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  • richardmitnick 2:34 pm on October 20, 2017 Permalink | Reply
    Tags: , , , Comets, , ,   

    From Universe today: “Where Do Comets Come From? Exploring the Oort Cloud” 

    universe-today

    Universe Today

    19 Oct , 2017
    Fraser Cain

    Oort cloud Image by TypePad, http://goo.gl/NWlQz6


    Oort Cloud NASA

    Oort Cloud, The layout of the solar system, including the Oort Cloud, on a logarithmic scale. Credit: NASA, Universe Today

    Before I get into this article, I want to remind everyone that it’s been several decades since I’ve been able to enjoy a bright comet in the night sky. I’ve seen mind blowing auroras, witnessed a total solar eclipse with my own eyeballs, and seen a rocket launch. The Universe needs to deliver this bright comet for me, and it needs to do it soon.

    By writing this article now, I will summon it. I will create an article that’ll be hilariously out of date in a few months, when that bright comet shows up.

    Like that time we totally discovered a supernova in the Virtual Star Party, by saying there wasn’t a supernova in that galaxy, but there was, and we didn’t get to make the discovery.

    Anyway, on to the article. Let’s talk about comets.

    See the full article here .

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  • richardmitnick 8:53 am on August 31, 2017 Permalink | Reply
    Tags: , , , Comets, , deflected comets and a closer look at the triggers of cosmic disaster, , Heavy stellar traffic, , TRAPPIST–South national telescope at ESO's La Silla Observatory   

    From Max Planck Institute for Astronomy: “Heavy stellar traffic, deflected comets, and a closer look at the triggers of cosmic disaster” 

    Max Planck Institute for Astronomy

    Max Planck Institute for Astronomy

    August 31, 2017

    Science Contact
    Bailer-Jones, Coryn
    Coryn Bailer-Jones
    Phone: (+49|0) 6221 528-224
    calj@mpia.de

    Public Information Officer
    Markus Pössel
    Public Information Officer
    Phone:(+49|0) 6221 528-261
    poessel@hda-hd.de

    4
    Image of the Week
    Close stellar encounters from the first Gaia data release
    Figure 1: The open circles show the time (horizontal axis) and distance (vertical axis) of the closest approach of stars to the Sun. Negative times indicate times in the past from today. Each point has been calculated as the median of the distribution of a swarm of surrogate particles which have been integrated through a Galactic potential. The “error” bars show the limits of the 5% and 95% percentiles of these distributions (which together form an asymmetric 90% confidence interval). That is, the swarm is used to propagate the uncertainties in the TGAS measurements to uncertainties in the perihelion parameters. The background colour (scale on the right) indicates the estimated completeness of the TGAS survey. That is, if all TGAS stars had radial velocities (and most do not), this gives the probability that a star with any particular perihelion parameters would be present in TGAS. Image credit: Coryn Bailer-Jones

    1
    Image of the Comet C/2012 S1 (ISON), taken with the TRAPPIST–South national telescope at ESO’s La Silla Observatory on the morning of Friday 15 November 2013, whose likely origin is the Oort cloud. This comet is definitely not colliding with Earth, but it shows the typical appearance of comets entering the inner solar system, including the typical tail made of gas and dust. Image: TRAPPIST/E. Jehin/ESO


    ESO Belgian robotic Trappist-South National Telescope at Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

    As stars pass close by our solar system, they can nudge comets from the distant Oort cloud into the inner regions around the Sun. Thus, stellar encounters are an important factor in determining the risk of large cosmic impacts on Earth. Now, Coryn Bailer-Jones from the Max Planck Institute for Astronomy has used data from the ESA satellite Gaia to give the first systematic estimate of the rate of such close stellar encounters. Every million years, up to two dozen stars pass within a few light-years of the Sun, making for a near-constant state of perturbation. The results have been published in the journal Astronomy & Astrophysics.

    Oort Cloud NASA

    ESA/GAIA satellite

    Comets colliding with Earth are among the more violent and extensive cosmic catastrophes that can befall our home planet. The best known such impact is the one which, 66 million years ago, caused or at least hastened the demise of the dinosaurs (although it is not known whether the blame in this case falls on a comet or an asteroid).

    It must be said that, to the best of current knowledge, impacts with regional or even global consequences are exceedingly rare, and occur at a rate of no more than one per million years. Also, monitoring systems give us a fairly complete inventory of larger asteroids and comets, none of which is currently on a collision course with Earth.

    Still, the consequences are serious enough that studies of the causes of comet impacts are not purely academic. The prime culprits are stellar encounters: stars passing through our Sun’s cosmic neighborhood. The outskirts of our solar system are believed to host a reservoir of cold and icy objects – potential comets – known as the Oort cloud. The gravitational influence of passing stars can nudge these comets inwards, and some will begin a journey all the way to the inner solar system, possibly on a collision course with Earth. That is why knowledge of these stellar encounters and their properties has a direct impact on risk assessment for comet impacts.

