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  • richardmitnick 5:58 am on September 13, 2014 Permalink | Reply
    Tags: , , , Comets, ,   

    From SPACE.com: “Comets: Formation, Discovery and Exploration” 

    space-dot-com logo

    SPACE.com

    November 15, 2010
    Charles Q. Choi

    Comets – Overview

    A comet is an icy body that releases gas or dust. They are often compared to dirty snowballs, though recent research has led some scientists to call them snowy dirtballs. Comets contain dust, ice, carbon dioxide, ammonia, methane and more. Some researchers think comets might have originally brought some of the water and organic molecules to Earth that now make up life here.

    Comets orbit the sun, but most are believed to inhabit in an area known as the Oort Cloud,

    oort
    Artists rendering of the Kuiper Belt and Oort Cloud.

    far beyond the orbit of Pluto. Occasionally a comet streaks through the inner solar system; some do so regularly, some only once every few centuries. Many people have never seen a comet, but those who have won’t easily forget the celestial show.

    halley
    Halley’s Comet as photographed May 8, 1910, by Dr. G.W. Ritchey using the 60-inch (1.5-meter) telescope at Mount Wilson Observatory, Calif., during the comet’s last appearance. The head of the comet and the beginning of its long tail are shown. Short, straight streaks are background stars. Credit: NASA/JPL

    Physical Characteristics

    The solid nucleus or core of a comet consists mostly of ice and dust coated with dark organic material, with the ice composed mainly of frozen water but perhaps other frozen substances as well, such as ammonia, carbon dioxide, carbon monoxide and methane. The nucleus might have a small rocky core.

    As a comet gets closer to the sun, the ice on the surface of the nucleus begins turning into gas, forming a cloud known as the coma.

    coma

    Radiation from the sun pushes dust particles away from the coma, forming a dust tail, while charged particles from the sun convert some of the comet’s gases into ions, forming an ion tail. Since comet tails are shaped by sunlight and the solar wind, they always point away from the sun.

    The nuclei of most comets are thought to measure 10 miles (16 km) or less. Some comets have comas that can reach nearly 1 million miles (1.6 million kilometers) wide, and some have tails reaching 100 million miles (160 million kilometers) long.

    We can see a number of comets with the naked eye when they pass close to the sun because their comas and tails reflect sunlight or even glow because of energy they absorb from the sun. However, most comets are too small or too faint to be seen without a telescope.

    Comets leave a trail of debris behind them that can lead to meteor showers on Earth. For instance, the Perseid meteor shower occurs every year between August 9 and 13 when the Earth passes through the orbit of the Swift-Tuttle comet.

    Orbital Characteristics

    Asteroids classify comets based on the durations of their orbits around the sun. Short-period comets need roughly 200 years or less to complete one orbit, long-period comets take more than 200 years, and single-apparition comets are not bound to the sun, on orbits that take them out of the solar system. Recently, scientist have also discovered comets in the main asteroid belt — these main-belt comets might be a key source of water for the inner terrestrial planets.

    ast
    The inner Solar System, from the Sun to Jupiter. Also includes the asteroid belt (the white donut-shaped cloud), the Hildas (the orange “triangle” just inside the orbit of Jupiter), the Jupiter trojans (green), and the near-Earth asteroids. The group that leads Jupiter are called the “Greeks” and the trailing group are called the “Trojans” (Murray and Dermott, Solar System Dynamics, pg. 107).

    Scientists think short-period comets, also known as periodic comets, originate from a disk-shaped band of icy objects known as the Kuiper belt beyond Neptune’s orbit, with gravitational interactions with the outer planets dragging these bodies inward, where they become active comets. Long-period comets are thought to come from the nearly spherical Oort cloud even further out, which get slung inward by the gravitational pull of passing stars.

    Some comets, called sun-grazers, smash right into the sun or get so close that they break up and evaporate.

    Naming

    In general, comets are named after their discoverer, either a person. For example, comet Shoemaker-Levy 9 got its name because it was the ninth short-periodic comet discovered by Eugene and Carolyn Shoemaker and David Levy. Spacecraft have proven very effective at spotting comets as well, so the names of many comets incorporate the names of missions such as SOHO or WISE.

    NASA SOHO
    NASA/SOHO

    NASA Wise Telescope
    NASA/WISE

    mc
    Comet McNaught C/2009 R1 was visible on June 6, 2010. Credit: Michael Jäger


    Formation

    Astronomers think comets are leftovers from the gas, dust, ice and rocks that initially formed the solar system about 4.6 billion years ago.

