humans of a live giant squid swimming at depth (around 900 m below the surface) was filmed earlier this year, and while a snippet has already hit the internet, the full footage is set to air Sunday evening on the Discovery channel (and has been broadcast on a Japanese television program). The short clip that’s already been released shows a graceful creature, gliding in a pitch-black, seemingly empty, ocean. A shot of its body shows its huge eye looking, if I can anthropomorphize the squid for a moment, almost baleful. (Though if I were swimming along in the deep ocean and were suddenly confronted with a submarine with lights, I’d probably look pretty baleful too.)

Giant squid are the world’s second largest largest invertebrates (behind the colossal squid), reaching up to 13 m in length. Much of this length is in the two hooked tentacles it uses to hunt, though there is no part of the giant squid that is not outsized. The tentacles can grow up to ~ 8 m, the arms are a comparatively puny ~2 m, the mantle (ie, the body) can be up to 2.25 metres long.

Giant Squid diagram

Artist’s rendition of a giant squid. Squid is broadly, but not at all rigorously, to scale.

The eyes are huge too, with a diameter approaching that of a dinner plate. The eyes, like much of the squid’s anatomy and behaviour, is still somewhat of a mystery: virtually no sunlight penetrates down to the depths that the squid lives at, so why does the squid for such a huge eye? It takes an enormous amount of energy to develop such a huge eye, and if there’s no light to be seen, that energy seems like a waste. One of the leading theories is that the eyes are used to detect the light from bioluminescent creatures, especially when they’re dispersing in the path of a sperm whale.

For more on the anatomy and behaviour of the giant squid, it’s hard to do better than this post from Deep Sea News. They also have an excellent link round-up of all things giant squid.

But its impressive physical qualities have enchanted not only scientists and admirers of weird marine creatures; the giant squid has a giant tentacle in the world’s marine lore. The giant squid lives in all the oceans, and is often thought to be the inspiration for the kraken. It’s huge, fearsome (it has hooks on the tentacles!), and lives in a murky world that we have only just started to be able to explore. It’s not surprising that these creatures are cast as the villain in sea-lore, but it’s not like the giant squid is a single-minded creature out for blood. Sure, I wouldn’t want to be on the wrong end of its beak, but I wouldn’t want to be on the wrong end of a killer whale or a leopard seal either. Yet we have children’s movies about orcas, and footage of a leopard seal gently trying to teach a photographer how to hunt penguins was all over the internet a while back. We don’t treat either of them as capital-m Monsters, so why the giant squid? It’s not even at the top of its food chain — while the image of the giant squid and the sperm whale struggling and fighting is culturally pervasive, in reality, the squid doesn’t stand much of a chance against the whale. I have a suspicion that some of the giant squid’s reputation is due to it being an invertebrate: to a vertebrate, land-dwelling species, squids are profoundly weird looking creatures. When humans first came across the giant squid, say in their fishing nets, there was probably not that much context handy for the sailors to make sense of these huge, intimidating creatures. We don’t have much contact with them — we’re only just getting footage of them in their natural habitat! — and we haven’t had time for any sort of image rehabilitation to take hold culturally. This video has gotten a lot of press so far, so it’ll be interesting to see how, if at all, it starts to change our collective perception of these elusive, strange creatures. I’ll update this post when I can find a video of the full Discovery Channel show.

In the mean time, if you’re interested in watching a dissection of a giant squid, the Museum Victoria in Australia has video of the dissection of a giant squid caught in a fishing net off Australia in 2008. It’s long, but the scientists go through the squid’s anatomy in some detail, and it’s well worth the time.

December 6th

December 6th is National Day of Remembrance and Action on Violence Against Women here, and this year it’s the 23rd anniversary of the École Polytechnique Massacre. In the past year, the long gun registry, which was put in place in 1995 after considerable debate (and pressure from women’s groups and gun control advocates), has been unceremoniously scrapped. One of the perceived front-runners in the Liberal leadership race now contends that it was a failure, even though he previously voted for keeping it. Each year there’s fewer and smaller memorial services and recognition of the day, as it fades out of the collective memory and into a shadowy box labelled “History.” I’m not an advocate of dwelling on the past, but I think the massacre’s anniversary is an important touchstone in Canadian women’s history, and I’m concerned that that seems to be a minority opinion. There’s not a lot of touchstones in Canadian women’s history.

