Stardust NExT: Mission to Comet Tempel 1

A bonus round is something one usually associates with the likes of a TV game show, not a pioneering deep space mission. “We are definitely in the bonus round,” said Stardust-NExT Project Manager Tim Larson of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “This spacecraft has already flown by an asteroid and a comet, returned comet dust samples to Earth, and now has almost doubled its originally planned mission life. Now it is poised to perform one more comet flyby.”

Could comets have brought water to Earth?

Comets preserve important clues to the early history of the solar system. They are believed to have contributed some of the volatiles that make up our oceans and atmosphere. They may even have brought to Earth the complex molecules from which life arose. For these reasons, the Committee on Planetary and Lunar Exploration (COMPLEX) has emphasized the direct exploration of comets by spacecraft. The investigation of comets also addresses each of the three strategic objectives for solar system exploration enunciated in NASA’s Space Science Enterprise Strategy (SSES) 2003.

- To learn how the solar system originated and evolved to its current state.
- To understand how life begins and determine the characteristics of the solar system that led to the origin of life.
- To catalog and understand the potential impact hazard to Earth from space.

The Stardust-NExT mission will contribute significantly to the first and last of these objectives by obtaining essential new data on Tempel 1 and capitalize on the discoveries of earlier missions such as Deep Impact to determine how cometary nuclei were constructed at the birth of the solar system and increase our understanding of how they have evolved since then. The Stardust-NExT mission provides NASA with the unique opportunity to study two entirely different comets with the same instrument. By doing this scientist will be able to more accurately compare its existing data set.

The primary science objectives of the mission are as follows:

• To extend our understanding of the processes that affect the surfaces of comet nuclei by documenting the changes that have occurred on comet Tempel 1 between two successive perihelion passages.
• To extend the geologic mapping of the nucleus of Tempel 1 to elucidate the extent and nature of layering and help models of the formation and structure of comet nuclei.
• To extend the study of smooth flow deposits, active areas, and known exposure of water ice.
• On February 14, 2011, at a projected distance of 200 km, the Stardust-NExT spacecraft will obtain high-resolution images of the coma and nucleus, as well as measurements of the composition, size distribution and flux of dust emitted into the coma. Additionally, Stardust-NExT will update the data gathered in 2005 by the Deep Impact mission on the rotational phase of the comet.

Other Objectives:

• If possible, to characterize the crater produced by Deep Impact in July 2005 to better understand the structure and mechanical properties of cometary nuclei and elucidate crater formation processes on them.
• Measure the flux and mass distribution of dust particles within the coma using the DFMI instrument.
• Analyze the composition of dust particles within the coma using the CIDA instrument.
• Monitor comet activity over 60 days on approach using imaging.

Artist concept of NASA's Stardust-NExT mission, which will fly by comet Tempel 1 on Feb. 14, 2011.

A Successful Prime Mission

NASA’s Stardust spacecraft was launched on Feb. 7, 1999, on a mission that would explore a comet as no previous mission had. Before Stardust, seven spacecraft from NASA, Russia, Japan and the European Space Agency had visited comets – they had flight profiles that allowed them to perform brief encounters, collecting data and sometimes images of the nuclei during the flyby.

Like those comet hunters before it, Stardust was tasked to pass closely by a comet, collecting data and snapping images. It also had the ability to come home again, carrying with it an out-of -this-world gift for cometary scientists – particles of the comet itself. Along the way, the telephone booth-sized comet hunter racked up numerous milestones and more than a few “space firsts.”

In the first round of its prime mission, Stardust performed observations of asteroid Annefrank, only the sixth asteroid in history to be imaged close up. After that, Stardust racked up more points of space exploration firsts. It became the first spacecraft to capture particles of interstellar dust for Earth return. It was first to fly past a comet and collect data and particles of comet dust (hurtling past it at almost four miles per second) for later analysis. Then, it was first to make the trip back to Earth after traveling beyond the orbit of Mars (a two-year trip of 1.2 billion kilometers, or 752 million miles). When Stardust dropped off its sample return capsule from comet Wild 2, the capsule became the fastest human-made object to enter Earth’s atmosphere. The mission was also the first to provide a capsule containing cometary dust specimens, speciments that will have scientists uncovering secrets of comets for years to come.

With such a high tally of “firsts” on its scoreboard, you’d think Stardust could receive a few parting gifts and leave the game. And an important part of the original spacecraft is currently enjoying retirement – albeit a high-profile one: Stardust’s 100-pound sample return capsule is on display in the main hall (Milestones of Flight) of the Smithsonian’s National Air and Space Museum in Washington. But the rest of NASA’s most-seasoned comet hunter is still up there – and there is work still to be done.

“We placed Stardust in a parking orbit that would carry it back by Earth in a couple of years, and then asked the science community for proposals on what could be done with a spacecraft that had a lot of zeros on its odometer, but also had some fuel and good miles left in it,” said Jim Green, director of NASA’s Planetary Science Division.

Moving into the Bonus Round

In January 2007, from a stack of proposals with intriguing ideas, NASA chose Stardust-NExT (Stardust’s Next Exploration of Tempel). It was a plan to revisit comet Tempel 1 at a tenth of the cost of a new, from-the-ground-up mission. Comet Tempel 1 was of particular interest to NASA. It had been the target of a previous NASA spacecraft visit in July 2005. That mission, Deep Impact, placed a copper-infused, 800-pound impactor on a collision course with the comet and observed the results from the cosmic fender-bender via the telescopic cameras onboard the larger part of Deep Impact, a “flyby” spacecraft observing from a safe distance.

“The plan for our encounter is to be more hospitable to comet Tempel 1 than our predecessor,” said Joe Veverka, principal investigator of Stardust-NExT from Cornell University in Ithaca, N.Y. “We will come within about 200 kilometers [124 miles] of Tempel 1 and view the changes that took place over the past five-and-a-half years.”

That period of time is significant for Tempel 1 — it is the period of time it takes the comet to orbit the sun once. Not much happens during a comet’s transit through the chilly reaches of the outer solar system. But when it nears perihelion (the point in its orbit that an object, such as a planet or a comet, is closest to the sun), things begin to sizzle.

“Comets can be very spectacular when they come close to the sun, but we still don’t understand them as well as we should,” said Veverka. “They are also messengers from the past. They tell us how the solar system was formed long ago, and Stardust-NExT will help us understand how much they have changed since their formation.”