    Comet Life Cycle
    Departure
    Some comets are not bound to the sun, on orbits that take them out of the solar system.

    Extinction

    Comets lose ice and dust each time they come near the sun, leaving behind trails of debris. Eventually, they can lose all their ices, with some turning into fragile, inactive objects similar to asteroids.

    Breakup

    Other comets, upon losing all their ices, break up and dissipate into clouds of dust.

    Collisions

    The orbits comets take sometimes end with them colliding with planets and their moons. Many impact craters seen in the solar system were caused by such collisions.

    History

    In antiquity, comets inspired both awe and alarm, “hairy stars” resembling fiery swords that appeared unpredictably in the sky. Often, comets seemed to be omens of doom — the most ancient known mythology, the Babylonian “Epic of Gilgamesh,” described fire, brimstone, and flood with the arrival of a comet, and Emperor Nero of Rome saved himself from the “curse of the comet” by having all possible successors to his throne executed. This fear was not just limited to the distant past — in 1910, people in Chicago sealed their windows to protect themselves from what they thought was the comet’s poisonous tail.

    For centuries, scientists thought comets traveled in the Earth’s atmosphere, but in 1577, observations made by Danish astronomer Tycho Brahe revealed they actually traveled far beyond the moon. Isaac Newton later discovered that comets move in elliptical, oval-shaped orbits around the Sun, and correctly predicted that they could return again and again.

    Chinese astronomers kept extensive records on comets for centuries, including observations of Halley’s Comet going back to at least 240 BC, historic annals that have proven valuable resources for later astronomers.

    A number of recent missions have ventured to comets.NASA’s Deep Impact collided an impactor into Comet Tempel 1 in 2005 and recorded the dramatic explosion that revealed the interior composition and structure of the nucleus. In 2009, NASA announced samples the Stardust mission returned from Comet Wild 2 revealed a building block of life. The European Space Agency’s Rosetta is scheduled to orbit Comet Churyumov-Gerasimenko in 2014 and deploy a probe to make the first landing on a comet.

    deep
    NASA/Deep Impact

    NASA Stardust spacecraft
    NASA/Stardust

    Famous Comets

    Halley’s Comet is likely the most famous comet in the world, even depicted in the Bayeux Tapestry that chronicled the Battle of Hastings of 1066. It becomes visible to the naked eye every 76 years when it nears the sun. When Halley’s Comet zoomed near Earth in 1986, five spacecraft flew past it and gathered unprecedented details, coming close enough to study its nucleus, which is normally concealed by the comet’s coma. The roughly potato-shaped, nine-mile-long (15 km) contains equal part ice and dust, with some 80 percent of the ice made of water and about 15 percent of it consisting of frozen carbon monoxide. Researchers believe other comets are chemically similar to Halley’s Comet. The nucleus of Halley’s Comet was unexpectedly extremely dark black — its surface, and perhaps those of most others, is apparently covered with a black crust of dust over most of the ice, and it only releases gas when holes in this crust expose ice to the sun.

    The comet Shoemaker-Levy 9 collided spectacularly with Jupiter in 1994, with the giant planet’s gravitational pull ripping the comet apart for at least 21 visible impacts. The largest collision created a fireball that rose about 1,800 miles (3,000 km) above the Jovian cloudtops as well as a giant dark spot more than 7,460 miles (12,000 km) across — about the size of the Earth —and was estimated to have exploded with the force of 6,000 gigatons of TNT.

    A recent, highly visible comet was Hale-Bopp, which came within 122 million miles (197 million kilometers) of Earth in 1997. Its unusually large nucleus gave off a great deal of dust and gas — estimated at roughly 18 to 25 miles (30 to 40 kilometers) across — appeared bright to the naked eye.

    When Earth crosses the path of a comet, even if the comet hasn’t been around for a few years, leftover dust and ice can create increased numbers of meteors in what’s known as a meteor shower.

    See the full article here.

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  • richardmitnick 4:19 pm on August 11, 2014 Permalink | Reply
    Tags: , , , Comets, , , , , ,   

    From NASA/Goddard: “NASA’s 3-D Study of Comets Reveals Chemical Factory at Work” 

    NASA Goddard Banner

    NASA Goddard Space flight Center

    August 11, 2014
    Elizabeth Zubritsky
    NASA’s Goddard Space Flight Center, Greenbelt, Maryland
    301-614-5438
    elizabeth.a.zubritsky@nasa.gov

    Nancy Neal-Jones
    NASA’s Goddard Space Flight Center, Greenbelt, Maryland
    301-286-0039
    nancy.n.jones@nasa.gov

    A NASA-led team of scientists has created detailed 3-D maps of the atmospheres surrounding comets, identifying several gases and mapping their spread at the highest resolution ever achieved.

