Researchers discover that aspartate is a limiter of cell proliferation
Scientia — Mitochondria are well known for their role as powerhouses in our cells, using respiration to release the energy in the food we eat and trapping that energy in the molecule adenosine triphosphate, or ATP.
A cell division observed. Cancer risk increases with the rate of cell divisions. Image: Thomas Ried/NCI Center for Cancer Research
In two companion papers published this week in Cell, MIT researchers reveal why proliferating cells — including those in tumors — require mitochondrial respiration. While there are other ways to make ATP, cells can’t proliferate without access to electron acceptors provided by respiration.
For proliferation in cells, there must be plenty of aspartate present to create all of the new cell’s RNA and DNA, as well as its proteins. Aspartate is an amino acid, one of the fundamental building blocks of proteins, but unlike the others it is not readily available in the bloodstream — indeed, it seems the body may actively limit blood levels of the amino acid — so each mammalian cell has to make its own. Furthermore, to make aspartate and nucleic acids, cells need to have a place to put extra electrons, because the end product has fewer electrons than the food cells ingest.
“This is a problem that all proliferating cells must solve,” says Matthew Vander Heiden, the Eisen and Chang Career Development Associate Professor of Biology, and a member of MIT’s Koch Institute for Integrative Cancer Research. “It is a problem in metabolism I had not considered before, but there are people in the bacterial world who have spent lots of time on it.”
Surplus of electrons
Vander Heiden and his colleagues have been investigating the ways in which mammalian cells solve this problem, to get those excess electrons out of the way.
They used cancer cells whose mitochondria — organelles that have their own DNA — were genetically modified to disable respiration. With no intervention, these cells fail to proliferate, and their population gradually declines as some of the cells die off. Add some aspartate, however, and their population grows exponentially, showing that the cells were not able to create their own aspartate without respiration.
The researchers then took the experiment a step further to discover the exact role respiration was playing in the production of aspartate. If certain nutrients, such as pyruvate, that can act as electron acceptors are added to the disabled cells, they are able to proliferate just as well, even without aspartate. This suggests that the cells are able to make aspartate using the added pyruvate as a place to put extra electrons when oxygen is not available. This finding is important for cancer research, because it’s a loophole cancer cells can use to get around any attack on their respiration.
“That’s the name of the game for tumors. They’ve got to grow bigger,” says Celeste Simon, a professor of cell and developmental biology at the University of Pennsylvania, who was not involved in the research. “We didn’t appreciate that aspartate was so important. The assumption was that it was about generating metabolic building blocks.”
Simon and her colleagues work on metabolic problems in renal cancer. “What Matt’s paper tells us is that cells with defects in their electron transfer chains become dependent on pyruvate, which serves as an alternative electron acceptor for generating aspartate,” she says.
Since tumors have limited access to nutrients and oxygen, they likely generate aspartate in a different way. Knowing that cancer may be dependent on pyruvate to serve as an alternative electron acceptor, as one way to get around checks on its growth, means that researchers can look at ways to close that loophole.
Writing in the same issue of Cell, David Sabatini, a professor of biology at MIT and member of the Whitehead Institute and the Koch Institute, reports on his use of a different approach to determine the link between aspartate and cell respiration. Sabatini and his colleagues conducted a genetic screen using the genome-editing tool CRISPR, which revealed that without the enzyme GOT1, cells will die when respiration is inhibited. Under normal circumstances, GOT1 consumes aspartate to transfer electrons into the mitochondria.
Upon further study, the researchers found that when respiration is disabled, GOT1 will attempt to compensate for the lack of mitochondrial aspartate synthesis by catalyzing the reverse reaction, generating — instead of consuming — aspartate in the cytosol, or intracellular fluid. The researchers confirmed that pyruvate will promote this aspartate synthesis, rescuing cell proliferation by creating a place to put extra electrons.
“Our work reveals that the main role of respiration in cell proliferation is not energy production, but rather making this simple amino acid, aspartate,” says Kivanc Birsoy, a postdoc in Sabatini’s lab. “This result was quite surprising for us.”
Benefits beyond cancer
It’s not just cancer research that might benefit from this key insight. For people who suffer from mitochondrial diseases, their conditions — many of them rare — often involve problems in cell respiration.
“These are usually viewed in terms of ATP, but some of them might also have to do with electron acceptors,” Vander Heiden says. He also notes that in diseases of aging, mitochondria often seem to malfunction, and some of these defects could result from an electron imbalance.
To be doubly sure that pyruvate’s role as an electron acceptor was what enabled aspartate production, Vander Heiden tried the same process using another nutrient that only serves as an electron acceptor and fulfills none of the other functions of pyruvate in the cell. The results were identical.
Even the fully functional control cells seemed to benefit slightly from improved access to electron acceptors and aspartate — a possible lead for future research on aspartate as a bottleneck in normal cell proliferation.
Beyond its near-future medical research applications, the discovery is considered an important advance in basic cell biology.
Researchers mount successful attacks against popular Tor anonymity network — and show how to prevent them…Phew
Scientia — With 2.5 million daily users, the Tor network is the world’s most popular system for protecting Internet users’ anonymity. For more than a decade, people living under repressive regimes have used Tor to conceal their Web-browsing habits from electronic surveillance, and websites hosting content that’s been deemed subversive have used it to hide the locations of their servers.
Researchers at MIT and the Qatar Computing Research Institute (QCRI) have now demonstrated a vulnerability in Tor’s design. At the Usenix Security Symposium this summer, they will show that an adversary could infer a hidden server’s location, or the source of the information reaching a given Tor user, by analyzing the traffic patterns of encrypted data passing through a single computer in the all-volunteer Tor network.
Fortunately, the same paper also proposes defenses, which representatives of the Tor project say they are evaluating for possible inclusion in future versions of the Tor software.
“Anonymity is considered a big part of freedom of speech now,” says Albert Kwon, an MIT graduate student in electrical engineering and computer science and one of the paper’s first authors. “The Internet Engineering Task Force is trying to develop a human-rights standard for the Internet, and as part of their definition of freedom of expression, they include anonymity. If you’re fully anonymous, you can say what you want about an authoritarian government without facing persecution.”
Layer upon layer
Sitting atop the ordinary Internet, the Tor network consists of Internet-connected computers on which users have installed the Tor software. If a Tor user wants to, say, anonymously view the front page of The New York Times, his or her computer will wrap a Web request in several layers of encryption and send it to another Tor-enabled computer, which is selected at random. That computer — known as the guard — will peel off the first layer of encryption and forward the request to another randomly selected computer in the network. That computer peels off the next layer of encryption, and so on.
The last computer in the chain, called the exit, peels off the final layer of encryption, exposing the request’s true destination: the Times. The guard knows the Internet address of the sender, and the exit knows the Internet address of the destination site, but no computer in the chain knows both. This routing scheme, with its successive layers of encryption, is known as onion routing, and it gives the network its name: “Tor” is an acronym for “the onion router.”
In addition to anonymous Internet browsing, however, Tor also offers what it calls hidden services. A hidden service protects the anonymity of not just the browser, but the destination site, too. Say, for instance, that someone in Iran wishes to host a site archiving news reports from Western media but doesn’t want it on the public Internet. Using the Tor software, the host’s computer identifies Tor routers that it will use as “introduction points” for anyone wishing to access its content. It broadcasts the addresses of those introduction points to the network, without revealing its own location.
If another Tor user wants to browse the hidden site, both his or her computer and the host’s computer build Tor-secured links to the introduction point, creating what the Tor project calls a “circuit.” Using the circuit, the browser and host identify yet another router in the Tor network, known as a rendezvous point, and build a second circuit through it. The location of the rendezvous point, unlike that of the introduction point, is kept private.
Traffic fingerprinting
Kwon devised an attack on this system with joint first author Mashael AlSabah, an assistant professor of computer science at Qatar University, a researcher at QCRI, and, this year, a visiting scientist at MIT; Srini Devadas, the Edwin Sibley Webster Professor in MIT’s Department of Electrical Engineering and Computer Science; David Lazar, another graduate student in electrical engineering and computer science; and QCRI’s Marc Dacier.
