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  • richardmitnick 2:51 pm on November 19, 2014 Permalink | Reply
    Tags: , , , Comets, ,   

    From ESA: “Rosetta Continues into its Full Science Phase” 

    ESASpaceForEuropeBanner
    European Space Agency

    19 November 2014
    No Writer Credit

    With the Philae lander’s mission complete, Rosetta will now continue its own extraordinary exploration, orbiting Comet 67P/Churymov–Gerasimenko during the coming year as the enigmatic body arcs ever closer to our Sun.

    ESA Rosetta spacecraft
    ESA/Rosetta

    p67
    Comet Churyumov–Gerasimenko as seen by Rosetta

    Last week, ESA’s Rosetta spacecraft delivered its Philae lander to the surface of the comet for a dramatic touchdown.

    ESA Rosetta Philae Lander
    Rosetta’s Philae Lander

    The lander’s planned mission ended after about 64 hours when its batteries ran out, but not before it delivered a full set of results that are now being analysed by scientists across Europe.

    Rosetta’s own mission is far from over and the spacecraft remains in excellent condition, with all of its systems and instruments performing as expected.

    “With lander delivery complete, Rosetta will resume routine science observations and we will transition to the ‘comet escort phase’,” says Flight Director Andrea Accomazzo.

    “This science-gathering phase will take us into next year as we go with the comet towards the Sun, passing perihelion, or closest approach, on 13 August, at 186 million kilometres from our star.”

    cr
    Rosetta control room

    On 16 November, the flight control team moved from the large Main Control Room at ESA’s Space Operations Centre in Darmstadt, Germany, where critical operations during landing were performed, to a smaller Dedicated Control Room, from where the team normally flies the craft.

    Since then, Rosetta has performed a series of manoeuvres, using its thrusters to begin optimising its orbit around the comet for the 11 scientific instruments.

    “Additional burns planned for today, 22 and 26 November will further adjust the orbit to bring it up to about 30 km above the comet,” says Sylvain Lodiot, Spacecraft Operations Manager.

    From next week, Rosetta’s orbit will be selected and planned based on the needs of the scientific sensors. After arrival on 6 August, the orbit was designed to meet the lander’s needs.

    On 3 December, the craft will move down to height of 20 km for about 10 days, after which it will return to 30 km.

    p
    Rosetta path after 12 November

    With the landing performed, all future trajectories are designed purely with science as the driver, explained Laurence O’Rourke and Michael Küppers at the Rosetta Science Operations Centre near Madrid, Spain.

    “The desire is to place the spacecraft as close as feasible to the comet before the activity becomes too high to maintain closed orbits,” says Laurence.

    “This 20 km orbit will be used by the science teams to map large parts of the nucleus at high resolution and to collect gas, dust and plasma at increasing activity.”

    Planning the science orbits involves two different trajectories: ‘preferred’ and ‘high-activity’. While the intention is always to fly the preferred path, Rosetta will move to the high-activity trajectory in the event the comet becomes too active as it heats up.

    “This will allow science operations to continue besides the initial impact on science planning that such a move would entail,” adds Michael.

    “Science will now take front seat in this great mission. It’s why we are there in the first place!” says Matt Taylor, Rosetta Project Scientist.

    “The science teams have been working intensively over the last number of years with the science operations centre to prepare the dual planning for this phase.”

    When solar heat activates the frozen gases on and below the surface, outflowing gas and dust particles will create an atmosphere around the nucleus, known as the coma.

    Rosetta will become the first spacecraft to witness at close quarters the development of a comet’s coma and the subsequent tail streaming for millions of kilometres into space. Rosetta will then have to stay further from the comet to avoid the coma affecting its orbit.

    In addition, as the comet nears the Sun, illumination on its surface is expected to increase. This may provide sufficient sunlight for the DLR-operated Philae lander, now in hibernation, to reactivate, although this is far from certain.

    Early next year, Rosetta will be switched into a mode that allows it to listen periodically for beacon signals from the surface.


    Rosetta orbiting the comet

    Regular updates on Rosetta’s continuing mission and its scientific explorations will be posted in the mission blog, via http://blogs.esa.int/rosetta.

    See the full article, with video, here.

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    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 7:04 am on November 18, 2014 Permalink | Reply
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    From NYT: “So Far Away, Yet So Near to Us” 

    New York Times

    The New York Times

    NOV. 17, 2014
    JOHN NOBLE WILFORD

    Philae is talking to us,” announced the manager in charge of the little piece of machinery that had just achieved the first landing on a comet, a frozen remnant from the formation of the solar system. “We are on the comet.”

    ph
    Philae

    ESA Rosetta spacecraft
    ESA/Rosetta with Philae

    Note the familiar, almost casual tone. It was as if the first thing the probe did on arrival was to call home, like a traveler with an ever-ready iPhone. The flight had taken forever, and that was some landing — bouncing around and finally winding up almost halfway across the surface. The European Space Agency’s probe was “talking” about its comet landing on Wednesday after a 10-year, four-billion-mile journey.