So the spacecraft that had traveled farther afield than any of its predecessors was being sent out again in the name of scientific opportunity. In between spacecraft and comet lay four-and-a-half years, over a billion kilometers (646 million miles), and more than a few hurdles along the way.

Your Mileage May Vary

“One of the challenges with reusing a spacecraft designed for a different prime mission is you don’t get to start out with a full tank of gas,” said Larson. “Just about every deep-space exploration spacecraft has a fuel supply customized to get the job done, with some held in reserve for contingency maneuvers and other uncertainties. Fortunately, the Stardust mission navigation team did a great job, the spacecraft operated extremely well, and there was an adequate amount of contingency fuel aboard after its prime mission to make this new comet flyby possible – but just barely.”

Just how much fuel is in Stardust’s tanks for its final act?

“We estimate we have a little under three percent of the fuel the mission launched with,” said Larson. “It is an estimate, because no one has invented an entirely reliable fuel gauge for spacecraft. There are some excellent techniques with which we have made these estimates, but they are still estimates.”

One of the ways mission planners can approximate fuel usage is to look at the history of the vehicle’s flight and how many times and for how long its rocket motors have fired. When that was done for Stardust, the team found their spacecraft’s attitude and translational thrusters had fired almost half-a-million times each over the past 12 years.

“There is always a little plus and minus with each burn. When you add them all up, that is how you get the range of possible answers on how much fuel was used,” said Larson.

Fuel is not the only question that needs to be addressed on the way to a second comet encounter. Added into the mix is the fact a comet near the sun can fire off jets of gas and dust that can cause a change in its orbit, sometimes in unexpected ways, potentially causing a precisely designed cometary approach to become less precise. Then there are the distances involved. Stardust will fly past comet Tempel 1 on almost the opposite side of the sun from Earth, making deep-space communication truly, well, deep space. Add into the mix the Stardust spacecraft itself. Launched when Bill Clinton was in the White House, Stardust has been cooked and frozen countless times during its trips from the inner to outer solar system. It has also weathered its fair share of radiation-packed solar storms. But while its fuel tank may be running near-empty, that doesn’t mean Stardust doesn’t have anything left in the tank.

“All this mission’s challenges are just that – challenges,” said Larson. “We believe our team and our spacecraft are up to meeting every one of them, and we’re looking forward to seeing what Tempel 1 looks like these days.”

The Final Payoff

Larson, Veverka and the world will get their chance beginning a few hours after the encounter on Monday, Feb. 14, at about 8:56 p.m. PST (11:56 p.m. EST), when the first of 72 bonus-round images of the nucleus of comet Tempel 1 are downlinked.

All images of the comet will be taken by the spacecraft’s navigation camera – an amalgam of spare flight-ready hardware left over from previous NASA missions: Voyager (launched in 1977), Galileo (launched in 1989), and Cassini (launched in 1997). Each image will take about 15 minutes to transmit. The first five images to be received and processed on the ground are expected to include a close up of Tempel 1′s nucleus. All data from the flyby (including the images and science data obtained by the spacecraft’s two onboard dust experiments) are expected to take about 10 hours to reach the ground. Stardust-NExT is a low-cost mission that will expand the investigation of comet Tempel 1 initiated by NASA’s Deep Impact spacecraft. JPL, a division of the California Institute of Technology in Pasadena, manages Stardust-NExT for the NASA Science Mission Directorate, Washington, D.C. Joe Veverka of Cornell University, Ithaca, N.Y., is the mission’s principal investigator. Lockheed Martin Space Systems, Denver Colo., built the spacecraft and manages day-to-day mission operations.

Mission Details

The Stardust-NExT will utilize the existing spacecraft to flyby comet Tempel 1 and observe changes since NASA’s Deep Impact mission visited it in 2005. Stardust-NExT will provide NASA with a first-time opportunity to compare observations of a single comet made at close range during two successive perihelion passages, at low risk and low cost.

In 2005, Tempel 1 made its closest approach to the sun, possibly changing the surface of the comet. With a 3-year trajectory, the mission flight plan is designed in a similar way to that of the original mission, with an Earth gravity assist (EGA) in 2009 to achieve the flyby of Tempel 1 in 2011. The original flight path of the Stardust spacecraft to Wild 2 included an EGA in 2001.

Mission Design and Navigation:
The Stardust spacecraft divert maneuver that followed the release of the sample return capsule (SRC) was intentionally designed to place the spacecraft in a trajectory that returns to Earth in case the SRC release that occurred January 15 had failed. Thus the current orbit intrinsically provides the Earth gravity-assist (EGA) flyby opportunity in 2009, which enables the Tempel 1 encounter. The mission duration, from the divert maneuver after SRC release (January 15, 2006) to the February 14, 2011 Tempel 1 encounter, is a little over 5 years. The date of encounter will be optimized during the mission to account for improved knowledge of the comet’s ephemeris during cruise, and to maximize the probability of viewing the Deep Impact impact crater. Table F-1 summarizes the principal characteristics of the comet encounter.

Table F-1. Tempel 1 Encounter Characteristics
Flyby date	February 14, 2011
Distance	200 km
Velocity	10.9 km/s
Approach Phase angle	81.6°
Closest Approach Point	200 km altitude, 40° south of direction to the Sun
Solar Distance	1.55 AU
Earth Distance	2.25 AU

Mission Trajectory:
The trajectory consists of four loops of the sun in two separate orbits. Loops 1 and 2 represent the orbit the spacecraft bus was left in after the sample return on January 15, 2006. The EGA on January 14, 2009 places the spacecraft in the final heliocentric orbit (Loops 3 and 4) intercepting Tempel 1 on February 14, 2011 (39d after the comet’s perihelion). This profile is very similar to the launch-to-Wild 2 phase of the Stardust primary mission.

Figure F-1. Stardust-NExT trajectory, with one EGA prior to Tempel 1 encounter, provides for an uncomplicated mission simpler than the Stardust prime mission.

The maneuver plan is shown in Table F-2. Of the three deep space maneuvers (DSM’s), only the first is deterministic. This maneuver targets the EGA in January, 2009. Other DSM’s adjust the arrival time at Tempel 1. Ranges of favorable locations for DSMs (2 and 3) are indicated. Their exact location will be optimized during the mission.

