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  • richardmitnick 10:33 am on November 19, 2014 Permalink | Reply
    Tags: Asteroids, , , , , ,   

    From SPACE.com: “Asteroid Found with Rings! First-of-Its-Kind Discovery Stuns Astronomers (Video, Images)” 

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    SPACE.com

    March 26, 2014
    Nola Taylor Redd

    Scientists have made a stunning discovery in the outer realm of the solar system — an asteroid with its own set of rings that orbits the sun between Saturn and Uranus. The space rock is the first non-planetary object ever found to have its own ring system, researchers say.

    The pair of space rock rings encircle the asteroid Chariklo. They were most likely formed after a collision scattered debris around the asteroid, according to a new study unveiled today (March 27). The asteroid rings also suggests the presence of a still-undiscovered moon around Chariklo that’s keeping them stable, researchers said.

    “We weren’t looking for a ring and didn’t think small bodies like Chariklo had them at all, so the discovery — and the amazing amount of detail we saw in the system — came as a complete surprise!” study leader Felipe Braga-Ribas, of the National Observatory in Brazil said in a statement today.

    Astronomers used seven telescopes, but just one revealed the pair of rings orbiting the rocky Chariklo. The asteroid’s 155-mile diameter (250 kilometers) is dwarfed by the giant gas planets, the only other bodies known to have rings.

    “This discovery shows that size is not important in order to have — or not have — rings,” Felipe Braga-Ribas, of the National Observatory in Brazil, told Space.com by email.

    An asteroid among giants

    On June 3, 2013, Braga-Ribas led a team of astronomers in observing Chariklo as it passed in front of a distant star — a process known as an occultation. As the asteroid traveled, it blocked light from the star, enabling scientists to learn more about it.

    The astronomers were surprised to discover that a few seconds before and after the main occultation, the light dimmed slightly, indicating that something circled the rocky asteroid. By comparing the data gathered from seven different telescopes, the team was able to identify the shape, size and orientation of the rings.

    The system consists of a dense, 4-mile-wide (7 km) ring near the planet, and a smaller 2-mile-wide (3 km) ring farther out.

    From the surface of the asteroid, “they would be two spectacular sharp and really bright rings, crossing all the sky,” Braga-Ribas said. “They would be noticeably close, as they are at about 1/1,000 of the moon’s distance from us,” he added.

    He went on to say that the larger, inner ring would block the view of the outer ring from the ground. The rings are similar to those around Saturn, in that both are very dense, bright and possibly formed by rock and water ice. But their scales are quite different.

    “The whole Chariklo system would fit about 12 times in the Cassini Division,” Braga-Ribas said, referring to the largest gap in Saturn’s rings.

    Particles orbiting Chariklo also travel more slowly — only tens of meters per second, compared with tens of kilometers per second in the rings of Saturn.

    While Saturn is the most well-known ringed body in the solar system, Jupiter, Neptune and Uranus also have their own, fainter rings. These gas giants significantly dwarf the smaller asteroid.

    Astronomers utilized seven telescopes, most of which were located in South America. Of them, only the European Southern Observatory’s La Silla telescope in Chile was able to capture the small gap between the rings.

    ESO LaSilla Long View
    ESO/LaSilla

    “This was possible due to the use of the ‘Lucky Imager,’ a fast and sensible camera that obtained a sequence of images like a video at a rate of 10 images per second,” Braga-Ribas said. “As the stellar occultation by both rings lasted for 0.6 seconds in total, it was able to ‘see’ the rings in detail.”

    The other telescopes had exposure times greater than 0.7 seconds, so they were only able to observe a single gap in the light.

    What’s so special about this asteroid to make it have rings?
    “Chariklo seems to be nothing special, otherwise,” Joseph Burns, of Cornell University, told Space.com by email. Burns was not a member of Braga-Ribas’ team, but he studies planetary rings and the small bodies of the solar system. He authored a perspective article that appeared alongside the new findings.