    The “we” echoes a famous human-machine flight relationship, Lindbergh’s solo crossing of the Atlantic in “The Spirit of St. Louis.” Here, the distant robotic messenger and the human receiver — the “we” — are also collaborators in reaching a new milestone in flight. Philae had made it to the surface on Comet 67P/Churyumov-Gerasimenko, an icy, rocky place only two and a half miles wide and 317 million miles from Earth.

    67
    Comet 67P/Churyumov-Gerasimenko

    Now, as even the most stalwart human explorers remain confined to lower Earth orbit for the foreseeable future, the search for discovery in the outer reaches of the solar system is left to robotic probes. They are conceived by humans to go where humans themselves cannot go. But that does not preclude the development of a strong human-machine bond over years of building, testing and flying a mission.

    Minders of these machines may spend half a career on an idea they will then cast into the heavens, and wait through what may seem like another half-career for it to reach its destination and send back results. The human-machine bond can be tight. Even no-nonsense scientists and engineers find themselves personalizing such a consuming life experience as well as a trusted machine.

    Sometimes, they too are guilty of the transgression they warn laypeople against: anthropomorphism, the attribution of human form and behavior to nonhuman or even inanimate forms. A machine is talking to us. It was shaken up by the three-bounce landing, at last coming to rest near a sheltering rock face (not a choice place, as it prevents sunlight from reaching the lander’s solar panels, which were counted on to charge its batteries). Poor Philae may not have long to live.

    What could be more natural than treating the probe in almost human terms when you have spent at least a decade, waking and dreaming, with machinery on which such care is bestowed that it penetrates to your very core? Your dog may or may not be your best friend, and who knows about the cat? But Philae talks to you.

    Finding something to relate to is a never-ending struggle for humans, as spacecraft and telescopes draw attention to unworldly realms. Thomas A. Mutch of Brown University was the principal geologist for the Viking missions in 1976 to search for possible life on Mars. When the first Viking landed on Mars and started transmitting pictures of the immediate surface, Dr. Mutch (known to all as Tim) focused his excitement on a single rock near of the craft’s footpads. The rock was red, as was nearly everything around on the russet plain, and so the geologist had something he could relate to. He would deal with the big picture in time.

    NASA Viking 1
    NASA/Viking 1

    Reporters don’t always resist the temptation to make homey comparisons of faraway encounters. In 1983, the Pioneer 10 spacecraft crossed the orbit of Pluto. Though it has since been stripped of full planetary standing, Pluto still represents a frontier into a greater unknown. Pioneer had flown by and photographed Jupiter and Saturn and was still going. Writing about this, I kept hearing the rhythm of the Little Engine That Could.

    NASA Pioneer 10
    NASA/Pioneer 10

    So I sought to put the same bug in the reader’s ear: Like the little engine that could, this was the little spacecraft that would probably push on to the frontier of interstellar space and still be living to tell the tale.

    Antoine de Saint-Exupéry, a French author, might have been able to understand our problem with perspective, in a universe so vast in which we are so small. Aside from his books on early aviation, he wrote about the Little Prince, who lived on a small asteroid where he cared for a single rose. The book was written for children, but with grown-ups very much in mind.

    A fox the little prince meets has some of the wisest lines. “One sees clearly only with the heart,” he says. “What is essential is invisible to the eye.”

    See the full article here.

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  • richardmitnick 4:34 pm on November 12, 2014 Permalink | Reply
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    From Brown: ” Questions for Peter Schultz – What can we learn by landing on a comet?” 

    Brown University
    Brown University

    November 12, 2014
    Contact: Kevin Stacey 401-863-3766

    ps
    Critical moment Peter Schultz and colleagues react to news that the ESA’s Philae Lander has reached the surface of the comet. Photo: Mike Cohea/Brown University

    On Wednesday, Nov. 12, 2014, the European Space Agency landed a spacecraft on the surface of a comet for the first time. Scientists hope data returned from the Rosetta spacecraft’s Philae Lander might not only offer a new perspective on the nature of comets, but also shed light the evolution of the solar system.

    ESA Rosetta spacecraft
    ESA/Rosetta

    ESA Rosetta Philae Lander
    Philae Lander

    Brown geoscientist Peter Schultz, who was not involved in the ESA mission, is a veteran of three prior missions to comets and asteroids (NASA’s Deep Impact, Stardust-NExT, and EPOXI missions). He spoke with science writer Kevin Stacey about Rosetta.