    Now, Bailer-Jones has published the first systematic estimate of the rate of such stellar encounters. The new result uses data from the first data release (DR1) of the Gaia mission that combines new Gaia measurements with older measurements by ESA’s Hipparcos satellite. Crucially, Bailer-Jones modeled each candidate for a close encounter as a swarm of virtual stars, showing how uncertainties in the orbital data will influence the derived rate of encounters.

    Bailer-Jones found that within a typical million years, between 490 and 600 stars will pass the Sun within a distance of 16.3 light-years (5 parsecs, to use a unit more common in professional astronomy) or less. Between 19 and 24 stars will pass at 3.26 light-years (1 parsec) or less. All these hundreds of stars would be sufficiently close to nudge comets from the Oort cloud into the solar system. The new results are in the same ballpark as earlier, less systematic estimates that show that when it comes to stellar encounters, traffic in our cosmic neighborhood is rather heavy.

    The current results are valid for a period of time that reaches about 5 million years into the past and into the future. With Gaia’s next data release, DR2 slated for April 2018, this could be extended to 25 million years each way. However, astronomers intending to go even further and search for the stars that might be responsible for hurling a comet towards the dinosaurs will need to know our home galaxy and its mass distribution in much more detail than we currently do – a long-term goal of the researchers involved in Gaia and related projects.
    Background information

    The research described here is published as C. A. L. Bailer Jones, The completeness-corrected rate of stellar encounters with the Sun from the first Gaia data release in the journal Astronomy & Astrophysics.

    E-print on arXiv
    ESA picture of the week
    ESA press release

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  • richardmitnick 2:06 pm on July 25, 2017 Permalink | Reply
    Tags: , , , Comets, , , , ,   

    From JPL: “Large, Distant Comets More Common Than Previously Thought” 

    NASA JPL Banner

    JPL-Caltech

    July 25, 2017
    Elizabeth Landau
    Jet Propulsion Laboratory, Pasadena, Calif.
    818-354-6425
    elizabeth.landau@jpl.nasa.gov

    1
    This illustration shows how scientists used data from NASA’s WISE spacecraft to determine the nucleus sizes of comets. They subtracted a model of how dust and gas behave in comets in order to obtain the core size. Credit: NASA/JPL-Caltech.

    2
    An animation of a comet. Credit: NASA/JPL-Caltech.

    Comets that take more than 200 years to make one revolution around the Sun are notoriously difficult to study. Because they spend most of their time far from our area of the solar system, many “long-period comets” will never approach the Sun in a person’s lifetime. In fact, those that travel inward from the Oort Cloud — a group of icy bodies beginning roughly 186 billion miles (300 billion kilometers) away from the Sun — can have periods of thousands or even millions of years.

    Oort Cloud NASA

    NASA’s WISE spacecraft, scanning the entire sky at infrared wavelengths, has delivered new insights about these distant wanderers.

    NASA/WISE Telescope

    Scientists found that there are about seven times more long-period comets measuring at least 0.6 miles (1 kilometer) across than had been predicted previously. They also found that long-period comets are on average up to twice as large as “Jupiter family comets,” whose orbits are shaped by Jupiter’s gravity and have periods of less than 20 years.

    Researchers also observed that in eight months, three to five times as many long-period comets passed by the Sun than had been predicted. The findings are published in The Astronomical Journal.

    “The number of comets speaks to the amount of material left over from the solar system’s formation,” said James Bauer, lead author of the study and now a research professor at the University of Maryland, College Park. “We now know that there are more relatively large chunks of ancient material coming from the Oort Cloud than we thought.”

    The Oort Cloud is too distant to be seen by current telescopes, but is thought to be a spherical distribution of small icy bodies at the outermost edge of the solar system. The density of comets within it is low, so the odds of comets colliding within it are rare. Long-period comets that WISE observed probably got kicked out of the Oort Cloud millions of years ago. The observations were carried out during the spacecraft’s primary mission before it was renamed NEOWISE and reactivated to target near-Earth objects (NEOs).

    “Our study is a rare look at objects perturbed out of the Oort Cloud,” said Amy Mainzer, study co-author based at NASA’s Jet Propulsion Laboratory, Pasadena, California, and principal investigator of the NEOWISE mission. “They are the most pristine examples of what the solar system was like when it formed.”

    Astronomers already had broader estimates of how many long-period and Jupiter family comets are in our solar system, but had no good way of measuring the sizes of long-period comets. That is because a comet has a “coma,” a cloud of gas and dust that appears hazy in images and obscures the cometary nucleus. But by using the WISE data showing the infrared glow of this coma, scientists were able to “subtract” the coma from the overall comet and estimate the nucleus sizes of these comets. The data came from 2010 WISE observations of 95 Jupiter family comets and 56 long-period comets.

    The results reinforce the idea that comets that pass by the Sun more often tend to be smaller than those spending much more time away from the Sun. That is because Jupiter family comets get more heat exposure, which causes volatile substances like water to sublimate and drag away other material from the comet’s surface as well.