I am a woman, a physicist, and a feminist. I am exactly the sort of person that Lépine was trying to silence, so it’s important to me to take a moment to reflect both on how fortunate I am to live in a time and place where I can pursue a scientific career and an advanced degree, and on how much more work there is to be done to reduce gender inequality and drive out the ignorant attitudes and outright misogyny that allows attitudes like Lépine’s to flourish. Each year around this time there’s usually some dreck written (almost invariably by a man) about how Lépine was a lone madman, and there’s no cultural significance to the fact that he actively sought out women to murder and explicitly said that he was killing them because they were women (and assumed feminists), and right on cue, there’s an article that can only in the more generous of worlds be called drivel published in the National Post yesterday that does just that. I’m not linking to it (google it if you feel like spiking your blood pressure in anger), but the (male) author posits that the real victims are men, Conservatives, and anyone who is against the long gun registry. Apparently all three groups are “bitterly attacked” every year around the anniversary, and that’s totally more important than the fact that women face vastly disproportionate amounts of violence (domestic, sexual, physical, institutional, economic,…) every single day. If we ladies realized that we’ve bruised a few men’s egos and just stopped acknowledging that one of the most public acts of violence against women in Canadian history occurred, then everything would be peaches and sunshine!

Absolutely not. We need to drag misogyny out into the light, call it what it is, and work to dismantle it, not wring our collective hands about the dented egos of men who make every issue primarily about themselves. Dented egos do not trump institutionalized violence, and the fact that this sort of dreck can still be published in a national newspaper is indication enough that there is still considerable work to be done.

So every December 6th, regardless of how much work I have on my desk or have managed to clear off my desk, I sit down and do science. Thankfully, actions like Lépine’s are rare, but the attitude and cultural narrative that informed his actions is still pervasive, and women are still woefully underrepresented in STEM fields at all levels. It’s a small action, but it’s important to me that on a day where women were silenced for pursuing what was perceived by Lépine (and plenty of others) to be men’s rightful work, I continue to contribute my voice and my work to a similarly male-dominated field. I’m currently working on writing a paper for publication, and it’s the first paper I’m working on in my PhD. I don’t expect that scores of people will read it, but I’m proud that I can contribute to academic literature, and I’m proud to put my female name on my work. I’m fortunate that I can be a part of normalizing the presence of women and their contributions to science, so that hopefully, women and girls who follow me will have an easier path.

Memorial plaque commemorating the 14 murdered women: Geneviève Bergeron, Hélène Colgan, Nathalie Croteau, barbara Daigneault, Anne-Marie Edward, Maud Haviernick, Maryse Laganière, Maryse Leclair, Anne-Marie Lemay, Sonia Pelletier, Michèle Richard, Annie St-Arneault, Annie Turcotte, and Barbara Klucznik Widajewicz.

It’s Been A Busy Week For Space Science, Part II: Mars

There were four major announcements regarding various spacecraft last week, but the last post (on Messenger finding water ice on Mercury and Voyager 1 discovering a new region of the heliosphere) got long. So, let’s talk about Mars! Curiosity found percholates in a soil sample used to calibrate some of the instruments and make sure everything’s in working order, and NASA announced a return to Mars in the coming years.

Martian soils are complex (or at least that one patch of them is)

This announcement, regardless of what it was going to be about, was bound to be at least a bit of a letdown, since due to a misinterpretation of some ambient scientific enthusiasm, many people were expecting A Big Announcement. But, given the complexity of the rover and the array of complex analysis tools on board, news that everything is in fine working order is good news. Curiosity analyzed some loose soil in an area called Rocknest, which appears similar to other environments encountered by Pathfinder, Spirit, and Opportunity. The soil analysis was done with the APXS (alpha-particle x-ray spectrometer), the CheMin (Chemistry and Mineralogy), and the SAM (Sample Analysis at Mars), and along with verifying that everything was in good working order, the SAM detected perchlorates in the soil. Percholrates are salts with a (Cl O4) ion, and they’ve been found in other soil samples by the Pheonix lander. Perchlorates are very reactive, and there’s speculation that they may be accompanied by carbon compounds. Carbon was detected during the analysis, but it’s not entirely clear if it was from the soil sample or from a small contamination from Earth. Sulphur compounds were also discovered in the soil.

On an unrelated note, am I the only person who keeps hearing “Loch Ness” instead of “Rocknest”?

References:
NASA Mars rover analyzes first soil samples

NASA plans to return to Mars in 2020

After the interesting but still relatively minor announcement about the soil analysis on Mars, NASA announced Monday that a new rover modelled on Curiosity would be landing on Mars in 2020. Much of technology will be reused, including the elaborate landing gear and the much of the chassis, which helps keep the cost (relatively) low given NASA’s continual budget pressures. To support this new mission, NASA is planning support missions too, including:

  • MAVEN, launching in 2013, which will monitor the Martian atmosphere
  • InSight, launching in 2016, which will look at the deep interior of the planet using seismologic and geologic analysis
  • significant participation in the European Space Agency’s Electra (2016) and ExoMars (2018) missions.