    Can you give us a bit of background on this comet?

    This particular comet (officially, 67P/Churyumov-Gerasimenko) goes around the sun about every 6.5 years and was discovered by two Ukranian astronomers (Klim Churyumov and Svetlana Gerasimenko) in 1969.

    comet
    67P/Churyumov-Gerasimenko

    As happens to many short-period comets, it was tugged by Jupiter’s gravity during a close encounter early in 1959. This tug changed its orbit, reducing its closest approach to the sun from 2.7 times the distance from the Earth (an astronomical unit, AU) to the sun to only 1.3 AU. The nucleus rotates on its axis every 12.4 hours but has changed due to jets of gas and dust that are released every time it gets close to the sun. As we now are finding out, cometary nuclei come in all shapes and sizes. This particular nucleus has two large lobes. One is about 2.5 miles across; the other is about 1.5 miles.

    Why was this comet chosen as a target for Rosetta and Philae?

    This comet was not the first choice for the mission, but the rocket that was to carry the spacecraft failed in 2002, which caused a delay. The orbit of this particular comet, however, allowed doing the same mission design, with a few tweaks. The key was to identify a comet that would allow a slow approach to the nucleus so that the spacecraft could rendezvous and then orbit.

    Could you talk about some of the technical challenges involved in landing on a comet?

    ESA scientists and engineers knew that it would be difficult to land on a cometary nucleus, especially because nothing was known about its surface. In fact, the mission was launched in 2002, before NASA’s Deep Impact mission saw the nucleus of 9P/Tempel 1 close-up for the first time, and before we knew anything about the density of a cometary nucleus. As Rosetta first captured its close-up view, it was clear that this nucleus was very different: patches of smooth surfaces, irregular depressions with steep-sided cliffs, and block fields. The Philae Lander will touch down in one of the smooth patches, approaching the surface at around two miles per hour (a slow walking pace). Certain areas look like soft snow while others regions are filled with blocks. As a result, it may be difficult to grab hold or stay put. Engineers designed “harpoons” that should have grabbed on while the lander’s legs are designed to keep the Lander from bouncing off. That’s critical because the escape speed is only about 1 mile per hour.

    What kinds of experiments will Philae be carrying out on the surface?

    Experiments on the lander make a wide range of measurements including the composition at the comet’s surface, the strength and density of the surface, temperature, the nature of compounds from about nine inches below the surface (using drills and instruments), isotopic ratios, magnetic field measurements. One instrument will probe the interior of a nucleus for the first time by sending radio waves from Philae to the orbiting Rosetta. Another will listen to the inside of the nucleus as it cracks and creeks when gas is released. This is like geophysicists and geochemists exploring a field site on Earth, but millions of miles away.

    What, ultimately, do scientists hope to learn by actually landing on a comet?

    In 2005, Deep Impact slammed into the nucleus of a comet in order to expose and measure ices and dust below. This time, Philae provides a softer touch. There’s much to be learned by landing on the surface. One of the key measurements is the relative abundance of heavy and light hydrogen, which may be a key to understanding the source of water on Earth. In addition, a lander is the only way to understand more about the strength of the surface and to understand how its atmosphere (the coma) changes as the comet goes around the sun. If successful, scientists will have a better understanding of how comets work.

    See the full article here.

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  • richardmitnick 3:54 pm on November 12, 2014 Permalink | Reply
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    From ESA: Philae landing on 67P/Churyumov–Gerasimenko 

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    European Space Agency

    This is the best I could find, obviously an animation. Hopefully something more real later.

    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 4:43 am on November 12, 2014 Permalink | Reply
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    From ESA/Rosetta: “Rosetta and Philae Go for Separation” 

    ESASpaceForEuropeBanner
    European Space Agency

    12 November 2014
    No Writer Credit

    Following a night of critical Go/NoGo decisions, Rosetta and Philae are cleared for separation, despite a problem onboard the lander. The mission is set to become the first in history to touch down on a comet.

    ESA Rosetta spacecraft
    ESA/Rosetta

    ESA Rosetta Philae Lander
    Philae on Rosetta

    During checks on the lander’s health, it was discovered that the active descent system, which provides a thrust to avoid rebound at the moment of touchdown, cannot be activated.

    At touchdown, landing gear will absorb the forces of the landing while ice screws in each of the probe’s feet and a harpoon system will lock Philae to the surface. At the same time, the thruster on top of the lander is supposed to push it down to counteract the impulse of the harpoon imparted in the opposite direction.

    “The cold gas thruster on top of the lander does not appear to be working so we will have to rely fully on the harpoons at touchdown,” says Stephan Ulamec, Philae Lander Manager at the DLR German Aerospace Center.

