News Feeds

Quickie with Steve: Global Warming and Ocean Currents; News Items: Infrared Contact Lenses, Trees Respond to Solar Eclipse, Affective Polarization, The Brain's Motor Switchboard, New Dwarf Planet Candidate; Discussion: The Effect of Science Fiction; Your Questions and E-mails: HHS Cancels Vaccine Contract; Science or Fiction

Today we have a historical/natural history post by reader Lou Jost, who works as a naturalist and evolutionary biologist at a field station in Ecuador.

A diatom sample from the HMS Challenger expedition of 1872-76

The Challenger in 1873, painting by Swine

The HMS Challenger was a British naval ship equipped with both sail and steam power. At the urging of scientists, and riding the wave of popular curiosity about our then-poorly-known planet, the ship was converted by the Royal Society of London to become the world’s first specialized oceanographic vessel. It went on a mission from 1872 to 1876 to systematically explore the world’s oceans, especially the scientifically almost completely unknown Southern Ocean near Antarctica. This mission was the 19th century equivalent of a trip to the moon or to Mars (except that this  HMS Challenger mission had a much more interesting and diverse subject region!).

One of the navigators, Herbert Swine, made contemporaneous drawings and paintings on site, including the two HMS Challenger images I have shared here (though these were probably polished somewhat for publication). He also published his lively diaries of his time on the expedition, in two volumes, just before he died of old age. He was the last survivor of the crew.

A map of the expedition

The voyage of exploration went 80,000 miles, lasted 1250 days, and circumnavigated the globe. They made systematic chemical, temperature, and depth readings across the globe, taking biological specimens along the way. They discovered over 4000 new species, from vertebrates to phytoplankton, and lost several lives along the way. They were the first to systematically explore the mid-Atlantic Ridge, and by pure chance they also discovered the Marianas Trench,  the deepest part of the Pacific Ocean. In 1950-1951 a modern vessel, again bearing the name Challenger in a homage to the original, found the deepest part of any ocean, the “Challenger Deep”, just 50 miles from the HMS Challenger’s deepest depth record.

The Challenger at work

The immense number of samples obtained by the crew of the Challenger took 19 years to analyze and publish, in 50 volumes. Specimens were sent to many scientists of the time, and some of these still circulate today. Among the most interesting organisms they sampled are diatoms. Diatoms are single-celled organisms that make up much of the oceans’ phytoplankton, and their most notable features are the finely sculpted glass cases called “frustules” that enclose them. These glass frustules are often preserved intact for tens of millions of years, sometimes forming enormous deposits of pure frustules known as “diatomaceous earth” on the beds of ancient lakes and oceans. Some of these deposits are so big that millions of tons of diatom frustules thousands of years old are whipped up by the wind in dry parts of Africa every year, and then cross the Atlantic by air and rain down on the Amazon basin in South America.

The expedition of the HMS Challenger launched the most systematic study of the 19th century on the diatoms of the Southern Ocean. They sampled at regular intervals during their voyage, and at multiple depths, including very deep water that had never before been studied, discovering new species of diatoms such as Asteromphalus challengerensis, named after the vessel (using bad Latin unfortunately). The samples were distributed to diatomists around the world, who carefully mounted them on microscope slides using special mountants of high-refractive-index liquid, designed to make the transparent diatom frustule more visible under standard microscopic illumination. Some of these Challenger diatom slides come up for sale periodically, and I could not resist buying one that appeared in eBay.

Increasing zooms of the diatoms on the slide:

This one slide, from 1873 during an Antarctic visit, has hundreds of individuals consisting of maybe a couple of dozen species. There are also many broken diatom fragments. Among the individuals, I was lucky enough to find several examples of what appear to be the aforementioned A. challengerensis. This is a rare species which is found only in water that is within 1 degree Centigrade of freezing. The taxonomy of this species and its relatives is in flux as we learn more about how the structures change with age.

Two slides of the species A. challengerensis:

Some of the taxonomic problems of these diatoms is caused by their weird way of replication. Diatoms can’t grow like a normal organism because they are in a glass case, so instead they shrink, each half of the frustule making a new matching half that is slightly smaller than the parent half-frustule, so that the two new halves each nest inside their parent half-frustule. Then they separate. Here is a nice illustration of this:

The population thus has a large spread of different sizes, and it appears that some frustule features may change as they get smaller, causing taxonomic confusions in the case of A. challengerensis and others.  By the way, eventually the smallest ones go through a sexual reproductive phase that builds a new full-sized frustule, so that the cycle can start over. This is really weird. Later I hope to write long post about the utterly astounding, almost unbelievable biology of diatoms.

Darwin published his theory of evolution just 13 years before this expedition, and evolution was on everyone’s mind, and the commander of the ship was an “early adopter” of the theory. At the time there was still not much clarity about the predictions of the theory. It was widely believed that the cold dark oceans would preserve “living fossils” similar to the earliest forms of life on earth. The expedition did not find this to be true, and so it actually was a slight setback for evolutionary theory. They unfortunately missed the hydrothermal vents which do indeed shed light on the origins of life.