Table F-2. Maneuver plan targets EGA and Tempel 1 encounter with few maneuvers
Maneuver	Epoch	Comment	Execution Date (UTC)
DSM1	Entry + 603d	EGA Targeting	9/19/07
DSM1_CU	DSM1 + 30d	Cleanup	10/19/07
EGA1	E-30d	EGA Targeting	12/16/08
EGA2	E – 10d	EGA Targeting	1/5/09
EGA2a	E – 1d	EGA Targeting	1/13/09
DSM2	T1 – 1y	Arrival Time Adjust	2/12/10
DSM2_CU	DSM2 + 30d	Cleanup	3/14/10
T0	T1-120d	T1 Targeting	10/18/10
T1 (DSM3)	T1-30d	T1 Targeting	1/15/11
T2	T1 – 10d	T1 Targeting	2/4/11
T3	T1 – 2d	T1 Targeting	2/12/11
T4	T1 – 18h	T1 Targeting	2/14/11
T5	T1 – 6h	T1 Targeting (Contingency)	2/14/11

The Stardust navigation team has chosen to place the closest approach point 40° southward of the direction to the Sun, at a longitude that offers the most favorable viewing opportunity of the Deep Impact crater at closest approach. Periodically, reevaluate the aimpoint during the mission, taking into account the most recent information available about the predicted uncertainty of the comet’s rotation state at encounter, until the time shortly before DSM2 (deep space maneuver) at which a selection of a final aimpoint for targeting.

Controlling the arrival time to target our chosen aimpoint is the greatest mission design challenge of Stardust-NExT. In order to successfully control the arrival time as discussed above, two conditions must be met: (1) we must be able to predict the rotation rate and rotational state of the comet with sufficient accuracy to reliably compute the right arrival time, and (2) we must have sufficient DV onboard to change the arrival time as needed.

[Credit: NASA]

Superluminal Speed in Gases..!!

Scientists have apparently broken the universe’s speed limit. For generations, physicists believed there is nothing faster than light moving through a vacuum – a speed of 186,000 miles per second. But in an experiment in Princeton, N.J., physicists sent a pulse of laser light through cesium vapor so quickly that it left the chamber before it had even finished entering. The pulse traveled 310 times the distance it would have covered if the chamber had contained a vacuum.

This seems to contradict not only common sense, but also a bedrock principle of Albert Einstein’s theory of relativity, which sets the speed of light in a vacuum, about 186,000 miles per second, as the fastest that anything can go. But the findings–the long-awaited first clear evidence of faster-than-light motion–are “not at odds with Einstein,” said Lijun Wang, who with colleagues at the NEC Research Institute in Princeton, N.J., report their results in today’s issue of the journal Nature.

“However,” Wang said, “our experiment does show that the generally held misconception that ‘nothing can move faster than the speed of light’ is wrong.” Nothing with mass can exceed the light-speed limit. But physicists now believe that a pulse of light–which is a group of massless individual waves–can.

To demonstrate that, the researchers created a carefully doctored vapor of laser-irradiated atoms that twist, squeeze and ultimately boost the speed of light waves in such abnormal ways that a pulse shoots through the vapor in about 1/300th the time it would take the pulse to go the same distance in a vacuum.

As a general rule, light travels more slowly in any medium more dense than a vacuum (which, by definition, has no density at all). For example, in water, light travels at about three-fourths its vacuum speed; in glass, it’s around two-thirds. The ratio between the speed of light in a vacuum and its speed in a material is called the refractive index. The index can be changed slightly by altering the chemical or physical structure of the medium. Ordinary glass has a refractive index around 1.5. But by adding a bit of lead, it rises to 1.6. The slower speed, and greater bending, of light waves accounts for the more sprightly sparkle of lead crystal glass.

The NEC researchers achieved the opposite effect, creating a gaseous medium that, when manipulated with lasers, exhibits a sudden and precipitous drop in refractive index, Wang said, speeding up the passage of a pulse of light. The team used a 2.5-inch-long chamber filled with a vapor of cesium, a metallic element with a goldish color. They then trained several laser beams on the atoms, putting them in a stable but highly unnatural state.

In that condition, a pulse of light or “wave packet” (a cluster made up of many separate interconnected waves of different frequencies) is drastically reconfigured as it passes through the vapor. Some of the component waves are stretched out, others compressed. Yet at the end of the chamber, they recombine and reinforce one another to form exactly the same shape as the original pulse, Wang said. “It’s called re-phasing.”

The key finding is that the reconstituted pulse re-forms before the original intact pulse could have gotten there by simply traveling though empty space. That is, the peak of the pulse is, in effect, extended forward in time. As a result, detectors attached to the beginning and end of the vapor chamber show that the peak of the exiting pulse leaves the chamber about 62 billionths of a second before the peak of the initial pulse finishes going in.That is not the way things usually work. Ordinarily, when sunlight–which, like the pulse in the experiment, is a combination of many different frequencies–passes through a glass prism, the prism disperses the white light’s components.

Image via Wikipedia

This happens because each frequency moves at a different speed in glass, smearing out the original light beam. Blue is slowed the most, and thus deflected the farthest; red travels fastest and is bent the least. That phenomenon produces the familiar rainbow spectrum.

But the NEC team’s laser-zapped cesium vapor produces the opposite outcome. It bends red more than blue in a process called “anomalous dispersion,” causing an unusual reshuffling of the relationships among the various component light waves. That’s what causes the accelerated re-formation of the pulse, and hence the speed-up. In theory, the work might eventually lead to dramatic improvements in optical transmission rates. “There’s a lot of excitement in the field now,” said Steinberg. “People didn’t get into this area for the applications, but we all certainly hope that some applications can come out of it. It’s a gamble, and we just wait and see.”

[Source: Time Travel Research Centre]

Coronal Heating Mystery Explained

Among the many constantly moving, appearing, disappearing and generally explosive events in the sun’s atmosphere, there exist giant plumes of gas — as wide as a state and as long as Earth — that zoom up from the sun’s surface at 150,000 miles per hour. Known as spicules, these are one of several phenomena known to transfer energy and heat throughout the sun’s magnetic atmosphere, or corona.

Thanks to NASA’s Solar Dynamics Observatory (SDO) and the Japanese satellite Hinode, these spicules have recently been imaged and measured better than ever before, showing them to contain hotter gas than previously observed. Thus, they may perhaps play a key role in helping to heat the sun’s corona to a staggering million degrees or more. (A number made more surprising since the sun’s surface itself is only about 10,000 degrees Fahrenheit.)   Just what makes the corona so hot is a poorly understood aspect of the sun’s complicated space weather system. That system can reach Earth, causing auroral lights and, if strong enough, disrupting Earth’s communications and power systems. Understanding such phenomena, therefore, is an important step towards better protecting our satellites and power grids. Solar physicist Dean Pesnell said:

The traditional view is that all heating happens higher up in the corona.  The suggestion in this paper is that cool gas is ejected from the sun’s surface in spicules and gets heated on its way to the corona. This doesn’t mean the old view has been completely overturned, but this is a strong suggestion that part of the spicule material gets heated to very high temperatures and provides some coronal heating.

