Category Archives: Science

Interplanetary Copters!

The last decade has seen an incredible bloom in small autonomous and remote controlled helicopters, AKA drones. It isn’t far wrong to call them ubiquitous, and probably the characteristic technology of the 2010s. (Sorry Siri.)

It isn’t surprising, then that NASA (the National Aeronautics and Space Admin.) has some ideas about what to do with robot helicopters.

This month it is confirmed that the next planned Mars rover will have a copter aboard [3].  (To date, this appears to be known as “The Mars Helicopter”, but surely it will need to be christened with some catchy moniker. “The Red Planet Baron”?  “The Martian Air Patrol”? “The Red Planet Express”?)

This won’t be a garden variety quad copter.  Mars in not Earth, and, in particular, Mars “air” is not Earth air. The atmosphere is thin, real thin, which means less lift.  On the other hand, gravity is less than on Earth. The design will feature larger rotors spinning much faster than Terra copters.

Operating on Mars will have to be autonomous, and the flying conditions could be really hairy. Martian air is not only thin, it is cold and dusty.  And the terrain is unknown.  The odds of operating without mishap are small. The first unexpected sand storm, and it may be curtains for the flyer.  Mean time to failure may be hours or less.

Limits of power and radios means that the first mission will be short range. Unfortunately, a 2 kilo UAV will probably only do visual inspections of the surface, albeit with an option for tight close ups.  Still it will extend the footprint of the rover by quite a bit, and potentially enable atmospheric sampling.


This isn’t the only extraterrestrial copter in the works.  If Mars has a cold, thin atmosphere, Saturn’s moon Titan may have methane lakes and weather, and possibly an ocean under the icy surface.   Titan also has a cold thick atmosphere, and really low gravity—favorable for helicopters!

Planning for a landing on this intriguing world is looking at a copter, called “Dragonfly” [1, 2]. The Dragonfly design is a bit larger, and is an octocopter. <<link>>  (It is noted that it should be able to continue to operate even if one or more rotors break.)  Dragonfly is also contemplated to have a nuclear power source—Titan is too far away for solar power to be a useful option.

Titan is a lot farther away than Mars, and communications will be difficult due to radiation and other interference.  The Dragonfly will have to be really, really autonomous.

Flying conditions on Titan are unknown, but theoretically could include clouds, rain, snow, storms, who knows.  The air is methane and hydrocarbons which could gum up the flyer. Honestly, mean time to failure could be zero—it may not be able to even take off.


Both these copters are significantly different from what you might buy at the hobby store or build in your local makerspace.  But prototypes can be flown on Earth, and the autonomous control algorithms are actually not that different from Earth bound UAVs. This is a good thing, because we have to program them here, before we actually send them off.

In fact, I think this is one of the advantages of small helicopters for this use. Flying is flying, once you adjust for pressure, density, etc. It’s probably not as tricky as driving on unknown terrain.  We should be able to design autonomous software that works OK on Mars and Titan.  (Says Bob, who doesn’t have to actually make it work.)


Finally, I’ll note that a mission to Titan should ideally include an autonomous submarine or better, a tunneling submarine, to explore the lakes and cracks. I’m sure this is under study, but I don’t know that it will be possible on the first landing.


  1. Evan Ackerman, How to Conquer Titan With a Nuclear Quad Octocopter, in IEEE Spectrum – Automation. 2017. https://spectrum.ieee.org/automaton/robotics/space-robots/how-to-conquer-titan-with-a-quad-octocopter
  2. Dragonfly. Dragonfly Titan Rotorcraft Lander. 2017, http://dragonfly.jhuapl.edu/.
  3. Karen Northon, Mars Helicopter to Fly on NASA’s Next Red Planet Rover Mission, in NASA News Releases. 2018. https://www.nasa.gov/press-release/mars-helicopter-to-fly-on-nasa-s-next-red-planet-rover-mission

 

We must go to Titan! We must go to Europa!

Ice Worlds, Ho!

Robot Wednesday

Roman Lead Pollution in Greenland Ice Cores

While it lasts, the ancient ice of Earth contains a record of the atmosphere, containing tiny bubbles of air, as well as whatever was in the air, including pollen and volcanic ash.  Ice also preserves traces of human activity, AKA pollution.

