DECCAN HERALD 3
Tuesday, January 31, 2017
Spectrum science
A LESS RISKY SURGERY
Researchers have made a tiny imaging probe to make brain surgery safer. This will let surgeons ‘see’ at-risk blood vessels to avoid causing fatal bleeds.
in the quest for clues on Mars biGGeStever As nASA’s Mars rover Curiosity continues its exploration, we are learning more and more previously unknown facts about the red planet. rishabh Shukla provides details of its launch and the recent findings
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ugust 6, 2012 is a date to be remembered in National Aeronautics and Space Administration’s (NASA) history. On this day, it’s most successful Mars rover, Curiosity, landed on the Martian soil with the distinction of being the most precise landing in the history of Martian exploration. Curiosity is more than just a rover; it is a mobile laboratory that has uncovered a lot of previously unknown facts about the red planet. Having known that the Martian environment was, at one time, well suited to support microbial life, Curiosity is now busy searching for traces of microbial life on the planet. Curiosity’s stint at uncovering the secrets of Mars was initially planned for 23 months. Owing to its success, it has now been extended indefinitely. In its four years of crawling on the Martian soil at a speed of five cm per second, it has covered a distance of about 14.6 kilometres. It has hiked up Aeolis Mons aka Mount Sharp, a 5.5 kilometre high mountain in the Gale crater, walked on the plains of Aeolis Palus, a plain in the crater, and has studied the Martian climate and geology. The data collected by Curiosity would be used for planning a manned mission to Mars in mid-2030s. Curiosity is the largest and most complex of the rovers launched by NASA. “Its mission was to determine whether the red planet ever was, or is, habitable for microbial life. Curiosity’s primary scientific goal was to explore and quantitatively assess a local region on Mars’ surface as a potential habitat for Mars life. As a part of this, it is exploring biological potential, geology and geochemistry, the role of water, and hazards to life in the region around its landing site,” explains Dr Gajanana Birur, a principal engineer in the Mechanical Engineering division at NASA’s Jet Propulsion Laboratory. Daunting challenge Curiosity was launched on November 26, 2011, from the Cape Canaveral Air Force Station, Florida, USA. After travelling a distance of 570 million kilometres in space for eight months, it entered the Martian orbit to land. The launch of the biggest ever rover to Mars had its set of challenges. “The biggest challenge faced during the eight-month cruise was the last part of the journey — Entry, Descent, and soft Landing (EDL). An aeroshell, carrying the rover inside its womb, entered the Martian environment and this phase lasted for six minutes,” elaborates Dr Gajanana. “A unique technique, called the actively pumped fluid loop technology, was used to keep Curiosity and its spacecraft at safe temperatures, where two independent active fluid loops removed waste heat from the rover.” Additionally, traditional spacecraft thermal control techniques such as insulation blankets and temperature sensors were also used alongside the active fluid loop. Landing on Mars was another daunting challenge, and just one in two such landings are successful. “One of the biggest challenges of the mission was that the rover inside the entry body had to reduce its speed from about 13,000 miles per hour to two miles per hour at the touchdown on the Mars surface in six minutes,” says Dr Gajanana. Hence, they devised a
FINDING LIFE Curiosity (below) is searching for traces of microbial life on Mars.
specialised landing sequence. This used a giant parachute, a rocket-controlled descent vehicle and an apparatus called a ‘sky crane’ that lowered the rover on a tether for landing. “This was done because other landing techniques used during previous rover missions could not safely accommodate the much larger and heavier rover,” explains Dr Gajanana. “Also, a supersonic parachute had to be designed and tested for the first time for this landing sequence.” Choosing the best landing site in an unknown terrain was another crucial aspect for a smooth landing. Even with the best of the technologies, landing on an uneven, rocky terrain could result in a crash. “It was well known that selecting the landing site for Curiosity would profoundly influence the nature and quality of the scientific return from the mission. Three criteria were used for the selection — evidence suggestive of a past or present habitable environment, ability of the mission to meet or exceed all engineering and safety constraints, and the acceptable operational performance,” states Dr Gajanana. In fact, NASA appointed a Landing Site Steering committee, which had come up with four final landing sites of which the final site, Gale Crater, was selected in July 2011. But what makes the rover so heavy? Curiosity has 17 cameras on-board — eight for hazard detection, four for navigation, two for multiple spectra images, one for chemical analysis, and two for helping the movement of the robotic arm and the base. It also has a cleaning system that removes the dust from surface to be analysed, sample acquisition and preparation tools, tools to scoop soil, drill into rocks and sort samples by particle size and deliver them to the on-board lab. Curiosity also works like a lab technician, quite literally! Its high-resolution cameras search for interesting features
Curiosity has confirmed that the Martian atmosphere was thicker in the past, similar to that of earth today.