    Chariklo may not be the only nonplanetary body to have rings, Braga-Ribas said. “Rings may be a much more common property than we thought,” he said.

    The research and Burns’ accompanying article were published online today (March 26) in the journal Nature.

    Chariklo’s ‘toy ring’

    Chariklo is the largest of the centaurs, several bodies in the outer solar system whose orbits cross — and are changed by — the outer planets. The centaurs share characteristics with both asteroids and comets, and are thought to come from the Kuiper Belt region beyond Pluto. Rocky Chariklo appears to be more asteroid than comet in composition, according to the paper.

    kb
    Kuiper Belt

    This placement may help to explain the presence of Chariklo’s rings and their absence in the asteroid belt that lies between Mars and Jupiter. The rocky inner planets and the asteroid belt lie closer to the sun, and experience stronger forces from the solar wind, which can more efficiently blow small particles away from objects they might otherwise orbit, Braga-Ribas said.

    Collisions in the fast-moving asteroid belt are also violent processes due to their faster orbital speeds. Crashes between the nearby rocky bodies may wind up hurling any potential ring material away too quickly. The collision that likely created Chariklo’s rings would have had to have been a slow-moving impact. The asteroid’s small size means it has very little gravity, allowing fast-moving objects to easily escape from its orbit; the asteroid would only have been able to hold on to slower-traveling objects.

    The presence of a ring system answers questions about why the asteroid has brightened since observations in 2008. Originally viewed edge-on, the rings have become visible over the last five years as their inclination changed.

    Twice in its 29-year orbit, Saturn’s rings act the same way, appearing as a thin line to observers on Earth, Burns said. “This behavior confounded Galileo, as viewed through his crude telescope, on his discovery of Saturn’s rings,” Burns said. “It took many more observers and nearly 50 years before the rings’ nature was understood by Christiaan Huygens.”

    The age of the rings remains another mystery. Over the course of a few million years, the small pieces of a ring system should spread out. Because they are still contained as a ring, the authors concluded that either the system is very young, or the asteroid hosts a small moon that shepherds and confines the particles in their orbit. The moon would be about as massive as both rings combined, and would easily escape detection given Chariklo’s great distance.

    “Shepherds are the preferred — and basically only — explanation,” Burns said. “But Saturn’s and Uranus’ rings have many gaps where we should see shepherds and we don’t. Something is missing in our understanding. Maybe studying Chariklo’s toy rings will bring us ideas.”

    If a missing moon circles the asteroid, keeping the rings in line, then the system could have lasted since the dawn of the solar system, Braga-Ribas said, adding that the disturbance of the gas giant that moved Chariklo to its present-day orbit would require a very close pass to disturb the ring system, indicating that they could have survived the migration.

    Studying the stability of Chariklo’s rings can tell astronomers about the environment required to form and maintain them — a process that can be used to understand the dynamics of the early stages of the solar system.

    On a wider scale, the tiny ringed asteroid can also help scientists to understand more about how galaxies form.

    “The shepherd mechanism seems to be universal from the giant planets to the small minor planet,” Braga-Ribas said. “This mechanism may be acting in other kinds of debris discs, such as proto-planetary nebulae and galaxies.”

    See the full article, with other material, here.

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  • richardmitnick 5:21 pm on November 14, 2014 Permalink | Reply
    Tags: Asteroids, , , , ,   

    From JPL: “New Map Shows Frequency of Small Asteroid Impacts, Provides Clues on Larger Asteroid Population” 

    JPL

    November 14, 2014
    Media Contact
    DC Agle
    Jet Propulsion Laboratory, Pasadena, Calif.
    818-393-9011
    agle@jpl.nasa.gov

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

    bolide
    This diagram maps the data gathered from 1994-2013 on small asteroids impacting Earth’s atmosphere to create very bright meteors, technically called “bolides” and commonly referred to as “fireballs”. Sizes of red dots (daytime impacts) and blue dots (nighttime impacts) are proportional to the optical radiated energy of impacts measured in billions of Joules (GJ) of energy, and show the location of impacts from objects about 1 meter (3 feet) to almost 20 meters (60 feet) in size. Image Credit: Planetary Science