Data and insight from these missions will inform the scientific direction of the 2020 rover.

I understand why NASA is taking this tack: funding is tight, to say the least, and so far Curiosity is a raging success. The landing went smoothly, all the instruments are in good working order, and the rover is immensely popular. That last bit is really important, because have a popular, very visible mission not only gives NASA a lot of good press — it gives NASA a lot of political capital, which is critical to maintaining funding. NASA has played the PR game very well, and it’s paying off. Couple a very popular and so far successful mission with a plan for another mission that is budgeted to cost less, and that’s a much easier sell to politicians who control the funding than saying “we want to go try something new again.” It’s a safe option, and there’s plenty of good reasons to take that safe option.

But it’s safe, and while there’s plenty we still don’t know about Mars, there’s plenty we still don’t know about lots of other objects in the solar system too (including oceans on our own planet, but that’s another post entirely.). Concentrating on Mars makes sense if we’re heading towards sample return (ie, having a component of the craft gather rocks or soil and return them to Earth) or eventually putting a human on Mars, and that’s what NASA is gunning for. But given the immense gap between landing a rover on Mars and landing a human on Mars, the increasing funding pressures, and the lack of a driving cultural pressure like the Cold War to spur on extreme exploration, I’m not entirely convinced that we’ll see sample return or a human on Mars in the not-wildly-distant future. I understand why NASA is trying to shoot for that, and there’s good economic and political reasons to build on Curiosity’s success — I’m just not entirely convinced that it’s a line of exploration that’ll come to it’s ultimate fruition.

However, I’d love to be proven wrong.

References:
New NASA Rover to Launch in 2020
A 2020 Return to Mars? (National Geographic)
Mars Beyond 2009

It’s Been A Busy Week For Space News

In the past week, there’ve been four major announcements from various space exploration missions. Messenger found solid water ice on the surface of Mercury, Voyager 1 has not left the solar system like initially thought, and the structure of the heliosphere is different than what we thought, Curiosity found organic molecules on the surface of Mars, and NASA is sending another rover to Mars in 2020. That’s a lot of big news for one week! This post covers the Messenger and Voyager announcements, and the next post (coming soon!) covers the two Martian announcements.

Messenger finds solid ice on Mercury

Out of all of these announcements, this is the one that astounds me. Mercury is the innermost planet, sitting in an eccentric orbit (ie, the orbit is shaped like an ellipse rather than a circle) 0.30 to 0.46 AU from the Sun, and it is also very small. It has virtually no atmosphere, since it doesn’t have much gravity to hold one in place, and the solar wind pushes gases off the planet. Because it has such a thin (and highly variable) atmosphere, there’s little insulation on the planet, and the temperature varies wildly from day (~700 K at the equator, ~550 K near the poles) to night (~100 K near the equator, ~50K near the poles). This is not planet where one’d expect to find what amount to glaciers! But there are two things that make solid surface ice possible: the presence of craters, and the planet’s spin.

Spin axes of Mercury and Earth

Spin axes of Mercury (left) and Earth (right). Poles on Mercury do not experience the relatively extreme seasonal shifts in light that Earth’s poles do.

Like any rocky planet, the surface of Mercury is not smooth, and there are craters and canyons from impacts with asteroids and comets. These craters can have steep, deep walls, which act as sunshades for the bottom of the crater. Additionally, Mercury is a very upright planet — the axis around which it rotates is nearly vertical. This means that in the polar regions, there are regions at the bottom of craters and cayons that never see direct sunlight. Because the surface temperature is so strongly dependent on incoming heat from the sun (ie, when the sun goes down, the temperatures fall ~600 degrees), the bottoms of these canyons stay cold (often ~120 K).

Shadown line due to lip of the crater.

Shadow line due to lip of the crater. At the poles, sunlight comes in at a much more oblique angle; the angle is exaggerated here since picture is not to scale. Region shaded in blue is shaded by the lip of the crater, and remains cold.

Ice vs frozen volatiles

Ice vs. frozen volatiles. Blue line indicates the shadow line, black material is frozen non-ice volatiles (including carbon compounds), and red is water ice. Note that there is a sliver of red under the black material outside of the shadow region, and in the shadow region ice dominates (though other materials may be present).