on surrounding rocks and if it finds one, the ChemCam vaporises a small part to study its composition. If the composition is intriguing, Curiosity uses its robotic arm to look up the rock with a microscope and an X-ray spectrometer. It then drills the rocks to collect powdered samples that is analysed by other instruments onboard. Finally, once the results are obtained, it sends the data to its controllers at NASA. Curiosity is the only rover till date that has the ability to drill holes. Centre stage of exploration Curiosity has quenched some of our curiosity about the red planet. It has ascertained the absence of atmospheric methane, analysed some of the meteorites on Mars and confirmed that the Martian atmosphere was thicker in the past, similar to that of Earth today. The next big task for Curiosity is to explore the foothills of Mount Sharp for biosignatures. An undeterred explorer, Curiosity moves on despite its punctured titanium tyres, a fact revealed by its recent selfie! Mars is currently at the centre stage of planetary exploration by world’s major space agencies. Its Earth-like features like an atmosphere that can ward off harmful radiations, a comparable gravitational force, presence of water, volcanoes, seasonal weather and a hospitable temperature might make the planet boom with life, someday. Until then, two rovers — Spirit and Curiosity — roam about freely in the company of 14 orbiters orbiting the planet, including Indian Space Research Organisation’s Mangalyaan. “Such missions will help us reach new heights and reveal the unknown, so that what we do and learn will benefit the humankind,” Dr Gajanana signs off. (The author is with Gubbi Labs, a Bengaluru-based research collective)
Gene-modified ants shed light on animal societies evolution Scientists have identified the molecular & neural cues that spur ants to act like nurses and queens. the research can help get a fundamental understanding of how a complex biological system works, reports natalie Angier
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hether personally or professionally, Daniel Kronauer of Rockefeller University, USA is the sort of biologist who leaves no stone unturned. Currently, Daniel and his colleagues are assaying the biology, brain, genetics and behaviour of a single species of ant in ambitious, uncompromising detail. The researchers have painstakingly handdecorated thousands of clonal raider ants, Cerapachys biroi, with bright dots of pink, blue, red and lime-green paint, a colourcoded system that allows computers to track the ants’movements 24 hours a day. The scientists have manipulated the DNA of these ants, creating what Daniel says are the world’s first transgenic ants. Among the surprising results is a line of Greta Garbo (a Swedish-born American actress)typesthatdefythestandardantpreference for hypersociality and instead just want to be left alone. The researchers also have identified the molecular and neural cues that spur ants to act like nurses and feed the young or to act like queens and breed more young. Daniel’s lab’s ambitions are lofty and pragmatic. “Our ultimate goal is to have a fundamental understanding of howacomplexbiologicalsystemworks,”he said.Danielandhisco-authorsdescribetheir workinaseriesofrecentreportsthatappear in Proceedings of the National Academy of Sciences, The Journal of Experimental Biology and others. The researchers hope to turn the clonal raider ant into a model organism, right up there with laboratory stalwarts such as E. coli and Drosophila. But while bacteria and fruit flies have proved invaluable for addressing fundamental questions like how genes operate, Daniel’s model ants offer scientists the chance to explore, under controlled conditions, the origin and evolution of animal societies.
at its most seductively cerebral, yet it may well reveal insights into human disease, like why cancer cells ignore all stop signals from their surroundings, or why the brain turns in on itself during depression. “By studying the neuromodulators that make ants so sensitive to their social environment,”Daniel said, “we could learn something fundamental about autism and depression along the way.” Mixed signals Beyond its amenable weediness, the clonal raider ant seems almost custom-tailored for experimentation. The world’s some 12,000 known species of ants display a varietyofreproductiveandsurvivalstrategies. The most familiar examples are the fully eusocial ants, in which many sterile female workers do all the chores, a single large queen lays all the eggs, and a sprinkling of male ants, or drones, supply the sperm. Among clonal raider ants, there are no permanently designated workers and queens. Instead, all the ants in a colony switch back and forth from one role to the other. About half the time, they behave like workers, gathering food for their young — generally, by raiding the nests of other ants and stealing their larvae. The rest of the time, they go into queen mode and all colony members lay eggs together. Moreover, there are no male raider ants: The eggs develop parthenogenetically, without sperm, creating phalanxes of genetically identical female clones. The ants’ unusual mix of genetic uniformity and wildly protean conduct offers a powerful tool for cracking the old nature-versus-nurture conundrum. Daniel’s researchers have been mapping out the interplay between genes and environmental cues in shaping essential behaviours like reproduction and sociality. Reporting in the journal Current Biology, Daniel and his colleagues described the strictness with which a colony of clonal ants synchronised its schedule: Now everyone lays eggs, now the eggs hatch into larvae, now the adults shut down their ovaries and instead attend to the hungry young. On occasions, though, an ant’s ovaries remain animated when they should be suspended, and other ants can detect the illicit activity through telltale hydrocarbon signatures on the offender’s cuticle. Policing ants soon move in on the hyperovarian individual, drag it out of the nest, hold it down and pull it apart. Why is it important to kill off an ant that might breed offseason? Daniel compared the police ants to the body’s immune system, and the rebel ant to cancer. When the ant police come knocking, there’s no rock big enough to hide you.