The researchers’ attack requires that the adversary’s computer serve as the guard on a Tor circuit. Since guards are selected at random, if an adversary connects enough computers to the Tor network, the odds are high that, at least on some occasions, one or another of them would be well-positioned to snoop.
During the establishment of a circuit, computers on the Tor network have to pass a lot of data back and forth. The researchers showed that simply by looking for patterns in the number of packets passing in each direction through a guard, machine-learning algorithms could, with 99 percent accuracy, determine whether the circuit was an ordinary Web-browsing circuit, an introduction-point circuit, or a rendezvous-point circuit. Breaking Tor’s encryption wasn’t necessary.
Furthermore, by using a Tor-enabled computer to connect to a range of different hidden services, they showed that a similar analysis of traffic patterns could identify those services with 88 percent accuracy. That means that an adversary who lucked into the position of guard for a computer hosting a hidden service, could, with 88 percent certainty, identify it as the service’s host.
Similarly, a spy who lucked into the position of guard for a user could, with 88 percent accuracy, tell which sites the user was accessing.
To defend against this type of attack, “We recommend that they mask the sequences so that all the sequences look the same,” AlSabah says. “You send dummy packets to make all five types of circuits look similar.”
“For a while, we’ve been aware that circuit fingerprinting is a big issue for hidden services,” says David Goulet, a developer with the Tor project. “This paper showed that it’s possible to do it passively — but it still requires an attacker to have a foot in the network and to gather data for a certain period of time.”
“We are considering their countermeasures as a potential improvement to the hidden service,” he adds. “But I think we need more concrete proof that it definitely fixes the issue.”
Bioluminescence in lanternsharks appears to help with reproduction
Scientia — A small team of researchers with members from Belgium, Sweden and Germany has a found what they believe is a possible explanation for bioluminescence in lanternsharks. In their paper, Julien Claes, Dan-Eric Nilsson, Jérôme Mallefet and Nicolas Straube describe field experiments they conducted watching the sharks to learn if the luminescence was tied to their behavior, genetic testing they conducted and what they found in doing so.
Etmopterus spinax. Credit: sharks.org
Lanternsharks live in the ocean off the coast of Iceland and northern Europe all the way down to South Africa, generally in deep water—water so deep that there is no light. As the researchers report, most species of the small shark have developed bioluminescence, though until now, the reason for it has remained a mystery—it does not appear to offer a means of attracting prey or warding off predators and it would seem counterproductive towards hiding from predators.
To find out, the team studied the sharks in their natural environment and also in large holding tanks—on the lookout for any behaviors that might be related to their ability to light up. They noted that males and females have light producing organs known as photophores on different parts of their bodies, and that both have the organs very near their external sex organs.
After the careful study of the sharks, the team determined that the purpose of the bioluminescence was to help with finding a mate—with light coming from different body parts it becomes much easier for the sharks to differentiate between genders in the dark. They also noted that the sharks shimmy as they swim, twisting their bodies back and forth which causes the light they emit to appear to flick on and off, which the team believes is meant to confuse predators—in some cases it might be mistaken for light matching the surroundings causing the shark to appear invisible.
Genetic testing of the sharks showed much more species diversity than was thought—they found 36 in all and suspect the bioluminescence was partly responsible, because it allows for maintaining reproductive isolation. But it also contributes to a slow reproductive rate, which the team notes, has led to them being classified as “near threatened” in northern waters.
What is a Bioluminescence lanternshark?
A Bioluminescence Lanternshark also known as the velvet belly lanternshark (or simply velvet belly, Etmopterus spinax) is a species of dogfish shark in the family Etmopteridae.
One of the most common deepwater sharks in the northeastern Atlantic Ocean, the velvet belly is found from Iceland and Norway to Gabon and South Africa at a depth of 70–2,490 m (230–8,170 ft).
A small shark generally no more than 45 cm (18 in) long, the velvet belly is so named because its black underside is abruptly distinct from the brown coloration on the rest of its body. The body of this species is fairly stout, with a moderately long snout and tail, and very small gill slits. Like other lanternsharks, the velvet belly is bioluminescent, with light-emitting photophores forming a species-specific pattern over its flanks and abdomen. These photophores are thought to function in counter-illumination, which camouflages the shark against predators. They may also play a role in social interactions.
Young velvet bellies feed mainly on krill and small bony fish, transitioning to squid and shrimp as they grow larger. There is evidence that individuals also move into deeper water as they age. This species exhibits a number of adaptations to living in the deep sea, such as specialized T-cells and liver proteins for dealing with the higher concentrations of heavy metals found there. Velvet bellies often carry a heavy parasite load. It is ovoviviparous, giving birth to litters of six to 20 young every two to three years. This species has virtually no commercial value, but large numbers are caught as bycatch in deepwater commercial fisheries. Although it has been assessed as of Least Concern by the International Union for Conservation of Nature, the heavy fishing pressure throughout its range and its slow reproductive rate are raising conservation concerns.
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Chondrichthyes Subclass: Elasmobranchii Order: Squaliformes Family: Etmopteridae Genus: Etmopterus Species: E. spinax
Habitat of the lanternshark
The range of the velvet belly is in the eastern Atlantic, extending from Iceland and Norway to Gabon, including the Mediterranean Sea, the Azores, the Canary Islands, and Cape Verde. It has also been reported off Cape Province, South Africa. This shark mainly inhabits the outer continental and insular shelves and upper slopes over mud or clay, from close to the bottom to the middle of the water column. It is most common at a depth of 200–500 m (660–1,640 ft), though in the Rockall Trough, it is only found at a depth of 500–750 m (1,640–2,460 ft). This species has been reported from as shallow as 70 m (230 ft), and as deep as 2,490 m (8,170 ft).
Pictures of lanternsharks
– Credit and Resource –
More information: The presence of lateral photophores correlates with increased speciation in deep-sea bioluminescent sharks, DOI: 10.1098/rsos.150219
Scientia — Nearly all life on Earth depends on photosynthesis, the conversion of light energy into chemical energy. Oxygen-producing plants and cyanobacteria perfected this process 2.7 billion years ago. But the first photosynthetic organisms were likely single-celled purple bacteria that began absorbing near-infrared light and converting it to sulfur or sulfates about 3.4 billion years ago.
University of Illinois researchers used the Titan supercomputer at the Oak Ridge Leadership Computing Facility to create a model of a complete 100-million-atom photosynthetic chromatophore. The final chromatophore model contained about 16,000 lipids and 101 proteins, including the five major types of proteins that contribute to the clockwork of processes that result in the conversion of light energy to ATP. Credit: Abhi Singharoy and Melih Sener, UIUC
Found in the bottom of lakes and ponds today, purple bacteria possess simpler photosynthetic organelles—specialized cellular subunits called chromatophores—than plants and algae. For that reason, Klaus Schulten of the University of Illinois at Urbana–Champaign (UIUC) targeted the chromatophore to study photosynthesis at the atomic level.
As a computational biophysicist, Schulten unites biologists’ experimental data with the physical laws that govern the behavior of matter. This combination allows him to simulate biomolecules, atom by atom, using supercomputers. The simulations reveal interactions between molecules that are impossible to observe in the laboratory, providing plausible explanations for how molecules carry out biological functions in nature.
In 2014, a team led by Schulten used the Titan supercomputer, located at the US Department of Energy’s (DOE’s) Oak Ridge National Laboratory, to construct and simulate a single chromatophore. The soccer ball-shaped chromatophore contained more than 100 million atoms—a significantly larger biomolecular system than any previously modeled. The project’s scale required Titan, the flagship supercomputer at the Oak Ridge Leadership Computing Facility (OLCF), a DOE Office of Science User Facility, to calculate the interaction of millions of atoms in a feasible time frame that would allow for data analysis.
“For years, scientists have seen that cells are made of these machines, but they could only look at part of the machine. It’s like looking at a car engine and saying, ‘Oh, there’s an interesting cable, an interesting screw, an interesting cylinder.’ You look at the parts and describe them with love and care, but you don’t understand how the engine actually works that way,” Schulten said. “Titan gave us the fantastic level of computing we needed to see the whole picture. For the first time, we could go from looking at the cable, the screw, the cylinder to looking at the whole engine.”