    “We achieved truly first-of-a-kind mapping of important molecules that help us understand the nature of comets,” said Martin Cordiner, a researcher working in the Goddard Center for Astrobiology at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Cordiner led the international team of researchers.

    Almost unheard of for comet studies, the 3-D perspective provides deeper insight into which materials are shed from the nucleus of the comet and which are produced within the atmosphere, or coma. This helped the team nail down the sources of two key organic, or carbon-containing, molecules.

    The observations were conducted in 2013 on comets Lemmon and ISON using the Atacama Large Millimeter/submillimeter Array, or ALMA, a network of high-precision antennas in Chile. These comets are the first to be studied with ALMA.

    ALMA Array
    ALMA

    The ALMA observations combine a high-resolution 2-D image of a comet’s gases with a detailed spectrum at each point. From these spectra, researchers can identify the molecules present at every point and determine their velocities (speed plus direction) along the line-of-sight; this information provides the third dimension – the depth of the coma.

    “So, not only does ALMA let us identify individual molecular species in the coma, it also gives us the ability to map their locations with great sensitivity,” said Anthony Remijan, a scientist with the National Radio Astronomy Observatory, one of the organizations that operates ALMA, and a co-author of the study.

    The researchers reported results for three molecular species, focusing primarily on two whose sources have been difficult to discern (except in comet Halley). The 3-D maps indicated whether each molecule was flowing outward evenly in all directions or coming off in jets or in clumps.

    In each comet, the team found that two species – formaldehyde and HNC (made of one hydrogen, one nitrogen and one carbon) – were produced in the coma. For formaldehyde, this confirmed what researchers already suspected, but the new maps contained enough detail to resolve clumps of the material moving into different regions of the coma day-by-day and even hour-by-hour.

    For HNC, the maps settled a long-standing question about the material’s source. Initially, HNC was thought to be pristine interstellar material coming from the nucleus of a comet, whereas later work suggested other possible sources. The new study provided the first proof that HNC is produced during the breakdown of large molecules or organic dust in the coma.

    “Understanding organic dust is important, because such materials are more resistant to destruction during atmospheric entry, and some could have been delivered intact to early Earth, thereby fueling the emergence of life,” said Michael Mumma, Director of the Goddard Center for Astrobiology, and a co-author on the study. “These observations open a new window on this poorly known component of cometary organics.”

    The observations, published today by the Astrophysical Journal Letters, also were significant because modest comets like Lemmon and ISON contain relatively low concentrations of crucial molecules, making them difficult to probe in depth with Earth-based telescopes. The few comprehensive studies of this kind so far have been conducted on bright, blockbuster comets, such as Hale-Bopp. The present results extend them to comets of only moderate brightness.

    This research was funded by the NASA Astrobiology Institute through the Goddard Center for Astrobiology and by NASA’s Planetary Atmospheres and Planetary Astronomy programs. ALMA is an international astronomy facility. Its construction and operations are led on behalf of Europe by the European Southern Observatory, on behalf of North America by the U.S. National Radio Astronomy Observatory (NRAO) and on behalf of East Asia by the National Astronomical Observatory of Japan.

    See the full article here.

    NASA’s Goddard Space Flight Center is home to the nation’s largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

    Named for American rocketry pioneer Dr. Robert H. Goddard, the center was established in 1959 as NASA’s first space flight complex. Goddard and its several facilities are critical in carrying out NASA’s missions of space exploration and scientific discovery.

    NASA

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  • richardmitnick 6:39 am on August 5, 2014 Permalink | Reply
    Tags: , , , Comets, ,   

    From The New York Times: “A Celestial Traveler Closes on Mars” 

    New York Times

    The New York Times

    AUG. 4, 2014
    MARC KAUFMAN

    One day early last year, the Australian comet hunter Robert H. McNaught spotted something unusual from his post at the Siding Spring Observatory in the foothills of the Warrumbungle Mountains.

    As a member of a team sponsored by NASA that searches the skies for potentially dangerous asteroids and comets, he generally focuses on objects that orbit the sun on the same plane as the planets. But coming up from below that plane was a comet that had apparently originated in the Oort cloud, a vast, primordial region that surrounds the solar system.