I wrote at the beginning of this post that the HMS Challenger expedition was the 19th Century analogue of space exploration. So it was fitting that NASA decided to name one of the space shuttles “Challenger”, after the two scientific ships which carried that name. The photo above shows Challenger orbiting over the ocean 110 years after the original HMS Challenger sailed that same ocean. Unfortunately, as in the original Challenger expedition, people died on that space shuttle in the name of science, a reminder that exploration on the margins of what is known will always be risky, and the participants are real heroes of their age.

Solar storms have the potential to cause catastrophic damage. One that occurred around the end of October 2003 (now called the 2003 Halloween Storm) caused an estimated $27B in damages. That number will only increase as humanity has become more reliant on space-based and electrical infrastructure. However, if we could predict when storms would hit with some accuracy and adjust our use of the technologies that could be affected, we could avoid the worst damage. But, as of now, we don't have such a system that could help predict the types of events that could cause that damage accurately enough. That is where a new Sun activity monitoring system, described in a recent paper by Leonidas Askianakis of the Technical University of Munich, would help.

How can fission-powered propulsion help advance deep space exploration, specifically to the outer planets like Jupiter, Saturn, Uranus, and Neptune? This is what a recent study presented at the 56th Lunar and Planetary Science Conference (LPSC) hopes to address as a pair of researchers from India investigated the financial, logistical, and reliability of using fission power for future deep space missions. This study has the potential to help scientists, engineers, and future astronauts develop next-generation technologies as humanity continues to expand its presence in space.

The grainy videos from the Apollo Moon landings are treasured historical artifacts. For many of us, that footage will be lodged in our minds until our final synaptic spark sputters out. But like all technology since the space race days, video technology has advanced enormously, and the next Moon landings will be captured in high-definition video. The ESA is so focused on getting it right that they're practicing filming lunar landings in a special studio that mimics the conditions on the lunar surface.

Students recently unveiled their invention of a robotic actuator -- the 'muscle' that converts energy into a robot's physical movement -- that has the ability to detect punctures or pressure, heal the injury and repair its damage-detecting 'skin.'

Students recently unveiled their invention of a robotic actuator -- the 'muscle' that converts energy into a robot's physical movement -- that has the ability to detect punctures or pressure, heal the injury and repair its damage-detecting 'skin.'

Researchers proposed a novel strategy for using a magnetic field to boost the efficiency of single-atom catalysts -- thus speeding up helpful reactions used for ammonia production and wastewater treatment.

A series of studies sheds light on the origins and characteristics of intermediate-mass black holes.

A new method for predicting underwater landslides may improve the resilience of offshore facilities.

Today we have a guest post from reader Coel Hellier, who does this kind of stuff for a living. His text deals with the recent kerfuffle about whether a nearby planet shows an atmospheric gas indicative of life.  I particularly like the details about how scientists go about analyzing a question like this. His text is indented, and he’s added the illustrations.

Is the dimethyl sulphide in the atmosphere of exoplanet K2-18b real?

Everyone is interested in whether there is life on other planets. Thus the recent claim of a detection of a biomarker molecule in the atmosphere of an exoplanet has attracted both widespread attention and some skepticism from other scientists.

The claim is that planet K2-18b, 124 light years from Earth, shows evidence of dimethyl sulfide (DMS), a molecule that on Earth arises from biological activity. Below is an account of the claim; I try to include more science than the does mainstream media, but do so largely with pictures in the hope that the non-expert can follow the argument.

Transiting exoplanets such as K2-18b are discovered owing to the periodic dips they cause in the light of the host star:

And here is the lightcurve of K2-18b, as observed by the James Webb Space Telescope, showing the transit that led to the claim of DMS by Madhusudhan et al.:

If we know the size of the star (deduced from knowing the type of star from its spectrum), the fraction of light that is blocked then tells you the size of the planet.

But we also need to know its mass. One gets that from measuring how much the host star is tugged around by the planet’s gravity, and that is obtained from the Doppler shift of the star’s light.

The black wiggly line in the plot below is the periodic motion of the star caused by the orbiting planet. Quantifying this is made harder by lots of additional variation in the measurements (blue points with error bars), which is the result of magnetic activity on the star (“star spots”). But nevertheless, if one phases all the data on the planet’s orbital period (lower panel), then one can measure the planet’s mass (plot by Ryan Cloutier et al):

So now we have the mass and the size of the planet (and we also know its surface temperature since we know how far it is from its star, and thus how much heating it gets).  Combining that with some understanding of proto-planetary disks and planet formation. we can thus dervise models of the internal composition and structure of the planet.

The problem is that multiple different internal structures can add up to the same overall mass and radius. One has flexibility to invoke a heavy core (iron, nickel), a rocky mantle (silicates), perhaps a layer of ice (methane?), perhaps a liquid ocean (water?), and also an atmosphere.

This “degeneracy” is why Nikku Madhusudhan can argue that K2-18b is a “hycean” planet (hydrogen atmosphere over a liquid-water ocean) while others argue that it is instead a mini-Neptune, or that it has an ocean of molten magma.