Schulten’s chromatophore simulation is being used to understand the fundamental process of photosynthesis, basic research that could one day lead to better solar energy technology. Of particular interest: how hundreds of proteins work together to capture light energy at an estimated 90 percent efficiency.
Furthermore, the chromatophore project marks a shift in computational biophysics from analyzing the individual cell parts (e.g., a single protein) to analyzing the specialized systems of the cell (e.g., hundreds of proteins working together to carry out an autonomous function). This is a significant step toward the long-term goal of simulating an entire living organism.
Reconstructing Photosynthesis
When the purple bacteria Rhodobacter sphaeroides switches into photosynthetic mode, its inner membrane begins to change, bulging out into small, round vesicles that house the light-harvesting machinery.
Five major types of proteins arranged within two layers of lipids, or fats, contribute to the clockwork of processes that result in the conversion of light energy to adenosine triphosphate (ATP), the common fuel for cellular function across all branches of life.
During the initial steps of photosynthesis, two types of light-harvesting proteins absorb wavelengths of light that lift them into an excited state. This electronic excitation travels through the light-harvesting network to the third type of protein, known as the reaction center. Here, electrical energy is converted into an initial form of chemical energy. Molecules called quinols carry this chemical energy across the organelle to the fourth type of protein—the bc1 complex—where a charge separation process strips the quinol of electrons. This process triggers a current of protons in the fifth type of protein, known as ATP synthase, driving the molecule’s paddle wheel-like c-ring to produce ATP. A detailed video of this process narrated by Schulten can be seen below:
Schulten’s team solved the 100-million-atom model under an allocation on Titan, awarded through the Innovative and Novel Computational Impact on Theory and Experiment, or INCITE, program.
The team used experimental data gathered from atomic force microscopy and the molecular dynamics code NAMD to build and calculate the forces exerted by the spherical chromatophore’s millions of atoms. The final chromatophore model measured 70 nanometers across and contained about 16,000 lipids and 101 proteins. To ensure the simulation mirrored nature, the chromatophore was submerged in a virtual 100 nanometer cube of water—equal to the largest particle size that can fit through a surgical mask—at room temperature and pressure.
Titan, a Cray XK7 with a peak performance of 27 petaflops (or 27 quadrillion calculations per second), proved pivotal in the early stages of the project. By offloading computationally demanding calculations to Titan’s GPUs, the team was able to achieve two to three times the performance of a CPU-only simulation. Additionally, NAMD scaled efficiently to more than 8,000 of Titan’s 18,688 nodes. The combination of robust hardware and effective software allowed the team to resolve its model in a few months, a task that would have taken more than a year on a smaller machine.
“Titan helped us immensely because you need to run the simulation for a certain amount of time and on a large number of processors in order to improve the model,” said team member Abhi Singharoy, a postdoctoral fellow at the Beckman Institute at UIUC. “This project would have been impossible to do on another computer. Had we not achieved a stable model within the first few months, all our other aims would have been out of reach.”
Researchers earlier had leveraged Titan to resolve a flat, 20-million atom chromatophore patch as a stepping stone to the larger system. UIUC postdoctoral researchers Melih Sener and Danielle Chandler carried out the bulk of this initial work, arranging the proteins in accordance with atomic force microscopy data. A description of the 20-million-atom system was published in the August 2014 edition of Biophysical Journal.
Maximizing the Machine
With a stable model, the remarkable processes of the complete chromatophore—how its atoms move and coordinate within an active, energy-conversion system—can be studied in unprecedented detail.
Under a 150-million processor-hour allocation awarded through the 2015 INCITE program, the team is continuing to run its simulation and analyze the chromatophore for notable properties, such as the organelle’s optimum pH and salt concentration levels. Analysis and visualization of the organelle are being conducted using an application called VMD. Both VMD and NAMD originated with and continue to be developed by Schulten’s Theoretical and Computational Biophysics Group at UIUC. The applications support a global community of users.
NAMD calculates the motion of the chromatophore’s atoms in time steps of 2 femtoseconds, or 2,000 trillionths of a second. At this timescale, a 1-day, 4,000-processor run on Titan nets 16 nanoseconds (16 million femtoseconds), or 16 billionths of a second, of simulation time. By continuing to run the simulation—with the goal of capturing a microsecond (1,000 nanoseconds) of simulation time—slower-moving processes of the biomolecular system can be observed.
“With the time we’ve been allotted on Titan, we will actually be able to see a quinol move and the charge being transferred,” Singharoy said.
The OLCF is helping Schulten’s team manage and analyze the terabytes of data produced by the project. Typically, simulation data are transferred to a project’s home institution for analysis. Because of the size of the chromatophore, a transfer job can take days to complete—even using world-class networking resources.
To overcome this bottleneck, the OLCF worked to enable the graphics capabilities of Titan’s GPUs. Opening up Titan for hardware-accelerated graphics makes it possible for users to run VMD’s graphical interfaces in parallel with NAMD from any location, creating a near real-time “window” into calculations being performed on Titan. Such remote visualization would make it easier for researchers to view and manipulate their data while eliminating the file transfer. This VMD capability is expected to be available to users soon.
“We’re making the scientists much more productive,” said John Stone, a senior research programmer at UIUC and VMD’s lead developer. “Essentially, it will be like having a petascale computer on your laptop.”
– Credit and Resource –
More information: D. Chandler, J. Strümpfer, M. Sener, S. Scheuring, and K. Schulten. “Light Harvesting by Lamellar Chromatophores in Rhodospirillum photometricum.” Biophysical Journal 106, no. 11 (2014): 2503–2510. http://dx.doi.org/10.1016/j.bpj.2014.04.030.
With its biggest orbit maneuver since 2006, NASA’s Mars Orbiter will prepare this week for the arrival of NASA’s next Mars lander, InSight, next year.
A planned 77-second firing of six intermediate-size thrusters on July 29 will adjust the orbit timing of the veteran spacecraft so it will be in position to receive radio transmissions from InSight as the newcomer descends through the Martian atmosphere and touches down on Sept. 28, 2016. These six rocket engines, which were used for trajectory corrections during the spacecraft’s flight from Earth to Mars, can each produce about 22 newtons, or five pounds, of thrust.
“Without making this orbit change maneuver, Mars Reconnaissance Orbiter would be unable to hear from InSight during the landing, but this will put us in the right place at the right time,” said MRO Project Manager Dan Johnston of NASA’s Jet Propulsion Laboratory, Pasadena, California.
NASA’s Mars Reconnaissance Orbiter passes above a portion of the planet called Nilosyrtis Mensae in this artist’s concept illustration. Credits: NASA/JPL-Caltech
The orbiter will record InSight’s transmissions for later playback to Earth as a record of each event during the critical minutes of InSight’s arrival at Mars, just as MRO did for the landings of NASA’s Curiosity Mars rover three years ago, and NASA’s Phoenix Mars lander in 2008.
InSight will examine the deep interior of Mars for clues about the formation and early evolution of all rocky planets, including Earth.
MRO will continue its studies of Mars while preparing for the InSight arrival. MRO collects high-resolution imaging and spectral data, as well as atmospheric and sub-surface profiles. It has returned several times more data about the Red Planet than all other deep-space missions combined. It will also continue providing communication relay support for Mars rovers and making observations for analysis of candidate landing sites for future missions.
After the InSight landing, plans call for MRO to perform a pair of even larger maneuvers in October 2016 and April 2017 — each using the six intermediate-size thrusters longer than three minutes. These will return it to the orbit timing it has used since 2006, crossing the equator at about 3 a.m. and 3 p.m., local solar time, during each near-polar loop around the planet. To observe the InSight arrival, MRO will be in an orbit that crosses the equator at about 2:30 p.m. local solar mean time.
The last time the mission performed a maneuver larger than this week’s was on November 15, 2006. That maneuver fired the intermediate-size thrusters for 76 seconds to establish the original 3 p.m. Local Mean Solar Time (LMST) sun-synchronous condition after a six-month period of using dips into the upper atmosphere to alter the orbit’s shape. The spacecraft has three sets of thrusters. It used its most powerful set — six thrusters, each with 170 newtons, or 39 pounds of force — for about 27 minutes to first enter orbit when it arrived at Mars on March 10, 2006. It uses eight smaller thrusters most frequently, for small adjustments to course or orientation.