    The comet was well beyond Jupiter when Mr. McNaught sighted it, but he and other so-called comet modelers were nonetheless able to predict its 125,000-mile-per-hour path into the inner solar system. To their surprise and consternation, it appeared to be heading straight for Mars, and some of their most precious equipment.

    Comet trajectories are notoriously changeable, and more recent projections suggest the comet, named Siding Spring, is highly unlikely to strike the planet or to do much damage to the two NASA rovers on its surface or the five research satellites orbiting it.

    ss
    Comet Siding Spring, as captured before and after filtering by the Hubble Space Telescope, is expected to pass closest to Mars on Oct. 19. Credit NASA, ESA, and J.-Y. Li of Planetary Science Institute

    Comet map
    Comet Siding Spring will sweep past Mars in October, then follow other recent comets around the sun and back into deep space.

    Still, on Oct. 19, the comet is expected to pass within 82,000 miles of Mars, a stone’s throw in astronomical terms — one-third the distance between Earth and the moon, and much closer to Mars than any comet has come to Earth in recorded history.

    The dust, water vapor and other gases spewed by a comet can spread for tens of thousands of miles, so the upper reaches of the Martian atmosphere are expected to be showered by Siding Spring — perhaps briefly, perhaps more extensively. Shock waves may rock the atmosphere.

    The dust particles may be tiny, but when traveling at 125,000 m.p.h. (35 miles per second) they would pierce the skin of any satellite orbiting the planet. “Essentially, they would be like bullets out there,” said Richard Zurek, the chief scientist of the Mars program at NASA’s Jet Propulsion Laboratory.

    He added that although the danger to satellites and rovers appeared to be limited, there was a small possibility that the comet could break up as it approaches Mars — a fate similar to that of Comet ISON as it neared the sun last year. As a precaution, the five satellites’ orbits have been tweaked so they will be on the far side of the planet when the greatest threat from dust arrives.

    But for the most part, the initial worries have given way to excitement about the scientific opportunities presented by the very close encounter.

    The satellites and rovers — along with ground and space observatories such as the Spitzer and Hubble Space Telescopes — will offer a front-row seat to the event, which may provide important images and science for days.

    “This is an entirely unprecedented situation,” said James Green, director of NASA’s planetary science division and of its Mars program.

    ‘We have an opportunity to see what happens when a comet comes so close to a planet,” he continued. “We can follow the planet as it responds to the dust and water and shock, and hope to learn more about how it processes it all. Comets have played a huge role in transforming planets, and now we’ll see the process as it’s happening.”

    A ‘Dirty Snowball’

    Comet Siding Spring is especially interesting because of its formation in the Oort cloud during the early days of the solar system, making it a “long period” comet with an orbit of millions of years. What’s more, it is believed to be what comet specialists call a virgin — one that has never reached the inner solar system.

    As a result, its icy nucleus (the “dirty snowball” at the core of a comet) has never been thawed and reshaped, like those of comets that pass by more regularly.

    “We’ve studied the nuclei of comets before but never a long-period comet from the Oort cloud,” Dr. Zurek said. “The comet may well be bringing us primordial material unchanged since the creation of the solar system.”

    As luck would have it, Siding Spring will pass Mars just a month after the arrival of NASA’s newest orbiter, Maven, short for Mars Atmosphere and Volatile Evolution.

    NASA MAVEN
    NASA/MAVEN

    That satellite has instruments designed to study the Martian atmosphere, and in particular how water vapor and other material escape into space. Siding Spring may well produce atmospheric dynamics that the Maven team expected to study in a far more static state.

    “If particles from the comet hit the atmosphere, we’ll absolutely be able to measure what happens,” said Bruce Jakosky, principal investigator for the satellite mission. Initially worried that the comet could damage Maven just as its mission began, he now sees the flyby as exploration science at its best.

    “We’ll follow how different chemical processes play out and will be looking to see if the arrival of those fast-moving dust particles, with all their energy, heats up the atmosphere,” he said. “We know there were lots of comet and asteroid impacts and near misses on early Mars, and now we’re in a position to learn about some possible consequences.”

    The implications for Mars science are substantial. The Curiosity rover has confirmed and substantially expanded earlier findings that Mars was warmer and much wetter a long time ago. But the question of how and when the planet lost those potentially life-supporting conditions remains largely unresolved.

    NASA Curiosity

    Because all the cameras orbiting above Mars are designed to focus on the planet, they are not expected to produce the best images of the flyby. That role is likely to be played by the Hubble and by observatories on Earth. Some believe that Curiosity might be lucky and snap an image of the comet passing above.

