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Prof. A's Science Fix- Aug 10 2012 Edition

There is no denying that the biggest news in science this week comes from NASA. Something very exciting has just happened:

 

NASA Curiosity Rover landed safely on Mars! Michel was the first one to sound the alarm at our site on August 5th: “Something very exciting is going to happen tonight. The SUV-sized NASA rover Curiosity is to touch down on Mars at 1:30 AM (Florida time.) If it makes it in one piece to the surface - an incredible feat in itself - a set of fascinating experiments will begin with the robotic chemical lab that's on board” And then on August 6th, the fantastic news, as described by Michel: “Curiosity is now open for business on Mars. Humanity has successfully put a semi-autonomous robot jam-packed with high-res sensors and fancy software on a tiny rock fourteen light-minutes away. That's an impressive demonstration of the power of scientific predictions. I don't know how long is the NASA list of things that could go wrong but I bet it is astronomical. Now the coming weeks will be critical. Before going anywhere Curiosity will test its subsystems and deploy its paraphernalia. That's another gazillion things that could go wrong. But these people are good - think the Voyagers, Cassini, Apollo 11 - pretty much the best that we have”.

Check out how the NASA scientists and technicians celebrated:

And do not miss the BBC special on the Curiosity Rover, here on our site. Courtesy of Mohamed.

And now that Curiosity is going to give us so much data, perhaps we should start thinking about the future of Mars: colonization? Some scientists have already started thinking about colonizing microbes.

 

Engineering life to survive on Mars and aid human colonization. Curiosity has landed safely on Mars and is ready to start exploring for possible signs of past life on the Red Planet. As for life on Mars in the present tense, it is not a very life-friendly environment, even for microbes. It is very cold (average temperature is minus 80 degrees Fahrenheit, though there is water in its ice caps) and the atmosphere is 95% carbon dioxide. Even for extremophile microbes, it would be a challenge. But right here on Earth there are scientists working to engineer bacteria that could potentially live on Mars, and even help humans to colonize Mars, by producing food or extract minerals. Their work is carried out under the International Genetically Engineered Machines (iGEM) challenge, a synthetic biology competition for students. The goal is to engineer microbes to perform new tasks. A collaborative team from Stanford and Brown universities have created a “Hell Cell”, that Ben Geilich, the student team captain from Brown University, defines as “a genetic box of crayons for extremophile conditions.” The Hell Cell is a collection of genetic modules, that the students call “BioBricks”, engineered from DNA from a variety of organisms, including a radiation-resistant bacterium capable sequesters large amounts of manganese, a special strain of E. coli, capable of resisting to cold and droughts, and even a cold-resistant species of Siberian beetle that makes proteins that can serve as “antifreeze”. The BioBricks are currently being introduced into E. coli, which is a favorite model in microbiology labs, but it can be used in other bacterial species as well. In addition to the Hell Cell, the team is developing bacteria that could extract rare metals from the silica that coats most electronic devices. Releasing life on Mars would be problematic if Curiosity finds some living microbes there, because there is no telling what engineered bacteria could do to the local microbiota, but if there isn’t any life there, it would be a bit easier to make the argument for releasing engineered microbes on Mars.

 

Meanwhile, on our own Blue Planet, the evidence for the huge impact that our presence is having on the globe we share with so many other creatures keeps mounting.

 

Caffeine pollution in the Pacific Ocean coast off the US Northwest. Maybe we humans do drink too much coffee; maybe there are too many Starbucks around the globe. Or perhaps we just need to be much more careful about how we dispose of our waste. The waters off the coast of Oregon are now caffeinated, and we have no idea what effect caffeinated seas can have on aquatic wildlife. Interestingly, caffeine levels off potentially polluted areas, that is near sewage-treatment plants and larger communities were below the detectable limit (9 nanograms per liter) but the wilder coastlines in more remote areas were comparatively highly caffeinated, at about 45 nanograms per liter. The possible explanation is that monitoring is more stringent near developed areas, and in more remote areas, the contamination could be coming from on-site waste disposal systems, like septic systems, that are not monitored as much as waste coming from sewage systems. Also, Oregon cities are relatively small so the sewage plants don’t process a huge volume of waste. Bigger cities such as Boston have been found to be pumping fairly high levels of caffeine in the harbor, from its sewage plants. Caffeine has been documented in waters around the world, including the Puget Sound, the North Sea, and the Mediterranean (all those espressos and Turkish coffees!). Caffeine is thought of as a good tracer for the presence of other human contaminants, such as pharmaceuticals, fragrances, detergents, hormones, etc. Aquatic plants and animals are getting hit with a whole slew of substances whose effects on the ecosystem are totally unknown. Marine biologists have found that in the lab, caffeine levels similar to the ones found offshore affect intertidal mussels, causing them to produce specialized proteins in response to environmental stress. This could in theory result in a change in growth rate, or less offspring, and these changes may end up affecting the whole food chain.  Other human contaminants have been shown to have drastic effects already: at a remote Ontario Lake, estrogen from birth control pills has caused fish populations to collapse.

