News Article | April 17, 2017
After two decades of development and "heartbreak", scientists are on the verge of sending missions to explore the ocean world of Europa. Could this be our best shot at finding life elsewhere in the Solar System? Orbiting the giant planet Jupiter is an icy world, just a little smaller than Earth's moon. From a distance, Europa appears to be etched with a nexus of dark streaks, like the product of a toddler's chaotic scribbling. Close up, these are revealed to be long linear cracks in the ice, many of which are filled with an unknown contaminant that scientists have dubbed the "brown gunk". Elsewhere, the surface is tortured and irregular, as if massive slabs of ice have drifted, spun and flipped over in slush. Jupiter's immense gravity helps generate tidal forces that repeatedly stretch and relax the moon. But the stresses that created Europa's smashed up terrain are best explained by the ice shell floating on an ocean of liquid water. "The fact that there's liquid water underneath the surface which we know from previous missions, in particular from the magnetometer observations made by the Galileo spacecraft as it flew past [in the 1990s], makes it one of the most exciting potential targets to look for life," says Prof Andrew Coates of UCL's Mullard Space Science Laboratory in Surrey, UK. Europa's dark, briny deep might extend 80-170km into the moon's interior, meaning it could be holding twice as much liquid water as there is in all of Earth's oceans. And while water is one vital prerequisite for life, Europa's ocean might have others - such as a source of chemical energy for microbes. What's more, the ocean may communicate with the surface through a number of means, including warm blobs of ice from below rising up through the ice shell - which could be tens of kilometres thick. So studying the surface could provide clues to what's going on deep below. Now, Nasa is priming two missions to explore this intriguing world. Both have been discussed here at the 48th Lunar and Planetary Science Conference (LPSC) in Houston. The first is a flyby mission called Europa Clipper that would likely launch in 2022. The second is a lander mission that would follow a few years later. "We're really trying to get at Europa's potential habitability, the ingredients for life: water, and whether there's chemical energy for life," he tells me. "We do that by trying to understand the ocean and the ice shell, the composition and the geology. And mixed into those is the level of current activity at Europa." Clipper carries a payload of nine instruments, including a camera that will image most of the surface; spectrometers to understand its composition; ice-penetrating radar to map the ice shell in three dimensions and find water beneath the ice shell; and a magnetometer to characterise the ocean. However, since the Galileo spacecraft provided evidence for an ocean in the 1990s, we've learned that Europa isn't one of a kind. "One of the most amazing and significant discoveries of the past decade or so in planetary exploration is that you can't swing a dead cat in the outer Solar System without hitting an ocean world," says Clipper's programme scientist Curt Niebur, from Nasa headquarters in Washington DC. At Saturn's moon Enceladus, for example, ice from a subsurface ocean gushes into space through fissures at the south pole. The saturnian satellite could also get a dedicated mission in the 2020s, but Dr Niebur believes Europa stands out: "Europa is much larger than Enceladus and has more of everything: more geological activity, more water, more space for that water, more heat, more raw ingredients and more stability in its environment." But there's something else that marks the moon out: its neighbourhood. Europa's orbital path takes it deep into Jupiter's powerful magnetic field, which traps and speeds up particles. The resulting belts of intense radiation fry spacecraft electronics, limiting the durations of missions to months or even weeks. That said, this radiation also drives reactions on Europa's surface, yielding chemicals called oxidants. On Earth, biology exploits the chemical reactions between oxidants and compounds known as reductants to supply the energy needed for life. However, the oxidants made on the surface are only useful to Europan microbes if they can get down into the ocean. Fortunately, the process of convection that pushes warm blobs of ice upwards might also drive surface material down. Once in the ocean, oxidants could react with reductants made by seawater interacting with the rocky ocean floor. "You need both poles of the battery," explains Robert Pappalardo. For scientists like Bob Pappalardo and Curt Niebur, the impending missions are the realisation of a two-decades-long dream. Since the first Europa mission concepts were drawn up in the late 1990s, one promising proposal after another has been thwarted. During the noughties, the US and Europe even pooled resources on a mission that would have sent separate spacecraft to Europa and Jupiter's larger ice moon Ganymede. But the plan was cancelled amid budget cuts, with the European part evolving into the Juice mission. "I don't think there's been a Europa mission over the past 18 years that I have not either had my fingers in or has not passed under my eye," says Curt Niebur. "It's been a long road. The road to launch is always a rocky one, and it's always full of heartbreak. We've experienced that more than most on Europa." Exploring Europa is costly - though no more so than other Nasa "flagship" missions such as Cassini or the Curiosity rover. There are inherent engineering challenges, such as operating within Jupiter's radiation belts. Spacecraft instruments need to be shielded with materials such as titanium metal but, says Dr Pappalardo, "you can only shield them so much because they have to be able to see Europa". So to keep Clipper safe, Nasa is going to stray from the rulebook somewhat. "The assumption always was: Galileo flew past Europa, so the