    One especially powerful orbiting camera, however, has a chance of capturing what is considered the most important and interesting part of the comet — its nucleus, the “dirty snowball.” Little changed for billions of years, the ball of dust and ice warms as it enters the inner solar system and emits a vast surrounding cloud of material called the coma, followed by the long tail. The camera, named HiRise for High Resolution Imaging Science Experiment, produces finely detailed images that have revolutionized our understanding of the Martian surface; now its operators will try to do the same for the comet’s primordial nucleus.

    NASA HiRise Camera

    It will be tricky. Observations by NASA’s Swift satellite suggest that the fast-moving nucleus is small, a half-mile to several miles across. “The geometry is definitely challenging,” said Alfred McEwen, the principal investigator for HiRise. “We’ll be orbiting Mars rapidly, and the comet will be whizzing by. And HiRise is designed to look down at Mars, not out at a comet.”

    NASA SWIFT Telescope
    NASA/SWIFT

    But especially if the nucleus is large, he said, HiRise might be able to capture at least a handful of pixels that would illustrate the primordial core of Siding Spring — the first images of a long-period nucleus.

    Dr. McEwen said the team also planned to photograph jets of water vapor and dust that often shoot out of the nucleus.

    A Journey From the Oort Cloud

    As described by NASA, Comet Siding Spring spent billions of years in the Oort cloud, named for the 20th-century Dutch astronomer Jan Oort, who first predicted its existence.

    Most comets that form in the Oort cloud stay in place, orbiting the sun once every million to 30 million years. Sometimes, however, gravitational forces from nearby stars, or giant planets that many scientists believe wander in space, push a comet out of orbit and send it toward the sun. For Comet Siding Spring, that voyage has taken a million years.

    Astronomers will also be using Earth and space observatories to identify the comet’s chemical makeup. Of particular interest is what carbon-based organic compounds might be detected. These compounds, the building blocks of life, are known to reside in comets and asteroids. NASA’s Stardust mission to the comet Wild 2 collected samples in 2006. In labs, scientists found not only organics in the stardust, but small yet detectable amounts of evolved amino acids.

    Daniel P. Glavin, an astrobiologist at NASA’s Goddard Spaceflight Center, was part of the team that found the amino acids in Wild 2, and now he is on the Curiosity science team. He called the Siding Spring flyby a useful reminder of how organics, with their potential to connect and form life, could be delivered from afar.

    “We don’t know how life begins, but we do know that organics are necessary,” Dr. Glavin said. “And how do organics appear? Maybe they’re formed on the surface of a planet like Earth, or maybe they get delivered by comets like Siding Spring.”

    One of the main goals of the Curiosity mission is to search for organic compounds that might help show whether Mars was once habitable.

    Siding Spring is not expected to get close enough to send organic compounds to the surface, but Dr. Green, NASA’s Mars program director, does not want to take any chances. Although Curiosity will be in a defensive position for the flyby, he has plans for the small scoop that the rover uses to deliver crushed rock samples to the instruments inside.

    “What I told the Curiosity team is that the chances are very slight that organics or comet dust would fall on the rover,” he said. “But we should have the scoop out to catch some just in case.”

    See the full article here.

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  • richardmitnick 11:08 am on August 3, 2014 Permalink | Reply
    Tags: , , , Comets, ,   

    From SPACE.com: “European Spacecraft to Attempt Historic Comet Rendezvous This Week” 

    space-dot-com logo

    SPACE.com

    August 02, 2014
    Mike Wall

    After a 10-year, 4-billion-mile journey through deep space, a European probe will finally arrive at its comet destination this week.

    The European Space Agency’s Rosetta spacecraft is scheduled to rendezvous with Comet 67P/Churyumov-Gerasimenko on Wednesday (Aug. 6). If all goes according to plan, Rosetta will on that day become the first probe ever to orbit a comet — and, in November, the first to drop a lander onto the surface of one of these icy wanderers.

    ESA Rosetta spacecraft
    ESA/Rosetta

    “For the first time, we will rendezvous with a comet, for the first time we will escort a comet as it passes through its closet approach to the sun and — the cherry on the top — for the first time, we will deploy a lander,” Rosetta project scientist Matt Taylor told Space.com via email. “The rendezvous is therefore a key milestone in the mission.”