    A map released today by NASA’s Near Earth Object (NEO) Program reveals that small asteroids frequently enter and disintegrate in the Earth’s atmosphere with random distribution around the globe. Released to the scientific community, the map visualizes data gathered by U.S. government sensors from 1994 to 2013. The data indicate that Earth’s atmosphere was impacted by small asteroids, resulting in a bolide (or fireball), on 556 separate occasions in a 20-year period. Almost all asteroids of this size disintegrate in the atmosphere and are usually harmless. The notable exception was the Chelyabinsk event which was the largest asteroid to hit Earth in this period. The new data could help scientists better refine estimates of the distribution of the sizes of NEOs including larger ones that could pose a danger to Earth.

    Finding and characterizing hazardous asteroids to protect our home planet is a high priority for NASA. It is one of the reasons NASA has increased by a factor of 10 investments in asteroid detection, characterization and mitigation activities over the last five years. In addition, NASA has aggressively developed strategies and plans with its partners in the U.S. and abroad to detect, track and characterize NEOs. These activities also will help identify NEOs that might pose a risk of Earth impact, and further help inform developing options for planetary defense.

    The public can help participate in the hunt for potentially hazardous Near Earth Objects through the Asteroid Grand Challenge, which aims to create a plan to find all asteroid threats to human populations and know what to do about them. NASA is also pursuing an Asteroid Redirect Mission (ARM) which will identify, redirect and send astronauts to explore an asteroid. Among its many exploration goals, the mission could demonstrate basic planetary defense techniques for asteroid deflection.

    For more information about the map and data, go to:

    http://neo.jpl.nasa.gov

    For details about ARM, and the Asteroid Grand Challenge, visit:

    http://www.nasa.gov/asteroidinitiative

    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 10:43 am on October 24, 2014 Permalink | Reply
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    From astrobio.net: “The Abundance of Water in Asteroid Fragments” 

    Astrobiology Magazine

    Astrobiology Magazine

    Oct 24, 2014
    Aaron L. Gronstal

    A new study could provide insights about the abundance of water in fragments from a famous asteroid.

    two
    These colorful images are of thin slices of meteorites viewed through a polarizing microscope. Part of the group classified as HED meteorites for their mineral content (Howardite, Eucrite, Diogenite), they likely fell to Earth from 4 Vesta. Credit: NASA / JPL-Caltech / Hap McSween (Univ. Tennessee), A. Beck and T. McCoy (Smithsonian Inst.)

    The study focused on a mineral called apatite, which can act as a record of the volatiles in materials, including things like magma and lunar rocks. Volatiles are chemical elements with low boiling points (like water), and are usually associated with a celestial bodies’ crust or atmosphere.

    By looking at the apatite in meteorites, the team was able to determine the history of water in these rocks from space.

    The meteorites they chose to study are known as the Howardite-Eucrite-Diogenite (HED) meteorites. These meteorites are a subset of the achondrite meteorites, which are stony meteorites that do not have any chondrites (round grains that were formed from molten droplets of material floating around in space before being incorporated into an asteroid).

    vesta
    Vesta closeup. Credit: NASA

    Studying the composition of meteorites can provide important clues about how asteroids and other rocky bodies form and evolve. Volatile elements influence processes important to planet formation, such as melting and eruption processes.

    HED meteorites are especially interesting because scientists think they originated from the crust of the asteroid Vesta – a large body in the main asteroid belt that was recently visited by NASA’s Dawn spacecraft. Behind Ceres, Vesta is the second largest object in the asteroid belt and is sometimes referred to as a protoplanet.

    Vesta is a relic of the ancient Solar System and can help astrobiologists understand our system’s formation and evolution. This information provides clues about conditions in the Solar System that led to the formation of a habitable planet – the Earth.

    Interestingly, the team’s results from the HED meteorites are similar to studies on the Earth and Moon, and could support theories that water in all three objects (Vesta, the Earth, and the Moon) came from the same source.