    “Our results mean there’s an evolutionary difference between Jupiter family and long-period comets,” Bauer said.

    The existence of so many more long-period comets than predicted suggests that more of them have likely impacted planets, delivering icy materials from the outer reaches of the solar system.

    Researchers also found clustering in the orbits of the long-period comets they studied, suggesting there could have been larger bodies that broke apart to form these groups.

    The results will be important for assessing the likelihood of comets impacting our solar system’s planets, including Earth.

    “Comets travel much faster than asteroids, and some of them are very big,” Mainzer said. “Studies like this will help us define what kind of hazard long-period comets may pose.”

    NASA’s Jet Propulsion Laboratory in Pasadena, California, managed and operated WISE for NASA’s Science Mission Directorate in Washington. The NEOWISE project is funded by the Near Earth Object Observation Program, now part of NASA’s Planetary Defense Coordination Office. The spacecraft was put into hibernation mode in 2011 after twice scanned the entire sky, thereby completing its main objectives. In September 2013, WISE was reactivated, renamed NEOWISE and assigned a new mission to assist NASA’s efforts to identify potentially hazardous near-Earth objects.

    For more information on WISE, visit:

    https://www.nasa.gov/wise

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    NASA JPL Campus

    Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

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  • richardmitnick 9:02 am on April 4, 2017 Permalink | Reply
    Tags: , , , Comets,   

    From Astronomy Now: “See a trio of comets in the April sky” 

    Astronomy Now bloc

    Astronomy Now

    2 April 2017
    Ade Ashford

    1
    Comet 41P/Tuttle–Giacobini–Kresák in the constellation of Draco was about magnitude +6.5 on the night of 1-2 April when captured in this three-minute integration with a colour Starlight Xpress Ultrastar camera at the f/2 HyperStar focus of the author’s Celestron C11 Schmidt-Cassegrain telescope. AN image by Ade Ashford.

    Despite the glow of a waxing Moon, early April is a good time to catch a glimpse of two interesting comets that are currently circumpolar from the British Isles, meaning that they are sufficiently close to the North Celestial Pole such that they neither rise or set, visible throughout the hours of darkness.

    Comet 41P/Tuttle–Giacobini–Kresák, a periodic comet that orbits the Sun every 5.4 years, is predicted to fade from magnitude +6.7 to +7.6 during the month. Comet 41P passes just 0.6 degrees north of Thuban, otherwise known as alpha (α) Draconis, at 2am BST on 3 April. By 11 April, 41P lies between eta (η) and theta (θ) Draconis; then the comet passes just 0.6 degrees from beta (β) Draconis – the magnitude +2.8 star known as Rastaban in the head of the celestial dragon – eight days later.

    4
    Comets 41P/Tuttle–Giacobini–Kresák in Draco and C/2015 V2 (Johnson) in Hercules are very well placed for Northern Hemisphere observers during April — particularly in the dark of the Moon. Click on the graphic for a detailed PDF finder chart suitable for printing and use outside at the telescope. AN graphic and finder chart by Ade Ashford.

    Comet 41P crosses the border into neighbouring Hercules on 20 April, a constellation where another bright comet resides this month. C/2015 V2 (Johnson) is a hyperbolic comet destined to leave the Solar System but predicted to brighten a full magnitude to +7.4 by the end of April. C/2015 V2 lies between naked-eye stars tau (τ) and upsilon (υ) Herculis at 12am BST on 22 April, and between the latter and phi (φ) Herculis on 25 April.

    5
    Displaying more of a tail than Comet 41P, C/2015 V2 (Johnson) in the constellation of Hercules was about magnitude +8 on the night of 1-2 April when captured in this seven-minute integration with a colour Starlight Xpress Ultrastar camera at the f/2 HyperStar focus of the author’s Celestron C11 Schmidt-Cassegrain telescope. AN image by Ade Ashford.

    There’s also a bright comet in the morning sky. C/2017 E4 (Lovejoy) was discovered by Australian comet hunter Terry Lovejoy last month and is currently a seventh-magnitude object in eastern Pegasus, currently some 7 degrees northeast of magnitude +2.4 star epsilon (ε) Pegasi, otherwise known as Enif. C/2017 E4 (Lovejoy) presently rises in the east-northeast around 3am BST from the British Isles.

    See the full article here .

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  • richardmitnick 12:32 pm on December 30, 2016 Permalink | Reply
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    From JPL-Caltech: “NASA’s NEOWISE Mission Spies One Comet, Maybe Two” 

    NASA JPL Banner

    JPL-Caltech

    December 29, 2016
    DC Agle
    Jet Propulsion Laboratory, Pasadena, Calif.
    818-354-5011
    agle@jpl.nasa.gov

    Laurie Cantillo /
    NASA Headquarters, Washington
    202-358-1077
    laura.l.cantillo@nasa.gov

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

    1
    An artist’s rendition of 2016 WF9 as it passes Jupiter’s orbit inbound toward the sun. Image credit: NASA/JPL-Caltech.