Even after the planned 2017 maneuver, the spacecraft’s remaining supply of hydrazine propellant is projected to be more than 413 pounds (about 187 kilograms), equivalent to about 19 years of consumption in normal operations.
New model may explain emergence of self-replication on early Earth
A schematic drawing of template-assisted ligation, shown in this model to give rise to autocatalytic systems. Credit: Maslov and Tkachenko
Scientia — When life on Earth began nearly 4 billion years ago, long before humans, dinosaurs or even the earliest single-celled forms of life roamed, it may have started as a hiccup rather than a roar: small, simple molecular building blocks known as “monomers” coming together into longer “polymer” chains and falling apart in the warm pools of primordial ooze over and over again.
Then, somewhere along the line, these growing polymer chains developed the ability to make copies of themselves. Competition between these molecules would allow the ones most efficient at making copies of themselves to do so faster or with greater abundance, a trait that would be shared by the copies they made. These rapid replicators would fill the soup faster than the other polymers, allowing the information they encoded to be passed on from one generation to another and, eventually, giving rise to what we think of today as life.
Or so the story goes. But with no fossil record to check from those early days, it’s a narrative that still has some chapters missing. One question in particular remains problematic: what enabled the leap from a primordial soup of individual monomers to self-replicating polymer chains?
A new model published this week in The Journal of Chemical Physics, from AIP Publishing, proposes a potential mechanism by which self-replication could have emerged. It posits that template-assisted ligation, the joining of two polymers by using a third, longer one as a template, could have enabled polymers to become self-replicating.
“We tried to fill this gap in understanding between simple physical systems to something that can behave in a life-like manner and transmit information,” said Alexei Tkachenko, a researcher at Brookhaven National Laboratory. Tkachenko carried out the research alongside Sergei Maslov, a professor at the University of Illinois at Urbana-Champaign with joint appointment at Brookhaven.
Origins of Self-Replication
Self-replication is a complicated process—DNA, the basis for life on earth today, requires a coordinated cohort of enzymes and other molecules in order to duplicate itself. Early self-replicating systems were surely more rudimentary, but their existence in the first place is still somewhat baffling.
Tkachenko and Maslov have proposed a new model that shows how the earliest self-replicating molecules could have worked. Their model switches between “day” phases, where individual polymers float freely, and “night” phases, where they join together to form longer chains via template-assisted ligation. The phases are driven by cyclic changes in environmental conditions, such as temperature, pH, or salinity, which throw the system out of equilibrium and induce the polymers to either come together or drift apart.
According to their model, during the night cycles, multiple short polymers bond to longer polymer strands, which act as templates. These longer template strands hold the shorter polymers in close enough proximity to each other that they can ligate to form a longer strand—a complementary copy of at least part of the template. Over time, the newly synthesized polymers come to dominate, giving rise to an autocatalytic and self-sustaining system of molecules large enough to potentially encode blueprints for life, the model predicts.
Polymers can also link together without the aid of a template, but the process is somewhat more random—a chain that forms in one generation will not necessarily be carried over into the next. Template-assisted ligation, on the other hand, is a more faithful means of preserving information, as the polymer chains of one generation are used to build the next. Thus, a model based on template-assisted ligation combines the lengthening of polymer chains with their replication, providing a potential mechanism for heritability.
While some previous studies have argued that a mix of the two is necessary for moving a system from monomers to self-replicating polymers, Maslov and Tkachenko’s model demonstrates that it is physically possible for self-replication to emerge with only template-assisted ligation.
“What we have demonstrated for the first time is that even if all you have is template-assisted ligation, you can still bootstrap the system out of primordial soup,” said Maslov.
The idea of template-assisted ligation driving self-replication was originally proposed in the 1980s, but in a qualitative manner. “Now it’s a real model that you can run through a computer,” said Tkachenko. “It’s a solid piece of science to which you can add other features and study memory effects and inheritance.”
Under Tkachenko and Maslov’s model, the move from monomers to polymers is a very sudden one. It’s also hysteretic—that is, it takes a very certain set of conditions to make the initial leap from monomers to self-replicating polymers, but those stringent requirements are not necessary to maintain a system of self-replicating polymers once one has leapt over the first hurdle.
One limitation of the model that the researchers plan to address in future studies is its assumption that all polymer sequences are equally likely to occur. Transmission of information requires heritable variation in sequence frequencies—certain combinations of bases code for particular proteins, which have different functions. The next step, then, is to consider a scenario in which some sequences become more common than others, allowing the system to transmit meaningful information.
Maslov and Tkachenko’s model fits into the currently favored RNA world hypothesis—the belief that life on earth started with autocatalytic RNA molecules that then lead to the more stable but more complex DNA as a mode of inheritance. But because it is so general, it could be used to test any origins of life hypothesis that relies on the emergence of a simple autocatalytic system.
“The model, by design, is very general,” said Maslov. “We’re not trying to address the question of what this primordial soup of monomers is coming from” or the specific molecules involved. Rather, their model shows a physically plausible path from monomer to self-replicating polymer, inching a step closer to understanding the origins of life.
Waiter, there’s an RNA in my Primordial Soup—Tracing the Origins of Life, from Darwin to Today
Nearly every culture on earth has an origins story, a legend explaining its existence. We humans seem to have a deep need for an explanation of how we ended up here, on this small planet spinning through a vast universe. Scientists, too, have long searched for our origins story, trying to discern how, on a molecular scale, the earth shifted from a mess of inorganic molecules to an ordered system of life. The question is impossible to answer for certain—there’s no fossil record, and no eyewitnesses. But that hasn’t stopped scientists from trying.
Over the past 150 years, our shifting understanding of the origins of life has mirrored the emergence and development of the fields of organic chemistry and molecular biology. That is, increased understanding of the role that nucleotides, proteins and genes play in shaping our living world today has also gradually improved our ability to peer into their mysterious past.
When Charles Darwin published his seminal On the Origin of the Species in 1859, he said little about the emergence of life itself, possibly because, at the time, there was no way to test such ideas. His only real remarks on the subject come from a later letter to a friend, in which he suggested a that life emerged out of a “warm little pond” with a rich chemical broth of ions. Nevertheless, Darwin’s influence was far-reaching, and his offhand remark formed the basis of many origins of life scenarios in the following years.
In the early 20th century, the idea was popularized and expanded upon by a Russian biochemist named Alexander Oparin. He proposed that the atmosphere on the early earth was reducing, meaning it had an excess of negative charge. This charge imbalance could catalyze existing a prebiotic soup of organic molecules into the earliest forms of life.
Oparin’s writing eventually inspired Harold Urey, who began to champion Oparin’s proposal. Urey then caught the attention of Stanley Miller, who decided to formally test the idea. Miller took a mixture of what he believed the early earth’s oceans may have contained—a reducing mixture of methane, ammonia, hydrogen, and water—and activated it with an electric spark. The jolt of electricity, acting like a strike of lightening, transformed nearly half of the carbon in the methane into organic compounds. One of the compounds he produced was glycine, the simplest amino acid.
The groundbreaking Miller-Urey experiment showed that inorganic matter could give rise to organic structures. And while the idea of a reducing atmosphere gradually fell out of favor, replaced by an environment rich in carbon dioxide, Oparin’s basic framework of a primordial soup rich with organic molecules stuck around.
The identification of DNA as the hereditary material common to all life, and the discovery that DNA coded for RNA, which coded for proteins, provided fresh insight into the molecular basis for life. But it also forced origins of life researchers to answer a challenging question: how could this complicated molecular machinery have started? DNA is a complex molecule, requiring a coordinated team of enzymes and proteins to replicate itself. Its spontaneous emergence seemed improbable.
In the 1960s, three scientists—Leslie Orgel, Francis Crick and Carl Woese—independently suggested that RNA might be the missing link. Because RNA can self-replicate, it could have acted as both the genetic material and the catalyst for early life on earth. DNA, more stable but more complex, would have emerged later.
Today, it is widely believed (though by no means universally accepted) that at some point in history, an RNA-based world dominated the earth. But how it got there—and whether there was a simpler system before it—is still up for debate. Many argue that RNA is too complicated to have been the first self-replicating system on earth, and that something simpler preceded it.