Spicules were first named in the 1940s, but were hard to study in detail until recently, says Bart De Pontieu of Lockheed Martin’s Solar and Astrophysics Laboratory, Palo Alto, Calif. whose work on this subject appears in the January 7, 2011 issue of Science magazine. In visible light, spicules can be seen to send large masses of so-called plasma – the electromagnetic gas that surrounds the sun — up through the lower solar atmosphere or photosphere. The amount of material sent up is stunning, some 100 times as much as streams away from the sun in the solar wind towards the edges of the solar system. But nobody knew if they contained hot gas.

[Image  Details:  Spicules on the sun, as observed by the Solar Dynamics Observatory. These bursts of gas jet off the surface of the sun at 150,000 miles per hour and contain gas that reaches temperatures over a million degrees. Credit: NASA Goddard/SDO/AIA]

Now, De Pontieu’s team — which included researchers at Lockheed Martin, the High Altitude Observatory of the National Center for Atmospheric Research (NCAR) in Colorado and the University of Oslo, Norway — was able to combine images from SDO and Hinode to produce a more complete picture of the gas inside these gigantic fountains. Tracking the movement and temperature of spicules relies on successfully identifying the same phenomenon in all the images. One complication comes from the fact that different instruments “see” gas at different temperatures. Pictures from Hinode in the visible light range, for example, show only cool gas, while pictures that record UV light show gas that is up to several million degrees.

To show that the previously known cool gas in a spicule lies side by side to some very hot gas requires showing that the hot and cold gas in separate images are located in the same space. Each spacecraft offered specific advantages to help confirm that one was seeing the same event in multiple images. First, Hinode: In 2009, scientists used observations from Hinode and telescopes on Earth to, for the first time, identify a spicule when looking at it head-on. (Imagine how tough it is, looking from over 90 million miles away, to determine that you’re looking at a fountain when you only have a top-down view instead of a side view.) The top-down view of a spicule ensures an image with less extraneous solar material between the camera and the fountain, thus increasing confidence that any observations of hotter gas are indeed part of the spicule itself.

The second aid to tracking a single spicule is SDO’s ability to capture an image of the sun every 12 seconds. “You can track things from one image to the next and know you’re looking at the same thing in a different spot,” says Pesnell. “If you had an image only every 12 minutes, then you couldn’t be sure that what you’re looking at is the same event, since you didn’t watch its whole history.”

 

[Image Details: Artist's concept of the Solar Dynamics Observatory. 05/12/08 Credit: NASA/Goddard Space Flight Center Conceptual Image Lab]

Bringing these tools together, scientists could compare simultaneous images in SDO and Hinode to create a much more complete image of spicules. They found that much of the gas is heated to a hundred thousand degrees, while a small fraction of the gas is heated to millions of degrees. Time-lapsed images show that this hot material spews high up into the corona, with much of it falling back down towards the surface of the sun. However, the small fraction of the gas that is heated to millions of degrees does not immediately return to the surface.”Given the large number of spicules on the Sun, and the amount of material in the spicules, if even some of that super hot plasma stays aloft it would make a fair contribution to coronal heating,” says Scott McIntosh from NCAR, who is part of the research team.

Of course, De Pontieu cautions that this does not yet solve the coronal heating mystery. The main result, he says, is that they’re challenging theorists to incorporate the possibility that some coronal heating occurs at lower heights in the solar atmosphere. His next step is to help figure out how much of a role spicules play by studying how spicules form, how they move so quickly, how they get heated to such high temperatures in a short time, and how much mass stays up in the corona. Astrophysicist Jonathan Cirtain, who is the U.S. project scientist for Hinode at NASA’s Marshall Space Flight Center, Huntsville, Ala. points out that incorporating such new information helps address an important question that reaches far beyond the sun. “This breakthrough in our understanding of the mechanisms which transfer energy from the solar photosphere to the corona addresses one of the most compelling questions in stellar astrophysics: How is the atmosphere of a star heated?” he says. “This is a fantastic discovery, and demonstrates the muscle of the NASA Heliophysics System Observatory, comprised of numerous instruments on multiple observatories.”

 Hinode is the second mission in NASA’s Solar Terrestrial Probes program, the goal of which is to improve understanding of fundamental solar and space physics processes. The mission is led by the Japan Aerospace Exploration Agency (JAXA) and the National Astronomical Observatory of Japan (NAOJ). The collaborative mission includes the U.S., the United Kingdom, Norway and Europe. NASA Marshall manages Hinode U.S. science operations and oversaw development of the scientific instrumentation provided for the mission by NASA, academia and industry. The Lockheed Martin Advanced Technology Center is the lead U.S. investigator for the Solar Optical Telescope on Hinode.
  
 [Source: NASA]

T. Rex might have Run Faster

As far as killing machines go, T. rex was arguably the paleo-title holder. Now thanks to a closer look at the beast’s rear end, scientists may have upped the ante. Apparently, the dinosaur sported some of the beefiest tail muscles, which powered a swift run.
Result:T. rex could have run downany other dinosaur in its environment, the research suggests. Until now, scientists thought Tyrannosaurus rex’s tail served only to counterbalance the weight of the dinosaur’s enormous head. Contrary to earlier theories, T. rex had more than just junk in its trunk.

To get a peg on how powerful T.rex’s tail was, scientists compared it with the tails of modern-day reptiles, such as crocodiles, Komodo dragons, brown basilisk lizards, veiled chameleons and green iguanas. To do so, he dissected several of the modern reptiles to look for evidence in the bones for insertion points of muscles — basically, bone correlates he could use to reconstruct a reptile’s musculature (for specimens for which only bones were available, such as T. rex). He found the single largest tail muscle in these reptiles was the M. caudofemoralis, which attaches to the femur.

While most of the muscles in thetail are responsible for swishing, curling and stabilizing the tail — they’re involved in tail movement— the primary function of M. caudofemoralis is in locomotion. As that muscle contracts, it brings the femur back, putting it in a position to push off of and move forward.