    NASA’s NEOWISE mission has recently discovered some celestial objects traveling through our neighborhood, including one on the blurry line between asteroid and comet. Another–definitely a comet–might be seen with binoculars through next week.

    NASA/WISE Telescope
    NASA/WISE Telescope

    An object called 2016 WF9 was detected by the NEOWISE project on Nov. 27, 2016. It’s in an orbit that takes it on a scenic tour of our solar system. At its farthest distance from the sun, it approaches Jupiter’s orbit. Over the course of 4.9 Earth-years, it travels inward, passing under the main asteroid belt and the orbit of Mars until it swings just inside Earth’s own orbit. After that, it heads back toward the outer solar system. Objects in these types of orbits have multiple possible origins; it might once have been a comet, or it could have strayed from a population of dark objects in the main asteroid belt.

    2016 WF9 will approach Earth’s orbit on Feb. 25, 2017. At a distance of nearly 32 million miles (51 million kilometers) from Earth, this pass will not bring it particularly close. The trajectory of 2016 WF9 is well understood, and the object is not a threat to Earth for the foreseeable future.

    A different object, discovered by NEOWISE a month earlier, is more clearly a comet, releasing dust as it nears the sun. This comet, C/2016 U1 NEOWISE, “has a good chance of becoming visible through a good pair of binoculars, although we can’t be sure because a comet’s brightness is notoriously unpredictable,” said Paul Chodas, manager of NASA’s Center for Near-Earth Object (NEO) Studies at the Jet Propulsion Laboratory in Pasadena, California.

    As seen from the northern hemisphere during the first week of 2017, comet C/2016 U1 NEOWISE will be in the southeastern sky shortly before dawn. It is moving farther south each day and it will reach its closest point to the sun, inside the orbit of Mercury, on Jan. 14, before heading back out to the outer reaches of the solar system for an orbit lasting thousands of years. While it will be visible to skywatchers at Earth, it is not considered a threat to our planet either.

    NEOWISE is the asteroid-and-comet-hunting portion of the Wide-Field Infrared Survey Explorer (WISE) mission. After discovering more than 34,000 asteroids during its original mission, NEOWISE was brought out of hibernation in December of 2013 to find and learn more about asteroids and comets that could pose an impact hazard to Earth. If 2016 WF9 turns out to be a comet, it would be the 10th discovered since reactivation. If it turns out to be an asteroid, it would be the 100th discovered since reactivation.

    What NEOWISE scientists do know is that 2016 WF9 is relatively large: roughly 0.3 to 0.6 mile (0.5 to 1 kilometer) across.

    It is also rather dark, reflecting only a few percent of the light that falls on its surface. This body resembles a comet in its reflectivity and orbit, but appears to lack the characteristic dust and gas cloud that defines a comet.

    “2016 WF9 could have cometary origins,” said Deputy Principal Investigator James “Gerbs” Bauer at JPL. “This object illustrates that the boundary between asteroids and comets is a blurry one; perhaps over time this object has lost the majority of the volatiles that linger on or just under its surface.”

    Near-Earth objects (NEOs) absorb most of the light that falls on them and re-emit that energy at infrared wavelengths. This enables NEOWISE’s infrared detectors to study both dark and light-colored NEOs with nearly equal clarity and sensitivity.

    “These are quite dark objects,” said NEOWISE team member Joseph Masiero, “Think of new asphalt on streets; these objects would look like charcoal, or in some cases are even darker than that.”

    NEOWISE data have been used to measure the size of each near-Earth object it observes. Thirty-one asteroids that NEOWISE has discovered pass within about 20 lunar distances from Earth’s orbit, and 19 are more than 460 feet (140 meters) in size but reflect less than 10 percent of the sunlight that falls on them.

    The Wide-field Infrared Survey Explorer (WISE) has completed its seventh year in space after being launched on Dec. 14, 2009.

    JPL manages NEOWISE for NASA’s Science Mission Directorate at the agency’s headquarters in Washington. The Space Dynamics Laboratory in Logan, Utah, built the science instrument. Ball Aerospace & Technologies Corp. of Boulder, Colorado, built the spacecraft. Science operations and data processing take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.

    Data from the NEOWISE mission are available on a website for the public and scientific community to use. A guide to the NEOWISE data release, data access instructions and supporting documentation are available at:

    http://wise2.ipac.caltech.edu/docs/release/neowise/

    Access to the NEOWISE data products is available via the on-line and API services of the NASA/IPAC Infrared Science Archive.

    A list of peer-reviewed papers using the NEOWISE data is available at:

    http://neowise.ipac.caltech.edu/publications.html

    See the full article here .