This spring an international team reports on a careful study of the chemistry of 423 meters of ice cores from Greenland, which they date to run from 1200 BCE to 1200 CE, some 2500 years [1].

The measurement found fluctuating traces of lead and copper apparently dating to historical times.  Given the location of Greenland, these metals presumably reflect emissions into the atmosphere from Europe.  The new study corroborate earlier isotopic analyses, showing that prevailing winds would transport emissions from ancient European activity to Greenland, while other putative sources would have little representation in Greenland ice. The study also compared the temporal patterns to lead traces in peat bogs, and found them to match.

The lead particulates are hypothesized to be from silver lead mining activity, in which high temperature smelting used lead as part of the process of recovering silver.  The process would have emitted lead into the air at major mining sites, such as Spain.  These would blow to Greenland, leaving a record of the mining activities in the ice.

While the record is variable and uncertain, there are periods of sustained high levels of lead in the record.  These were found to correllate with overall economic activity and presumably the intensity of mining.

The researchers report swings in mining that match recorded wars in Spain, which they argue reflects the disruption and intensification of silver mining due to political developments.

“The repeated pattern of dips in production coinciding with the outbreak of wars primarily affecting the Iberian Peninsula, and then recovery again after the end of each war, suggests that warfare caused major interruptions to lead–silver production during the middle and late Roman Republic.” (p. 2)

The sustained peace of Pax Romana is detectable in a long period of high lead levels in the Greenland ice, which ends at the time of a great plague.  This period probably reflects emissions from a number of sites in Northern Europe besides Spain. This peak drops off around 9CE, “coincident with Roman abandonment of territory to the east of the Rhine, including the Sauerland mines, after three legions were annihilated in the Teutoburg forest.” (p. 3)

The activity remained low until circa 800CE, a time when mining was intensified in medieval France and Britain. There is an earlier spike that is attributed to Phoenician activity, though there is no detailed record of mining in that period.

Finally, they find that these fluctuations in lead pollution tracked the metal content of Roman currency. Drops in the lead in Greenland correspond to periods of lower silver content in coins, presumably due to low production from silver mines.

“The fluctuations in lead–silver mining and smelting indicated by the Greenland lead pollution record and estimated lead emissions were directly reflected in the fineness and metallurgy of Rome’s silver coinage, the denarius…” (p. 3)

This is a pretty cool study, and the detailed dating of the records is pretty impressive.  Cross referencing peat bogs, volcanic activity, and historical records is a good idea, though I worry that the study is combining multiple imperfect measurements, hoping the combination is better rather than worse.

A key of the study is the simulation of the atmospheric deposition, and I worry that it is logically circular.  This kind of simulation is tricky under any circumstance, and projecting thousands of years into the past is problematic. The researchers are well aware of this, and are reasonably careful about how they use the simulations. They look at general circulation patterns, not short term events, projecting from the last century of detailed data reports.

There are two questions that nag me about though.  First, there is an assumption that the general circulation is basically unchanged over the last 3000 years. I’m not sure that is true, but it may well be true for the effects of interest in this study (i.e., wind blown particles transported from Europe to Greenland).  I simply don’t know. If there was a big enough change in wind patterns during the period, this could show up as a drop in lead that has nothing to do with mining activity.

The study makes a number of claims about the sensitivity of the Greenland ice record to sources in different geographical locations (Figure 1 in the paper).  Mostly, this is a matter of distance, which is straightforward.  But they also find some substantial differences in locations not that far apart (Spain versus Britain versus  Germany), from which they infer proportionate responsibility for the lead pollution.

Essentially, they work backward from the measured lead to various potential sources where ancient mining was known to have occurred. Granting these calculations are mainly correct, they are mainly looking at known sources from the historical and archaeological record. If there are other sources, they would be difficult to detect in this methodology, and they would be misestimating the contributions of the known sources. If there are other mines unaccounted for, the whole result could be way off.

Future work may be able to extract detailed isotope composition from the deposits, which might reveal the sources more directly. I fear that that will be difficult to achieve from these ice cores.