    A long wait

    The 1.3-billion-euro ($1.75 billion at current exchange rates) Rosetta mission blasted off in March 2004, kicking off a long and circuitous journey through the solar system. The probe has swung around the sun five times and zoomed past Earth on three separate speed-boosting flybys, European Space Agency (ESA) officials said.

    The probe was asleep during a decent chunk of its decade-long trip; mission team members woke Rosetta up in January to prepare for the upcoming rendezvous, ending a record-setting 957 days of hibernation.

    Rosetta is homing in on the 2.5-mile-wide (4 kilometers) Comet 67P/Churyumov-Gerasimenko, which takes about 6.5 years to complete one lap around the sun. The comet’s elliptical orbit takes it beyond Jupiter at its farthest point from the sun and between Mars and Earth at its closest point.

    The rendezvous operation actually consists of 10 different maneuvers, which began in early May and will conclude with a final engine burn on Wednesday. These moves will end up slowing Rosetta’s speed relative to 67P from 1,790 mph (2,880 km/h) at the end of the probe’s hibernation to 2 mph (3 km/h) — walking speed — at the time of orbital insertion, Taylor said.

    “It is challenging; it’s never been done before,” Taylor said. “Other [comet] missions have been flybys at high speed and about 100 kilometers or more distance.”

    Learning about comets

    Rosetta will provide some more deep-space drama in November, when the mother ship drops a lander called Philae onto the surface of 67P. Philae will drill into the comet to take samples and capture images from the surface of the body, ESA officials said.

    ESA Rosetta Philae
    ESA/Rosetta Philae

    The Rosetta mothership and Philae will tag along with 67P as it approaches and then swings around the sun, noting how the comet changes during the trip. The duo’s observations should reveal a great deal about comet composition, which in turn should help researchers better understand solar system evolution, mission officials have said. (Comets are primitive and relatively pristine building blocks left over from the solar system’s formation.)

    Taylor and other mission team members are very much looking forward to this “escort phase,” which is slated to run from Wednesday through the end of the nominal mission in December 2015.

    “All the time we are looking, and sniffing the comet, and with the lander (over a shorter time period) scratching and sniffing,” Taylor said. “All this will provide us with an unprecedented view of a comet, its nucleus and coma and how this all works!”

    See the full article, with more photos, here.

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  • richardmitnick 4:33 pm on February 12, 2014 Permalink | Reply
    Tags: , Comets, , Near Earth Objects (NEOS)   

    From ESO: “ESA/ESO Collaboration Successfully Tracks Its First Potentially Threatening Near-Earth Object” 


    European Southern Observatory

    See the full article here.

    21 January 2014 [Don't know how I missed this biggie]

    The first Near-Earth Object (NEO) recovery campaign has been successfully carried out by a new collaboration between the European Space Agency (ESA) and ESO. Up to now the asteroid 2009 FD had been ranked among the top five objects in a list of the most dangerous objects, but new observations with ESO’s Very Large Telescope (VLT) have now shown that it is far less likely to hit the Earth than had been feared. [So, maybe I did not miss it, maybe I just skipped it.]

    neo

    ESO VLT
    VLT

    NEOs are asteroids or comets with orbits around the Sun that come very close to the Earth’s orbit. More than 600 000 asteroids are known in the Solar System, and more than 10 000 of them are NEOs. Their sizes range from metres to tens of kilometres. Some NEOs could hit our planet and, depending on their size, produce considerable damage. While the chance of a large object hitting the Earth is very small, it could produce a great deal of destruction and loss of life.

    A new collaboration between ESA and ESO takes place within a global effort by the United Nations and its Committee on the Peaceful Uses of Outer Space (UNCOPUOS). In the wake of the Chelyabinsk event over Russia last February, there is renewed interest in global action on the NEO threat. The UNCOPUOS Action Team, including ESO, put forward recommendations for an international response to the NEO impact threat to form an International Asteroid Warning Network, which the UN General Assembly approved in October 2013.

    ESO’s unique capabilities to observe very faint (but still threatening) NEOs complement ESA’s efforts to discover and track these objects. New observations of asteroid 2009 FD performed with ESO’s 8.2-metre Very Large Telescope on Cerro Paranal in Chile resulted in good quality position measurements. These data have now been accepted by the IAU Minor Planet Center, the official organisation in charge of collecting observational data for minor planets. Both the European NEODyS system and the JPL-based Sentry system performed orbit determination and impact monitoring using these new VLT observations.

    The NEO Segment of ESA’s Space Situational Awareness (SSA) aims to coordinate and combine information from different sources, and analyse them to predict possible impact with the Earth, and assess danger, and analyse possible mitigations, including the deflection of a menacing asteroid.