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    NASA JPL Campus

    Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

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  • richardmitnick 7:56 am on September 26, 2016 Permalink | Reply
    Tags: , , Comets,   

    From phys.org: “Astronomers image newly discovered comet” 

    physdotorg
    phys.org

    September 26, 2016
    Tricia Ennis

    1
    Credit: Slooh

    Earlier this week, Slooh member Bernd Lütkenhöner and Slooh astronomer Paul Cox were able to image the newly discovered Comet C/2016 R3 (Borisov) under extraordinary conditions. The comet had been close to the Sun since its discovery on September 11, 2016, by Gennady Borisov, making it extremely difficult to observe.

    It had already fallen out of reach of other telescopes around the world by September 16th, but Lütkenhöner and Cox managed to image it on September 20th using Slooh’s robotic Half Metre telescope at their flagship observatory at the Institute of Astrophysics of the Canary Islands.

    iac-telescopes-campus
    IAC

    Cox said, “We usually observe objects when they’re high in the sky, so we’re peering through as little of our atmosphere as possible. But in this case, the comet was only observable in the last 30-minutes before dawn, when it was only 5° above the horizon in a rapidly brightening sky. Given the factors stacked against us, we were amazed when we managed to pinpoint the faint and diffuse fuzz ball in our images.”

    “We may have obtained the last observations of this comet for the next 100 or even 100,000 years,” said Lütkenhöner. The reason for that huge timespan is that the orbit of this comet hasn’t been fixed with any certainty. Added Cox, “Our latest observations will help determine the orbit of the comet with greater certainty.”

    The comet is set to make its closest approach to the Sun (perihelion) on October 12, 2016. Says Cox, “We don’t even know if the comet will survive its journey around the Sun, but if it does, it will remain an extremely difficult object to image because of its proximity to the Sun from Earth’s perspective—but we’ll still give it a try!”

    Astronomers require further observations of the comet to confirm whether this is a new discovery or a recovery of a comet discovered in 1915, Comet C/1915 R1 (Mellish).

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    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 6:45 am on April 29, 2016 Permalink | Reply
    Tags: , , Comets, Earth Has Mystery Gas Delivered from Space,   

    From SA: “Earth Has Mystery Gas Delivered from Space” 

    Scientific American

    Scientific American

    April 28, 2016
    Anthony King, ChemistryWorld

    1
    Credit: Wikimedia Commons/NASA/JPL-Caltech

    Xenon from deep within the Earth’s mantle has shone a light on the planet’s formation and early evolution. The isotopic signature of this earthly xenon has been shown to resemble that of primitive meteorites and differs markedly from the profile of the gas found in the atmosphere, which is mysteriously missing most of its xenon.

    The origin of Earth’s volatile elements such as water, carbon and nitrogen remains a puzzle. It is difficult to determine if these elements originated from solar gas after the solar system formed or were delivered by asteroids or comets.

    A new study, which sampled xenon from carbon dioxide-rich mineral spring gas from the volcanic Eifel province in Germany, points to an asteroidal origin for part of the volatile elements trapped in Earth’s mantle—planetary bodies whose remnants now lie between Mars and Jupiter. The mysterious xenon in the atmosphere came from elsewhere, possibly comets.

    ‘We conclude that this [mantle] component was contributed by asteroids when the proto-Earth was still building up,’ notes senior author Bernard Marty at the University of Lorraine, France. ‘The ancestor atmosphere xenon was contributed later on at the Earth’s surface, by late bombardments, and never mixed up with mantle xenon.’ This late bombardment occurred around 800 million years after Earth’s formation and might have involved cometary bodies. The isotopic signature of xenon on comets is unknown, however.

    The extraterrestrial chondritic xenon found in the mantle has been isolated for 4.45 billion years. It also proves that volcanism in Eifel relates to upwelling from the deep mantle, likely to be over 700 km deep.

    ‘It’s a small step forward to show that mantle xenon came from meteorites, but the big step forward is showing that this component is not related to the atmosphere,’ says Christopher Ballentine, a geochemist at the University of Oxford, UK, who was not involved with this work.

    Atmospheric xenon’s origin was not just from outgassing of the mantle and is more complex, Ballentine explains. ‘Nobody has measured xenon composition in comets yet, so maybe that is the source,’ he adds. Around 90% of the xenon expected to be in Earth’s atmosphere is missing, with various theories posited. The enigma of the ‘missing xenon’ and where it went is one of the big unsolved puzzles in geochemistry.

    ‘Understanding xenon really is a lynchpin for understanding the early formation of volatiles. And resolving how volatiles arrived at the planet tells us something fundamental about the way in which the planets formed,’ Ballentine says.