When Mercury is hit with comets or asteroids, the impact deposits not only the rocky material, but often frozen ice and volatile compounds, including carbon compounds. (Note that most carbon compounds are called “organic” — this does not mean that they were created by living organisms, or are indicative of the presence of organisms.) The ice and other volatiles migrate around the planet, vapourizing in the hot regions and condensing out in the cold, and some of the material winds up in the polar regions; material that lands in the cold patches sticks around. Additionally, the organics and non-water volatiles can act as a blanket in the transition regions, where it’s cold, but it’s not quite cold enough (or consistently enough) to sustain surface ice. In these regions, the volatiles protect a layer of ice that sits just below the surface.

NASA confirmed this with a variety of instruments. Messenger mapped the topography of the polar regions of Mercury to high precision, which allows NASA to calculate which craters have cold bottoms. The reflectivity of the surface was mapped; since ice reflects a lot of light, bright spots at the poles are evidence of solid surface ice. In contrast, organic material has a very low reflectivity, and shows up dark. The bottom of several of the polar craters had a large dark area with a smaller bright patch hugging the crater wall, which is exactly what you’d expect to see if ice and organic material were forming what amount to glaciers on the surface of Mercury. The evidence is further confirmed by the signature of hydrogen in the neutron background of the planet. A background field of neutrons is present around planets, due to interactions between the material of the planet and cosmic rays. As cosmic rays hit the surface of the planet, they interact with the material of the planet (often penetrating below the surface), and neutrons are released in the reactions. These neutrons bounce around and out of the surface, and can be detected from an orbitting spacecraft. Hydrogen (bound in water) is a very good absorber of neutrons, so patches where few neutrons are detected are regions where hydrogen (water, or ice) is likely to be found. Messenger found dark spots (so indications of high hydrogen concentrations) in the same places where the reflectivity was high and the surface temperature was consistently cold. Adding this all up means that there is frozen water in the polar regions on the surface of Mercury!

References:
Messenger finds new evidence for water ice at Mercury’s poles
Map of the permanently shadowed areas

Voyager 1 finds that the edge of the solar system is not where we thought it’d be

Voyagers 1 and 2 were launched way back in 1977, and have been slowly and steadily making their way to the outer edge of the solar system. (These are the spacecraft with the golden records, etched with samples of images and sounds of life on Earth, compiled by a committee headed by Carl Sagan.) Both Voyagers passed by Jupiter in 1979 and Saturn in 1980, and Voyager 2 passed by Uranus and Neptune in 1986 and 1989 respectively (Voyager 1 missed both planets); they’ve been drifting out of the solar system for the past 23 years.

There is a boundary between the heliosphere (which is the region where there is a solar wind, or a field of charged particles emitted by the Sun) and outer space (perhaps better called interstellar space), and earlier this year, there were indications that Voyager 1 was pretty much at what we thought that boundary was. Previously, this is what we thought the edge of the heliosphere looked like:

Schematic of the heliosphere

Schematic of the heliosphere. The solid red line indicates the termination shock (where the solar wind abruptly slows to subsonic speeds), and the solid blue line outside it indicates the heliopause, or the edge of the heliosphere (defined as the region where solar wind exists). The region between these two boundaries is the heliosheath, where both solar wind and cosmic rays can be found. Outside the heliosphere (ie, outside the blue ring) is the interstellar medium.

Solar wind zips along at 400 km/s, but it slows when it starts to interact with the interstellar medium (ie, outer space). As the wind interacts more and more with the interstellar medium, the wind slows down. The point where it slows to below the speed of sound is called the termination shock, and it marks the beginning of the edge of the heliosphere. Voyager 1 passed it in December 2004, and Voyager 2 in May 2006. The region between the termination shock and the heliopause (ie, the border between the heliosphere and outer space, or the outermost edge of the solar system) is the heliosheath, and it’s a region where the solar wind interacts strongly with the interstellar medium, and becomes turbulent. Voyager detected all this as expected, and reported in 2010 that the solar wind had no more outward velocity, that is, the particles were not pushing outwards towards outer space, but were moving around laterally. This isn’t the edge of the heliosphere, since there are still particles of solar origin: they’re just not (collectively) moving outwards anymore.

What NASA expected to see was as the charged particles of solar origin dropped off, the cosmic rays form interstellar space would increase. The particle data from Voyager 1 shows this pattern: there are extremely well defined sharp dips in the amount of solar particles which correlate to increases in the number of detected cosmic rays, and then there’s a sharp, longer, drop-off in solar particles.