    The successful observations of 2009 FD show that having access to a large telescope such as the VLT is a great opportunity for the NEO Coordination Centre, since it gives a chance to obtain accurate positional observations of very faint objects [2], which is only possible using the largest telescopes.

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  • richardmitnick 6:01 am on January 16, 2014 Permalink | Reply
    Tags: , , , Comets, ,   

    From ESA: “The most important alarm clock in the Solar System” 

    ESASpaceForEuropeBanner
    European Space Agency

    16 January 2014

    For further information, please contact:

    Markus Bauer
    ESA Science and Robotic Exploration Communication Officer
    Tel: +31 71 565 6799
    Mob: +31 61 594 3 954
    Email: markus.bauer@esa.int

    Fred Jansen
    ESA Rosetta mission manager
    Email: fjansen@rssd.esa.int

    Matt Taylor
    ESA Rosetta project scientist
    Email: matthew.taylor@esa.int

    At 10:00 GMT on Monday, the most important alarm clock in the Solar System will wake up ESA’s sleeping Rosetta spacecraft.

    ESA Rosetta spacecraft
    Rosetta

    Rosetta is chasing comet 67P/Churyumov–Gerasimenko and, since its launch in 2004, has made three flybys of Earth and one of Mars to build up enough speed and get on a trajectory towards the comet. It has also encountered asteroids Steins and Lutetia along the way.

    Operating on solar energy alone, the spacecraft was placed into a deep space slumber in mid-2011 as it cruised far from the Sun and out towards the orbit of Jupiter. To prepare for its long sleep, Rosetta was oriented so that its solar arrays faced the Sun and put into a once per minute spin for stability.

    The only devices left running were its computer and several heaters.

    Thirty-one months later, Rosetta’s orbit has brought it back to within only 673 million kilometres of the Sun, and there is finally enough solar energy to power the spacecraft fully again. It is time to wake up.

    Rosetta’s computer is programmed to carry out a sequence of events to re-establish contact with Earth on 20 January, starting with an ‘alarm clock’ at 10:00 GMT.

    Immediately after, the spacecraft’s startrackers will begin to warm up, taking around six hours.

    Then its thrusters will fire to stop the slow rotation. A slight adjustment will be made to Rosetta’s orientation to ensure that the solar arrays are still facing directly towards the Sun, before the startrackers are switched on to determine the spacecraft’s attitude.

    Once that has been established, Rosetta will turn directly towards Earth, switch on its transmitter and point its high-gain antenna to send its signal to announce that it is awake.

    Because of Rosetta’s vast distance – just over 807 million kilometres from Earth – it will take 45 minutes for the signal to reach the ground stations. The first opportunity for receiving a signal on Earth is expected between 17:30 GMT and 18:30 GMT.

    Deep space tracking dishes will be listening out for the signal, starting with NASA’s ‘big ears’ – the 70 m-diameter station at Goldstone, California, followed by, as the Earth rotates, the Canberra station in eastern Australia. ESA’s New Norcia 35 m antenna, in Western Australia, would be next in line to await the signal’s arrival.

    Whenever the signal is received, it will be relayed immediately to ESOC, ESA’s Operations Centre in Darmstadt, Germany.

    This exciting moment will be announced to the world straightaway via the @ESA_Rosetta twitter account.

    Once mission controllers have verified Rosetta’s health, each of its scientific instruments will be switched back on and checked out, an effort that will take several months as the spacecraft continues to eat up the remaining 9 million kilometres separating it from the comet.

    In May, Rosetta will make a major manoeuvre to line up for arriving at its target comet in August. If all goes well, it will become the first space mission to rendezvous with a comet, the first to attempt a landing, and the first to follow a comet as it swings around the Sun.

    Comets are considered to be the primitive building blocks of the Solar System and likely helped to ‘seed’ Earth with water, and perhaps even the ingredients for life. But many fundamental questions about these enigmatic objects remain, and through its comprehensive, close-up study of comet 67P/Churyumov–Gerasimenko, Rosetta aims to unlock the secrets within.

    A press event will be held at ESOC on 20 January to celebrate the wake up. An overview of the day-long event can be found here. The briefings will be livestreamed at http://www.esa.int/rosetta and http://www.livestream.com/eurospaceagency.

    See the full article here.

    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.