    See the full article here.

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  • richardmitnick 8:01 am on October 24, 2014 Permalink | Reply
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    From SETI: “New Insights on the Origin of the triple asteroid system (87) Sylvia” 


    SETI Institute

    Oct 24, 2014
    Franck Marchis, Senior Research Scientist

    Combining observations from the world’s largest telescopes with those from smaller instruments used by amateur astronomers, a team of scientists has discovered that the large main-belt asteroid (87) Sylvia has a complex interior. This has been deduced by using the motions of the two moons orbiting the main asteroid as probes of the object’s density distribution. The complex structure is probably linked to the way the multiple system was formed.

    two
    Description Discovery of the two moons Romulus and Remus of the asteroid (87) Sylvia
    Date 24 January 2007
    Adaptive Optics observations of (87) Sylvia, showing its two satellites, Remus and Romulus

    The findings were announced last year at the 45th annual Division of Planetary Sciences meeting in Denver, Colorado and were published last month in the journal Icarus.

    The asteroid (87) Sylvia is the first known to have two moons. One moon was discovered in 2001, and the second was found in 2005 by a team led by Franck Marchis, senior research scientist at the Carl Sagan Center of the SETI Institute. Since then, the team has continued to make new observations of the system using 8 to 10 m-class telescopes, including those at the Keck Observatory, the European Southern Observatory, and Gemini North.

    Keck Observatory
    Keck Observatory Interior
    Keck

    ESO VLT Interferometer
    ESO VLT Interior
    ESO VLT

    Gemini North telescope
    Gemini North Interior
    Gemini North

    syl
    (credit: Danielle Futselaar/SETI Institute).
    An artist’s rendition of the triple system showing the large 270-km asteroid Sylvia surrounded by its two moons – Romulus and Remus – gives a pictorial representation of this intriguing triple system.

    The differentiated interior of the asteroid is shown in a cutaway diagram. The primary asteroid may have a dense, regularly-shaped core, surrounding by fluffy or fractured material. The outer moon, named Romulus, is known to be strongly elongated, possibly having two lobes, as suggested by a recently observed occultation recorded by amateur astronomers.

    “Combined observations from small and large telescopes provide a unique opportunity to understand the nature of this complex and enigmatic triple asteroid system,” Marchis said. “Thanks to the presence of these moons, we can constrain the density and interior structure of an asteroid, without the need for a spacecraft’s visit. Knowledge of the internal structure of asteroids is key to understanding how the planets of our solar system formed.”

    The article Physical and dynamical properties of the main belt triple Asteroid (87) Sylvia, published last month in Icarus, is co-authored by J. Berthier, F. Vachier, B. Carry from IMCCE-Obs de Paris, J. Durech from Charles University, Prague, and F. Marchis from the SETI Institute and Obs. de Paris.

    Reference
    Berthier, J., F. Vachier, F. Marchis, J. Ďurech, and B. Carry. 2014. Physical and Dynamical Properties of the Main Belt Triple Asteroid (87) Sylvia. Icarus 239 (September): 118–30. doi:10.1016/j.icarus.2014.05.046.

    Abstract
    We present the analysis of high angular resolution observations of the triple Asteroid (87) Sylvia collected with three 8-10 m class telescopes (Keck, VLT, Gemini North) and the Hubble Space Telescope. The moons’ mutual orbits were derived individually using a purely Keplerian model. We computed the position of Romulus, the outer moon of the system, at the epoch of a recent stellar occultation which was successfully observed at less than 15 km from our predicted position, within the uncertainty of our model. The occultation data revealed that the Moon, with a surface-area equivalent diameter Ds=23.1±0.7km, is strongly elongated (axes ratio of 2.7±0.32.7±0.3), significantly more than single asteroids of similar size in the main-belt. We concluded that its shape is probably affected by the tides from the primary. A new shape model of the primary was calculated combining adaptive-optics observations with this occultation and 40 archived light-curves recorded since 1978. The difference between the J2=0.024-0.009+0.016 derived from the 3-D shape model assuming an homogeneous distribution of mass for the volume equivalent diameter Dv=273±10km primary and the null J2 implied by the Keplerian orbits suggests a non-homogeneous mass distribution in the asteroid’s interior.