    “We’ll need some luck not to land on a boulder or a steep slope.”

    “There were various problems with the preparation activities overnight but we have decided to ‘go’. Rosetta is lined up for separation,” says Paolo Ferri, ESA’s head of mission operations.

    Thus despite the potential problem concerning the moment of touchdown, separation will proceed on the planned timeline.

    Separation will occur in space at 08:35 GMT / 09:35 CET, but it will take the radio signals from the transmitter on Rosetta 28 minutes and 20 seconds to reach Earth and be transferred to the Rosetta Mission Control Centre at ESA’s Space Operations Centre in Darmstadt, Germany.

    That means we must wait until about 09:03 GMT / 10:03 CET for confirmation the separation has happened correctly.

    The Go/No-Go decisions leading up to this milestone began last night at 19:00 GMT / 20:00 CET, with the first confirming that Rosetta is in the correct orbit for delivering Philae to the surface at the required time.

    The second Go was given at midnight (GMT), confirming that the commands to control separation and delivery are complete and ready to upload to Rosetta. The Go also confirmed that Rosetta’s overall health is good, and that the orbiter is ready to perform.

    At 02:35 GMT / 03:35 CET the third GO was given after a final verification that the lander is ready for touchdown.

    The final manoeuvre by Rosetta was conducted at 07:35 GMT / 08:35 CET, which is taking Rosetta to a point about 22.5 km from the comet’s centre for separation.
    Philae separation

    The manoeuvre was followed by the final Go/No-Go decision that verified the two spacecraft, the orbit, the ground stations, the ground systems and the teams are ready for landing.

    After separation, we will not hear from Philae for some two hours until the lander establishes a communication link with Rosetta. Philae cannot send its data to Earth directly – only via Rosetta.

    The descent to the surface of Comet 67P/Churyumov–Gerasimenko will take around seven hours, so confirmation of a successful touchdown is expected in a one-hour window centred on 17:02 GMT / 18:02 CET.

    “We are anxious but excited,” said Jean-Pierre Bibring, lead lander scientist, during this morning’s press briefing. “It is not every day that we try to land on a comet.”

    Follow the event live via http://www.esa.int/rosetta

    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 9:30 am on November 11, 2014 Permalink | Reply
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    From NYT: “Philae Lander Nears a Cosmic Touchdown” 

    New York Times

    The New York Times

    NOV. 10, 2014
    KENNETH CHANG

    In its 10-year chase of a comet, the European Space Agency’s ambitious Rosetta mission has pushed the edges of engineering ingenuity.

    ESA Rosetta spacecraft
    ESA/Rosetta

    After three slingshot flybys of Earth to fling it at ever faster speeds to catch up with its target, Rosetta was so far from the sun that its solar arrays could not generate enough electricity, and it was, by design, put into hibernation for two and a half years.

    To the relief of mission managers, Rosetta woke up from its cold, deep sleep as scheduled in January. In August, it finally pulled up alongside the comet, known as 67P/Churyumov-Gerasimenko, both flying closer to the sun at 34,400 miles per hour. In the months since, Rosetta has snapped photographs just 4.5 miles above the craggy surface.

    Now it is about to attempt its greatest feat yet: drop a small lander onto the comet.

    On Wednesday, at 3:35 a.m. Eastern time, the 220-pound lander, named Philae, is scheduled to detach from Rosetta and be pulled downward by the comet’s gravity. Signals from Rosetta will take nearly 30 minutes to travel more than 300 million miles to mission control in Darmstadt, Germany.

    ESA Rosetta Philae Lander
    Philae

    Philae will be aimed at a landing site that covers about a third of a square mile; the area looks relatively smooth and clear of boulders but is still close to streams of dust and gas shooting off the surface.

    Seven hours later, give or take some minutes, Philae is to bump onto the surface. The comet, 2.5 miles wide, is so small and its gravity so slight that even after that long fall, Philae will be traveling no faster than walking pace.

    comp
    A composite image of Comet 67P, where the Philae lander is scheduled to land after detaching from the Rosetta orbiter. Credit European Space Agency

    To keep the lander from bouncing, thrusters will fire for 15 seconds, pressing it against the surface, and a harpoon will shoot into the comet to anchor Philae.

    Both the European Space Agency and NASA, which contributed three instruments to the $275 million lander mission, will broadcast coverage on their websites.

    In this era of social media and anthropomorphized spacecraft, Philae and Rosetta have their own Twitter feeds: @Philae2014 and @ESA_Rosetta. “I’m so ready!” a Twitter post announced Sunday.

    Scientists hope that Philae and its 10 instruments will conduct 64 hours of work before its batteries drain.

