Couretsy of the CDC, The complex life cycle of Opisthorchis viverrini.

In Southeast Asia, an all-too-common parasite is known to increase the incidence of bile duct cancer in infected individuals. A paper just released in PLoS Pathogens shows how this happens. Knowing the molecular pathway that leads from parasite infection to cancer will almost certainly speed up the search for a cure for this cancer, and will probably add to our understanding of cancer in general.

Cancer is, of course, a category of diseases rather than a single disease. What holds cancer together as a coherent set of conditions is the inappropriate increase of cell proliferation in some tissue or another. Cell proliferation is, of course, normal and expected at some times and places. When an organism is growing there is quite a bit of proliferation. When a wound is healing, cell division must be sped up. Therefore, mechanisms have evolved to increase the rate of cell division, and many cancers are simply this mechanism operating in an inappropriate and sometimes out of control way.

The cause of inappropriate cell proliferation can be a genetic mutation, caused in turn by the chance mutation of an already susceptible gene, or by some kind of chemical or physical irritant.

Or it can be a fluke.

A fluke is a kind of worm in the class Trematoda. There are about 20,000 species of Trematoda, and many of them are parasites that live in mollusks and vertebrates. Commonly, Trematoda spend part of their life cycle in a mollusk, then move to a vertebrate host, and then move back to the mollusk host, as they reproduce alternatively using asexual and sexual mechanisms.

Opisthorchis viverrini, also known as the Southeast Asian or Oriental liver fluke, lives in a certain genus of freshwater snails and in humans, and when it lives in humans, it seems to predispose the humans to cholangiocarcinoma, which is cancer of the bile ducts.

The research reported yesterday identified a certain protein that is very similar to a human growth hormone, but that is found in and produced by the fluke.

Scientists knew that a particular protein of a type known as granulin was produced by the fluke, and it was known that other versions of granulin cause unchecked proliferation of cells. So they isolated the gene for the fluke version of the granulin, and placed the gene in bacteria which allows the production of sufficient quantities of the protein to use in experiments. This, in turn, allowed them to test the hypothesis that this fluke-produced protein acts like other granulin molecules in causing cancer-like growth of cells.

It turns out that fluke produced granulin is an effective cancer-causing agent.

The fluke appears to use the granulin to induce cell growth for its own nutrient supply. In addition, the fluke-produced granulin induces specific antibodies in the host that neutralize the granulin. So, there seems to be something of an arms race between parasite (fluke) and host (human).

Now that the protein is both characterized and linked to the cancer, it may be possible to produce a drug that will fight it, or to refocus efforts on the fluke infection itself to reduce the prevalence of this cancer. Also, the Opisthorchis viverrini system may now serve as a useful model for the study of growth hormone induced cancers.

Another reason that this research is very important is that there were two very strong hypotheses for the prevalence of this cancer in southeast Asia. The fluke could have caused the cancer by simply irritating the cells where the fluke lives. Alternatively, the people in regions where this fluke are common also have a diet high in a particular chemical compound called nitrosamines, abundant in the fermented fish eaten in the region, and thought to be possibly cancer-causing. While this research does not rule those ideas out, it does strongly suggest that fluke-excreted granulin is the culprit that should be addressed first.

This research is published in an OpenAccess journal, so you can read the original by clicking here.

NASA’s Spitzer Space Telescope has discovered a new ring around Saturn.  This ring is very different from those previously known. In some ways, this ring resembles the “accretionary disk” found around some stars more than it resembles the thin, orderly rings that Saturn is famous for.

The new ring is much larger than any of the planet’s other rings and is tilted about 27 degrees off the main plane of rings. It starts about six million kilometers out from the planet, and is about 12 million kilometers wide. The moon Phoebe orbits just within this ring and is tentatively thought to be responsible for the ring’s existence. It would appear that as Phoebe circles around Saturn, it occasionally collides with comets, which are obliterated, with the debris from the collision contributing to the ring.

This ring is different from the other rings not only in its angle, but also in its thickness. The better known Saturnian rings are very thin (about 10 meters thick), but this mega-ring measures about 2.5 million kilometers thick. That is roughly 20 times the diameter of Saturn. As Anne Verbiscer, one of the authors of the study reporting this feature, puts it, “This is one supersized ring. If you could see the ring [from Earth], it would span the width of two full moons’ worth of sky, one on either side of Saturn.”