    See the full article here.

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  • richardmitnick 10:06 am on September 16, 2014 Permalink | Reply
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    From SPACE.com: “US Military’s Meteor Explosion Data Can Help Scientists Protect Earth” 

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    SPACE.com

    September 15, 2014
    Leonard David

    The U.S. Air Force and NASA have ironed out problems that prevented scientists from obtaining a steady stream of military tracking data on meteor explosions within Earth’s atmosphere.

    Ever since the meteor explosion over Chelyabinsk, Russia, in February 2013, scientists have been hungry for data that can help them assess the threat of fireballs, meteors and near-Earth objects (NEOs).

    Meteor detonations within Earth’s atmosphere can be seen by U.S. military sensors on secretive spacecraft. Using this government data, in early 2013, NASA’s Jet Propulsion Laboratory (JPL) launched a new website to share the details of meteor explosion events.

    But earlier this year, the site became stagnant, with no new updates. Due to budget cuts and personnel reductions, NASA’s military partner was no longer able to carry out the work.

    Repairing the meteor explosions pipeline

    However, documents are now in place to ensure that the site is updated with a constant stream of data on meteor explosions, which are also known as bolides. In January 2013, the Air Force Space Command’s Air, Space and Cyberspace Operations directorate formalized its work with NASA’s Science Mission directorate with a memorandum of agreement (MOA).

    bolide
    Artist’s view of 2013 fireball explosion over Chelyabinsk, Russia — termed a “superbolide” event. Credit: Don Davis

    “The MOA was amended effective June 24, 2014, in order to ensure that the flow of bolide data to the scientific community is uninterrupted,” a representative for the U.S. Air Force Space Command’s Space and Missile Systems Center (SMC), which oversees military space systems, told Space.com. “With added language to the formal MOA, SMC will provide bolide data on a consistent basis and alleviate any concerns of data flow getting cut off.”

    Furthermore, there is a separate SMC team at Schriever Air Force Base in Colorado that’s responsible for the processing and dissemination of the data, the SMC representative said.

    Trove of data

    bos
    Data gleaned from hush-hush satellite sensors can be folded into other data sets to better model just how much the Earth is on the receiving end of incoming natural objects. Picture shows Sandia National Laboratories researcher Mark Boslough reviewing a supercomputer simulation of an asteroid fireball exploding in Earth’s atmosphere. Credit: Randy Montoya/Sandia

    One big reason why the military data on bolides is so important is that there is increasing evidence that Earth is on the receiving end of a sizable amount of natural asteroid/comet material, otherwise known as “spacefall.”

    By reviewing military-sensor data collected over the years, scientists hope to better understand spacefall rates. However, all of the data isn’t available just yet.

    “The plan is to release all appropriate data, although it will take some time for processing to occur,” the SMC representative told Space.com. “The Air Force has maintained a database of all detected events. The archived raw data requires very intricate and specific processing through a software program so that it can be useful to an external organization.”

    The data will give scientists a better idea of the population of very small asteroids that regularly encounter the Earth, and help researchers estimate how many larger objects may exist, said Lindley Johnson, NEO program executive within the Planetary Science Division of NASA’s Science Mission Directorate in Washington, D.C.

    Peter Brown, director of the Center for Planetary Science and Exploration at the University of Western Ontario in Canada, called the partnership a “major step forward.”

    “Speaking from the science community perspective, I would say this partnership and agreement between Air Force Space Command and NASA is a major step forward in terms of being able to study and analyze small impactors,” Brown told Space.com.

    For example, the data from the JPL fireball website helps correlate U.S. government sensor observations of fireballs with infrasound detections by the International Monitoring System (IMS), a network overseen by the Comprehensive Nuclear-Test-Ban Treaty Organization.