Particles and magnetic field detected by Voyager 1

Particles and magnetic field detected by Voyager 1. As the solar particles dip, the cosmic rays increase, and the strength of the magnetic field increases. Note that the direction of the magnetic field does not shift at all. (Click for full size.) Image credits: Left panel: NASA/JPL-Caltech/GSFC Right panel:NASA/JPL-Caltech/GSFC/University of Delaware Images available from http://www.nasa.gov/mission_pages/voyager/telecon20121203.html

What wasn’t expected was the magnetic field data. Magnetic fields have a magnitude (or strength) and a direction; NASA expected that when Voyager hit interstellar space, the direction of the magnetic field would shift from the solar magnetic field the structure of the interstellar magnetic field. The magnitude would likely shift as well, but the shift in direction is the key indicator of the edge of the heliosphere. This wasn’t observed: while the magnitude of the magnetic field increases after the steep drop-off in solar particles (and there are noisy increases during the brief windows leading up to the eventual drop-off), the direction of the magnetic field remains constant. This indicates that the solar magnetic field is still present, and Voyager is not yet out of the heliosphere. But this increase in the strength of the magnetic field, along with the changes in the particles detected, leads scientists to conclude that the two magnetic fields (solar and interstellar) are connected in this region, which allows the charged particles of both origins to zip along more quickly. Solar particles can stream outwards into interstellar space, and cosmic rays can stream inwards towards the sun. The edge of this region (dubbed the “magnetic highway”) fluctuates, and the initial, short dips and peaks in the data are due to the edge of the magnetic highway fluctuating inwards towards the sun. Voyager appears to now be beyond the fluctuating edge of the highway.

Voyager is the first object to reach the edge of the heliosphere, and scientists suspect that this is the last stage before it finally exits the heliosphere all together, probably some time in the next year or two. But this magnetic highway stage wasn’t anticipated, so who knows what other surprises Voyager has in store for us!

References:
Voyager 1 Encounters New Region in Deep Space
Voyager mission site at JPL

In the News: Experimental Lakes Area Up for Sale?!

I’ve not written much here about the current slash-and-burn effort of the Harper government on federal environmental research (mostly through Environment Canada and the Department of Fisheries and Oceans), and at this point there’s been so many cuts and so many groups dismantled, laid off, or functionally crippled that I don’t even know where I’d begin. One of the initiatives cut is the Experimental Lakes Area, a group of 58 lakes in northern Ontario that have been set aside for whole-lake research on everything from acid rain to fresh-water contaminants to lake ecology. The ELA is unique in the world, has been running very successfully for 44 year (generating an impressive stack of research), and costs about $2 million a year to operate. It is expected to cost substantially more than that to close the project, but in the name of “cost cutting” (…right…) the Harper government has cut the funding and shut the program down.

But!

Apparently they’re looking to sell the ELA to an unspecified “interested party.” The negotiations are happening in secret (of course), so it’s totally unclear what terms the area is being sold under. The land it sits on is held by the Ontario government, not the federal one, and since the terms being negotiated are secret, I’m not sure what, if any, issues of jurisdiction would come up.

What’s really appalling is that this was a scientific jewel for the federal government. It’s known by scientists around the world (at least scientists who do research in fresh-water environments), it’s produced excellent and very important research, and it’s run on a comparative shoestring. There’s no reason to close it or sell it — other than ideological. This government has no use for good regulatory environmental research, and is hacking away at the research groups and stations that do that work. (See also: the Polar Environment Atmospheric Research Laboratory [PEARL] near Eureka, in the very High Arctic.) To first cut the funding, and then turn around and sell the area is a kick in the teeth after a slap in the face to Canadian environmental science. Since the parameters are all secret, there’s no indication of what sort of science will be done by the buyers, but if it’s in private hands, there’s no reason to believe that the scientific program will stay at all on course. Will the results of the research be publicly available? Will there be any requirement that the work done must be documented in some way, for regulatory purposes? What sort of regulation will the lakes have, if they’re not being managed by a federal department? Those are important questions to answer, and I doubt we’ll get any satisfactory answer.

Furthermore, who is funding the organization that’s buying the area, and will their interests influence the research done and the results published? From the news article linked above:

Despite the lack of public information, the coalition of scientists working to save the facility insist the IISD is the only current contender in the talks.

They say they’re concerned that a policy group doesn’t have what it takes to run an active research station. They’re also worried that the IISD’s funders — which include energy companies such as Enbridge and Suncor — could taint the research coming out of the ELA.

If this is accurate, then a world-class, governmentally run research facility known for rigourous, independent research is going to become a greenwashing research site for oil companies. Just what Canadians need!