An artist’s conception of the ring as it would appear if you had infrared detecting eyes. Saturn is the tiny dot in the middle as indicated. (Image credit: NASA/JPL-Caltech/Keck)

The ring appears to be made out of very dispersed particles of ice and dust, which were visible to the Spitzer telescope using its infrared detectors. The particles are spread out so thinly that if you were in the thickest part in a spacecraft, you would not easily detect the ring’s existence. The Spitzer instruments were able to “see” the ring only because they were very sensitive to even tiny amounts of infrared radiation emanating from the particles making up the ring.

The discovery helps solve a mystery regarding the Saturnian moon Iapetus. Iapetus has an odd appearance whereby one side is bright and the other is really dark, in a pattern resembling a yin-yang symbol. The dark area is called the Cassini Regio, after Giovanni Cassini who discovered Iapetus in 1671 and later described its dark side.

Photograph of Iapetus taken by the Cassini spacecraft. (Image credit: NASA/JPL/Space Science Institute)

Iapetus, the previously known rings of Saturn and most of Saturn’s moons circle in one direction, while the newly discovered mega ring circles the other way. It appears that the material from this ring splatters Iapetus—think of bugs hitting a windshield—as the moon and the ring move in opposite directions.

For more information, see NASA’s Spitzer Space Telescope web site.

It is difficult to study albatross because they fly hundreds of kilometers across open ocean, flying faster than a boat can sail, to find food. Since you can’t just follow them, and since their open ocean feeding area is very large, observing albatross feeding behavior can’t be done reliably.

The new study addressed this problem by using miniature digital cameras attached to the backs of four birds breeding at colonies on Bird Island, South Georgia in the Southern Ocean. The resulting pictures showed albatrosses foraging in groups while at sea to collect food for their chicks. The cameras included a depth meter and a thermometer. The depth information was intended to indicate when the albatross would dive underwater for food, and the temperature meter indicates when the bird is settled on the sea surface or dives into water.

The following diagram shows what these information resulting from an instrument-fitted albatross flight looks like:

Diagram of albatross flight, courtesy of PLoS One

The X-axis is time, showing that this particular flight that took over two hours. The squiggly line along the top indicates temperature and the vertical lines along the lower part of the chart indicate depth. The bird appears to make four dives and later on sits on the water for a while (indicated by the cooling down without a dive event). The camera took photographs on a regular basis, and the Xes in the diagram indicate a photograph with another organism in it, generally another albatross. This shows that the albatross tracked in this diagram dived and presumably fed in the vicinity of other birds. The X with the red circle indicates a photograph of special interest, this one:

Albatrosses following an orca. Courtesy of PloS One

Here you can see two birds, one higher and one lower than the bird with the camera, and the three birds together seem to be closing in on a whale. This is an orca, a.k.a. killer whale.

This image showed that the killer whale broke the surface and that three other albatrosses were also apparently following the whale. This image was, unfortunately, followed by subsequent images that were obscured by feathers. However, the rapidly decreasing external temperature suggests that the bird landed on the sea surface after the encounter with the killer whale…

The camera is small, weighing about 82 grams. Although the camera slightly changes the aerodynamic shape of the albatross, it did not affect the breeding success of the study birds. In all, over 28,000 pictures were taken with the albatross mounted cameras. According to Dr Richard Phillips from British Antarctic Survey (BAS), “These images are really interesting. They show us that albatrosses associate with marine mammals in the same way as tropical seabirds often do with tuna. In both cases the prey (usually fish) are directed to the surface and then it’s easy hunting for the birds.”

The lunar south pole as it will appear on the night of impact. Photo Credit - NMSU / MSFC Tortugas Observatory.

On Friday, October 9, two space ships will crash into the moon, and you will be able to see it happen.

All you need to do is find the crater Cabeus, which is near the Moon’s south pole. Be watching at 11:30 UT (That’s 4:30 a.m. Pacific Time, 6:30 a.m. Central.) Bring your telescope. It should be a pretty good telescope. According to NASA:

“We expect the debris plumes to be visible through mid-sized backyard telescopes 10 inches and larger,” says Brian Day of NASA/Ames. Day is an amateur astronomer and the Education and Public Outreach Lead for LCROSS. “The initial explosions will probably be hidden behind crater walls, but the plumes will rise high enough above the crater’s rim to be seen from Earth.”