    After that, if the dust and gas rising from the comet do not obscure too much sunlight, Philae’s solar panels are to recharge the batteries enough to provide an hour’s worth of observation every couple of days. Engineers expect Philae to survive until next March, when the surface of the comet becomes too hot.

    Philae is a high-risk, high-reward gamble. The lander could miss its mark, touch down on a boulder and topple over, or land in shadows where solar arrays cannot produce enough power.

    If it succeeds, scientists will have a breathtaking view from the surface of a comet. If it fails, mission managers say, Rosetta will still be a resounding success with the slew of data coming back from the orbiter. Planetary scientists have never had a look at a comet so close up for so long.

    Previous spacecraft missions have zoomed by comets at high speeds, providing only brief examinations. By contrast, Rosetta will be a constant companion as Comet 67P approaches the sun, swings around and heads out again, its instruments potentially providing more than two years of data.

    “We will watch this comet evolve,” Matt Taylor, the project scientist, said during a news briefing last week. “It’s never been done before.”

    Even at its brightest, Comet 67P will not be visible to the naked eye from Earth. At its closest point to the sun, it is still as far away as Earth. At the other end of its 6.5-year orbit, it is as far from the sun as Jupiter.

    Still, the changes on Comet 67P have been considerable already. Rosetta initially measured about 0.3 liters of water coming off the comet every second, Dr. Taylor said. “This is increasing,” he said. “We’re talking of kilos per second now coming off.” (A liter of water has a mass of one kilogram.)

    By the middle of next year, the comet will be spraying hundreds of liters of water a second, Dr. Taylor said.

    The comet has already provided a number of surprising findings, beginning with its shape. Instead of something roughly round, “we saw the duck,” Dr. Taylor said, referring to Comet 67P’s two-lobed structure that somewhat resembles a rubber bathtub toy.

    Among the gases that Rosetta has detected coming off the comet are hydrogen sulfide (the scent of rotten eggs), ammonia, methane, hydrogen cyanide, sulfur dioxide and formaldehyde. “It may be not be the perfume that some of us would choose to wear,” Dr. Taylor said. “It’s a bit smelly.”

    He added, “At least there’s some alcohol, which some of us might enjoy.”

    Or not — the alcohol in the comet is methanol, also known as wood alcohol, which is poisonous and can cause blindness when imbibed.

    In preparation for the landing operation, Rosetta has moved farther from the comet. On Tuesday, it will take a sharp turn toward the comet on a not-quite collision course.

    To get the lander to the selected site, Rosetta will have to drop Philae at the right time at the right spot at an altitude of 14 miles from the comet’s center while traveling at the right velocity.

    Up to that point, if anything looks not quite right, mission managers have several opportunities to stop and regroup and plan for another day.

    But after Philae is let go, the mission managers can only be helpless onlookers. The thrusters are not capable of making any midcourse corrections.

    “We cannot actively steer the trajectory of the landing on descent,” said Andrea Accomazzo, the flight director. “That’s the part that worries me most, because I have no control.”

    See the full article here.

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  • richardmitnick 5:21 pm on November 10, 2014 Permalink | Reply
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    From ESA Rosetta: “Measuring comet 67P/C-G” 

    ESASpaceForEuropeBanner
    European Space Agency

    ESA Rosetta spacecraft
    ESA/Rosetta

    This post provides a summary of some of the essential physical parameters of Comet 67P/Churyumov-Gerasimenko, as measured by Rosetta ahead of and since its 6 August rendezvous. This is an on-going process and the numbers will be updated as newer data are obtained, analysed, and made available.

    One of the key things is the so-called “shape model”, meaning a 3D model of the comet based on images from the OSIRIS and NAVCAM cameras. In a previous post we showed a render of one of the first shape models derived from OSIRIS data. Here we are releasing a more recent OSIRIS shape model in .wrl and .obj format, suitable for loading into 3D graphics applications (click the links to download).

    smp
    Comet 67P/C-G dimensions. Images: NAVCAM (19 August image); dimensions: OSIRIS

    Because roughly 30% of the ‘dark side’ of 67P/C-G has not been resolved and analysed fully yet, the shape model is very incomplete over those regions. As a result, some of the derived parameters for the comet are only best estimates at present. These include the volume and the global density, the latter depending on the mass and the volume.

    The table below summarises the approximate dimensions of 67P/C-G and other known parameters derived from observations made by Rosetta, with the instrument with which the measurement was made also indicated. Links are provided to earlier posts where some of these numbers have been previously presented.