next mission has to be an orbiter. That's just how we do business," says Dr Niebur. But rather than orbit Europa, Clipper will instead reduce its exposure to mission-shortening radiation by orbiting Jupiter, and make at least 45 close flybys of the icy moon over three-and-a-half years. "We realised we could avoid those technical challenges of orbiting Europa, make the mission much more achievable and still get the science we want if we fly past it a lot," says Clipper's programme scientist. The strength of sunlight near Europa is about a 30th of what it is at Earth. But Nasa decided it could power Clipper with solar panels rather than the radioactive generators some other outer planet missions have used. "All those years of study forced us to burn away our pre-conceptions and get us to really focus on reality, not on our wish-list... to focus on the best science," says Curt Niebur. In 2011, a National Research Council report re-stated the importance of exploring the icy moon. Even so, Nasa remained wary because of the cost. But the support on Capitol Hill has been pivotal. A Europa venture has bipartisan backing, and in Republican Congressman John Culberson - the chair of the particular House Appropriations Subcommittee with jurisdiction over Nasa's budget - the mission has had a unique champion. The 60-year-old Texan lawmaker has been entranced by Europa ever since observing it through the Celestron 8 telescope he bought himself as a high school graduation present. Over the last four years, the subcommittee he chairs has channelled money to scientists working on Europa, even when the space agency's chief wasn't asking for it. Generous investment means that much more of the technical work has been completed on Clipper than is normal for a mission at its stage (phase B) in the Nasa project cycle. The lander is at an earlier stage of development, called pre-phase A, but a report on the mission's science value was discussed at a workshop here at the LPSC. The lander has received no funding in the President's 2018 budget request for Nasa. But Dr Jim Green, director of planetary science at the agency, tells me: "That mission in particular is tremendously exciting, because it tells us the science we have to do from the surface of a moon that's really hard to get to. "We still have quite the process to go through, do the due diligence, understanding the kind of measurements we need to make. Then we'll work with the administration in the future at the right time to see if, budgetarily, we can move forward with it." Some innovative Europa lander concepts have been proposed over the last two decades, reflecting the scientific bounty to be had by touching down. Dr Geraint Jones of the Mullard Space Science Laboratory has worked on one concept called a penetrator. "They haven't been flown in space before, but it's a really promising technology," he explains. A projectile deployed from a satellite hits the surface "really hard, at about 300m/second, about 700 miles an hour", exposing pristine ice for analysis by onboard instruments, which could be designed to withstand the impact. By contrast, Nasa's forthcoming lander would put down softly with the help of the Sky Crane technology used to drop the Curiosity rover safely on Mars in 2012. During the touchdown, it will use an autonomous landing system to detect and avoid surface hazards in real time. Clipper will provide the reconnaissance for a landing site. "I like to think of it as finding that right oasis, where there might be water close to the surface. Maybe it's warm and maybe it has organic materials," says Bob Pappalardo. The craft would be equipped with a sensitive instrument payload and a counter-rotating saw to help get at fresher samples below the radiation-processed surface ice. "The lander is all about hitting the freshest, most pristine sample possible. One way to do that is to dig deep, another way is going to where there is some kind of eruption on the surface - like a plume - that's dropping very fresh material onto the surface," says Curt Niebur. In recent years, the Hubble telescope has made tentative observations of plumes of water-ice erupting from beneath Europa, much as they do on Enceladus. But there's no point in the lander going to the site of a decades-old eruption, it would need to visit the location of a much more recent plume. So scientists need to understand what's controlling these geysers: for example, Clipper will determine whether the plumes are correlated with any hot spots on the surface. Earth's seas are teeming with life, so it can be hard for us to contemplate the prospect of a sterile, 100km-plus deep ocean on Europa. But the scientific threshold for detecting life is set very high. So will we be able to recognise alien life if it's there? "The goal of the lander mission is not simply to detect life [to our satisfaction], but to convince everyone else that we have done so," Dr Niebur explains. "It does no good for us to invest in this mission if all we create is scientific controversy." Thus, the lander's science definition team came up with two ways to address this. First, any detection of life has to be based on multiple, independent lines of evidence from direct measurements. "There's no silver bullet; you don't do one measurement and say: 'aha, eureka we've found it'. You look at the sum total," says Dr Niebur. Second, the scientists have come up with a framework to interpret those results, some of which might be positive, while others negative: "It creates a decision tree that marches through all the different variables. Following all these different paths, the end result is: yes, we've found life, or no we haven't," he says. At the lander workshop here at the LPSC, Nasa's Kevin Hand described the process as "biosignature bingo". Now, the team will have to see if the scientific community is persuaded. Curt Niebur explains: "I want to have that discussion now, today, years before we launch so that we can all be focused on analysing the data once we land."