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  • richardmitnick 12:12 pm on December 22, 2015 Permalink | Reply
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    From RAS: “Giant comets could pose danger to life on Earth” 

    Royal Astronomical Society

    Royal Astronomical Society

    22 December 2015
    Media contacts
    Robert Massey
    Royal Astronomical Society
    Tel: +44 (0)7802 877 699
    rm@ras.org.uk

    Diana Blamires
    University of Buckingham
    diana.blamires@buckingham.ac.uk

    Science contacts
    Dr David Asher
    dja@arm.ac.uk
    Professor Mark Bailey
    meb@arm.ac.uk
    Armagh Observatory
    Northern Ireland
    Tel: +44 (0)28 3752 2928
    http://star.arm.ac.uk

    Professor Bill Napier
    University of Buckingham
    Tel (Ireland): +353 87361 8376
    bill_napier121@hotmail.com

    Professor Duncan Steel
    University of Buckingham
    Tel (New Zealand): +64 4889 0241
    tma1@duncansteel.com

    1
    Because they are so distant from the Earth, Centaurs appear as pinpricks of light in even the largest telescopes. Saturn’s 200-km moon Phoebe, depicted in this image, seems likely to be a Centaur that was captured by that planet’s gravity at some time in the past. Until spacecraft are sent to visit other Centaurs, our best idea of what they look like comes from images like this one, obtained by the Cassini space probe orbiting Saturn. NASA’s New Horizons spacecraft, having flown past Pluto six months ago, has been targeted to conduct an approach to a 45-km wide trans-Neptunian object at the end of 2018. Credit: NASA/JPL-Caltech/Space Science Institute.

    NASA Cassini Spacecraft
    NASA/Cassini

    2
    The outer solar system as we now recognise it. At the centre of the map is the Sun, and close to it the tiny orbits of the terrestrial planets (Mercury, Venus, Earth and Mars). Moving outwards and shown in bright blue are the near-circular paths of the giant planets: Jupiter, Saturn, Uranus and Neptune. The orbit of Pluto is shown in white. Staying perpetually beyond Neptune are the trans-Neptunian objects (TNOs), in yellow: seventeen TNO orbits are shown here, with the total discovered population at present being over 1,500. Shown in red are the orbits of 22 Centaurs (out of about 400 known objects), and these are essentially giant comets (most are 50-100 km in size, but some are several hundred km in diameter). Because the Centaurs cross the paths of the major planets, their orbits are unstable: some will eventually be ejected from the solar system, but others will be thrown onto trajectories bringing them inwards, therefore posing a danger to civilisation and life on Earth. Credit: Duncan Steel.

    A team of astronomers from Armagh Observatory and the University of Buckingham report that the discovery of hundreds of giant comets in the outer planetary system over the last two decades means that these objects pose a much greater hazard to life than asteroids. The team, made up of Professors Bill Napier and Duncan Steel of the University of Buckingham, Professor Mark Bailey of Armagh Observatory, and Dr David Asher, also at Armagh, publish their review of recent research in the December issue of Astronomy & Geophysics (A&G), the journal of the Royal Astronomical Society.

    The giant comets, termed centaurs, move on unstable orbits crossing the paths of the massive outer planets Jupiter, Saturn, Uranus and Neptune. The planetary gravitational fields can occasionally deflect these objects in towards the Earth.

    Centaurs are typically 50 to 100 kilometres across, or larger, and a single such body contains more mass than the entire population of Earth-crossing asteroids found to date. Calculations of the rate at which centaurs enter the inner solar system indicate that one will be deflected onto a path crossing the Earth’s orbit about once every 40,000 to 100,000 years. Whilst in near-Earth space they are expected to disintegrate into dust and larger fragments, flooding the inner solar system with cometary debris and making impacts on our planet inevitable.

    Known severe upsets of the terrestrial environment and interruptions in the progress of ancient civilisations, together with our growing knowledge of interplanetary matter in near-Earth space, indicate the arrival of a centaur around 30,000 years ago. This giant comet would have strewn the inner planetary system with debris ranging in size from dust all the way up to lumps several kilometres across.

    Specific episodes of environmental upheaval around 10,800 BCE and 2,300 BCE, identified by geologists and palaeontologists, are also consistent with this new understanding of cometary populations. Some of the greatest mass extinctions in the distant past, for example the death of the dinosaurs 65 million years ago, may similarly be associated with this giant comet hypothesis.

    Professor Napier comments: “In the last three decades we have invested a lot of effort in tracking and analysing the risk of a collision between the Earth and an asteroid. Our work suggests we need to look beyond our immediate neighbourhood too, and look out beyond the orbit of Jupiter to find centaurs. If we are right, then these distant comets could be a serious hazard, and it’s time to understand them better.”

    The researchers have also uncovered evidence from disparate fields of science in support of their model. For example, the ages of the sub-millimetre craters identified in lunar rocks returned in the Apollo program are almost all younger than 30,000 years, indicating a vast enhancement in the amount of dust in the inner Solar system since then.

    See the full article here .

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    The Royal Astronomical Society (RAS), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science.

     
  • richardmitnick 4:17 pm on December 10, 2015 Permalink | Reply
    Tags: , , Comets, Molecular Oxygen,   

    From phys.org: “Could molecular oxygen be common on comets?” 

    physdotorg
    phys.org

    December 10, 2015
    Tomasz Nowakowski

    Temp 1
    An image of Halley’s Comet taken in 1986. Credit: NASA

    A team of researchers, encouraged by the latest discovery of ESA’s Rosetta spacecraft of molecular oxygen (O2) on the comet 67P/Churyumov-Gerasimenko, are going over comet 1P/Halley (known as Halley’s Comet) with a fine-tooth comb, searching for the traces of this essential molecule.