These simulations are aligned with known history, but that is (literally) post hoc reasoning. Basically, they are able to find explanatory events for major changes in the lead pollution, including at least one surprise (i.e., the outsized effects of the Antonine plague, among sever plagues and wars).  Yet there are plenty of other events that do not show up in the lead pollution record.  I would note that the history of the metallic content of Roman coins is complicated, and not necessarily tied to the production of silver as the key factor.

In short, the perceived correlation between the ice core records and historical events is self-confirming.  Who knows how many alternative events might be chosen that do not match the ice cores as well?

In any case, the study doesn’t actually reveal any new findings. It shows that ancient industrial activity may well be reflected in Greenland ice, and that pollution seems to be correlated with the overall mining activity in Europe and the Mediterranean (but not China or other more distant locals). In fact, it would be surprising if this were not true.

What the study does seem to prove is that methods have improved to be able to at least provide detailed support for this kind of historical hypothesis, even if it isn’t really able to confirm or deny detailed hypotheses.


  1. Joseph R. McConnell, Andrew I. Wilson, Andreas Stohl, Monica M. Arienzo, Nathan J. Chellman, Sabine Eckhardt, Elisabeth M. Thompson, A. Mark Pollard, and Jørgen Peder Steffensen, Lead pollution recorded in Greenland ice indicates European emissions tracked plagues, wars, and imperial expansion during antiquity. Proceedings of the National Academy of Sciences, 2018. http://www.pnas.org/content/early/2018/05/08/1721818115.abstract

Sitting on Dinosaur Nests

It has long been known that many species of dinosaurs laid eggs. Eggs and eggshells have been found, sometimes with identifiable embryos.  And nests have been found with strong evidence of parental minding.  We don’t know all the different ways dinosaurs may have built nests and tended their eggs, but we know that some made nests on the ground and apparently sat on the eggs similar to modern birds.

Of course, modern birds are relatively small and light compared to their theropod ancestors. Sitting on eggs is a delicate matter, so how would a half-ton mama manage it?

This month an international team reports a study of dinosaur nests which suggests that many species sat on their nests, even very large animals [2].  The trick is how the nest is arranged.

The study examined well preserved fossil nests of several related species ranging from approximately 40 kg to 1500 kg in body weight.  For comparison, a contemporary ostrich will weigh about 100 kg, so these animals ranged much larger than birds.

All the species in this family laid eggs in a circle, with a mound in the middle and a ditch around the outside. The nests in this study were mostly open, i.e., were not buried as with modern crocodiles. As might be expected, the larger species laid larger eggs which probably had thicker and stronger shells. However, eggshells cannot be too strong, or the baby can’t get out, so even the bigger eggs would be fragile.

Regardless of nest size, all eggs are inclined and arranged in a radial pattern within a ring-shaped clutch “ ([2], p.3)

The key finding is that the outer ditch and center mound were larger in the larger species. That is, larger animals laid their (generally larger) eggs in a larger diameter circle, with more room in the middle.  This makes sense, assuming that the center area was a place where the parent could stand and sit.

Image caption Illustration: nesting behaviours of large and small oviraptorosaurs Image credit: Masato Hattori. [From BBC]
The authors note that this adaptation is not seen in contemporary birds. They speculate that this arrangement may have meant less contact with the eggs for the larger animals, which may be less advantageous than other styles, including the nesting styles of contemporary birds.  Perhaps this factor selects for relatively small body size accompanied by sitting directly on eggs in the next.

By the way, other investigations suggest that these eggs were probably blue-green.


  1. Mary Halton, Dinosaur parenting: How the ‘chickens from hell’ nested, in BBC News -Science & Environment. 2018. http://www.bbc.com/news/science-environment-44071223
  2. Kohei Tanaka, Darla K. Zelenitsky, Junchang Lü, Christopher L. DeBuhr, Laiping Yi, Songhai Jia, Fang Ding, Mengli Xia, Di Liu, Caizhi Shen, and Rongjun Chen, Incubation behaviours of oviraptorosaur dinosaurs in relation to body size. Biology Letters, 14 (5) 2018. http://rsbl.royalsocietypublishing.org/content/14/5/20180135.abstract

Neurochemically Implanted Memory

Yet another “impossible” finding from California—implanted memories.

Researchers from UCLA report a rather elegant study that showed the transfer of memory by transferring RNA from one snail to another [1].   The study is pretty clear evidence that the RNA some how encodes the memory, which means that it likely is encoded in the genome of the neurons (i.e., as some form of epigenetic change in specific cells).