News Article | May 18, 2017
NASA Wednesday informed the science community to prepare for a planned competition to select science instruments for a potential Europa lander. While a Europa lander mission is not yet approved by NASA, the agency's Planetary Science Division has funding in Fiscal Year 2017 to conduct the announcement of opportunity process. "The possibility of placing a lander on the surface of this intriguing icy moon, touching and exploring a world that might harbor life is at the heart of the Europa lander mission," said Thomas Zurbuchen, associate administrator of NASA's Science Mission Directorate in Washington. "We want the community to be prepared for this announcement of opportunity, because NASA recognizes the immense amount of work involved in preparing proposals for this potential future exploration." The community announcement provides advance notice of NASA's plan to hold a competition for instrument investigations for a potential Europa lander mission. Proposed investigations will be evaluated and selected through a two-step competitive process to fund development of a variety of relevant instruments and then to ensure the instruments are compatible with the mission concept. Approximately 10 proposals may be selected to proceed into a competitive Phase A. The Phase A concept study will be limited to approximately 12 months with a $1.5 million budget per investigation. At the conclusion of these studies, NASA may select some of these concepts to complete Phase A and subsequent mission phases. Investigations will be limited to those addressing the following science objectives, which are listed in order of decreasing priority: In early 2016, in response to a congressional directive, NASA's Planetary Science Division began a study to assess the science and engineering design of a future Europa lander mission. NASA routinely conducts such studies—known as Science Definition Team (SDT) reports—long before the start of any mission to gain an understanding of the challenges, feasibility and science value of the potential mission. The 21-member team began work almost one year ago, submitting a report to NASA on Feb. 7. The agency briefed the community on the Europa Lander SDT study at recent town halls at the 2017 Lunar and Planetary Science Conference (LPSC) at The Woodlands, Texas, and the Astrobiology Science Conference (AbSciCon) in Mesa, Arizona. The proposed Europa lander is separate from and would follow its predecessor—the Europa Clipper multiple flyby mission - which now is in preliminary design phase and planned for launch in the early 2020s. Arriving in the Jupiter system after a journey of several years, the spacecraft would orbit the planet about every two weeks, providing opportunities for 40 to 45 flybys in the prime mission. The Clipper spacecraft would image Europa's icy surface at high resolution, and investigate its composition and structure of its interior and icy shell. More information: To view the Europa Lander Science Definition Team report, see solarsystem.nasa.gov/europa/technical.cfm
Bethani A.,LPSC |
Bevan A.J.,Queen Mary, University of London |
Hays J.,Queen Mary, University of London |
Stevenson T.J.,Queen Mary, University of London
Journal of Physics: Conference Series | Year: 2016
We review the concept of support vector machines (SVMs) and discuss examples of their use. One of the benefits of SVM algorithms, compared with neural networks and decision trees is that they can be less susceptible to over fitting than those other algorithms are to over training. This issue is related to the generalisation of a multivariate algorithm (MVA); a problem that has often been overlooked in particle physics. We discuss cross validation and how this can be used to improve the generalisation of a MVA in the context of High Energy Physics analyses. The examples presented use the Toolkit for Multivariate Analysis (TMVA) based on ROOT and describe our improvements to the SVM functionality and new tools introduced for cross validation within this framework.