    ESA Rosetta spacecraft
    ESA/Rosetta

    The new study, led by Martin Rubin of the University of Bern, Switzerland, shows that molecular oxygen is also present on 1P/Halley and therefore might be common on other comets.

    The scientists used the data from the Neutral Mass Spectrometer (NMS) instrument aboard ESA’s Giotto probe, which passed 1P/Halley in 1986.

    ESA Giotto
    ESA/Giotto

    They found that O2 is the third most abundant species on this celestial body. The results were published on Dec. 4 in the Astrophysical Journal Letters.

    Giotto approached Halley’s nucleus at a distance of 596 kilometers. Despite being hit by the comet’s small particles, the spacecraft gathered important scientific data during a flyby lasting only few minutes. This close encounter enabled the chemical characterization of the material being ejected from the comet. The results indicated that Halley releases mainly water and carbon monoxide. The data showed also traces of methane, ammonia, other hydrocarbons, as well as iron and sodium. Now, Rubin and his colleagues report abundant amounts of molecular oxygen in the comet’s coma.

    “Our investigation indicates that a production rate of O2 with respect to water is, indeed, compatible with the obtained Halley data, and therefore that O2 might be a rather common and abundant parent species,” the scientist wrote in the paper.

    The first comet on which molecular oxygen was detected is 67P/Churyumov-Gerasimenko, representing Jupiter family comets originating from the Kuiper belt.

    3
    Objects of the Kuiper belt (blue). Plot displays the known positions of objects in the outer Solar System within 60 astronomical units (AU) from the Sun. Epoch as of January 1, 2015.

    The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) found this molecule in October 2015, and since then, the scientists have wondered whether the O2 abundance is peculiar to comet 67P/Churyumov-Gerasimenko or Jupiter family comets in general. The new results hint that the existence of molecular oxygen could also be characteristic for the Oort cloud family of comets that includes Halley.

    4
    This graphic shows the distance from the Oort cloud to the rest of the Solar System and two of the nearest stars measured in astronomical units. The scale is logarithmic, with each specified distance ten times further out than the previous one.

    “We now have an indication for abundant O2 in the comas of two comets, one from the Oort cloud and the other from the Kuiper belt or possibly the scattered disk. This is particularly interesting, as both families of comets are believed to have formed at different locations in our early solar system,” the paper reads.

    The authors of the new study also address what caused the abundance of molecular oxygen on Halley. One possible explanation offered by the scientists is that the O2 has already been formed through irradiation of ices in the molecular cloud phase and the oxygen remained trapped before the comet eventually formed. According to the scientists, the close abundance of oxygen on both comets, despite very different dynamical histories and erosion rates, confirms this hypothesis.

    Comets are essential to improving our understanding of the origins of life. These icy leftovers from the planet-forming process have been preserved at low temperatures since their formation. Thus, the cometary material could provide invaluable hints on how solar system was created.

    Now, when we know that the presence of molecular oxygen is not unique to one comet, a new chapter opens in the search for the ingredients of life on the icy visitors from the outskirts of the solar system. With that in mind, further studies could reveal a vast number of comets rich in oxygen, water and even organic compounds.

    Explore further: Image: Jet activity at the neck of the Rosetta comet

    More information: http://iopscience.iop.org/article/10.1088/2041-8205/815/1/L11/meta;jsessionid=F9A1FE045288EA9414874579F8C6EC06.c3.iopscience.cld.iop.org M. Rubin et al. MOLECULAR OXYGEN IN OORT CLOUD COMET 1P/HALLEY, The Astrophysical Journal (2015). DOI: 10.1088/2041-8205/815/1/L11

    Abstract
    Recently, the ROSINA mass spectrometer suite on board the European Space Agency’s Rosetta spacecraft discovered an abundant amount of molecular oxygen, O2, in the coma of Jupiter family comet 67P/Churyumov–Gerasimenko of O2/H2O = 3.80 ± 0.85%. It could be shown that O2 is indeed a parent species and that the derived abundances point to a primordial origin. Crucial questions are whether the O2 abundance is peculiar to comet 67P/Churyumov–Gerasimenko or Jupiter family comets in general, and also whether Oort cloud comets such as comet 1P/Halley contain similar amounts of molecular oxygen. We investigated mass spectra obtained by the Neutral Mass Spectrometer instrument during the flyby by the European Space Agency’s Giotto probe of comet 1P/Halley. Our investigation indicates that a production rate of O2 of 3.7 ± 1.7% with respect to water is indeed compatible with the obtained Halley data and therefore that O2 might be a rather common and abundant parent species.

    See the full article here .