If you live in the eastern part of the United States or anywhere towards daylight (east) from there, it may be too bright. Hawaii is ideal within the US, but anywhere west of the Mississippi is a potential viewing spot. I live four blocks east of the Mississippi, so I guess I’ll have to drag my telescope down to the shore and canoe across for better viewing!

There is another way to see the impacts: Tune in NASA TV. Coverage starts at 3:15 a.m. PDT. In some areas, you may get that station on your local cable system.

But why are the spaceships crashing into the Moon? Has something gone terribly wrong? Are we being invaded by aliens?

Well, this is an experiment cooked up by NASA to see if there is water on the Moon. First, a rocket called The Centaur will hit the moon. This rocket weighs about 2,200 kg and it is going fast, so there will be a great deal of energy released. A huge plume of debris will be blown up as much as 10 kilometers. This plume will be observed from earth, the Hubble space telescope, and the Lunar Reconnaissance Orbiter (LRO), and analyzed for presence of water.

However, close behind The Centaur will be the LCROSS space ship. This craft has instrumentation on it that will allow a much more detailed analysis of the plume. LCROSS will fly into the plume sent up by The Centaur, analyze the material really fast, and send its data back to earth. And then … it will also crash into the moon.

“If there’s water there, or anything else interesting, we’ll find it,” says Tony Colaprete of NASA Ames, the mission’s principal investigator.

LCROSS will hit the moon about four minutes after The Centaur. The most interesting statement in NASA’s press release regarding this experiment is probably this one:

“Remember, we’ve never done this before. We’re not 100% sure what will happen, and big surprises are possible.”

If you are interested in viewing this spectacular lunar experiment at a public event (and the public events are quite diverse as to what they offer, see if there is one in your area and refer to the LCROSS Viewer’s Guide.

An artist's rendering of the asteroid impact that took place 65 million years ago and likely killed off nearly every large vertebrate species on the planet, including, many think, the dinosaurs. Don Davis/NASA

An important finding was reported last week in the same issue of Science as the new studies of Ardipithecus, and unfortunately, overshadowed by the news of the 4-million-year-old hominid.  This finding may turn out to be even more important because it relates not to the evolution of a single species, but to the recovery of life in general on Earth following one of the greatest catastrophes ever.

I’m referring to a paper by Julio Sepúlveda and others called “Rapid Resurgence of Marine Productivity After the Cretaceous-Paleogene Mass Extinction.”

Sepúlveda and colleagues examined marine sediments in Denmark that date to the period following the K-T mass extinction event. That event consisted of an impact on the Earth of a large asteroid 65 million years ago and the subsequent extinction of many species including all the dinosaurs. It is thought that there was a huge drop in the biological activity in the oceans after the event because the sun was largely blocked out, reducing photosynthesis in ocean-living algae. Without sun, the algae would have died off, and without algae, which are at the base of the oceanic food chain, other life forms in the ocean would die off or become very rare. The more widely accepted reconstructions of what happened indicate that this oceanic die-off did indeed happen, and that it took up to three million years for the ecosystems of the open ocean to recover from this impact. (Near-shore ecosystems have been thought to recover much more quickly.) The relatively lifeless post-impact open ocean is sometimes referred to as the “Stangelove ocean” in reference to the character in the apocalyptic movie “Dr. Strangelove.”

That previous research, however, was based on the examination of fossils of marine organisms including algae that leave an easily fossilized “skeleton” of silica, which indeed are sparse for a very long time after the impact. However, it is possible that certain types of organisms that do not leave behind fossils, such as cynobacteria, were abundant and would remain undetected in the fossil record.

The paper by Sepúlveda and colleagues used a different kind of evidence to look for open ocean biological activity and found it, in abundance, possibly within a century after the impact. If this proves to be true, then the darkening of the sky following the impact must have been fairly short term, and the observed long-term disruption of the ocean’s ecosystems must have a different explanation.

“Primary productivity came back quickly, at least in the environment we were studying,” according to Roger Summons, one of the paper’s authors.  “The atmosphere must have cleared up rapidly.  People will have to rethink the recovery of the ecosystems. It can’t be just [because of] the lack of food supply.”

The method this research team used was to look for isotopically distinct materials in the ocean sediments they examined, as well as molecules that could only have been formed by living things.

The sediments they looked in consist of a 37-centimeter-thick layer of clay in Denmark. Within this clay, which was deposited in relatively shallow near-shore environments, are hydrocarbon molecules produced by living organisms that are reasonably well preserved from 65 million years ago. These molecules indicate the existence of extensive open oceanic photosynthesis that would not have been possible under the “Strangelove ocean” model.