Graham Cairns-Smith, for instance, has argued since the 1960s that the earliest gene-like structures were not based on nucleic acids, but on imperfect crystals that emerged from clay. The defects in the crystals, he believed, stored information that could be replicated and passed from one crystal to another. His idea, while intriguing, is not widely accepted today.
Others, taken more seriously, suspect that RNA may have emerged in concert with peptides—an RNA-peptide world, in which the two worked together to build up complexity. Biochemical studies are also providing insight into simpler nucleic acid analogs that could have preceded the familiar bases that make up RNA today. It’s also possible that the earliest self-replicating systems on earth have left no trace of themselves in our current biochemical systems. We may never know, and yet, the challenge of the search seems to be part of its appeal.
Recent research by Tkachenko and Maslov, published July 28, 2015 in The Journal of Chemical Physics, suggests that self-replicating molecules such as RNA may have arisen through a process called template-assisted ligation. That is, under certain environmental conditions, small polymers could be driven to bond to longer complementary polymer template strands, holding the short strands in close enough proximity to each other that they could fuse into longer strands. Through cyclic changes in environmental conditions that induce complementary strands to come together and then fall apart repeatedly, a self-sustaining collection of hybridized, self-replicating polymers able to encode the blueprints for life could emerge.
– Credit and Resource –
More information: The article, “Spontaneous emergence of autocatalytic information-coding polymers,” by Alexei Tkachenko and Sergei Maslov, The Journal of Chemical Physics on July 28, 2015: http://scitation.aip.org/content/aip/journal/jcp/143/2/10.1063/1.4922545
Long-sought Massless particle phenomenon finally detected Weyl points, first predicted in 1929, observed for the first time.
Scientia — Part of a 1929 prediction by physicist Hermann Weyl — of a kind of massless particle that features a singular point in its energy spectrum called the “Weyl point” — has finally been confirmed by direct observation for the first time, says an international team of physicists led by researchers at MIT. The finding could lead to new kinds of high-power single-mode lasers and other optical devices, the team says.
For decades, physicists thought that the subatomic particles called neutrinos were, in fact, the massless particles that Weyl had predicted — a possibility that was ultimately eliminated by the 1998 discovery that neutrinos do have a small mass. While thousands of scientific papers have been written about the theoretical particles, until this year there had seemed little hope of actually confirming their existence.
“Every single paper written about Weyl points was theoretical, until now,” says Marin Soljačić, a professor of physics at MIT and the senior author of a paper published this week in the journal Science confirming the detection. (Another team of researchers at Princeton University and elsewhere independently made a different detection of Weyl particles; their paper appears in the same issue of Science).
Ling Lu, a research scientist at MIT and lead author of that team’s paper, says the elusive points can be thought of as equivalent to theoretical entities known as magnetic monopoles. These do not exist in the real world: They would be the equivalent of cutting a bar magnet in half and ending up with separate north and south magnets, whereas what really happens is you end up with two shorter magnets, each with two poles. But physicists often carry out their calculations in terms of momentum space (also called reciprocal space) rather than ordinary three-dimensional space, Lu explains, and in that framework magnetic monopoles can exist — and their properties match those of Weyl points.
The achievement was made possible by a novel use of a material called a photonic crystal. In this case, Lu was able to calculate precise measurements for the construction of a photonic crystal predicted to produce the manifestation of Weyl points — with dimensions and precise angles between arrays of holes drilled through the material, a configuration known as a gyroid structure. This prediction was then proved correct by a variety of sophisticated measurements that exactly matched the characteristics expected for such points.
Some kinds of gyroid structures exist in nature, Lu points out, such as in certain butterfly wings. In such natural occurrences, gyroids are self-assembled, and their structure was already known and understood.
Two years ago, researchers had predicted that by breaking the symmetries in a kind of mathematical surfaces called “gyroids” in a certain way, it might be possible to generate Weyl points — but realizing that prediction required the team to calculate and build their own materials. In order to make these easier to work with, the crystal was designed to operate at microwave frequencies, but the same principles could be used to make a device that would work with visible light, Lu says. “We know a few groups that are trying to do that,” he says.
A number of applications could take advantage of these new findings, Soljačić says. For example, photonic crystals based on this design could be used to make large-volume single-mode laser devices. Usually, Soljačić says, when you scale up a laser, there are many more modes for the light to follow, making it increasingly difficult to isolate the single desired mode for the laser beam, and drastically limiting the quality of the laser beam that can be delivered.
But with the new system, “No matter how much you scale it up, there are very few possible modes,” he says. “You can scale it up as large as you want, in three dimensions, unlike other optical systems.”
That issue of scalability in optical systems is “quite fundamental,” Lu says; this new approach offers a way to circumvent it. “We have other applications in mind,” he says, to take advantage of the device’s “optical selectivity in a 3-D bulk object.” For example, a block of material could allow only one precise angle and color of light to pass through, while all others would be blocked.
“This is an interesting development, not just because Weyl points have been experimentally observed, but also because they endow the photonics crystals which realize them with unique optical properties,” says Ashvin Vishwanath, a professor of physics at the University of California at Berkeley who was not involved in this research. “Professor Soljačić’s group has a track record of rapidly converting new science into creative devices with industry applications, and I am looking forward to seeing how Weyl photonics crystals evolve.”
Besides Lu and Soljačić, the team included Zhiyu Wang, Dexin Ye, and Lixin Ran of Zhejiang University in China and, at MIT, assistant professor of physics Liang Fu and John Joannopoulos, the Francis Wright Davis Professor of Physics and director of the Institute for Soldier Nanotechnologies (ISN). The work was supported by the U.S. Army through the ISN, the Department of Energy, the National Science Foundation, and the Chinese National Science Foundation.
In a new blow for the futuristic supersymmetry physics theory of the universe’s basic anatomy, experts reported new evidence of subatomic activity consistent with the Standard Model of particle physics.
New data from ultra high-speed proton collisions at Europe’s Large Hadron Collider (LHC) showed an exotic particle dubbed the “beauty quark” behaves as predicted by the Standard Model, said a paper in the journal Nature Physics.
Previous attempts at measuring the beauty quark’s rare transformation into a so-called “up quark” had yielded conflicting results. That prompted scientists to propose an explanation beyond the Standard Model—possibly supersymmetry.
But the latest observations were “entirely consistent with the Standard Model and removes the need for this hypothesis” of an alternative theory, Guy Wilkinson, leader of LHC’s “beauty experiment” told AFP.
“It would of course have been very exciting if we could show that there was something wrong with the Standard Model—I cannot deny that would have been sensational,” he said.
The Standard Model is the mainstream theory of all the fundamental particles that make up matter, and the forces that govern them.
But the model has weaknesses: it doesn’t explain dark matter or dark energy, which jointly make up 95 percent of the universe. Nor is it compatible with Einstein’s theory of general relativity—the force of gravity as we know it does not seem to work at the subatomic quantum scale.
Supersymmetry, SUSY for short, is one of the alternatives proposed for explaining these inconsistencies, postulating the existence of a heavier “sibling” for every particle in the universe.
This may also explain dark matter and dark energy.
A scientist looks at a section of the European Organisation for Nuclear Research Large Hadron Collider, during maintenance works in Meyrin, near Geneva on July 19, 2013
No proof of supersymmetric twins has been found at the LHC, which has observed all the particles postulated by the Standard Model—including the long-sought Higgs boson, which confers mass to matter.
Supersymmetry predicts the existence of at least five types of Higgs boson, but only one, believed to be the Standard Model Higgs, has so far been found.
Wilkinson said it was “too soon” to write off supersymmetry.
“It is very difficult to kill supersymmetry: it is a many-headed monster,” he said.
But “if nothing is seen in the next couple of years, supersymmetry would be in a much harder situation. The number of true believers would drop.”
Quarks are the most basic particles, building blocks of protons and neutrons, which in turn are found in atoms.
There are six types of quarks—the most common are the “up” and “down” quarks, while the others are called “charm”, “strange”, “beauty” and “top.”
The beauty quark, heavier than up and down quarks, can shift shape, and usually takes the form of a charm quark when it does.
Much more rarely, it morphs into an up quark. Wilkinson’s team have now measured—for the first time—how often that happens.