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    About Phys.org in 100 Words

    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 11:22 am on September 2, 2015 Permalink | Reply
    Tags: , Comets,   

    From JPL: “Comet Hitchhiker Would Take Tour of Small Bodies” 

    JPL

    Sep. 1, 2015
    Elizabeth Landau
    Jet Propulsion Laboratory, Pasadena, Calif.
    818-354-6425
    elizabeth.landau@jpl.nasa.gov

    1
    This artist concept shows Comet Hitchhiker, an idea for traveling between asteroids and comets using a harpoon and tether system. Credits: NASA/JPL-Caltech/Cornelius Dammrich

    Catching a ride from one solar system body to another isn’t easy. You have to figure out how to land your spacecraft safely and then get it on its way to the next destination. The landing part is especially tricky for asteroids and comets, which have low gravitational pull.

    A concept called Comet Hitchhiker, developed at NASA’s Jet Propulsion Laboratory, Pasadena, California, puts forth a new way to get into orbit and land on comets and asteroids, using the kinetic energy — the energy of motion — of these small bodies. Masahiro Ono, the principal investigator based at JPL, had “Hitchhiker’s Guide to the Galaxy” in mind when dreaming up the idea.

    “Hitchhiking a celestial body is not as simple as sticking out your thumb, because it flies at an astronomical speed and it won’t stop to pick you up. Instead of a thumb, our idea is to use a harpoon and a tether,” Ono said. Ono is presenting results about the concept at the American Institute of Aeronautics and Astronautics SPACE conference on September 1.

    A reusable tether system would replace the need for propellant for entering orbit and landing, so running out wouldn’t be an issue, according to the concept design.

    While closely flying by the target, a spacecraft would first cast an extendable tether toward the asteroid or comet and attach itself using a harpoon attached to the tether. Next, the spacecraft would reel out the tether while applying a brake that harvests energy while the spacecraft accelerates.

    This technique is analogous to fishing on Earth. Imagine you’re on a boat on a lake with a fishing pole, and want to catch a big fish. Once the fish bites, you would release more of the line with a moderate tension, rather than holding it tightly. With a long enough line, the boat will eventually catch up with the fish.

    2
    Comet Hitchhiker, shown in this artist rendering, is a concept for orbiting and landing on small bodies. Credits: NASA/JPL-Caltech/Cornelius Dammrich

    Once the spacecraft matches its velocity to the “fish” — the comet or asteroid in this case — it is ready to land by simply reeling in the tether and descending gently. When it’s time to move on to another celestial target, the spacecraft would use the harvested energy to quickly retrieve the tether, which accelerates the spacecraft away from the body.

    “This kind of hitchhiking could be used for multiple targets in the main asteroid belt or the Kuiper Belt, even five to 10 in a single mission,” Ono said.

    Ono and colleagues have been studying whether a harpoon could tolerate an impact of this magnitude, and whether a tether could be created strong enough to support this kind of maneuver. They used supercomputer simulations and other analyses to figure out what it would take.

    Researchers have come up with what they call the Space Hitchhike Equation, which relates the specific strength of the tether, the mass ratio between the spacecraft and the tether, and the change in velocity needed to accomplish the maneuver.

    In missions that use conventional propellant, spacecraft use a lot of fuel just to accelerate enough to get into orbit.

    “In Comet Hitchhiker, accelerating and decelerating do not require propellant because the spacecraft is harvesting kinetic energy from the target,” Ono said.

    For any spacecraft landing on a comet or asteroid, being able to slow down enough to arrive safely is critical. Comet Hitchhiker requires a tether made from a material that can withstand the enormous tension and heat generated by a rapid decrease in speed for getting into orbit and landing. Ono and colleagues calculated that a velocity change of about 0.9 miles (1.5 kilometers) per second is possible with some materials that already exist: Zylon and Kevlar.

    “That’s like going from Los Angeles to San Francisco in under seven minutes,” Ono said.

    But the bigger the velocity change required for orbit insertion, the shorter the flight time needed to get from Earth to the target — so if you want to get to a comet or asteroid faster, you need even stronger materials. A 6.2 mile-per-second (10 kilometer-per-second) velocity change is possible, but would require more advanced technologies such as a carbon nanotube tether and a diamond harpoon.

    Researchers also estimated that the tether would need to be about 62 to 620 miles long (100 to 1,000 kilometers) for the hitchhiking maneuver to work. It would also need to be extendable, and capable of absorbing jerks on it, while avoiding being damaged or cut by small meteorites.

    The next steps for studying the concept would be to do more high-fidelity simulations and try casting a mini-harpoon at a target that mimics the material found on a comet or asteroid.

    Comet Hitchhiker is in Phase I study through the NASA Innovative Advanced Concepts (NIAC) Program. NIAC is a program of NASA’s Space Technology Mission Directorate, located at the agency’s headquarters in Washington. Professor David Jewitt at the University of California, Los Angeles, partnered in this research.

    For a complete list of the selected proposals and more information about NIAC, visit:

    http://www.nasa.gov/niac

    For more information about the Space Technology Mission Directorate, visit:

    http://www.nasa.gov/spacetech

    See the full article here.

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    NASA JPL Campus

    Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

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