    Again, these values are preliminary and will likely change as the mission progresses and more data are available, and as the comet itself changes as it moves closer to the Sun. Similarly, other parameters such as the albedo of the comet will be added to this table, as they are made available by the instrument science teams.
    Dimensions (small lobe) 2.5 x 2.5 x 2.0 km OSIRIS
    Dimensions (large lobe) 4.1 x 3.2 x 1.3 km OSIRIS
    Rotation 12.4043 hours OSIRIS
    Spin axis Right ascension: 69 degrees; Declination: 64 degrees OSIRIS
    Mass 10^13 kg RSI
    Volume 25 km^3 OSIRIS
    Density 0.4 g/cm^3 RSI / OSIRIS
    Water vapour production rate 300 ml/sec (Jun 2014); 1–5 l/sec (Jul-Aug 2014) MIRO
    Surface temperature 205–230K (Jul-Aug 2014) VIRTIS
    Subsurface temperature 30–160K (Aug 2014) MIRO
    Gases detected Water, carbon monoxide, carbon dioxide, ammonia, methane, methanol ROSINA
    Dust grains A few tens of microns to a few hundreds of microns COSIMA
    (detections also by GIADA)

    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 5:05 pm on November 10, 2014 Permalink | Reply
    Tags: , , , Comets, ,   

    From SPACE.com: “Comet Dust Painted Red Planet’s Sky Yellow in Rare Mars Flyby” 

    space-dot-com logo

    SPACE.com

    November 07, 2014
    Calla Cofield

    A rare close encounter between Mars and a comet last month pummeled the Red Planet with cometary dust, which likely left a yellow glow in the Martian sky, scientists revealed today (Nov. 7).

    Scientists studying the Oct. 19 Mars flyby of Comet Siding Spring said they were shocked at the amount of dust the comet showered down on the Red Planet. While it’s too early to say exactly how much dust the comet actually dumped, early estimates peg it at about a few thousand kilograms, according to Nick Scheider, a lead scientist for a dust-measuring instrument used in the study.

    “We ended up with a lot more dust than we ever anticipated,” said Jim Green, director of NASA’s Planetary Science Division. “It surprised us.”

    ccc
    A compass and scale image for Comet Siding Spring and Mars was made from the photo by Hubble Space Telescope of the comet flying by the red planet.

    Green said models of the flyby underestimated the size of the comet’s dust tail and overestimated how much it would spread out before reaching Mars. NASA positioned its satellites behind Mars to protect them from the dust. In October, NASA scientist Michelle Thaller told Space.com that the dust particles could be traveling at speeds reaching 100,000 mph (27,777 km/h).

    ccs
    Comet Siding Spring Imaged by MRO
    Images of Comet Siding Spring, taken by the High Resolution Imaging Science Experiment (HiRISE) camera aboard the Mars Reconnaissnce Orbiter. HiRISE measured the comet’s nucleus to be 1.2 miles (2 km). Credit: NASA/Alan Delamere

    NASA Mars Reconnaisence Orbiter
    NASA/Mars Reconnaissnce Orbiter

    “Observing how comet dust slammed into the upper atmosphere makes me very happy we decided to put our spacecraft on the other side of Mars at the peak of the dust tail passage,” Green said today. “I believe hiding them like that really saved them.”

    The scientists using the High Resolution Imaging Science Experiment (HiRISE) camera, an instrument aboard the Mars Reconnaissance Orbiter, announced a refined value for the size of the comet’s nucleus — the solid, central portion made of rock and ice — of 1.2 miles (2 km), which is smaller than expected.

    The falling dust particles, just like meteors in Earth’s atmosphere, burn up as they go down, so the shower would have created a brilliant light show for anyone standing on Mars at the time. Different elements can create different colors when they burn, and Schneider said it is likely the sky would have had a distinctly yellow glow, due to high levels of sodium.

    sub
    The Mars Reconnaissance Orbiter’s Shallow Subsurface Radar (SHARAD) maps the Martian surface from orbit. The image shows two pictures of the Martian surface, taken by SHARAD before (top) and after (bottom) the dust shower. The dust obscured the signals, making bottom surface image blurry. Credit: NASA/Don Gurnett

    Schneider is instrument lead for the Imaging Ultraviolet Spectrograph, aboard the MAVEN spacecraft, which is the newest NASA satellite to arrive at Mars. The instrument also detected iron, zinc, potassium, manganese, nickel and chromium. The most noticeable difference in the composition of the dust, compared with the Martian atmosphere, was an overwhelming presence of magnesium.

    “We all were sort of pressed back in our chairs seeing this booming [magnesium] signal,” Schneider said. Magnesium in particular, along with iron are “not what you expect for atmospheric ingredients but they are what you expect from comet dust.”