Useful applications One key to the raider ant’s potential as a laboratory workhorse is its adaptability. Many ants are finicky. Not so Cerapachys. “It’s a weedy species,”Daniel said. “That’s true of a lot of model organisms — they have a global distribution, they’re good at invading disturbed habitats, and they’re good at being raised in a lab.” To trace the knotted skeins of antly social life, the researchers take a battery of approaches. They knock out ant genes or edit the lettering of ant genes and see how the ants respond. They ply ants with radioactively labeled neurochemicals and check where in the ants’brains the signaling molecules gain purchase. They measure ant movements by fractions of a millimetre as the insects perambulate along finely calibrated grids traced in ceramic. The project represents basic research The New York Times
TRACKING CHANGE Ants marked with colour-coded paints to allow computers to monitor their movements. PHOTO CREDIT: BEATRICE DE GEA/NYT
Spinning toy reinvented as low-tech centrifuge G
rowing up in India, Manu Prakash entertained himself with a bottle cap that spun around on two strings that he tugged with his fingers. As a physical biologist at Stanford University in California, he is now transforming that simple toy, called a whirligig, into a cheap tool to help diagnose diseases such as malaria. Manu started this project, the results of which were published in Nature Biomedical Engineering on January 10, 2017, after a research trip to Uganda in 2013. While visiting health care clinics, he noticed that most lacked a working centrifuge — or the electricity to power one — and could not separate blood samples to perform basic disease diagnostics. “One clinic used its broken centrifuge as a doorstop,” says Manu, a 2016 MacArthur “genius grant” winner who has also invented a foldable paper micro-
scope. “When we got back from Africa, we asked ourselves, ‘Can we do centrifugation with no electricity, using only human power?’” Other researchers have come up with low-tech, inexpensive centrifuges that used salad spinners and egg beaters, but these devices could manage only about 1,200 rotations per minute and took too long to process samples, says Manu. Hoping to do better, his team went on a shopping spree to a toy store, collecting spinning gizmos and filming them with a high-speed camera. Yo-yos spun too slowly (and required training to use). But whirligigs were both easy to operate and reached speeds of 10,000 rpm, comparable to a commercial centrifuge. Delighted by the whirligig’s performance, the researchers began exploring the mathematics underlying it in the hope of making improvements. Video footage
toy fast enough to hit that theoretical limit. But a new design made in the lab achieved 125,000 rpm — submitted to Guinness World Records last year as the fastest device to rotate with human power.
CHEAPER DIAGNOSIS A paper centrifuge, capable of separating out parasites like malaria from blood samples, in action. PHOTO CREDIT: STANFORD NEWS/KURT HICKMAN
revealed that the toy’s strings not only twist around each other as they wind and unwind, but also form coils similar to structures found in DNA. Solving the equations that describe the forces behind
that coiling revealed the specifications for an ideal whirligig — from the size of its disc to the thickness of its strings — capable of spinning a million times per minute. Human hands cannot spin the
Whether health care workers will be willing to spend that much time powering the paperfuge — either in a health care facility or out in the field — remains to be seen. Manu has partnered with the health care nonprofit PIVOT in Boston for a clinical trial in Madagascar, which will assess not only how easy the device is to use, but also its durability and reliability compared with commercial centrifuges. “We don’t know yet if the paperfuge will work,” says Matt Bonds, PIVOT cofounder and an economist at Harvard University in Cambridge, Massachusetts. “It would take a lot of evidence to convince people to abandon modern centrifuges, but having \ available as an alternative could open up a world of new possibilities.”
Hiding in plain sight “What makes this really special is that it takes something simple and reveals something superbly useful hiding just under our noses,” says Tadashi Tokieda, an applied mathematician at the University of Cambridge. After optimising the whirligig, Manu and his team then mounted plastic tubes for holding blood samples onto their paper device. Their final prototype, dubbed the paperfuge, can reach 20,000 rpm, separating plasma from blood in 1.5 minutes, and malaria parasites in 15 Devin Powell minutes. The New York Times