Ada Lovelace Day: Teachers Are Important

It’s Ada Lovelace Day! October 16th is a day dedicated to women in science, technology, engineering, and math and their stories. Ada Lovelace was the first computer programmer, writing algorithms for her friend Charles Babbage’s analytical engine, and is one of many too-often unsung female contributors to scientific fields. Many of the posts and discussions on Ada Lovelace day are about semi-famous or mostly obscure scientists, engineers, and mathematicians, but I want to write about some women a little closer to home: my high school teachers.

I was blessed with an array of really excellent math and science teachers (both male and female) all through high school, and while I suspect that I’d’ve ended up in science in some fashion regardless of my high school experience, those teachers helped me find my path in that direction. Lacking that support, I’d’ve probably found it eventually, but I’m not sure I’d’ve gone to university with the confidence and conviction that I was, in fact, in the right place for me; that self-assurance really helped me adjust to university life and flourish in my undergrad, even when things got stressful and difficult.

Not all my teachers were women, but those who were remain the clearer than most of the men in my memory, and made a larger imprint on my intellectual development than the male teaches did. I learned calculus from a tiny, very unassuming looking woman who could strike fear in the heart of any surly teenager who dared cross her, and I learned chemistry from a pair of outgoing, devil-may-care women who routinely flouted sense and featured explosions and dramatic chemical reactions in their classes. The three of them showed me that science and math was exciting, interesting, and accessible to me. Their enthusiasm for their subjects was palpable, and the encouraged their female students to stick with science and math; just the fact that they were there at the front of the classroom was proof that there was a place for women in science and math. I was fortunate to have male teachers who were also supportive, or at the the very least not discouraging to their female students, but hearing and seeing it from women, who’d lived the experience of being women in mostly-male fields, carried a lot more weight. Seeing them as successful teachers, respected by their departments and for the most part their students, showed me that you could be taken seriously as a woman in science. It’s one thing to hear someone say “you should stick with math, and there’s a place for you in the field,” but it’s another thing to see a women teaching math and chemistry, talking about their previous work experiences, and showing you it’s possible and within your grasp, even if you’re a woman.

When I was younger, I didn’t know much about the history of science, and I didn’t have much of a grasp of how women and their considerable contributions have been systematically erased from the annals of science. I didn’t have heroines (or heroes really, for that matter) to look up to to say “I want to be like Ada Lovelace, or Marie Curie, or Emily Noether, or Rosalind Franklin, or….” Maybe then, in the absence of knowledge of many more famous historical or contemporary women in science, the presence of women at the front of my classrooms took on a bit of extra importance. It’s certainly important to talk about the under-appreciated contributors to science, but there’s potential (and accessible!) role models for girls in classrooms, too.

There’s lots of organizations and groups that are working to normalize the place of women in science, but it seems sensible, given the namesake of the day, to suggest having a look at the Ada Initiative, which aims to get women involved in the open source and open access community (which is very heavily male, even by computer science standards). The full directory of Ada Lovelace Day posts is here, and includes posts from previous years, and is chock full of great reading material.

Robots in Spaaaaaaaace!

I realize that most of the hubbub about Curiosity, the newest Martian rover mission, was in August after the successful landing and subsequent initial instrument tests, but is it ever too late to talk about robots on other planets? No! Consider this my tiny endeavour to keep space science in the public’s eye, even when NASA’s not just landed a small car right side up on another planet with perfect precision.

Curiosity successfully landed on August 5th, and after a perfect landing, and all the instruments are in excellent working order. The instruments on board are all described on the NASA Jet Propulsion Lab’s site, with a blurb about how they work and what sort of things they’re looking for. For this post, I’m going to focus on the Canadian instrument on board.

The Alpha Particle X-ray Spectrometer, or APXS, is the only all-Canadian contribution to the mission. It’s designed by Ralf Gellert, a professor at the University of Guelph (previously known best for cows with windows in their stomachs and pigs with phosphate-reduced poop), built by Macdonald-Dettwiler Associates (who also built the Canadarm), funded by the Canadian Space Agency, and the research involves a group at Guelph as well as people at a few other Canadian universities. I’ve got some thoughts about what the APXS represents to Canadian science and science policy, but I’ll save that for a second post. I’ve heard press about various other instruments on board, including the laser spectrometer, the array of cameras, and the meteorological station, but not very much about how the APXS works and what it can do. So let’s talk about how it works!