 

And while we are on the subject of sea water, I just learned something amazing about our oceans that I have never hear of before: the presence of huge internal waves.

 

The largest waves in the sea are vertical! The only waves I knew existed are superficial, horizontally moving waves, like the ones we admire and sometimes surf, and tsunami waves who are huge but move horizontally. I’m not an oceanographer, but if I was one, I’d be enthralled too, with the biggest waves in the ocean: internal waves. These occur deep below the surface. They can’t be seen from shore, but they are so HUGE that they can be seen from space! (See satellite photo of the Strait of Gibraltar; the crests are the internal wave surface signature; this internal wave is caused by the tides forcing water to flow back and forth over the Gibraltar sill). Internal waves are similar to shore waves: they undulate, have crests and troughs, and break. Surface waves and internal waves are both caused by the meeting of two fluids of different densities. For surface waves, the two fluids are very different, because they are air and water. For internal waves, the two fluids are water of different densities: the deeper the seawater, the denser it is. There are many density layers therefore many chances for internal waves to occur. The almost infinite number of density layers at different depths means that they can move vertically. Internal waves can move water up and down over 200 meters (~600 feet); they have been hypothesized to be capable of sinking submarines. Internal waves can travel thousands of miles; for example, internal waves generated in Hawaii have been tracked by satellite propagating all the way to Alaska. Internal waves (of air) also occur in the atmosphere, they are ones that cause a choppy flight over mountains).  They occur at the Sun too. 

 

And thinking about the water and organisms that live there permanently or temporarily, here is a fascinating little adaptation that allows a terrestrial organism to walk underwater.

 

Beetle walks underwater on dry feet. This story reminds us of the astonishing adaptations that make animals so nicely fitted to their habitats. We are all familiar with the ability that insects have to walk on totally flat surfaces, such as a flying walking up your living room window. It's so mundane that we don't even bother thinking about why they can do that. It's the thousands of hairs (setae) on an insects's feet or claws that allow them to be so "sticky". Some insects have oily hairs on their feet too. The European green dock beetle (Gastrophysa viridula), like most beetles, can walk on flat surfaces, but it can also walk underwater, on the bottom of a body of water, with the same ease as in dry land. It's not that the beetle is not heavy; it floats, like all beetles, so how does it manage to walk underwater? Scientists at the University of Kiel (Germany) and the National Institute for Material Science in Tuskuba (Japan), just had to find out.  So they got a couple dozen beetles and let them walk off a stick onto the bottom of a lab water bath, where the metallic green beautiful insects just kept on walking. duo captured 29 wild beetles, and allowed them to walk off a stick onto the bottom of a water bath. Once there, they kept on walking. They took pictures of the beetles' footsteps, and they realized that their oily hairs trapped tiny bubbles that displaced water and created a minuscule patch of dry land under each step, so that the sticky hairs could operate normally, by capillary adhesion. They confirmed it was the bubbles that did the trick, because if they added a tiny amount of detergent to the water, the surfactant action disrupted the bubbles and the hapless beetles immediately floated to the surface. Air cushions inspired by the beetle's feet could one day be used to improve locomotion underwater for man-made machines. 

 

But, in contrast to the beetle, another notoriously sticky creature does not fare so well when walking on water.