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  • richardmitnick 1:25 pm on November 26, 2013 Permalink | Reply
    Tags: , , , Comets, , , ISON   

    From ESO: “New Image of Comet ISON” 


    European Southern Observatory

    18 November 2013

    This new view of Comet C/2012 S1 (ISON) was taken with the TRAPPIST national telescope at ESO’s La Silla Observatory on the morning of Friday 15 November 2013. Comet ISON was first spotted in our skies in September 2012, and will make its closest approach to the Sun in late November 2013.

    lasilla
    Lasilla

    trappist
    TRAnsiting Planets and PlanetesImals Small Telescope

    ison
    ISON

    TRAPPIST has been monitoring comet ISON since mid-October, using broad-band filters like those used in this image. It has also been using special narrow-band filters which isolate the emission of various gases, allowing astronomers to count how many molecules of each type are released by the comet.

    Comet ISON was fairly quiet until 1 November 2013, when a first outburst doubled the amount of gas emitted by the comet. On 13 November, just before this image was taken, a second giant outburst shook the comet, increasing its activity by a factor of ten. It is now bright enough to be seen with a good pair of binoculars from a dark site, in the morning skies towards the East. Over the past couple of nights, the comet has stabilised at its new level of activity.

    These outbursts were caused by the intense heat of the Sun reaching ice in the tiny nucleus of the comet as it zooms toward the Sun, causing the ice to sublimate and throwing large amounts of dust and gas into space. By the time ISON makes its closest approach to the Sun on 28 November (at only 1.2 million kilometres from its surface — just a little less than the diameter of the Sun!), the heat will cause even more ice to sublimate. However, it could also break the whole nucleus down into small fragments, which would completely evaporate by the time the comet moves away from the Sun’s intense heat. If ISON survives its passage near the Sun, it could then become spectacularly bright in the morning sky.

    The image is a composite of four different 30-second exposures through blue, green, red, and near-infrared filters. As the comet moved in front of the background stars, these appear as multiple coloured dots.

    TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope) is devoted to the study of planetary systems through two approaches: the detection and characterisation of planets located outside the Solar System (exoplanets), and the study of comets orbiting around the Sun. The 60-cm national telescope is operated from a control room in Liège, Belgium, 12 000 km away.

    See the full article here.

    Visit ESO in Social Media-

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    ESO Main

    ESO, European Southern Observatory, builds and operates a suite of the world’s most advanced ground-based astronomical telescopes.


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  • richardmitnick 2:58 pm on September 16, 2013 Permalink | Reply
    Tags: , Comets, ,   

    From Livermore Lab: “It’s a shock: Life on Earth may have come from out of this world” 


    Lawrence Livermore National Laboratory

    09/15/2013
    Anne M Stark, LLNL, (925) 422-9799, stark8@llnl.gov

    A group of international scientists including a Lawrence Livermore National Laboratory researcher have confirmed that life really could have come from out of this world. The team shock compressed an icy mixture, similar to what is found in comets, which then created a number of amino acids – the building blocks of life. The research appears in advanced online publication Sept. 15 on the Nature Geoscience journal website.

    atoms
    Comets contain elements such as water, ammonia, methanol and carbon dioxide that could have supplied the raw materials, in which upon impact on early Earth would have yielded an abundant supply of energy to produce amino acids and jump start life.

    This is the first experimental confirmation of what LLNL scientist Nir Goldman first predicted in 2010 and again in 2013 using computer simulations performed on LLNL’s supercomputers, including Rzcereal and Aztec.

    Goldman’s initial research found that the impact of icy comets crashing into Earth billions of years ago could have produced a variety of prebiotic or life-building compounds, including amino acids. Amino acids are critical to life and serve as the building blocks of proteins. His work predicted that the simple molecules found in comets (such as water, ammonia, methanol and carbon dioxide) could have supplied the raw materials, and the impact with early Earth would have yielded an abundant supply of energy to drive this prebiotic chemistry.

    In the new work, collaborators from Imperial College in London and University of Kent conducted a series of experiments very similar to Goldman’s previous simulations in which a projectile was fired using a light gas gun into a typical cometary ice mixture. The result: Several different types of amino acids formed.

    “These results confirm our earlier predictions of impact synthesis of prebiotic material, where the impact itself can yield life-building compounds,” Goldman said. “Our work provides a realistic additional synthetic production pathway for the components of proteins in our solar system, expanding the inventory of locations where life could potentially originate.”

    See the full article here.

    Operated by Lawrence Livermore National Security, LLC, for the Department of Energy’s National Nuclear Security
    Administration
    DOE Seal
    NNSA

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