    Independent check

    Researchers can calibrate the current global detection efficiency of the IMS, Brown said. This U.S. government sensor-infrasound comparison also provides an independent check on the fireball energies and flags unusual events, he said.

    “The timely release of this information on the JPL website now also permits rapid follow-up of interesting bolides to facilitate time-sensitive studies, such as meteorite or airborne dust recovery, for the first time,” Brown said.

    In addition, the data contain a “potential goldmine of information,” particularly regarding meteorite-producing fireballs and their pre-atmospheric orbits, as well as information that helps address the general question of meteorite-asteroid linkages, he said.

    Regular space rock reports

    But in order for the data to be useful, it must be distributed regularly, scientists say.

    “The [Air Force] responses sound positive,” said Clark Chapman, asteroid expert with the Southwest Research Institute in Boulder, Colorado.”But the proof of any change in practices will come with actual, regular distribution of such information to interested scientists, hopefully very shortly after a detected event,” he told Space.com.

    Chapman said he and other specialists look forward to receiving timely and regular reports of bolide events via the Air Force/NASA relationship.

    To view the “Fireball and Bolide Reports” website, overseen by NASA’s Near-Earth Object Program, visit http://neo.jpl.nasa.gov/fireballs/.

    See the full article here.

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  • richardmitnick 2:35 pm on September 4, 2014 Permalink | Reply
    Tags: Asteroids, , , ,   

    From SPACE.com: “Newfound Asteroid Will Give Earth Super-Close Shave on Sunday” 

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    SPACE.com

    September 04, 2014
    Miriam Kramer

    Earth is about to have a close encounter with a house-sized asteroid on Sunday (Sept. 7), when a space rock discovered just days ago will zoom by our planet at a range closer than some satellites. But have no fear, NASA says the asteroid won’t hit Earth.

    The asteroid 2014 RC will safely buzz Earth at 2:18 p.m. EDT (1818 GMT) on Sunday. At that time, the asteroid will pass over New Zealand and fly just inside the orbits of the geosynchronous communications and weather satellites orbiting Earth about 22,000 miles (36,000 kilometers) above the planet’s surface, according to a NASA statement. That’s about 10 times closer to the Earth than the moon.

    “Asteroid 2014 RC was initially discovered on the night of August 31 by the Catalina Sky Survey near Tucson, Arizona, and independently detected the next night by the Pan-STARRS 1 telescope, located on the summit of Haleakalā on Maui, Hawaii,” NASA officials said in a statement.

    Pann-STARSR1 Telescope
    Pann-STARRS1 interior
    Pann-Stars 1 Telescope

    clock
    Asteroid 2014 RC will fly past Earth on September 7, 2014, as shown in this graphic.
    Credit: P. Chodas (NASA/JPL-Caltech)

    The asteroid will be very dim when it passes by Earth. Observers on the ground won’t be able to catch sight of it with the naked eye, but, weather permitting, intrepid amateur astronomers should be able to catch a glimpse of the fast-moving space rock through telescopes, according to NASA.

    You can also watch two webcasts featuring the asteroid flyby this weekend. The Slooh Community Observatory — an online organization that hosts live broadcast of celestial events — will begin their asteroid webcast on Sept. 6 at 10 p.m. EDT (0200 Sept. 7 GMT). The Virtual Telescope Project will also host a webcast featuring live images of the asteroid on Sept. 6 starting at 6 p.m. EDT (2200 GMT).

    At its close approach, the 60-foot (20 meters) asteroid will fly about 25,000 miles (40,000 km) from the center of Earth. The average radius of the Earth (the distance from the center of the planet to its surface) is about 3,959 miles (6,371 km).

    The speedy asteroid isn’t a threat to satellites orbiting Earth, and the space rock could even give scientists a special opportunity to learn more about asteroids because it will be so close to the planet, according to NASA.

    orbit
    The orbit of asteroid 2014 RC around the sun is shown in this graphic.
    Credit: NASA/JPL-Caltech

    NASA officials have also mapped out 2014 RC’s future orbits to see whether the near-Earth object might pose a threat to the planet in the future.