The APXS is a pop-can sized instrument mounted on the robotic arm on Curiosity that uses two types of radiation to determine the elemental composition of rocks, soils, and dirt on Mars. Six radioactive Curium-244 sources covered with a thin titanium foil sit around an X-ray detector. Curium (element 96), like all elements heavier than uranium (element 92), radioactively decays by emitting an alpha particle, which is 2 protons and 2 neutrons bound together. When curium emits an alpha particle, it decays to plutonium-240, which then decays with a number of daughter atoms and x-rays. The x-rays from plutonium and alpha particle from curium are the radiation used to analyze a sample; the other by-products are typically of lower energy and are filtered out from the radiation beam by a foil over the sources. This radiation streams out of the sources in all directions, but to focus the beam, a metal ring surrounds the sources and the detectors to absorb radiation radiating at a wide angle.

Photo and schematic of the APXS

Left: Photo of the APXS. The detector itself sits in the middle of of the ring behind the sources. Photo from JPL. Right: A schematic of how the APXS works. The instrument is shown as if it were pointing at a table-top. Picture from the University of Guelph.

Two kinds of radiation are used so that a wide range of elements can be detected. The alpha particles are used for Particle Induced X-ray Emission, or PIXE, which is used to detect elements with a low atmoic number. The X-ray radiation is used in X-ray Fluorescence, or XRF, and detects elements with a higher atomic number. Combining the the two technique means that elements from sodium (atomic number 11) to zirconium (atomic number 40) can all be clearly detected in the combined spectrum.

In PIXE analysis, particles (alpha particles here, but other particles like protons can also be used) are beamed at a sample. The particles are emitted with a known, fixed energy and collide with the atoms in the sample, where some of the particles will interact with the inner shells of the electron structure. Electrons in an atom sit in a series of increasingly energetic levels, each with a fixed energy. If a particle hits the atom and interacts with an electron, it imparts energy to the electron. Since the electron can only have a fixed amount of energy at any given level, if it gains energy it must jump up to a higher level, which leaves a gap in the original level it started at. An electron from a higher energy level (not necessarily the one that originally jumped up to a higher level) then falls down to fill the gap in the lower energy shell, and emits an X-ray with the difference in energy between the two levels to conserve energy. This is clearer with a picture!

Schematic of PIXE process.

Alpha particle comes in, excites electron and scatters off, then an electron (either the one that was bumped up in energy or another one) fall to a lower energy and the atom emits an X-ray carrying the difference in energy between the starting and finishing energy levels of the second electron (ie, the electron that drops down in energy).

The process is dependent on the inner (ie lower energy) shells of electrons interacting with the incoming particle. The particles are most likely to interact with the outermost shell or two of the electron levels of an atom, so if an atom has several shells, there’s too many electrons shielding the lower energy electrons for many interactions to occur. PIXE is then most effective for atoms with a low atomic number.

XRF does much the same thing, but instead of using a particle to induce the electron’s transition, it uses X-rays. X-rays are useful because they can interact more easily with a inner-shell electrons in heavier elements than the massive alpha-particles. XRF is then more useful for detecting heavier elements that PIXE cannot, but because the efficiency of the process is low at low atomic number, PIXE (which is a more efficient process at low atomic number) is needed to gather a robust spectrum.

But doing PIXE and XRF on Mars poses problems: even the very thin Martian atmosphere will absorb low energy X-rays, so the lightest element that the APXS can detect is sodium (atomic number 11). Hydrogen, carbon, nitrogen, and oxygen (atomic numbers 1, 6, 7, and 8 respectively) are all invisible to the APXS, and oxygen in particular is abundant in the samples. Most of the heavier elements are present as oxides, so the mineralogy becomes very important in the elemental analysis. Plus the atmosphere varies, like any atmosphere, and the temperature fluctuates, and generally the conditions are not as pristine as they are in a controlled lab setting. This means that there’s more calibration work needed on Mars than in the lab, and also that the invisible elements need to be carefully treated.

So when a sample is being analyzed, Curiosity’s robotic arm extends (slowly and carefully, to avoid any collisions) out towards the sample rock. A pressure sensor on the front of the instrument trips when the instrument touches the rock, and the protective doors that cover the aperture of the instrument when it’s not in use open. The electronics are switched on, and the detector starts to gather a spectrum of X-rays emitted at various energies from the sample. The instrument is left in place for a between a few minutes and a few hours to gather data, which is stored and then beamed back to Earth in the daily data dump. When it’s finished collecting data, the arm moves back from the rock, the doors close, and the next sample is chosen.

The spectra that come back look something like this:

A typical spectrum from the APXS, taken from Spirit

A typical APXS spectrum. The horizontal axis is energy of the detected x-ray, and the vertical axis is the number of x-rays of a given energy detected. Image from JPL.