Whoa!

Prof Glanzman said: “If memories were stored at synapses, there is no way our experiment would have worked.” (quoted in [2])

(Even back when I was an undergraduate psych major, I personally never believed that memories were stored in synapses, at least not entirely.  I’m gratified, if astonished, to learn of this RNA mechanism.  Told ya.)

The study itself used snails Aplysia californica, which have nice simple nerve systems. Essentially, some snails were “taught” to expect a shock, which made them pull into the shell for a period.  The trained snails stay in longer in response to a shock than untrained snails.

RNA from the trained snails was injected into untrained snails, which acquired the signal behavior.  Again: Whoa!

The report explains the methods, including the careful control conditions. Among other things, the study offers strong evidence that the RNA is modifying the DNA of the neurons (i.e., the memory is encoded in the DNA, and the RNA is transferring it from one neuron to another).  Furthermore, the RNA affects only sensory neurons, not motor neurons (i.e., the sensory learning is encoded only in sensory neurons).

Together, the results indicate that this case of sensory learning is encoded via the DNA of a subset of neurons (the “sensory” neurons), and is transferred to other neurons via RNA.  This would be a mechanism for memory “spreading” and strengthening, as whatever the trace is becomes encoded in more neurons.

There are many open questions here.  For one thing, this study does not reveal what modifications are happening in the DNA, and how they result in the behavioral change.  In the same vein, it isn’t known what controls which neurons are affected by this process.


Aside from the pure wonder of maybe identifying a DNA-based epigenetic mechanism for engrams, this study raises a lot of interesting questions to investigate.

First of all, this particular study is just one kind of ‘memory’, and a pretty simple one. However this case is encoding the engram, I would think that there are likely many ways that “memories” are encoded. There could be specific “codes” for different kinds of memories, and for different classes of neurons.

The localization of this effect is very intriguing.  The RNA picks up the memory from a specific neuron, and even though the RNA may float everywhere, it is picked up only by certain other neurons.  This suggests that neural specialization is tagged somehow in the DNA (epigenetically) in the neurons.  How does this work?

I also wonder about how this process interacts with all the other possible epigenetic actions.  There will be more than one “memory” floating around, and who knows what other signals, diseases, and what not.  How do these interact?  This complex of epigenetic process might ultimately have a role in forgetting, interference of different memories, and pathologies.  Wow, this is going to get complicated!

As a software guy, I wonder about the encoding scheme(s).  What is the “grammar” and other logical of this mechanism?  What sort of error detection/correction might exist?  Are there individual differences, i.e., idiomatic or group variations in memory encoding?

This study was short term. How does this mechanism operate over time.  For that matter, does the mechanism change over time. (Learning to learn?)  How does it unfold over the life of an animal?  Is it possible for a mother’s RNA to cross into a fetus, and if so, does than potentially affect the growth of an infant’s brain?

Philosophically, it is interesting to think about this RNA transfer as part of a spectrum of methods for transferring “engrams” from one organism to another.  Behavior and language might be seen as indirectly fiddling with the receiver’s genome (signal->perception->neural encoding->RNA->additional neural encodings).

It is also interesting to think about the subtle different between “genetic” and “epigenetic” mechanisms driving behavior.  Nature vs. nurture is kind of moot in a case where “nurture” is directly modifying “nature”!

 

  1. Alexis Bédécarrats, Shanping Chen, Kaycey Pearce, Diancai Cai, and David L. Glanzman, RNA from Trained Aplysia; Can Induce an Epigenetic Engram for Long-Term Sensitization in Untrained Aplysia. eneuro, 2018. http://eneuro.org/content/early/2018/05/14/ENEURO.0038-18.2018.abstract
  2. Shivani Dave, ‘Memory transplant’ achieved in snails, in BBC News – Science & Environment. 2018. http://www.bbc.com/news/science-environment-44111476

 

The Water Plumes Of Europa

Europa is interesting.  Very interesting.

It is one of at least seven “ocean worlds” in our solar system.

Orbiting Jupiter, Europa is warped and headed by the tides generated by Jupiter’s gravitation. This means that there is an ocean of liquid water, possibly larger than all of Earth’s oceans.