The way the analysis works can be understood this way: The ocean has a lot of dissolved carbon in it. This carbon exists in the form of more than one isotope. An isotope is a version of an element that is only a tiny bit different in its nuclear composition, and most elements lighter than Uranium have multiple non-radioactive isotopes. If there was no life in the ocean, the carbon would reach a certain equilibrium with respect to the proportion of each isotope, so sediments that included carbon would have a predictable ratio of these isotopes. (Note:  This has nothing to do with radiocarbon dating.  See this blog post for more on the potential confusion about that issue.)

Living forms use carbon, but when carbon is taken from the surrounding environment certain isotopes are incorporated into biological tissue more readily than others. Which isotopes are used and in what way by biological systems, and the exact reason for this, is complex and far beyond the scope of a mere blog post! Suffice it to say that when a geochemist looks at a sample of carbon, using very sensitive instruments, she can tell if this carbon has come from a non-biological system vs. a biological system. Beyond this, it is even possible to tell what kind of biological system is represented.

Sepúlveda’s team was able to tell that the carbon in these post-impact sediments could only have been assembled into these hydrocarbons (and other compounds) in a functioning open ocean ecosystem with plenty of algae photosynthesizing away at a pretty good clip. Since these sediments were deposited right after the impact, the “Strangelove” ocean theory, with a vast lifeless sea, is highly unlikely.

Cape Buffalo and calf. Photo courtesy of Wiki Commons

Greg Laden is guest-blogging this week while Sarah is on vacation. You can find his regular blog at Scienceblogs.com and Quiche Moraine.

We are talking mainly about bovids (cattle and antelope), which grow horns over their lifetime, and deer, which grow antlers every year. In most well known bovids and cervids, only the males grow the horns or antlers, but there are a few species where the females do as well.

For example, male and female cattle (including the many wild versions such as the African Cape Buffalo) and wildebeest (a kind of antelope) have horns, while in most other bovids only the males have horns. Both male and female caribou (a kind of deer) grow antlers each year, while in most other deer only the males do so.

This is actually a very complicated issue, and a new study of this question offers a new possible answer. But first, what did we think before this study?

There is one factor that explains most instances of female horns or antlers. The tiny monogamous deer and antelope tend to be much more “monomorphic” (that is, males and females look similar) than larger deer and antelope. These are small, pair-bonded, forest-dwelling species, and their horns or antlers are effective tools for defending territory or defending the young against small forest predators such as cats. Both the males and females have the horn or antler because they both use them, and for similar purposes. That is not particularly enigmatic.

It is also not hard to explain why in the vast majority of large cattle, antelope and deer species males and females are dimorphic (that is, males and females look different) in this trait, with only the males having the big appendages on their heads. In most of these species, males compete with each other, either in direct male-male competition or using a more show-off strategy to impress the females, in which the horns or antlers play an important role.

What’s harder to explain is this: In a small number of these large species, where the males compete over females, why do females also grow horns or antlers?

One early theory suggested that females in larger species could use these appendages for anti-predator defense. In other, smaller, species the females are better off hiding or running away. In my personal experience with wild Cape buffalo, this makes sense.  On many occasions while working in the Semliki Valley in the Congo, I encountered small herds of female buffalo with their young. As I would draw nearer in my vehicle, they would gather more closely and form a circle with the young in the center, watching me suspiciously and looking rather formidable, and the horns were very much part of that look. However, this does not seem to hold true for deer. In the largest deer species, females do not have antlers.

Another previous hypothesis, proposed by Richard Estes, who works with wildebeest in East Africa, suggests that horned or antlered females benefit by confusing adult males as to who the young males in the group are. This is a strategy to keep the young males in the group longer, so they can grow bigger before heading out on their own. Essentially, this is a trait that benefits mom (it makes her son more successful) but is manifest in her daughters. According to this idea, female horns or antlers should be found in species where competitive males are forced to hang around with each other more than in other species because they live in large herds that consist of “family” groups. This is, in fact, what is found in caribou and wildebeest, two of the prime example of antlered or horned females.