The horizontal axis is the energy of the detected X-ray, and the vertical axis is the number of X-rays detected at that energy. The spectra consist of peaks at specific energies, and the individual elements are identified by the energies of a series of characteristic electron transitions. The emitted x-ray of a given transition has a fixed energy, equal to the difference in energy between the two states of the electron. Since different elements have different atomic structures and different amounts of energy between the electron shells, the x-rays emitted by different elements undergoing either PIXE or XRF will have different energies. Working backwards, then, if a spectrum is collected and there is a peak at an energy corresponding to a transition of a given element, then that element is present in the sample. The precise composition of the sample is determined by calculating the relative area under each of the peaks.

The invisible elements complicate the analysis considerably, especially since there’s so much oxygen in the rocks. The mineralology of the rocks must be accounted for, and information from other instruments (including the cameras — visual identification is very helpful) is used to make initial estimates of the proportion of each element in its various oxidation states. For example, iron oxide may be ferrous (FeO) or ferric (Fe2O3), though to the spectrometer, it’s all just iron. So to do the analysis, knowledge about similar rocks on Earth is used to estimate the proportion of iron in each oxidation state. After all the expected oxygen from the bound minerals is accounted for, any “invisible element” left over may be bound water. Many minerals have water bound within the crystals, and Spirit and Opportunity found evidence of bound water in Martian rocks using this analysis.

Spirit and Opportunity were sent to Mars to find water in some form (and did!), while Curiosity was sent to examine whether or not at some point in its geological history, Mars could’ve sustained life. It’s important to note that it’s not looking for *life*, just evidence that conditions hospitable to life once occurred. Due to the raging success it’s had on Mars (the instrument on Opportunity is, to the best of my knowledge, still functioning, eight and a half years into a 90 day mission), other APXS’s are planned for missions to the Moon by the Indian and Russian space associations (the Chandrayaan-2 rover, landing hopefully in 2016) and to Comet 67P/Churyumov-Gerasimenko by the European Space agency (the Philae lander, landing in 2014).

More info:

  1. A summary of the APXS by the Canadian Space Agency
  2. One of the papers outlining the design of the first APXS used on Mars on the Pathfinder mission
  3. Major paper with results from the instrument on Spirit, one of the two Mars Exploration Rovers

The Scientists Strike Back

With some notable exceptions, scientists are not generally habitual rabble-rousers, at least not in their capacity as an Official Representative Unit of Science. In my experience, many of them have deep political convictions, and are not shy about sharing them, but going out on the street en masse as scientists (rather than as ordinary citizens) is not a common sight — I can’t remember the last time scientists took to the streets to protest policy. So when a couple thousand of scientists in lab coats and funeral wear converge on Parliament protesting the Death of Evidence, something is going on.

The Death of Evidence protest was organized by some scientists (mainly grad students, I believe) at the University of Ottawa, and was timed to coincide was a very large evolutionary biology and ecology conference in Ottawa to attract more marchers from across the nation. The list of policies that the protest was targeting is long and broad:

The Harper government has embarked on a systematic program to impede and divert the flow of scientific information to Canadians through two major strategies. The first involves the gutting of programs and institutions whose principal mandate is the collection of scientific evidence. Examples of this include:

  • Cutting the mandatory long-form national census.
  • Major budget reductions to research programs at Environment Canada, Fisheries and Oceans Canada, Library and Archives Canada, the National Research Council Canada, Statistics Canada, and the Natural Sciences and Engineering Research Council of Canada.
  • Decisions to close major natural and social science research institutions such as the world-renowned Experimental Lakes Area, the National Council of Welfare and the First Nations Statistical Institute.
  • Closing of The Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Nunavut

Mr. Harper’s second strategy is perhaps less overt, but even more insidious: to impede the bringing forward of scientific evidence into the public debate. Examples:

  • Not renewing the The National Science Advisor in 2008.
  • Dozens of instances of censoring of, impeded access to, and coercion of government scientists, a practice which Minister of Environment Peter Kent has justified as merely in keeping with “established practice”.
  • Shutting down the National Round Table on Environment and Economy (NRTEE), an arm’s length advisory body providing independent advice on environmental protection and economic development, because the government didn’t like its advice.

This is beyond death by a thousand papercuts: this is more like death by hundreds of axe wounds. I’m not saying that every federally-funded science initiative needs to be funded in perpetuity without any evidence (there’s that word again!) that it’s viable and productive research. I am saying that when multiple scientifically flourishing initiatives are having their funding unceremoniously ended, with no credible evidence presented to back up that decision, things start to fail the sniff test.

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