“We are delighted because it is the sort of measurement nobody thought was possible at the LHC,” he said. It had been thought that an even more powerful machine would be needed.
The revamped LHC, a facility of the European Organisation for Nuclear Research (CERN), was restarted in April after a two-year revamp to boost its power from eight to 13, potentially 14, teraelectronvolts (TeV).
“If you expect Earth-shattering news from the new run, it’s a bit early,” CERN director-general Rolf Heuer told journalists in Vienna Monday at a conference of the European Physical Society.
“The main harvest will come in the years to come, so you have to stay tuned.”
So far, the new run at 13 TeV has re-detected all the Standard Model particles except for the Higgs boson, but Heuer insisted: “We are sure that it is there.”
How Nanomaterials and UV light can “trap” chemicals for easy removal from soil and water.
Scientia — Many human-made pollutants in the environment resist degradation through natural processes, and disrupt hormonal and other systems in mammals and other animals. Removing these toxic materials — which include pesticides and endocrine disruptors such as bisphenol A (BPA) — with existing methods is often expensive and time-consuming. In come the Nanomaterials.
Nanoparticles that lose their stability upon irradiation with light have been designed to extract endocrine disruptors, pesticides, and other contaminants from water and soils. The system exploits the large surface-to-volume ratio of nanoparticles, while the photoinduced precipitation ensures nanomaterials are not released in the environment.
In a new paper published this week in Nature Communications, researchers from MIT and the Federal University of Goiás in Brazil demonstrate a novel method for using Nanomaterials and ultraviolet (UV) light to quickly isolate and extract a variety of contaminants from soil and water.
Ferdinand Brandl and Nicolas Bertrand, the two lead authors, are former postdocs in the laboratory of Robert Langer, the David H. Koch Institute Professor at MIT’s Koch Institute for Integrative Cancer Research. (Eliana Martins Lima, of the Federal University of Goiás, is the other co-author.) Both Brandl and Bertrand are trained as pharmacists, and describe their discovery as a happy accident: They initially sought to develop nanoparticles that could be used to deliver drugs to cancer cells.
Brandl had previously synthesized polymers that could be cleaved apart by exposure to UV light. But he and Bertrand came to question their suitability for drug delivery, since UV light can be damaging to tissue and cells, and doesn’t penetrate through the skin. When they learned that UV light was used to disinfect water in certain treatment plants, they began to ask a different question.
“We thought if they are already using UV light, maybe they could use our particles as well,” Brandl says. “Then we came up with the idea to use our particles to remove toxic chemicals, pollutants, or hormones from water, because we saw that the particles aggregate once you irradiate them with UV light.”
A trap for ‘water-fearing’ pollution
The researchers synthesized polymers from polyethylene glycol, a widely used compound found in laxatives, toothpaste, and eye drops and approved by the Food and Drug Administration as a food additive, and polylactic acid, a biodegradable plastic used in compostable cups and glassware.
Nanomaterials made from these polymers have a hydrophobic core and a hydrophilic shell. Due to molecular-scale forces, in a solution hydrophobic pollutant molecules move toward the hydrophobic nanoparticles, and adsorb onto their surface, where they effectively become “trapped.” This same phenomenon is at work when spaghetti sauce stains the surface of plastic containers, turning them red: In that case, both the plastic and the oil-based sauce are hydrophobic and interact together.
If left alone, these nanomaterials would remain suspended and dispersed evenly in water. But when exposed to UV light, the stabilizing outer shell of the particles is shed, and — now “enriched” by the pollutants — they form larger aggregates that can then be removed through filtration, sedimentation, or other methods.
The researchers used the method to extract phthalates, hormone-disrupting chemicals used to soften plastics, from wastewater; BPA, another endocrine-disrupting synthetic compound widely used in plastic bottles and other resinous consumer goods, from thermal printing paper samples; and polycyclic aromatic hydrocarbons, carcinogenic compounds formed from incomplete combustion of fuels, from contaminated soil.
The process is irreversible and the polymers are biodegradable, minimizing the risks of leaving toxic secondary products to persist in, say, a body of water. “Once they switch to this macro situation where they’re big clumps,” Bertrand says, “you won’t be able to bring them back to the nano state again.”
The fundamental breakthrough, according to the researchers, was confirming that small molecules do indeed adsorb passively onto the surface of nanoparticles.
“To the best of our knowledge, it is the first time that the interactions of small molecules with pre-formed nanoparticles can be directly measured,” they write in Nature Communications.
Nano cleansing
Even more exciting, they say, is the wide range of potential uses, from environmental remediation to medical analysis.
The polymers are synthesized at room temperature, and don’t need to be specially prepared to target specific compounds; they are broadly applicable to all kinds of hydrophobic chemicals and molecules.
“The interactions we exploit to remove the pollutants are non-specific,” Brandl says. “We can remove hormones, BPA, and pesticides that are all present in the same sample, and we can do this in one step.”
And the nanoparticles’ high surface-area-to-volume ratio means that only a small amount is needed to remove a relatively large quantity of pollutants. The technique could thus offer potential for the cost-effective cleanup of contaminated water and soil on a wider scale.
“From the applied perspective, we showed in a system that the adsorption of small molecules on the surface of the nanoparticles can be used for extraction of any kind,” Bertrand says. “It opens the door for many other applications down the line.”
This approach could possibly be further developed, he speculates, to replace the widespread use of organic solvents for everything from decaffeinating coffee to making paint thinners. Bertrand cites DDT, banned for use as a pesticide in the U.S. since 1972 but still widely used in other parts of the world, as another example of a persistent pollutant that could potentially be remediated using these nanomaterials. “And for analytical applications where you don’t need as much volume to purify or concentrate, this might be interesting,” Bertrand says, offering the example of a cheap testing kit for urine analysis of medical patients.
The study also suggests the broader potential for adapting nanoscale drug-delivery techniques developed for use in environmental remediation.
“That we can apply some of the highly sophisticated, high-precision tools developed for the pharmaceutical industry, and now look at the use of these technologies in broader terms, is phenomenal,” says Frank Gu, an assistant professor of chemical engineering at the University of Waterloo in Canada, and an expert in nanoengineering for health care and medical applications.
“When you think about field deployment, that’s far down the road, but this paper offers a really exciting opportunity to crack a problem that is persistently present,” says Gu, who was not involved in the research. “If you take the normal conventional civil engineering or chemical engineering approach to treating it, it just won’t touch it. That’s where the most exciting part is.”
NASA’s New Horizons Spacecraft Nears Historic July 14 Encounter with Pluto – April 14, 2015
Scientia — NASA’s New Horizons spacecraft is three months from returning to humanity the first-ever close up images and scientific observations of distant Pluto and its system of large and small moons.
“Scientific literature is filled with papers on the characteristics of Pluto and its moons from ground based and Earth orbiting space observations, but we’ve never studied Pluto up close and personal,” said John Grunsfeld, astronaut, and associate administrator of the NASA Science Mission Directorate at the agency’s Headquarters in Washington. “In an unprecedented flyby this July, our knowledge of what the Pluto systems is really like will expand exponentially and I have no doubt there will be exciting discoveries.”
This image of Pluto and its largest moon, Charon, was taken by the Ralph color imager aboard New Horizons on April 9, 2015, from a distance of about 71 million miles (115 million kilometers). It is the first color image ever made of the Pluto system by a spacecraft on approach. Credits: NASA
The fastest spacecraft ever launched, New Horizons has traveled a longer time and farther away – more than nine years and three billion miles – than any space mission in history to reach its primary target. Its flyby of Pluto and its system of at least five moons on July 14 will complete the initial reconnaissance of the classical solar system. This mission also opens the door to an entirely new “third” zone of mysterious small planets and planetary building blocks in the Kuiper Belt, a large area with numerous objects beyond Neptune’s orbit.
The flyby caps a five-decade-long era of reconnaissance that began with Venus and Mars in the early 1960s, and continued through first looks at Mercury, Jupiter and Saturn in the 1970s and Uranus and Neptune in the 1980s.
Reaching this third zone of our solar system – beyond the inner, rocky planets and outer gas giants – has been a space science priority for years. In the early 2000s the National Academy of Sciences ranked the exploration of the Kuiper Belt – and particularly Pluto and its largest moon, Charon – as its top priority planetary mission for the coming decade.