The new theory, proposed by Ted Stankowich of the University of Massachusetts and Tim Caro of the University of California at Davis, is that females benefit from having horns or antlers if they are of a body size or live in a habitat that makes it hard for them to hide. The more conspicuous the female, the more benefit they gain from horns or antlers, which would be needed for defense against predators.  (They may also benefit from competition with members of their own species for grazing spots.) This would explain caribou and wildebeest nicely, as they both live in very open country, as well as a lot of other species. This study was done by looking at a large sample of animals for traits related to body size and vegetation cover in the habitats they live in.  The sample included 82 species with female horns or antlers, of which 80 were “very conspicuous.”  According to the authors, who feel the two species that did not fit for reasons that can probably be explained, that is a nearly perfect match between theory and data.

More information on this story can be found here.

An example of an Acoelomorpha. Credit to Eric Rottinger/Kahikai.org

Darwin proposed that all species arose from a single common ancestor, and that this process involved almost uncountable branching events over eons of time. Working backwards, this means that an analysis of all of the living species should provide a “family tree” of life, showing, for instance, how all the monkeys are related to each other, and how the monkeys fit into the broader mammalian tree of life, and how the mammals fit as a branch on the vertebrate tree of life, and so on.

This is, of course, one of the main things scientists since Darwin have been working on, first using the physical appearance of living animals and fossils, and later using DNA. With DNA, however, it becomes difficult to unravel the details of the tree of life the farther back in time you look. This is because as parts of the DNA code change over time, it can randomly change back to an earlier code, which confuses the situation. This can be overcome by using a very large amount of data and a great deal of computer power and applying some powerful theories.

An international team of researchers has just come out with such a study of early bilaterians (bilaterally symmetrical animals, such as humans, fish and worms) that solves a long standing question in biology: Where in the evolutionary tree of life do we put a particular group of worms called the Acoelomorpha?

These very small flatworms are like the bilateral animals in many ways but lack some of the most important features that bilateral animals have … such as a gut. All bilateral animals have a gut lined with a specific kind of cell that facilitates digestion. Acoelomorpha, which is an entire phylum including about 350 species, “digest” food in an entirely different way. Some species take food into their body via a mouth, but that food does not enter a proper gut. Instead, pieces of food enter a sack full of special cells which then surround pieces of the food. The food is then broken down inside the cells. In some species, there is not even a space for the food to go into, though there is a mouth. In these species, the food is more or less shoved between the body cells of the organism where it is then digested.

Because of the lack of some of the key features of other bilateral animals, it has been difficult to place these creatures with certainty on the tree of life, so over the years this branch has been moved now and then from one place to another.

Casey Dunn at Brown University and sixteen colleagues from around the world claim that they have finally grafted Acoelomorpha where it belongs on the tree of life. Using a detailed and extensive analysis of DNA, they have placed Acoelomorpha just outside the other bilateral animals, as a sister clade to all other bilaterians (but still within the bliaterian group).

This is important for several reasons other than just putting Acoelomorpha in its proper place.

For one thing, it places the first split in the linage of bilaterians in its proper place. This, in turn, allows a better reconstruction of the last common ancestor of the bilaterians. Reconstructing the last common ancestor of any group of species is very important because differences between that ancestor and all of the subsequent species represent evolutionary events (or sequences of events). For example, Acoelomorpha lack a gut lined with special cells, lack two sexes, have sperm with two tails instead of one and have muscle tissues that are different from later bilaterians. One of the best ways to understand the evolution of key features of bilaterian guts, sexual reproduction and muscles would be to directly compare the early forms of these adaptations, as represented by Acoelomorpha, with the later forms.

Also, this finding might say something important about the evolution of the early bilateral animals. If it can be confirmed that Acoelomorpha truly existed back then as gut-free, using the method of enveloping its food that it is known to use today, then this indicates that a key evolutionary event at the origin of bilateral animals may have related to a change in how food was used as an energy source. It could be that the invention of the bilaterian gut is the very reason for their evolutionary success.

It is possible that this strange gut-free form of digestion, or any of the other traits that are unique to Acoelomorpha, evolved within that group early on in Acoelomorha history. The mere fact that a trait is simpler in one kind of animal than another does not guarantee that it represents the ancestral form. (For example, tapeworms pretty much lack a brain but evolved from ancestors that had brain-like structures.) Additional analysis would be needed to make it more certain, for instance, that this method of digestion represents the original, pre-bilateral (pre-gut) adaptation. But it probably does.

The work was published in the Proceedings of the Royal Society B.