Based on this information and information gleaned from studying skeletal specimens at museums, Persons digitally reconstructed the tails of modern reptiles, as well as T. rex and two other theropods (a group of bipedal, carnivorous dinosaurs) –Gorgosaurus libratus and Ornithomimus edmontonicus. T. rex would have a bulky tail, comparable to that of crocodiles. As it turns out, [its tail] was beefier than crocodiles. Its M. caudofemoralis would have also dwarfed those of Gorgosaurus and Ornithomimus. Overall, the muscle mass in T. rex’s tail has likely been underestimated by as much as 45 percent up until now.

Gotta run

As for how T. rex’s tail muscles got so giant, it was suggested that the development had to do with the tail’s structure. The tails of bothT. rex and modern reptiles are equipped with rib bones that are attached to vertebrae. Those ribs are located much higher on T. rex’s tail, leaving much more room along the lower end of the tail for the caudofemoralis muscles to bulk up and expand. Without rib bones to limit the size of the tail-locomotive muscles, they turned into robust powerhouses enabling T.rex to run..fast.

It looks like T. rex was suited to outrun all the other dinosaurs in its environment including duckbills, sauropods, horned dinosaurs and ankylosaurs. The new, bulkier tail painted by this study also suggests T. rexwas more stable overall, because the bigger tail muscles would’ve shifted the dinosaur’s center of mass back slightly. That means the dinosaur didn’t have to use as much energy to support its heft, and instead could focus that energy on running.
The results not only reveal how T. rex hunted and may have interacted with other dinosaurs (since now it could easily snag them), it also suggests a rewrite of dinosaur illustrations. Over time, as paleontologists learned more about dinosaurs, their drawings also got updates, morphing the animals into athletic, agile beasts that were much slimmer than in the past. However, as their bodies slimmed down, so did their rear ends.
[credit: LiveScience]

Earth-like Planets are Common in Universe!!

Planet Earth is not so special after all; there’s one orbiting roughly every one in four Sun-like stars, according to a five-year astronomy study. The study, published in the journal Science, used Hawaii’s twin 10-metre Keck telescopes to scan 166 sun-like stars within 80 light years, or about 757 trillion kilometres. The team spotted 22 planets around 33 of these stars by the gravitational tug of the planets – called the Doppler or radial velocity method.

23 Earths for every 100 Suns

Of about 100 typical Sun-like stars, one or two have planets the size of Jupiter, roughly six have a planet the size of Neptune,and about 12 have super-Earths between three and 10 Earth masses. How tough the search for habitable worlds would be wasn’t at all clear when NASA gave the Kepler team the go-ahead almost 10 years ago. Only huge, scorching-hot exoplanets larger than Jupiter had been found by then. Limitations in the technique mean astronomers can’t yet see planets up to three times Jupiter’s mass orbiting within one quarter of the distance of the Earth to the Sun (1 AU or almost 150 million kilometres), or smaller Earth-like planets much close in.

Image: The data, depicted here in this illustrated bar chart, show a clear trend. Small planets outnumber larger ones. Astronomers extrapolated from these data to estimate the frequency of the Earth-size planets — nearly one in four sun-like stars, or 23 percent, are thought to host Earth-size planets orbiting close in. Each bar on this chart represents a different group of planets, divided according to their masses. In each of the three highest-mass groups, with masses comparable to Saturn and Jupiter, the frequency of planets around sun-like stars was found to be 1.6 percent. For intermediate-mass planets, with 10 to 30 times the mass of Earth, or roughly the size of Neptune and Uranus, the frequency is 6.5 percent. And the super-Earths, weighing in at only three to 10 times the mass of Earth, had a frequency of 11.8 percent. NASA/JPL-Caltech/UC Berkeley[via: Centauri Dreams]

One of astronomy’s goals is to find eta-Earth (η-Earth), the fraction of Sun-like stars that have an Earth. This is a first estimate, and the real number could be one in eight instead of one in four. But it’s not one in 100, which is glorious news. What this means is that, as NASA develops new techniques over the next decade to find truly Earth-size planets, it won’t have to look too far. Greenhill’s expertise is in the ‘microlensing technique’, which looks at the bending of light of a source star by an intervening planet-star system and is particularly suitable for finding small-mass planets. He estimates between 32% and 100% of stars have planets two to 10 times the size of Earth in orbits ranging from 1¬-10 AU. That’s one heck of a lot of Earth-mass planets. I don’t care how small the probability of life is; some of them are bound to have water on them and will probably have life there.

Remark: It simply suggests that there could be more and more Earth like planet irrespective to our probablistic estimations. In a previous article , I’ve presented a detailed information about temporal temperature zones and wind maps, which supports my earlier speculation of planet being habitable . In that article you can see that wind flow maps of Gliese 581g are similar to wind map of planet Earth at various locations. All of these calculations and evidences dismay the idea of planet being inhabitable. Now this study presents even more optimistic speculation as to how common Earth like planets are. Rare Earth hypothesis goes to hell.

[Source: Cosmos Magazine]
[Note: In original article they referred 80million light years as ~757 trillion kilometers. There should be instead 80 light years.]

Key Enzyme in Microbial Immune System Discovered

Imagine a war in which you are vastly outnumbered by an enemy that is utterly relentless – attacking you is all it does. The intro to another Terminator movie? No, just another day for microbes such as bacteria and archaea, which face a never-ending onslaught from viruses and invading strands of nucleic acid known as plasmids. To survive this onslaught, microbes deploy a variety of defense mechanisms, including an adaptive-type nucleic acid-based immune system that revolves around a genetic element known as CRISPR, which stands for Clustered Regularly Interspaced Short Palindromic Repeats.

The crystal structure of the Csy4 enzyme (blue) bound to a crRNA molecule (orange). The crRNA contains nucletotide sequences that match those of foreign DNA from a virus or plasmid, enabling it to target and silence the invaders. (Image courtesy of the Doudna group)

Through the combination of CRISPR and squads of CRISPR-associated – “Cas” – proteins, microbes are able to utilize small customized RNA molecules to silence critical portions of an invader’s genetic message and acquire immunity from similar invasions in the future. To better understand how this microbial immune system works, scientists have needed to know more about how CRISPR’s customized small RNA molecules get produced. Answers have now been provided by a team of researchers with the Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley.