New Horizons – a compact, lightweight, powerfully equipped probe packing the most advanced suite of cameras and spectrometers ever sent on a first reconnaissance mission – is NASA’s answer to that call.
“This is pure exploration; we’re going to turn points of light into a planet and a system of moons before your eyes!” said Alan Stern, New Horizons principal investigator from Southwest Research Institute (SwRI) in Boulder, Colorado. “New Horizons is flying to Pluto – the biggest, brightest and most complex of the dwarf planets in the Kuiper Belt. This 21st century encounter is going to be an exploration bonanza unparalleled in anticipation since the storied missions of Voyager in the 1980s.”
Pluto, the largest known body in the Kuiper Belt, offers a nitrogen atmosphere, complex seasons, distinct surface markings, an ice-rock interior that may harbor an ocean, and at least five moons. Among these moons, the largest – Charon – may itself sport an atmosphere or an interior ocean, and possibly even evidence of recent surface activity.
“There’s no doubt, Charon is a rising star in terms of scientific interest, and we can’t wait to reveal it in detail in July,” said Leslie Young, deputy project scientist at SwRI.
Pluto’s smaller moons also are likely to present scientific opportunities. When New Horizons was started in 2001, it was a mission to just Pluto and Charon, before the four smaller moons were discovered.
The spacecraft’s suite of seven science instruments – which includes cameras, spectrometers, and plasma and dust detectors – will map the geology of Pluto and Charon and map their surface compositions and temperatures; examine Pluto’s atmosphere, and search for an atmosphere around Charon; study Pluto’s smaller satellites; and look for rings and additional satellites around Pluto.
Currently, even with New Horizons closer to Pluto than the Earth is to the Sun, the Pluto system resembles little more than bright dots in the distance. But teams operating the spacecraft are using these views to refine their knowledge of Pluto’s location, and skillfully navigate New Horizons toward a precise target point 7,750 miles (12,500 kilometers) from Pluto’s surface. That targeting is critical, since the computer commands that will orient the spacecraft and point its science instruments are based on knowing the exact time and location that New Horizons passes Pluto.
“Our team has worked hard to get to this point, and we know we have just one shot to make this work,” said Alice Bowman, New Horizons mission operations manager at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, which built and operates the spacecraft. “We’ve plotted out each step of the Pluto encounter, practiced it over and over, and we’re excited the ‘real deal’ is finally here.”
The spacecraft’s work doesn’t end with the July flyby. Because it gets one shot at its target, New Horizons is designed to gather as much data as it can, as quickly as it can, taking about 100 times as much data on close approach as it can send home before flying away. And although the spacecraft will send select, high-priority datasets home in the days just before and after close approach, the mission will continue returning the data stored in onboard memory for a full 16 months.
“New Horizons is one of the great explorations of our time,” said New Horizons Project Scientist Hal Weaver at APL. “There’s so much we don’t know, not just about Pluto, but other worlds like it. We’re not rewriting textbooks with this historic mission – we’ll be writing them from scratch.”
NASA’s New Horizons: Increasing Variety on Pluto’s Close Approach Hemisphere, and a ‘Dark Pole’ on Charon – June 22, 2015
NASA’s New Horizons spacecraft doesn’t pass Pluto until July 14 – but the mission team is making new discoveries as the piano-sized probe bears down on the Pluto system.
In a long series of images obtained by New Horizons’ telescopic Long Range Reconnaissance Imager (LORRI) May 29-June 19, Pluto and its largest moon, Charon, appear to more than double in size. From this rapidly improving imagery, scientists on the New Horizons team have found that the “close approach hemisphere” on Pluto that New Horizons will fly over has the greatest variety of terrain types seen on the planet so far. They have also discovered that Charon has a “dark pole” – a mysterious dark region that forms a kind of anti-polar cap.
“This system is just amazing,” said Alan Stern, New Horizons Principal Investigator, from the Southwest Research Institute, Boulder, Colorado. “The science team is just ecstatic with what we see on Pluto’s close approach hemisphere: Every terrain type we see on the planet—including both the brightest and darkest surface areas —are represented there, it’s a wonderland!
“And about Charon—wow—I don’t think anyone expected Charon to reveal a mystery like dark terrains at its pole,” he continued. “Who ordered that?”
These images, taken by New Horizons’ Long Range Reconnaissance Imager (LORRI), show numerous large-scale features on Pluto’s surface. When various large, dark and bright regions appear near limbs, they give Pluto a distinct, but false, non-spherical appearance. Pluto is known to be almost perfectly spherical from previous data. These images are displayed at four times the native LORRI image size, and have been processed using a method called deconvolution, which sharpens the original images to enhance features on Pluto. Credits: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
New Horizons scientists use a technique called deconvolution to sharpen the raw, unprocessed pictures that the spacecraft beams back to Earth; the contrast in these latest images has also been stretched to bring out additional details. Deconvolution can occasionally produce artifacts, so the team will be carefully reviewing newer images taken from closer range to determine whether some of the tantalizing details seen in these images persist. Pluto’s non-spherical appearance in these images is not real; it results from a combination of the image-processing technique and Pluto’s large variations in surface brightness.
“The unambiguous detection of bright and dark terrain units on both Pluto and Charon indicates a wide range of diverse landscapes across the pair,” said science team co-investigator and imaging lead Jeff Moore, of NASA Ames Research Center, Mountain View, California. “For example, the bright fringe we see on Pluto may represent frost deposited from an evaporating polar cap, which is now in summer sun.”
These recent images show the discovery of significant surface details on Pluto’s largest moon, Charon. They were taken by the New Horizons Long Range Reconnaissance Imager (LORRI) on June 18, 2015. The image on the left is the original image, displayed at four times the native LORRI image size. After applying a technique that sharpens an image called deconvolution, details become visible on Charon, including a distinct dark pole. Deconvolution can occasionally introduce “false” details, so the finest details in these pictures will need to be confirmed by images taken from closer range in the next few weeks. Credits: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
New Horizons is approximately 2.9 billion miles (4.7 billion kilometers) from Earth and just 16 million miles (25 million kilometers) from Pluto. The spacecraft and payload are in good health and operating normally.
One Million Miles to Go; Pluto is More Intriguing than Ever – July 13, 2015
Pluto as seen from New Horizons on July 11, 2015. Credits: NASA/JHUAPL/SWRI
On July 11, 2015, New Horizons captured a world that is growing more fascinating by the day. For the first time on Pluto, this view reveals linear features that may be cliffs, as well as a circular feature that could be an impact crater. Rotating into view is the bright heart-shaped feature that will be seen in more detail during New Horizons’ closest approach on July 14. The annotated version includes a diagram indicating Pluto’s north pole, equator, and central meridian. Credits: NASA/JHUAPL/SWRI
As NASA’s unmanned New Horizons spacecraft speeds closer to a historic July 14 Pluto flyby, it’s continuing to multi-task, producing images of an icy world that’s growing more fascinating and complex every day.
On July 11, 2015, New Horizons captured this image, which suggests some new features that are of keen interest to the Geology, Geophysics and Imaging (GGI) team now assembled at the Johns Hopkins University Applied Physics Lab in Laurel, Maryland. For the first time on Pluto, this view reveals linear features that may be cliffs, as well as a circular feature that could be an impact crater. Just starting to rotate into view on the left side of the image is the bright heart-shaped feature that will be seen in more detail during New Horizons’ closest approach.
The New Horizons spacecraft is now approaching a milestone – only one million miles to Pluto – which will occur at 11:23 p.m. EDT tonight, Sunday, July 12. It’s approaching Pluto after a more than nine-year, three-billion mile journey. At 7:49 AM EDT on Tuesday, July 14 the unmanned spacecraft will zip past Pluto at 30,800 miles per hour (49,600 kilometers per hour), with a suite of seven science instruments busily gathering data. The mission will complete the initial reconnaissance of the solar system with the first-ever look at the icy dwarf planet.