The proposed dispersal of giant varanid lizards from mainland Australia to the Indonesian islands of Timor, Flores and Java during the past 3 million years.

The world’s largest living lizard is the Komodo dragon (Varanus komodoensis), a type of “varanid” lizard. Despite the fact that Komodo dragons are very interesting and widely known, there is a lot missing in our understanding of their natural history. Now a study of fossil evidence from Australia, Timor, Flores, Java and India shows that Komodo Dragons most likely evolved in Australia and dispersed westward to Indonesia. Some of the fossils that have been studied are newly described, including a species from Timor, and some are material known for a long time.

Here’s the most important finding: The two main hypotheses for the origin of the Komodo dragon have been brought into question and replaced with a new and better hypothesis.

It was previously thought that one of the best explanations for the large size of the Komodo dragon was the “island effect.” On islands, some animals may get bigger because of an increasing reliance on lower quality food found on island—the larger body size accommodates a gut that can process the food. In other cases, animals get smaller for a variety of reasons. But mostly, islands have strange effects on many species because evolution in the small population can proceed very rapidly. The animals that are confined to islands for long periods of time may simply evolve into food niches (which often relate to body size) that their sister species on the mainland did not experience.

A second hypothesis for the large size of Komodo dragons is that they were once specialists in the hunting of the pygmy Stegodon (a small elephant). This is a sort of indirect island effect. The Stegodons got small because they lived on islands, and the lizards evolved to be large enough to eat them.

Both of these hypotheses—island effects and specialist Stegodon hunter—now seem unlikely. The new research

(A) Modern V. komodoensis skull. (B through H) Fossil skull bones.

indicates that Komodo dragons were really part of a distribution of related species of really large lizards across the region, including Australia. In fact, in comparison to some of these other lizards, Komodo dragons are kind of small.

In the words of Scott Hocknull, Senior Curator of Geosciences at the Queensland Museum and author of the paper, Australia is a hub for lizard evolution:

The fossil record shows that over the last four million years Australia has been home to the world’s largest lizards, including a five meter giant called Megalania (Varanus prisca). Now we can say Australia was also the birthplace of the three-meter Komodo dragon (Varanus komodoensis), dispelling the long-held scientific hypothesis that it evolved from a smaller ancestor in isolation on the Indonesian islands. Over the past three years, we’ve unearthed numerous fossils from eastern Australia dated from 300,000 years ago to approximately four million years ago that we now know to be the Komodo dragon. When we compared these fossils to the bones of present-day Komodo dragons, they were identical. This research also confirms that both giant lizards, Megalania (Varanus priscus) and the Komodo dragon (Varanus komodoensis), existed in Australia at the same time.

This research was published Tuesday in the Open Access journal PLoS ONE. You can access this paper here.

Citation: Hocknull SA, Piper PJ, van den Bergh GD, Due RA, Morwood MJ, et al. (2009) Dragon’s Paradise Lost: Palaeobiogeography, Evolution and Extinction of the Largest-Ever Terrestrial Lizards (Varanidae). PLoS ONE 4(9): e7241. doi:10.1371/journal.pone.0007241

You may know that much of the climate change on earth over the last two million years–the coming and going of ice ages–is caused by the “orbital geometry” of the planet. The amount of planetary tilt and the time of year the tilt occurs change over time. When the Northern Hemisphere is less tilted towards the sun on June 21st, and at the same time the Earth is as far from the sun in its elliptical orbit as it ever gets, ice age conditions prevail. This makes ice ages on Earth pretty regular, cyclic, events.

You also may know that a big chunk of Earth’s water is frozen into the ice caps.

You also may know that the history of Earth climate is preserved, in part, in changes in the ice in those ice caps.

Well, same for Mars!

Images from the Shallow Radar instrument on NASA's Mars Reconnaissance Orbiter. Pane "a" is a "radargram" cross section, showing distinct layers.

Previously developed climate models suggested that the last 300,000 years of Martian history experienced low-level swings in climate, while the prior 600,000 years experienced more severe swings, owing to differences in the tilt of the planet. Most of the water we know about on Mars is in the Martian polar caps. And now, we can see, using radar, evidence of climate change reflected in that ice. From NASA:

New, three-dimensional imaging of Martian north-polar ice layers by a radar instrument on NASA’s Mars Reconnaissance Orbiter is consistent with theoretical models of Martian climate swings during the past few million years.