In a study led by biochemist Jennifer Doudna, the  research team used protein crystallography beamlines at Berkeley Lab’s Advanced Light Source to produce an atomic-scale crystal structure model of an endoribonuclease called “Csy4.” Doudna and her colleagues have identified Csy4 as the enzyme in prokaryotes that initiates the production of CRISPR-derived RNAs (crRNAs), the small RNA molecules that target and silence invading viruses and plasmids. Doudna says:

Our model reveals that Csy4 and related endoribonucleases from the same CRISPR/Cas subfamily utilize an exquisite recognition mechanism to discriminate crRNAs from other cellular RNAs to ensure the selective production of crRNA for acquired immunity in bacteria. We also found functional similarities between the RNA recognition mechanisms in Cys4 and Dicer, the enzyme that plays a critical role in eukaryotic RNA interference.

Doudna is a leading authority on RNA molecular structures who holds joint appointments with Berkeley Lab’s Physical Biosciences Division and UC Berkeley’s Department of Molecular and Cell Biology and Department of Chemistry. She is also an investigator with the Howard Hughes Medical Institute (HHMI). The results of this latest research on CRISPR are reported in the journal Science in a paper titled “Sequence- and structure-specific RNA processing by a CRISPR endonuclease.” Co-authoring the paper with Doudna were Rachel Haurwitz, Martin Jinek, Blake Wiedenheft and Kaihong Zhou.

Image via Wikipedia

CRISPR is a unit of DNA, usually on a microbe’s chromosome, made up of “repeat” elements, base-pair sequences ranging from 30 to 60 nucleotides in length, separated by “spacer” elements, variable sequences that are also from 30 to 60 nucleotides in length. CRISPR units are found in about 40-percent of all bacteria whose genomes have been sequenced, and about 90-percent of archaea. A microbe might have several CRISPR loci within its genome and each locus might contain between four and 100 CRISPR repeat-spacer units. Doudna and her colleagues studied CRISPR in Pseudomonas aeruginosa, a common bacterium that is ubiquitous in the environment.

Rachel Haurwitz, a graduate student in Doudna’s research group and the first author on the Science paper, explains how the CRISPR/Cas immunity system works.

When a bacterium recognizes that it has been invaded by a virus or a plasmid, it incorporates a small piece of the foreign DNA into one of its CRISPR units as a new spacer sequence. The CRISPR unit is then transcribed as a long RNA segment called the pre-crRNA. The Csy4 enzyme cleaves this pre-crRNA within each repeat element to create crRNAs about 60 nucleotides long that will contain sequences which match portions of the foreign DNA. Cas proteins will use these matching sequences to bind the crRNA to the invading virus or plasmid and silence it.

Haurwitz says the CRISPR/cas system for silencing foreign DNA in prokaryotes is analogous to the way in which short interfering or siRNAs correct genetic problems in eukaryotes. Over time, the CRISPR/cas system will build up inheritable DNA-encoded immunity from future invasions by the same types of viruses and plasmids.

With their crystal structure model of the Csy4 enzyme bound to its cognate RNA, which features a resolution of 1.8 Angstroms, the Berkeley CRISPR research team has shown that Csy4 makes sequence-specific interactions in the major groove of the CRISPR RNA repeat stem-loop. Together with electrostatic contacts to the phosphate backbone, these interactions enable Csy4 to selectively bind to and cleave pre-crRNAs using phylogenetically conserved residues of the amino acids serine and histidine in the active site. Doudna says:

Our model explains sequence- and structure-specific processing by a large family of CRISPR-specific endoribonucleases.

Doudna and her colleagues produced their 1.8 Angstrom resolution crystallographic structure using the experimental end stations of Beamlines 8.2.1 and 8.3.1 at Berkeley Lab’s Advanced Light Source (ALS). Both beamlines are powered by superconducting bending magnets – “superbends” – and both feature state-of-the-art multiple-wavelength anomalous diffraction (MAD) and macromolecular crystallography (MX) capabilities. Beamline 8.2.1 is part of the suite of protein crystallography beamlines that comprise the Berkeley Center for Structural Biology.

The ALS and its protein crystallography beamlines continue to be a critical resource for our research.

The crRNAs used by the CRISPR/cas system for the targeted interference of foreign DNA join the growing ranks of small RNA molecules that mediate a variety of processes in both eukaryotes and prokaryotes. Understanding how these small RNA molecules work can improve our basic understanding of cell biology and provide important clues to the fundamental role of RNA in the evolution of life.

Says Doudna, “By investigating how bacteria produce and use small RNAs for selective gene targeting, we hope to gain insight into the fundamental features of the pathways that have proven evolutionarily useful for genetic control, both in the bacterial world and in the world of eukaryotes. Right now it looks like bacteria and eukaryotes have evolved entirely distinct pathways by which RNAs are used for gene regulation and that is pretty amazing!”

[Source: Berkley Lab]

Related Articles

• How bacteria acquire immunity: First theoretical description of bacterial system to silence viral genes (sciencedaily.com)

Mysterious Raisin’s Mountain on Titan Observed

Saturn’s moon Titan ripples with mountains, and scientists have been trying to figure out how they form. The best explanation, it turns out, is that Titan is shrinking as it cools, wrinkling up the moon’s surface like a raisin.

A new model developed by scientists working with radar data obtained by NASA’s Cassini spacecraft shows that differing densities in the outermost layers of Titan can account for the unusual surface behavior. Titan is slowly cooling because it is releasing heat from its original formation and radioactive isotopes are decaying in the interior. As this happens, parts of Titan’s subsurface ocean freeze over, the outermost ice crust thickens and folds, and the moon shrivels up. The model is described in an article now online in the Journal of Geophysical Research. Giuseppe Mitri, the lead author of the paper said:

Titan is the only icy body we know of in the solar system that behaves like this,” said  But it gives us insight into how our solar system came to be. An example of this kind of process can also be found on Earth, where the crumpling of the outermost layer of the surface, known as the lithosphere, created the Zagros Mountains in Iran.

[Image Details: This mosaic, made from radar images obtained by NASA's Cassini spacecraft, shows mountainous terrain on Saturn's moon Titan in the moon's northern hemisphere, north of the Aaru region. The annotated version shows topographic profiles measured by the radar instrument, with red-orange areas showing the highest elevation (in this image, 600 meters, or 2,000 feet, above the mean radius of Titan) and purple showing the lowest (in this image, 800 meters, or 2,600 feet, below the mean radius of Titan). That version also shows a grid for latitude and longitude. This region presents a mountain block near 52 degrees north latitude and 13 degrees east longitude.  The tallest features in this image are about 1,400 meters higher than the valley next to it.
Cassini's radar instrument obtained the black and white images making up the mosaic on July 22, Sept. 22, and Oct. 9, 2006. In radar images, objects appear bright when they are tilted toward the spacecraft or have rough surfaces. The topographical data were derived from the same flybys.  The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate. The Cassini orbiter was designed, developed and assembled at JPL. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the United States and several European countries.]