This ocean is covered by ice. The ice shell has not been conclusively measured, but it seems to be thin (10s of KM), and full of cracks through which tides drive ligquid water to the surface.

This active, water rich geology appears to have all the prerequisites for life. Water, chemicals, energy, tidal action, gnarly geometry.  These are the signatures of fertile habitats on Earth.  Is there life under the ice?  I, for one, want to know.

To date, we have limited direct measurements of Europa.  Hubble and ground based telescopes have imaged it from afar. In the first wave of exploration, the Voyagers flew by, and the Gallileo probe obtained the best images so far of Europa, with old and only partly working technology [2].

It is obvious why Europa is a high priority for additional visits with much better instrumentation and eventually, landers.

In the mean time, we can pour over the data we have.

This month researchers report an analysis of data from the Galileo mission from 1997.  The data is measurements of the magnetosphere and plasma that the spacecraft encountered as it passed close to Europa (200 KM).  This data features a transient event, which was difficult to interpret.

The new study suggests that the measurements are related to Europa, and, in fact, represent traces of a volcanic plume of water spewed into space.

This study developed a detailed computational simulation of the plasma and ions near Europa.  Introducing a plume consistent with the telescope observations, and showed that the model closely aligns with the hitherto unexplained measurements from Galileo.  They conclude that the spacecraft did, in fact, fly through the traces of a plume of water from inside Europa.

In itself, this result isn’t too surprising.  It does support hypotheses that Europa not only has an ocean and an active icy crust, but like Enceladus, Titan, and other moons, is volcanically active.

Where there are volcanoes, there is the possibility of life as we know it.

We must go to Europa.

  1. Kenneth Chang, Europa, Jupiter’s Ocean Moon, May Shoot Plumes of Water Into Space, in The New York Times. 2018: New York. https://www.nytimes.com/2018/05/14/science/europa-plumes-water.html
  2. Richard J. Greenberg, \Unmasking Europa: the search for life on Jupiter’s ocean moon. 2008, Copernicus Books: New York.
  3. Xianzhe Jia, Margaret G. Kivelson, Krishan K. Khurana, and William S. Kurth, Evidence of a plume on Europa from Galileo magnetic and plasma wave signatures. Nature Astronomy, 2018/05/14 2018. https://doi.org/10.1038/s41550-018-0450-z

 

A One D Material??

These days, I never know what is and isn’t scientifically possible.

So a headline about a “One-Dimensional Material Packs a Powerful Punch for Next Generation Electronics” caught my eye [2].  I don’t even know what that could mean.  I mean electrons are at least four dimensional, right?  So “electronics” would have to be at least that.

But you never know.  So I looked up the actual paper [1].

Right away, the title says it all: it’s “Quasi-1D”.  Not that I know exactly what that means.

In this context, “2D” means a sheet that is one atom thick.  So “1D” is a chain of atoms, one atom thick, and one atom wide.  (The also call them “nanoribbons”.)

The actual technique is interesting because it is a really good conductor, fifty times the current density of copper wire.  This is due to the fact that the nanoribbons are “single-crystal atomic chains in one direction”, which have no impurities or boundaries to scatter electrons.  Basically, electrons can flow extremely efficiently—in only one direction.

In short, this is a candidate for really tiny interconnects (something like 1 nm x 1 nm cross section) in really tiny devices.

This technology is said to be competitive with Carbon nanotubes for performance and may be easier to manufacture.

This is very cool, if technically still at least four dimensional.


  1. A. Geremew, M. A. Bloodgood, E. Aytan, B. W. K. Woo, S. R. Corber, G. Liu, K. Bozhilov, T. T. Salguero, S. Rumyantsev, M. P. Rao, and A. A. Balandin, Current Carrying Capacity of Quasi-1D ZrTe3 Van Der Waals Nanoribbons. IEEE Electron Device Letters, 39 (5):735-738, 2018. https://ieeexplore.ieee.org/document/8327938/
  2. Holly Ober, One-Dimensional Material Packs a Powerful Punch for Next Generation Electronics, in UCR Today. 2018. https://ucrtoday.ucr.edu/53240

 

 

More Insight Into the Frog Fungus Catastrophe

For the past several decades there has been an alarming world-wide decline in frogs and amphibians.  Many species all over the world have been dying from an epidemic of skin fungus [1]. It hasn’t been clear what has caused this die off, and I, for one, think we need to know what’s going on.