Alignment of the layering patterns with the modeled climate cycles provides insight about how the layers accumulated. These ice-rich, layered deposits cover an area one-third larger than Texas and form a stack up to 2 kilometers (1.2 miles) thick atop a basal deposit with additional ice.

“Contrast in electrical properties between layers is what provides the reflectivity we observe with the radar,” said Nathaniel Putzig…, a member of the science team for the Shallow Radar instrument on the orbiter. “The pattern of reflectivity tells us about the pattern of material variations within the layers.”

Essentially, the radar detects different amounts and/or kinds of dirt, and the ice is dirty in different ways. These vastly different climate periods (of more vs. less severe oscillation in climate change) probably leave behind different amounts of dirt in the ice. The radar can penetrate the ice and “see” these differences, with one period having more dirt than another.

There are two distinct models for how the dirt gets concentrated in the ice enough to be distinguished by the radar. One is that ice evaporates away more during some periods than others, leaving behind more dirt when the ice disappears, like the dirty snow during the late winter in northern cities. The other model simply has more dust in the atmosphere, and thus more dust falling on the ice, during certain periods. The present study supports the later model (more dust = dirtier ice). The radar reflectivity signal observed in this study is probably too coarse to link specific features of the signals with specific Martian “ice ages” so far.

“The radar has been giving us spectacular results,” said Jeffrey Plaut of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., a co-author of the paper. “We have mapped continuous underground layers in three dimensions across a vast area.”

Read more about this study.

The other images are different views of the polar cap using the radar images, and are explained in great detail on NASA’s site.

The Eastern Pacific black ghost shark. Photo courtesy of California Academy of Sciences

A new species of fish has been named from specimens collected over the last several decades off the coast of California.  It is called Hydrolagus melanophasma, and will go by the common name “Eastern Pacific black ghost shark.” This is the first new species of cartilaginous fish to be described from California waters since 1947, and is a member of the Chimaeridae family. Technically, according to ichthyologist Doug Long of the California Academy of Sciences, Hydrolagus melanophasma is “a big weird looking freaky thing. They have some shark characteristics and they have some that are very non-shark.”

Chimaeridae is a family of fish related to sharks.  Sometimes they are called ratfish. Sometimes they are called ghost sharks. Some have a venomous spine on their backs. They live in the ocean, usually quite deep, and the most recently discovered species in this family is gaining fame because it is said to have its sex organ on its head.

The ghost shark's tentaclum on its head is used to facilitate copulation with a female. It is not sufficient for reproduction. Photo courtesy of California Academy of Sciences

This “sex organ on the head” is actually quite normal for ghost sharks, though it is one of the big differences this sort of fish has with sharks. The feature in question is a tentaculum. A tentaculum is any of several sensory organs found on fish. In male ghost sharks the tentaculum is specially adapted as a grasping organ used during mating. So it is not the male’s penis, but rather, a grabby thing that the male uses to facilitate copulation with the female. So, referring to the ghost shark’s tentaculum as a “sex organ” on “its head” is a little like calling a finely chosen wine and just the right music a sex organ …. perhaps related to sex, but not sufficient for reproduction, anatomically speaking.

Hydrolagus melanophasma, was described in the September issue of the journal Zootaxa by a research team including California Academy of Sciences David Ebert (also with Moss Landing Marine Laboratories) and Douglas J. Long (also with the Oakland Museum of California) and Kelsey James, a graduate student at Moss Landing Marine Laboratories, and Dominique Didier from Millersville University in Pennsylvania.

The closest living relatives of the Chimaeras are sharks, and the Chimaera-shark split is probably about 400 million years ago, which is a long time ago by any standards. Chimaeras have cartilage instead of bone for skeletons, as do sharks. Chimaeras were once a very diverse and abundant group of species, and today are present in all oceanic waters though rare in any given locality.

The genus Hydrolagus means “water rabbit‚” and is so named because of its grinding tooth plates that resemble a rabbit’s front teeth. The term “melanophasma” means “black ghost” which is a refernce to the common term “ghost shark” as well as its dark, nearly black color. Hydrolagus melanophasma was originally collected as early as the mid 1960s, but went unnamed until now because its taxonomic relationships were unclear. This fish is found in deep water and is believed to range from the coast of Southern California, along the western coast of Baja California, and into the Sea of Cortez (Gulf of California). This species is known from a total of nine preserved museum specimens, and from video footage taken of it alive by a deep-water submersible in the Sea of Cortez.