Pluto is Dominated by the Feature Informally Named the “Heart” – July 14, 2015
Pluto nearly fills the frame in this image from the Long Range Reconnaissance Imager (LORRI) aboard NASA’s New Horizons spacecraft, taken on July 13, 2015 when the spacecraft was 476,000 miles (768,000 kilometers) from the surface. This is the last and most detailed image sent to Earth before the spacecraft’s closest approach to Pluto on July 14. The color image has been combined with lower-resolution color information from the Ralph instrument that was acquired earlier on July 13. This view is dominated by the large, bright feature informally named the “heart,” which measures approximately 1,000 miles (1,600 kilometers) across. The heart borders darker equatorial terrains, and the mottled terrain to its east (right) are complex. However, even at this resolution, much of the heart’s interior appears remarkably featureless—possibly a sign of ongoing geologic processes. Image Credit: NASA/APL/SwRI
The Icy Mountains of Pluto – July 15, 2015
New close-up images of a region near Pluto’s equator reveal a giant surprise: a range of youthful mountains rising as high as 11,000 feet (3,500 meters) above the surface of the icy body.
The mountains likely formed no more than 100 million years ago — mere youngsters relative to the 4.56-billion-year age of the solar system — and may still be in the process of building, says Geology, Geophysics and Imaging (GGI) team leader Jeff Moore of NASA’s Ames Research Center in Moffett Field, California.. That suggests the close-up region, which covers less than one percent of Pluto’s surface, may still be geologically active today.
Moore and his colleagues base the youthful age estimate on the lack of craters in this scene. Like the rest of Pluto, this region would presumably have been pummeled by space debris for billions of years and would have once been heavily cratered — unless recent activity had given the region a facelift, erasing those pockmarks.
“This is one of the youngest surfaces we’ve ever seen in the solar system,” says Moore.
Unlike the icy moons of giant planets, Pluto cannot be heated by gravitational interactions with a much larger planetary body. Some other process must be generating the mountainous landscape.
“This may cause us to rethink what powers geological activity on many other icy worlds,” says GGI deputy team leader John Spencer of the Southwest Research Institute in Boulder, Colo.
The mountains are probably composed of Pluto’s water-ice “bedrock.”
Although methane and nitrogen ice covers much of the surface of Pluto, these materials are not strong enough to build the mountains. Instead, a stiffer material, most likely water-ice, created the peaks. “At Pluto’s temperatures, water-ice behaves more like rock,” said deputy GGI lead Bill McKinnon of Washington University, St. Louis.
The close-up image was taken about 1.5 hours before New Horizons closest approach to Pluto, when the craft was 47,800 miles (77,000 kilometers) from the surface of the planet. The image easily resolves structures smaller than a mile across.
New Horizons Captures Two of Pluto’s Smaller Moons – July 21, 2015
Pluto’s moon Nix (left), shown here in enhanced color as imaged by the New Horizons Ralph instrument, has a reddish spot that has attracted the interest of mission scientists. The data were obtained on the morning of July 14, 2015, and received on the ground on July 18. At the time the observations were taken New Horizons was about 102,000 miles (165,000 km) from Nix. The image shows features as small as approximately 2 miles (3 kilometers) across on Nix, which is estimated to be 26 miles (42 kilometers) long and 22 miles (36 kilometers) wide.
Pluto’s small, irregularly shaped moon Hydra (right) is revealed in this black and white image taken from New Horizons’ LORRI instrument on July 14, 2015, from a distance of about 143,000 miles (231,000 kilometers). Features as small as 0.7 miles (1.2 kilometers) are visible on Hydra, which measures 34 miles (55 kilometers) in length.
While Pluto’s largest moon Charon has grabbed most of the lunar spotlight so far, these two smaller and lesser-known satellites are now getting some attention. Nix and Hydra – the second and third moons to be discovered – are approximately the same size, but their similarity ends there.
New Horizons’ first color image of Pluto’s moon Nix, in which colors have been enhanced, reveals an intriguing region on the jelly bean-shaped satellite, which is estimated to be 26 miles (42 kilometers) long and 22 miles (36 kilometers) wide.
Although the overall surface color of Nix is neutral grey in the image, the newfound region has a distinct red tint. Hints of a bull’s-eye pattern lead scientists to speculate that the reddish region is a crater. “Additional compositional data has already been taken of Nix, but is not yet downlinked. It will tell us why this region is redder than its surroundings,” said mission scientist Carly Howett, Southwest Research Institute, Boulder, Colorado. She added, “This observation is so tantalizing, I’m finding it hard to be patient for more Nix data to be downlinked.”
Meanwhile, the sharpest image yet received from New Horizons of Pluto’s satellite Hydra shows that its irregular shape resembles the state of Michigan. The new image was made by the Long Range Reconnaissance Imager (LORRI) on July 14, 2015 from a distance of 143,000 miles (231,000 kilometers), and shows features as small as 0.7 miles (1.2 kilometers) across. There appear to be at least two large craters, one of which is mostly in shadow. The upper portion looks darker than the rest of Hydra, suggesting a possible difference in surface composition. From this image, mission scientists have estimated that Hydra is 34 miles (55 kilometers) long and 25 miles (40 kilometers) wide. Commented mission science collaborator Ted Stryk of Roane State Community College in Tennessee, “Before last week, Hydra was just a faint point of light, so it’s a surreal experience to see it become an actual place, as we see its shape and spot recognizable features on its surface for the first time.”
Images of Pluto’s most recently discovered moons, Styx and Kerberos, are expected to be transmitted to Earth no later than mid-October.
Nix and Hydra were both discovered in 2005 using Hubble Space Telescope data by a research team led by New Horizons project scientist Hal Weaver, Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland. New Horizons’ findings on the surface characteristics and other properties of Nix and Hydra will help scientists understand the origins and subsequent history of Pluto and its moons.
NASA’s New Horizons Finds Second Mountain Range in Pluto’s ‘Heart’ – July 21, 2015
A newly discovered mountain range lies near the southwestern margin of Pluto’s Tombaugh Regio (Tombaugh Region), situated between bright, icy plains and dark, heavily-cratered terrain. This image was acquired by New Horizons’ Long Range Reconnaissance Imager (LORRI) on July 14, 2015 from a distance of 48,000 miles (77,000 kilometers) and sent back to Earth on July 20. Features as small as a half-mile (1 kilometer) across are visible.
Pluto’s icy mountains have company. NASA’s New Horizons mission has discovered a new, apparently less lofty mountain range on the lower-left edge of Pluto’s best known feature, the bright, heart-shaped region named Tombaugh Regio (Tombaugh Region).
These newly-discovered frozen peaks are estimated to be one-half mile to one mile (1-1.5 kilometers) high, about the same height as the United States’ Appalachian Mountains. The Norgay Montes (Norgay Mountains) discovered by New Horizons on July 15 more closely approximate the height of the taller Rocky Mountains.
The new range is just west of the region within Pluto’s heart called Sputnik Planum (Sputnik Plain). The peaks lie some 68 miles (110 kilometers) northwest of Norgay Montes.
This newest image further illustrates the remarkably well-defined topography along the western edge of Tombaugh Regio.
“There is a pronounced difference in texture between the younger, frozen plains to the east and the dark, heavily-cratered terrain to the west,” said Jeff Moore, leader of the New Horizons Geology, Geophysics and Imaging Team (GGI) at NASA’s Ames Research Center in Moffett Field, California. “There’s a complex interaction going on between the bright and the dark materials that we’re still trying to understand.”
While Sputnik Planum is believed to be relatively young in geological terms – perhaps less than 100 million years old – the darker region probably dates back billions of years. Moore notes that the bright, sediment-like material appears to be filling in old craters (for example, the bright circular feature to the lower left of center).
This image was acquired by the Long Range Reconnaissance Imager (LORRI) on July 14 from a distance of 48,000 miles (77,000 kilometers) and sent back to Earth on July 20. Features as small as a half-mile (1 kilometer) across are visible. The names of features on Pluto have all been given on an informal basis by the New Horizons team.
Pluto Dazzles in False Color – July 23, 2015
Videos of the Journey to Pluto from NASA
Views of Pluto From New Horizons’ Approach
Mountains on Pluto
Animated Flyover of Pluto’s Icy Mountain and Plains
Journey to Pluto Galary
– Credit and Resource –
A massive thank you to NASA for this awesome adventure. The people of planet Earth salute you