This spring a new study analyzed the genomes of the pathogens, and traces them back to a common ancestor in the mid twentieth century in Asia [3]. This finding suggests that a strain of fungus has spread from Korea to all parts of the world relatively recently.  The obvious suspect is human trade, including the pet trade.  It seems likely that the fungus was inadvertently carried with animals as part of the exotic pet trade, and has escaped into wild populations everywhere, mutating into local variants.

The research sequenced the whole genome of samples of the Batrachochytrium dendrobatidis from all continents affected, which have infected all classes of amphibians. The analysis improved earlier efforts, and developed a taxonomy indicating the fungus originated in East Asia. Further analysis suggests that the lineages diverge from the East Asian strain during the twentieth century.

(These findings are based on rather elaborate statistical reasoning which I admit I don’t understand very well.  In other words, I can neither confirm or debunk the specific findings myself.)

The overall conclusion points to the infection spreading from East Asia to many parts of the world at jsut the time when human trade, especially the trade in exotic pets, was exploding.  This conclusion is supported not only by the geographical evidence but the identification of the pathogen in contemporary trade animals (including scientific specimens).


If this conclusion holds up, it is both good and bad news.

It is good news that there isn’t some kind of mutant super fungus out there, or an unknown super vector spreading infection in some mysteriously sudden way. It is also good news that this isn’t directly due to climate changes or habitat losses, per se.

The cause is well understood:  Humans.  Again.  This is not the first, and will not be the last epidemic attributed to human trade.

Of course, it is bad news because the cat—or amphibian—is already out of the bag.  There isn’t much way to undo this, though clamping down on trading in amphibians could reduce further infection and reinfection. The odds on changing human behavior are, well, not so good, though.

The study also contains additional news, in that there are multiple pathogens now. [2] As the infection spread around the world, it has adapted and evolved in different locations and populations.  In fact, they found evidence that the alternative strains have met and recombined in several cases.  So there isn’t one malady, there is complicated and changing web of infections.


  1. BBC News, Origins of amphibian-killing fungus uncovered, in BBC News – Science & Environment 2018. http://www.bbc.com/news/science-environment-44075687
  2. Karen Lips, The hidden biodiversity of amphibian pathogens. Science, 360 (6389):604, 2018. http://science.sciencemag.org/content/360/6389/604.abstract
  3. Simon J. O’Hanlon, Adrien Rieux, Rhys A. Farrer, Gonçalo M. Rosa, Bruce Waldman, Arnaud Bataille, Tiffany A. Kosch, Kris A. Murray, Balázs Brankovics, Matteo Fumagalli, Michael D. Martin, Nathan Wales, Mario Alvarado-Rybak, Kieran A. Bates, Lee Berger, Susanne Böll, Lola Brookes, Frances Clare, Elodie A. Courtois, Andrew A. Cunningham, Thomas M. Doherty-Bone, Pria Ghosh, David J. Gower, William E. Hintz, Jacob Höglund, Thomas S. Jenkinson, Chun-Fu Lin, Anssi Laurila, Adeline Loyau, An Martel, Sara Meurling, Claude Miaud, Pete Minting, Frank Pasmans, Dirk S. Schmeller, Benedikt R. Schmidt, Jennifer M. G. Shelton, Lee F. Skerratt, Freya Smith, Claudio Soto-Azat, Matteo Spagnoletti, Giulia Tessa, Luís Felipe Toledo, Andrés Valenzuela-Sánchez, Ruhan Verster, Judit Vörös, Rebecca J. Webb, Claudia Wierzbicki, Emma Wombwell, Kelly R. Zamudio, David M. Aanensen, Timothy Y. James, M. Thomas P. Gilbert, Ché Weldon, Jaime Bosch, François Balloux, Trenton W. J. Garner, and Matthew C. Fisher, Recent Asian origin of chytrid fungi causing global amphibian declines. Science, 360 (6389):621, 2018. http://science.sciencemag.org/content/360/6389/621.abstract

 

PS.  Wouldn’t “Frog Fungus Catastrophe” be a good name for a band?