But one can hope to get more information from the detection of molecules in the planet’s atmosphere, a task that is one of the main design goals of the James Webb Space Telescope [JWST]. The basic idea is straightforward: During transit, some of the starlight will shine through the thin smear of atmosphere surrounding the planet, and the different molecules absorb different wavelengths of light in a pattern characteristic of that molecule (figure by ESA):

So one observes the star both during the transit and out of transit, and then subtracts the two, and the result is a spectrum of the planet’s atmosphere.

If the planet is a large gas giant with a fluffy, extended atmosphere and is orbiting a bright star (so that a lot of photons pass through the atmosphere), the results can be readily convincing. For example, here is a spectrum of exoplanet WASP-39b with features from different molecules labelled (figure by Tonmoy Deka et al):

[I include a plot of WASP-39b partly because I was part of the discovery team for the Wide Angle Search for Planets survey, but also because it is pretty amazing that we can now obtain a spectrum like that of the atmosphere of an exoplanet that is 700 light-years away, even while the planet itself is so small and dim and distant that we cannot even see it.]

The problem with K2-18b is that the star is vastly fainter and the planet much smaller than WASP-39b. This is at the limit of what even the $10-billion JWST can do.

When you’re subtracting two very-similar spectra (the in- and out-of-transit spectra)  to look for a rather small signal, any “instrumental systematics” matter a lot. Here is the same spectrum of K2-18b, as processed by several different “data reduction pipelines”, and as you can see the differences between them (effectively, the limits of how well we understand the data processing) are similar in size to the signal (plot by Rafael Luque et al):

The next problem is that there are a lot of different molecules that one could potentially invoke (with the constraint of making the atmospheric chemistry self-consistent). For example, here are the expected spectral features from eight different possible molecules (figure by Madhusudhan):

To finally get to the point, I show is the crucial figure below. Nikku Madhusudhan and colleagues argue — based on an understanding of planet formation, and on arguments that planets like K2-18b are hycean worlds [with a liquid water ocean under a hydrogen-rich atmosphere], and from considerations of atmospheric chemistry, in addition to careful processing and modelling of the spectrum itself — that the JWST spectrum of K2-18b is best interpreted as follows (the blue line is the model, the red error bars are the data):

This interpretation involves large contributions from DMS (dimethyl sulphide) and also DMDS (dimethyl disulphide) — the plot below shows the different contributions separated — and if so that would be notable, since on Earth those compounds are products of biological activity—mainly from algae.

In contrast, Jake Taylor analysed the same spectrum and argues that he can fit it adequately with a straight line, and that the spectral features are not statistically significant. Others point out that the fitted model contains roughly as many free parameters as data points. Meanwhile, a team led by Rafael Luque reports that they can fit the spectrum without invoking DMS or DMDS, and suggest that observations of another 25 transits of K2-18b would be needed to properly settle the matter.

There are several distinct questions here: Are the details of the data processing sufficiently understood? (perhaps, but not certainly); are the relevant spectral features statistically significant? (that’s borderline);  and, if the features are indeed real, are they properly interpreted as DMS? (theorists can usually think of alternative possibilities). Perhaps a fourth question is whether there are abiotic mechanisms for producing DMS.

This is science at the cutting edge (and Madhusudhan has been among those emphasizing the lack of certainty, though the doubts have not always been in news stories), and so the only real answer to these questions is that things are currently unclear. This is a fast-moving area of astrophysics and we’ll know a lot more in a few years.

Not all Full Moons are created the same. Follow the familiar Moon long enough, and you’ll notice something strange, as it seems to wander across the sky from north to south, from one cycle to the next. Welcome to the fantastic precession of our natural satellite the Moon. Last December, we saw the ‘Long Night’s Full Moon,’ as the Full Moon nearest to the solstice rode the highest in the sky for the last two decades. Now, its time for the southern hemisphere to get a turn, as the Moon heads steeply southward, on its way to Full on June 11th.

Researchers have developed algorithms that reconstruct a hidden image from the scrambled light waves that bounce off a wall, making it possible to see things behind a corner

The carbon dioxide removal industry is struggling to grow at the pace needed to have a significant role in meeting climate targets

Artificial intelligence has removed many of the barriers to understanding a new language, but there are still good reasons to do things the old-fashioned way

Most 9/11 first responders experienced improvement in PTSD symptoms about 10 years after the traumatic event, but approximately 10 per cent saw symptoms worsen even two decades later

Millions of women and teenage girls use oral contraception, but we are only now getting an idea of what effect these drugs have on our brains

Culture editor Alison Flood rounds up the New Scientist Book Club’s thoughts on our latest read, the science fiction classic Ringworld by Larry Niven

In this short extract from Kaliane Bradley's sci-fi novel, her protagonist makes a startling discovery about the nature of time

The Ministry of Time author Kaliane Bradley on how she made time travel work in her bestselling novel, the latest pick for the New Scientist Book Club