 

How to unstick a gecko. We have discussed the astonishing stickiness of gecko’s feet, which allows the little lizard to scurry up a glass surface with no difficulty whatsoever.  The secret is that the charismatic reptiles (I hear they even do TV commercials!) can exploit van der Waal’s forces. These molecular attractions are very weak, but the soles of geckos’ feet are covered with tiny, branched hairs that end in flattened pads. The hairs result produce a huge surface area, and the piling up of many weak van der Waal’s forces end up creating an extremely strong adhesive power. But geckos don’t normally live on glass, they live in tropical or sub-tropical areas. And they are likely to encounter rain and wet surfaces. So scientists set out to find out how they do on wet surfaces or if their feet were submerged in water.  They measure the force of adhesion by finding out what force it took to unstick a gecko from a wet surface, in the lab.  They used little harnesses on the geckos to gently tug on them with a device that applied measurable forces and record when the lizards let go of the surface. If they wetted their footpads, or if they submerged their legs, their adhesive force decreased ~20-30 times. They did better on misted glass, but after a few steps their toepads got saturated with water and they slipped. Knowing that water is like kryptonite fir their super adhesive powers is important because scientists are trying to develop super-adhesives for human use based on the gecko model. There are already “gecko tape” synthetics: University of Berkeley scientists have built a gecko-modeled adhesive that permits a car to drive up a very steep incline but only on a perfectly smooth, dry road.  Researchers at the University of Kiel (Germany) created a 20 X 20 cm square gecko tape that can hold the weight of an adult human.

 

And speaking of humans and sticky stuff, have you ever considered that tartar could end up being a boon and not only for hygienists?

 

Dental tartar in archaeology. The media glamorize what archaeologists do in the field: they travel to exotic places usually with beautiful whether and they excavate for artifacts and skeletons surrounded by throngs of adoring very young graduate students that do all the menial work. Of course, fieldwork is extremely important in archaeology but many people do not realize that labs and museums are full of drawers and drawers with skeletons and artifacts waiting to be studied. A lot of interesting stuff goes on in the lab, and technology helps dig out a lot of information from unsuspected places, for example tartar in ancient teeth. Christina Warinner, a geneticist at the Centre for Evolutionary Medicine at the University of Zurich, has been sampling and analyzing the dental calculus (tartar) that coats the teeth in fossil and ancient skull collections. Ancient humans accumulated as much as 600 milligrams of calculus on their teeth, a lot more than modern humans who brush their teeth and visit the dentist regularly, and typically have only about 30 milligrams. Tartar is a mineralized biofilm with food remnants and bacteria, and DNA can be extracted from it. Warinner in fact found that ~ 1000 times more DNA can be obtained from tartar than from the bones themselves. Of course, the DNA is not just human but also bacterial. She identified DNA from 2,000-4000 species of bacteria, including pathogens.  Analysis of DNA from ancient specimens will allow us to uncover the evolutionary history of human health and disease, and we could reconstruct a very detailed picture of the diet, infection and immunity from thousands of years ago, and figure out how these parameters interplayed.  Tartar now looks very appealing, and the bacteria in the biofilm certainly look very pretty under the microscope (see photo).

 

And here is a neat story that combines archeology with genetics, a perfect marriage when we want to study our forebears.

Corn cultivation and recent human evolution. The best known examples of recent human evolution is the adaptation to heights in certain populations (Tibet and the Andes) and lactase (the enzyme that digests lactose, or milk sugar) persistence in adulthood which allowed some European and African groups to consume dairy without unpleasant side effects, well past infancy. These adaptations happened in the last few tens of thousands of years. The lactase persistence mutations are especially intriguing, because their fixation into the population likely occurred as a consequence of a cultural change, in this case keeping herds. Now there is another example of culture-gene co-evolution, the first one from Native American populations, and it appears to be linked to maize cultivation. An article in PLoS One, describes an allele (a variant) of the ABCA1 gene, named Arg230Cys (meaning an arginine, which is an amino acid at position 230 is substituted by a cysteine (another amino acid), for those of you who are curious regarding nomenclature).  This allele has been found in 19 different Native American populations, from North, Central and South America, and it's no present on any other groups. It is associated with abnormally low production of HDL cholesterol (the "good" cholesterol) and with increased risk for obesity, diabetes, and heart disease. The area of DNA sequence around the Arg230Cys shows the typical reduced diversity which is the hallmark of what geneticists call a "selective sweep", indicating the variant was favored by selection. The researchers pinpoint the appearance of this polymorphism to between 19,000 years ago to 7,000 years ago. This is coincident with the domestication of Zea mays (maize or corn), as measured by the age of maize pollen found at archaeological sites. A staple crop can provide a more predictable food source compared to hunter-gatherer lifestyle but when the crop fails, it means famine. Scientists speculate that the allele makes carriers better at storing fat, which would be a sort of insurance against bad harvest years. Since DNA sequencing got faster and cheaper, new development in population genetics will sure show a few more interesting cases of culture-gene co-evolution

And going further back in time: it seems like every week we get news of a new ancestor.