    The Mars Reconnaissance Orbiter’s Shallow Subsurface Radar (SHARAD) spacecraft showed the effects of the dust on the Martian atmosphere. The SHARAD maps the Martian surface by sending radar blips from its orbit down to the ground. The image above shows the surface created by SHARAD, both before (top) and after (bottom) the dust shower. The dust clearly obscured the signals, making its surface image significantly blurrier.

    fc
    False color images of Comet Siding Spring as it neared Mars, taken by the High Resolution Imaging Science Experiment (HiRISE) camera aboard the Mars Reconnaissnce Orbiter.
    Credit: NASA/Alan Delamere

    The plus side of the overwhelming dust shower is that now NASA scientists have a trove of data to sift through, which will hopefully answer questions about the comet and its origins. Comet Siding Spring is from a region called the Oort Cloud, a massive ring of icy bodies beyond the orbit of Neptune.

    oort
    Image of the Oort Cloud, Wendy C Turgeon

    Green said scientists believe this is comet Siding Spring’s first trip to the inner solar system. The farthest point of its orbit may be 50,000 times the distance from the Earth to the sun, or about 1 light year. Siding Spring is also a remnant of the earliest days of the solar system, and living in such an icy environment may have helped preserve it. If scientists can analyze the comet, they may unlock new secrets from those early days of our local cosmic home.

    “Never before have we had the opportunity to observe an Oort Cloud comet up close,” Green said. While he says four to five Oort Cloud comets enter the inner solar system each year, they move too fast for a satellite to catch up to. Siding Spring was a special case. “Instead of going to the comet, it came to us.”

    See the full article, with video, here.

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  • richardmitnick 1:57 pm on October 10, 2014 Permalink | Reply
    Tags: , , , Comets, ,   

    Fromm NASA: “NASA Prepares its Science Fleet for Oct. 19 Mars Comet Encounter” 

    NASA

    NASA

    October 9, 2014
    Dwayne Brown
    Headquarters, Washington
    202-358-1726
    dwayne.c.brown@nasa.gov

    NASA’s extensive fleet of science assets, particularly those orbiting and roving Mars, have front row seats to image and study a once-in-a-lifetime comet flyby on Sunday, Oct. 19.

    Comet C/2013 A1, also known as comet Siding Spring, will pass within about 87,000 miles (139,500 kilometers) of the Red Planet — less than half the distance between Earth and our moon and less than one-tenth the distance of any known comet flyby of Earth.

    ss
    NASA’s Hubble Space Telescope Spots Mars-Bound Comet Sprout Multiple Jets

    Comet C/2013 A1 as seen by NASA’s Hubble Space Telescope The images above show — before and after filtering — comet C/2013 A1, also known as Siding Spring, as captured by Wide Field Camera 3 on NASA’s Hubble Space Telescope.

    NASA Hubble Telescope
    NASA/ESA Hubble

    NASA Hubble WFC3
    WFC3 on HUbble

    NASA released Thursday an image of a comet that, on Oct. 19, will pass within 84,000 miles of Mars — less than half the distance between Earth and our moon.

    The image on the left, captured March 11 by NASA’s Hubble Space Telescope, shows comet C/2013 A1, also called Siding Spring, at a distance of 353 million miles from Earth. Hubble can’t see Siding Spring’s icy nucleus because of its diminutive size. The nucleus is surrounded by a glowing dust cloud, or COMA, that measures roughly 12,000 miles across.

    The right image shows the comet after image processing techniques were applied to remove the hazy glow of the coma revealing what appear to be two jets of dust coming off the location of the nucleus in opposite directions. This observation should allow astronomers to measure the direction of the nucleus’s pole, and axis of rotation.

    Hubble also observed Siding Spring on Jan. 21 as Earth was crossing its orbital plane, which is the path the comet takes as it orbits the sun. This positioning of the two bodies allowed astronomers to determine the speed of the dust coming off the nucleus.

    “This is critical information that we need to determine whether, and to what degree, dust grains in the coma of the comet will impact Mars and spacecraft in the vicinity of Mars,” said Jian-Yang Li of the Planetary Science Institute in Tucson, Arizona.

    Discovered in January 2013 by Robert H. McNaught at Siding Spring Observatory, the comet is falling toward the sun along a roughly 1 million year orbit and is now within the radius of Jupiter’s orbit. The comet will make its closest approach to our sun on Oct. 25, at a distance of 130 million miles – well outside of Earth’s orbit. The comet is not expected to become bright enough to be seen by the naked eye.

    Siding Spring Observatory
    Siding Spring Observatory Interior
    Siding Spring Observatory

    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center in Greenbelt, Md., manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington.

    Siding Spring’s nucleus will come closest to Mars around 2:27 p.m. EDT, hurtling at about 126,000 mph (56 kilometers per second). This proximity will provide an unprecedented opportunity for researchers to gather data on both the comet and its effect on the Martian atmosphere.