Titan’s highest peaks rise up to about two kilometers (6,600 feet), comparable to the tallest summits in the Appalachian Mountains. Cassini was the first to spot Titan’s mountains in radar images in 2005. Several mountain chains on Titan exist near the equator and are generally oriented west-east. The concentration of these ranges near the equator suggests a common history.

While several other icy moons in the outer solar system have peaks that reach heights similar to Titan’s mountain chains, their topography comes from extensional tectonics — forces stretching the ice shell — or other geological processes. Until now, scientists had little evidence of contractional tectonics — forces shortening and thickening the ice shell. Titan is the only icy satellite where the shortening and thickening are dominant.

[Image Details: This mosaic, made from radar images obtained by NASA's Cassini spacecraft, shows parallel mountain chains on Saturn's moon Titan. The mountains appear along the northwest border of a region known as Xanadu, two degrees south latitude and minus 127 degrees west longitude. The annotated version shows a grid for latitude and longitude.  The tallest features in this image, which were mapped by the radar instrument, are about 1,900 meters taller than the surrounding plains. Scientists believe the structures rose up because the lithosphere, the outermost layer of the surface, folded up during deformation of the outer water ice shell. Cassini's radar instrument obtained the images on Feb. 15, 2005 and May 12, 2008. In radar images, objects appear bright when they are tilted toward the spacecraft or have rough surfaces.
For another view of this terrain, see PIA10654.]

Mitri and colleagues fed data from Cassini’s radar instrument into computer models of Titan developed to describe the moon’s tectonic processes and to study the interior structure and evolution of icy satellites. They also made the assumption that the moon’s interior was only partially separated into a mixture of rock and ice, as suggested by data from Cassini’s radio science team.

Scientists tweaked the model until they were able to build mountains on the surface similar to those Cassini had seen. They found the conditions were met when they assumed the deep interior was surrounded by a very dense layer of high-pressure water ice, then a subsurface liquid-water-and-ammonia ocean and an outer water-ice shell. So the model, Mitri explained, also supports the existence of a subsurface ocean.

Each successive layer of Titan’s interior is colder than the one just inside it, with the outermost surface averaging a chilly 94 Kelvin (minus 290 degrees Fahrenheit). So cooling of the moon causes a partial freezing of the subsurface liquid ocean and thickening of the outer water ice shell. It also thickens the high-pressure ice. Because the ice on the crust is less dense than the liquid ocean and the liquid ocean is less dense than the high-pressure ice, the cooling means the interior layers lose volume and the top “skin” of ice puckers and folds.

Since the formation of Titan, which scientists believe occurred around four billion years ago, the moon’s interior has cooled significantly. But the moon is still releasing hundreds of gigawatts of power, some of which may be available for geologic activity. The result, according to the model, was a shortening of the radius of the moon by about seven kilometers (four miles) and a decrease in volume of about one percent.

These results suggest that Titan’s geologic history has been different from that of its Jovian cousins, thanks, perhaps, to an interior ocean of water and ammonia. As Cassini continues to map Titan, we will learn more about the extent and height of mountains across its diverse surface.

[Credit: NASA/JPL-CALTECH]

Mars Voyage Won’t be Good for Us

Image via Wikipedia

If a human ever sets foot on Mars, will it be a giant step or an exhausted shuffle? Long-term space flight so weakens fitness that an astronaut heading to the Red Planet may lose up to half the power in key muscles in the course of the mission, scientists have found. The loss – equivalent to a crew member aged between 30 and 50 returning home with the muscles of an 80-year-old – would add a major danger to a trip already laden with peril, they said.

Muscles weaken at zero gravity

Researchers led by Robert Fitts of Marquette University, Wisconsin, took tiny samples of tissue from the calf muscles of nine U.S. and Russian astronauts who spent around six months on the International Space Station (ISS). The biopsies, taken 45 days before launch and on the day of return, showed dramatically how muscles atrophy in zero gravity. The losses in fibre mass, force and power translated into a decline of more than 40% in the capacity for physical work, Fitts reported.

Biggest muscles suffered the most

Ironically, beefing up before the trip had no impact on muscle loss. In fact, crew members who began with the biggest muscles turned out to have the biggest decline in muscle fitness.

Under one NASA scenario, a return trip to Mars using current rocket technology would take around three years, if a one-year stay on the planet is factored in.

If so, the decline in the most-affected muscles such as the calf could approach 50 percent, said Fitts.

Too weak to evacuate

Astronauts would tire faster doing even routine tasks, especially if they donned a space suit, and on returning to terrestrial gravity they could be so weak they might be unable to evacuate their spacecraft quickly in an emergency. Fitts said the results should not discourage humans from venturing farther into space. He Goes on:

Manned missions to Mars represent the next frontier, as the Western Hemisphere of our planet was 800 years ago. Without exploration, we will stagnate and fail to advance our understanding of the Universe.

Even so, the findings clearly show the need to improve fitness regimes in space so that astronauts are exposed to high-resistance exercise and the kinds of motions they experience on Earth, he said. Muscle loss adds to the long list of hazards facing a trip to Mars. In addition to technical dangers, astronauts face cancer-causing damage to DNA from cosmic radiation, loss of bone density and mental stress from prolonged incarceration.

In June, six men from Europe, Russia and China were locked away in a mock spaceship in a Moscow research institute for a year and a half to simulate a manned mission to Mars. The 520-day experiment comprises 250 days for the outward trip, 240 days for the return but only 30 days on the Martian surface.

[Via: ComosMagazine]

Related Articles

• Trip to Mars Would Turn Astronauts Into Weaklings (space.com)

Prehistoric Shark Found Alive..?

A while back, I have peer reviewed the possibility of  lake monster’s existence. In my article ‘The Mystery of Lake Monsters: Survived Reptiles or Illusion?‘ ,I have reviewed the whole case and questioned over the searching tactics of cryptozoologists. A quote from my previous article:

I think it is very difficult to take high quality and detailed photograph when such unknown and mysterious creature ,about which we have never listen nor seen, is before us. There are previously such creatures are present between us which were thought to be rumor till they were found, like gorilla which was reported as big meat eating monkey like creature, untill it was found alive in 1847. The another example is komodo found alive in 1912 in some islands of indonesia. It was first reported as big ,fierce, meat eating lizard and scientists were discarding its witnesses. The another third is Coelacanth found alive in in 1938. Now it is known as “living fossil”. Then how we can discard all witnesses of such monsters including Loch Ness monster? It is quite possible these creatures may still alive in deep sea and we have no access to them technically. How much we know about deep see?  There are critters which have been found about 600 feet below ice, clearly suggesting we have to know  more than we know till now. Why to confine yourself  just to search for known creatures. Without exploring the real phenomenon, directly depicting such creatures as myth is idiocy.