News Article | March 23, 2016
The New Horizons team used "principal component analysis" to get this false-color image that highlights the different regions of Pluto. Credit: NASA/New Horizons/JHAPL The New Horizons probe revealed the surface features of Pluto in rich detail when it reached the dwarf planet in July 2015. Some of the features look like snapshots of rivers and lakes that are locked firmly in place by Pluto's frigid temperatures. But now scientists studying the data coming back from New Horizons think that those frozen lakes and rivers could once have been liquid nitrogen. Pluto has turned out be a surprisingly active place. New Horizons has shown us what might be clouds in Pluto's atmosphere, mountains that might be ice volcanoes, and cliffs made of methane ice that melt away into the plains. If there were oceans and rivers of liquid nitrogen on the surface of Pluto, that would fit in with our evolving understanding of Pluto as a much more active planet than we thought. Richard Binzel, a New Horizons team member from MIT, thinks that lakes of liquid nitrogen could have existed some 800 or 900 million years ago. It all stems from Pluto's axial tilt, which at 120 degrees is much more pronounced than Earth's relatively mild 23 degree tilt. And computer modelling suggests that this tilt could have even been more extreme many millions of years ago. The result of this extreme tilt is that much more of Pluto's surface would have been exposed to sunlight. That may have warmed Pluto enough to allow liquid nitrogen to flow over the planet's surface. These kinds of changes to a planet's axial tilt, (and precession and eccentricity) affect a planet's climate in what are called Milankovitch cycles. The same cycles are thought to have a similar effect on Earth's climate, though not as extreme as on Pluto. According to Binzel, Pluto could be somewhere in between its temperature extremes, meaning that if Pluto will ever be warm enough for liquid nitrogen again, it could be hundreds of millions of years from now. "Right now, Pluto is between two extreme climate states," Binzel says. Alan Stern is a planetary scientist at the Southwest Research Institute, and New Horizons' Principal Investigator. He thinks that these long-cycle climate changes could have a very pronounced effect on Pluto, which has a nitrogen-rich atmosphere. In ancient times, Pluto's atmosphere could have been more dense than Mars'. "This opens up the possibility that liquid nitrogen may have once or even many times flowed on Pluto's surface," he said. More data from New Horizons is still on its way. About half is yet to arrive. That data, and further analysis, might discredit the fledgling idea that Pluto had and will have again lakes of liquid nitrogen. "We are just beginning to understand the long-term climate of Pluto," said Binzel. This week is the 47th Lunar and Planetary Science Conference (LPSC) in Houston. Members of the New Horizons team will be presenting almost 40 reports on Pluto and its system of moons at this conference. Stern's lecture, titled "The Exploration of Pluto," will be archived online at livestream.com/viewnow/LPSC2016. Explore further: Pluto sweats, and 5 other things you didn't know about the dwarf planet
News Article | November 17, 2016
BATON ROUGE, La., Nov. 17, 2016 /PRNewswire/ -- Entergy Louisiana, LLC today received approval from the Louisiana Public Service Commission to build a new natural gas-fired, combined-cycle power plant in St. Charles Parish. The LPSC vote clears the way for Entergy Louisiana to move...
Chatterjee A.,Harish Chandra Research Institute |
Drees M.,University of Bonn |
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012
In the framework of the minimal cosmological standard model, the ΛCDM model, the dark matter density is now known within an error of a few percent; this error is expected to shrink even further once PLANCK data are analyzed. Matching this precision by theoretical calculations implies that at least leading radiative corrections to the annihilation cross section of the dark matter particles have to be included. Here we compute one kind of large corrections in the context of the minimal supersymmetric extension of the Standard Model: corrections associated with two-point function corrections on chargino and neutralino (collectively denoted by χ) lines. These can be described by effective χ-fermion-sfermion and χ-χ-Higgs couplings. We also employ one-loop corrected χ masses, using a recently developed version of the on-shell renormalization scheme. The resulting correction to the predicted dark matter density depends strongly on parameter space, but it can easily reach 3%. © 2012 American Physical Society.
Nuclear Physics B - Proceedings Supplements | Year: 2010
We discuss how ATLAS has been preparing for the analysis of the first fb-1 of good data at 14 TeV in view of discovering new physics beyond the Standard Model. We show some ideas developed for understanding the backgrounds and we present as realistic as possible estimates of the reach of the experiment. © 2010 Elsevier B.V.
Abraham A.M.,LPSC |
International Journal of Applied Engineering Research | Year: 2014
Flow dynamics in a gas turbine is highly complex and is a challenging subject of research to the turbo machinery community. Studies show that axial gap between stationary blades and rotating blades in a turbine plays a major role in the performance of a turbine. This paper numerically analyses the effect of axial gap on the flow dynamics of a gas turbine consisting of a set of nozzle blades, two rows of rotor blades and a single row of stator blades. A fixed value of mass flow rate at inlet and pressure at exit are given as boundary conditions in all cases which helps to effectively assess the impact of changing axial gaps on the flow dynamics. Study also analyses the change in rotor torque and efficiency with increase in axial gap. © Research India Publications.
Nuovo Cimento della Societa Italiana di Fisica C | Year: 2010
Accurate predictions for both signal and background events at the LHC are of paramount importance in order to confirm even the smallest deviations from Standard Model predicitions. Next-to-leading order Monte Carlo event generators are an essential tool to reach that goal. Concerning the charged Higgs boson, NLO calculations of the production cross section already exist. Reiterating the calculation using a subtraction formalism enables us to implement the cross section into Monte Carlo generators, which can then be used by experiments. © Societ̀ Italiana di Fisica.
EPJ Web of Conferences | Year: 2013
The main purpose of these lectures is to provide the reader with the tools needed to data analysis in the framework of physics experiments. Basic concepts are introduced together with examples of application in experimental physics. The lecture is divided into two parts: probability and statistics. It is build on the introduction from "data analysis in experimental sciences" given in  © Owned by the authors, published by EDP Sciences, 2013.