 

Homo rudolfensis? Our tree keeps getting bushier. The earliest known human species is Homo habilis (that lived 2.3-1.4 million years ago).  It is the first species recognized to use tools and to begin looking human, compared to the australopthecines (“Lucy”).  H. habilis is not considered to be directly on our line, so there must be other Homo species out there who were our direct ancestors. One such species could be Homo rudolfensis, who lived ~1.9 million years ago and is known from a single skull, very similar to H. habilis. Throughout the years, paleoanthropologists have debated whether it is a separate species or just a variant of H. habilis.  Now three new fossils from Koobi Fora in Kenya may shed some light on the issue.  One of the specimens is represented by the upper jaw and part of the face from a juvenile (adolescent) from ~1.9 million years ago; it is definitively in the genus Homo and looks more like H. rudolfensis than H. habilis. The second fossil is a lower jaw, between 1.87 and 1.78 million years ago, and it is similar to the juvenile, which in turn is most similar to the original H. rudolfensis skull. The third fossil to be found is a fragment of lower jaw fragment, ~1.9 million years ago, and it is also similar to the juvenile and thus, to H. rudolfensis. These new fossils appear to confirm the existence of a species separate from H. habilis, and H. rudolfensis is a good bet for a classification, instead of designating a totally new species.  This does not “re-write the history of our soecies” as some newspapers have reported, but they are very important finding and have just been published in Nature. The leading authors are second and third generation Leakeys, what an incredible family! The leaders of the project are Meave and Louise Leakey, a mother-and-daughter team.  They are not assigning a fixed species to the fossils for now, as they prefer to wait for further discoveries. But their findings suggest that East Africa was teaming with hominin species, which presumably occupied different niches. One thing appears certain: human evolution was far from a straight line.

 

Highlighted VIDEO: A minute and a half science. Why is music so rewarding to us humans?

Is music humanity's drug of choice? What is the mysterious power behind its ability to captivate, stimulate and keep us coming back for more? Find out the scientific explanation of how a simple mixture of sound frequencies can affect your brain and body, and why it's not all that different than a drug like cocaine. Written and created by Mitchell Moffit (twitter @mitchellmoffit) and Gregory Brown (twitter @whalewatchmeplz).

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Comment by Michel on August 12, 2012 at 6:35pm

Yes, that's probably the target of each mission.
Before 1976 (Viking) they would have been lucky just to hit Mars.

Comment by Davy on August 12, 2012 at 4:06pm

I take it it is the possible area the science bots could have landed in their target area of Mars?

Viking = 10788 square miles. 

Pathfinder = 5500 square miles.  

Opportunity and Spirit = 1116 square miles. 

Phoenix = 744 square miles. 

Curiosity = 48 square miles. 

Comment by Doone on August 12, 2012 at 3:44pm

Comment by Davy on August 12, 2012 at 2:54pm

Awww! Ain't love grand.

Comment by Michel on August 12, 2012 at 2:28pm

Cute!
I wonder what color the dried dress will be.

Comment by Doone on August 12, 2012 at 2:00pm

There has been a lot of flooding in the Philippines but this couple does not care.

Comment by Adriana on August 11, 2012 at 3:45pm

Haha, archaeopteryx, yes, she looks like she has silicone implants.

Comment by archaeopteryx on August 11, 2012 at 2:18pm

RE: H. Erectus female --

I get the impression that she's had a little work done --

Comment by Adriana on August 11, 2012 at 1:24pm

@doone, I think that quantum mechanics article deserves its very own post in our group Science

Comment by Adriana on August 11, 2012 at 1:21pm

Apparently the facial hair is the same for male and female chimps.

Another interesting thought is: when did females of the genus Homo start having breasts similar to the ones we H. sapiens females have? (I mean, we have big breasts even if we are not lactating). I've seen breasts in museum reconstructions of H. erectus, for example, but I guess we can't know if they were present. This diorama for the American Museum of Natural history is an example. I forget if this was H. ergaster or H. habilis. [corection, this is H. erectus, I just checked)