As you can see in the quote I have pointed out out that we have already found creatures which were considered as myth and folklores by mainstream scientists. Here is news news from National Geographic Website which clearly strengthens my points. For the first time a sixgill shark has been filmed by team’s camera. Taking the scientists’ bait, a sixgill shark’s attack 4,600 feet (1,400 meters) below the surface of the Coral Sea off Australia is captured in a new video image.

Reaching roughly 13 feet (4 meters) long, the sixgill shark is among deep-sea species never before filmed at such depths, according to the the Queensland Brain Institute, which released the first images from new high-tech remote-control cameras this week.

Often referred to as prehistoric or a “living fossil” because of its resemblance to sharks that lived hundreds of millions of years ago, sixgills are being studied as part of the Deep Australia Project, an ongoing effort to discover the the evolutionary origins of human sight—making the sixgill’s night vision of particular interest to researchers. [Related: Hundreds of New Reef Creatures Found in Australia.]

A Loris, a beautiful creature with fur, which was thought to be extinct until recently it was found alive and photographed though it is not a prehistoric creature but compelling my points. Long thought to be extinct, one of the world’s rarest primates has been caught on camera for the first time, scientists announced Monday. [Related: 'Extinct' Bird Seen, Eaten. ]

Discovered in 1937 but “missing” for 60 years, Sri Lanka’s Horton Plains slender loris was presumed to have died out. In 2002 a fleeting nighttime sighting of something looking like the elusive tree-dweller, however, gave conservationists hope. Follow-up surveys led by the Zoological Society of London finally confirmed the lorises are alive—if not exactly well—in 2009, when two individuals were photographed and examined. Initial estimates after the rediscovery put the total world population at fewer than a hundred, said the society’s conservation biologist Craig Turner. And in this case, the world is limited to high cloud forests in the Horton Plains area (map)of central Sri Lanka—the animal’s only known habitat.

“Potentially this is the rarest primate we’re aware of today,” Turner said.

Lonely Lorises

About 8 inches (20 centimeters) long and weighing just 11 ounces (310 grams), the slow-moving loris has been doomed as forests have been felled for firewood and to make way for tea plantations and other farms, Turner said.

There’s no means for these lorises to move between the [remaining] forest patches. In terms of breeding and finding mates, it is very difficult for them. The real focus now has to be on the remaining forest areas and looking at how we can enhance and protect them, and also reconnect them to one another. [See: 'Extinct' Booby Exposed—Found 'Masked,' Using Alias.]

“New” Loris Also New Species?

The Horton Plains slender loris is generally classified as a subspecies of Sri Lanka’s red slender loris. But, thanks in part to the first ever pictures, researchers now believe the “extinct” loris could be a whole new species. Turner says:

It’s clearly very different physically. Compared to lowland lorises, the Horton Plains loris is “stockier, shorter limbed—and it’s got a much longer fur coat. Ongoing tests on DNA samples taken from the few individuals recorded to date should help to settle the issue.

Doesn’t it support my preamble?

Plants Are Really, Really Intelligent!

A while back, I wrote a a article in which I considered that ‘Intelligent Plant May Constitute Alien Civilization‘ based on two research papers. That was not a detailed, full of analysis article, but suggested some speculations. Now it seems that my speculations were correct about plant intelligence. Plants are able to “remember” and “react” to information contained in light, according to researchers.

Plants, scientists say, transmit information about light intensity and quality from leaf to leaf in a very similar way to our own nervous systems. These “electro-chemical signals” are carried by cells that act as “nerves” of the plants.

[The researchers used fluorescence imaging to watch the plants respond]

In their experiment, the scientists showed that light shone on to one leaf caused the whole plant to respond.

And the response, which took the form of light-induced chemical reactions in the leaves, continued in the dark.

This showed, they said, that the plant “remembered” the information encoded in light.

“We shone the light only on the bottom of the plant and we observed changes in the upper part,” explained Professor Stanislaw Karpinski from the Warsaw University of Life Sciences in Poland, who led this research.

He presented the findings at the Society for Experimental Biology’s annual meeting in Prague, Czech Republic.

“And the changes proceeded when the light was off… This was a complete surprise.”

In previous work, Professor Karpinski found that chemical signals could be passed throughout whole plants – allowing them to respond to and survive changes and stresses in their environment.

But in this new study, he and his colleagues discovered that when light stimulated a chemical reaction in one leaf cell, this caused a “cascade” of events and that this was immediately signalled to the rest of the plant by via specific type of cell called a “bundle sheath cell”.

The scientists measured the electrical signals from these cells, which are present in every leaf. They likened the discovery to finding the plants’ “nervous system”.

Thinking plants

What was even more peculiar, Professor Karpinski said, was that the plants’ responses changed depending on the colour of the light that was being shone on them. There were characteristic [changes] for red, blue and white light,” he explained. He suspected that the plants might use the information encoded in the light to stimulate protective chemical reactions. He and his colleagues examined this more closely by looking at the effect of different colours of light on the plants’ immunity to disease.

[The images showed chemical reactions in leaves that were not exposed to light]

“When we shone the light for on the plant for one hour and then infected it [with a virus or with bacteria] 24 hours after that light exposure, it resisted the infection,” he explained.

“But when we infected the plant before shining the light, it could not build up resistance.

“[So the plant] has a specific memory for the light which builds its immunity against pathogens, and it can adjust to varying light conditions.”

He said that plants used information encrypted in the light to immunise themselves against seasonal pathogens.

“Every day or week of the season has… a characteristic light quality,” Professor Karpinski explained.

“So the plants perform a sort of biological light computation, using information contained in the light to immunise themselves against diseases that are prevalent during that season.”

Professor Christine Foyer, a plant scientist from the University of Leeds, said the study “took our thinking one step forward”.

“Plants have to survive stresses, such as drought or cold, and live through it and keep growing,” she told BBC News.

“This requires an appraisal of the situation and an appropriate response – that’s a form of intelligence.

“What this study has done is link two signalling pathways together… and the electrical signalling pathway is incredibly rapid, so the whole plant could respond immediately to high [levels of] light.”

[Via: BBC]