    “This is a cosmic science gift that could potentially keep on giving, and the agency’s diverse science missions will be in full receive mode,” said John Grunsfeld, astronaut and associate administrator for NASA’s Science Mission Directorate in Washington. “This particular comet has never before entered the inner solar system, so it will provide a fresh source of clues to our solar system’s earliest days.”

    Siding Spring came from the Oort Cloud, a spherical region of space surrounding our sun and occupying space at a distance between 5,000 and 100,000 astronomical units. It is a giant swarm of icy objects believed to be material left over from the formation of the solar system.

    oort
    Oort Cloud

    Siding Spring will be the first comet from the Oort Cloud to be studied up close by spacecraft, giving scientists an invaluable opportunity to learn more about the materials, including water and carbon compounds, that existed during the formation of the solar system 4.6 billion years ago.

    Some of the best and most revealing images and science data will come from assets orbiting and roving the surface of Mars. In preparation for the comet flyby, NASA maneuvered its Mars Odyssey orbiter, Mars Reconnaissance Orbiter (MRO), and the newest member of the Mars fleet, Mars Atmosphere and Volatile EvolutioN (MAVEN), in order to reduce the risk of impact with high-velocity dust particles coming off the comet.

    NASA Mars Odessy Orbiter
    NASA/ Mars Odyssey Orbiter

    NASA Mars Reconnaisence Orbiter
    NASA/Mars Reconnaissance Orbiter

    NASA Mars MAVEN
    NASA/ Mars MAVEN

    The period of greatest risk to orbiting spacecraft will start about 90 minutes after the closest approach of the comet’s nucleus and will last about 20 minutes, when Mars will come closest to the center of the widening trail of dust flying from the comet’s nucleus.

    “The hazard is not an impact of the comet nucleus itself, but the trail of debris coming from it. Using constraints provided by Earth-based observations, the modeling results indicate that the hazard is not as great as first anticipated. Mars will be right at the edge of the debris cloud, so it might encounter some of the particles — or it might not,” said Rich Zurek, chief scientist for the Mars Exploration Program at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California.

    The atmosphere of Mars, though much thinner that Earth’s, will shield NASA Mars rovers Opportunity and Curiosity from comet dust, if any reaches the planet. Both rovers are scheduled to make observations of the comet.

    NASA Mars Opportunity Rover
    NASA/ Mars Opportunity rover

    NASA Mars Curiosity Rover
    NASA/Mars Curiosity Rover

    NASA’s Mars orbiters will gather information before, during and after the flyby about the size, rotation and activity of the comet’s nucleus, the variability and gas composition of the coma around the nucleus, and the size and distribution of dust particles in the comet’s tail.

    Observations of the Martian atmosphere are designed to check for possible meteor trails, changes in distribution of neutral and charged particles, and effects of the comet on air temperature and clouds. MAVEN will have a particularly good opportunity to study the comet, and how its tenuous atmosphere, or coma, interacts with Mars’ upper atmosphere.

    Earth-based and space telescopes, including NASA’s iconic Hubble Space Telescope, also will be in position to observe the unique celestial object. The agency’s astrophysics space observatories — Kepler, Swift, Spitzer, Chandra — and the ground-based Infrared Telescope Facility on Mauna Kea, Hawaii — also will be tracking the event.

    NASA Kepler Telescope
    NASA/Kepler

    NASA SWIFT Telescope
    NASA/Swift

    NASA Chandra Telescope
    NASA Chandra

    astro
    NASA ground-based Infrared Telescope Facility on Mauna Kea

    NASA’s asteroid hunter, the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE), has been imaging, and will continue to image, the comet as part of its operations. And the agency’s two Heliophysics spacecraft, Solar TErrestrial RElations Observatory (STEREO) and Solar and Heliophysics Observatory (SOHO), also will image the comet. The agency’s Balloon Observation Platform for Planetary Science (BOPPS), a sub-orbital balloon-carried telescope, already has provided observations of the comet in the lead-up to the close encounter with Mars.

    NASA Wise Telescope
    NASA WISE (NEOWISE)

    NASA STEREO spacecraft
    NASA/STEREO

    NASA SOHO
    NASA/SOHO

    NASA BOPPSNASA BOPPS

    Images and updates will be posted online before and after the comet flyby. Several pre-flyby images of Siding Spring, as well as information about the comet and NASA’s planned observations of the event, are available online at:

    http://mars.nasa.gov/comets/sidingspring

    See the full article here.

    The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

    President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

    Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

    NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble,
    Chandra, Spitzer ]and associated programs. NASA shares data with various national and international organizations such as from the Greenhouse Gases Observing Satellite.
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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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