    “While 2014 RC will not impact Earth, its orbit will bring it back to our planet’s neighborhood in the future,” NASA officials said in the same statement. “The asteroid’s future motion will be closely monitored, but no future threatening Earth encounters have been identified.”

    Scientists have found more than 10,000 near-Earth objects in the solar system.

    See the full, with video, article here.

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  • richardmitnick 1:10 pm on August 20, 2014 Permalink | Reply
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    FRom SPACE.com: “Roof-Crashing Meteorite Linked to Giant Impact that Made the Moon” 

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    SPACE.com

    August 19, 2014
    Elizabeth Howell

    A meteorite that crashed into a California house in 2012 can be traced back to the giant impact that formed Earth’s moon 4.5 billion years ago, a new study reveals.

    NASA’s Cameras for Allsky Meteor Surveillance system captured photos of the meteorite’s fiery fall from space on Oct. 17, 2012, allowing researchers to determine that it likely fell in the city of Novato, just north of San Francisco. This supposition was confirmed after Novato residents Lisa Webber and Glenn Rivera followed up on an odd noise from their garage roof.

    meteroite
    A meteorite breaks apart over the San Francisco Bay Area on Oct. 17, 2012 in this image, which is horizontally mirrored to show the time series, which runs from left to right.
    Credit: Robert P. Moreno Jr., Jim Albers and Peter Jenniskens

    The meteorite Webber and Rivera found looked black, likely as a result of impact shocks that occurred 64 to 126 million years after the solar system formed, researchers found — around the time that a mysterious planet slammed into Earth, ejecting into space massive amounts of material that coalesced into the moon.

    “Our investigation has revealed a long history that dates to when the moon formed from the Earth after a giant impact,” study leader Peter Jenniskens, a meteor astronomer with the SETI (Search for Extraterrestrial Intelligence) Institute who works at NASA’s Ames Research Center in California, said in a statement.

    “We now suspect that the moon-forming impact may have scattered debris all over the inner solar system and hit the parent body of the Novato meteorite,” added co-author Qing-zhu Yin of the University of California, Davis.

    The study team further determined that the meteorite’s parent body broke up again during another collision about 470 million years ago, unleashing a chain of debris in the main asteroid belt between Mars and Jupiter.

    The scientists traced the Novato meteorite to the Gefion asteroid family within the belt based on its age and its trajectory toward Earth. Novato’s parent rock was ejected from the asteroid belt about nine million years ago, but the story doesn’t end there.

    The meteorite’s orbit periodically brought it back to the asteroid belt. Based on the rock’s thermoluminesence — light re-emitted from stored radiation exposure when the material is heated up — scientists believe the meteorite’s parent asteroid experienced yet another crash 100,000 years ago.

    The resulting fragment that made it to Earth’s atmosphere was about 14 inches (35 centimeters) across and had a mass of about 176 pounds (80 kilograms), researchers said. Despite its violent path to the ground, some organic compounds did survive — specifically, some common hydrocarbon compounds. Scientists also found nonprotein amino acids that are rare on our own planet.

    The new study was published this month in the journal Meteoritics and Planetary Science.

    See the full article here.

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  • richardmitnick 3:20 pm on August 13, 2014 Permalink | Reply
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    From SPACE.com: “Potentially Dangerous Asteroid Is Actually a Pile of Rubble” 

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    SPACE.com

    August 13, 2014
    Charles Q. Choi

    An asteroid on NASA’s list of potential impact threats to the Earth is actually a pile of loosely connected rubble held together by forces weaker than the weight of a penny, scientists say.

    The discovery could be vital if humanity ever has to destroy a giant space rock before it hits Earth, researchers added.

    Astronomers investigated near-Earth asteroid 1950 DA, which is about four-fifths of a mile wide (1.3 kilometers). This asteroid currently has one of the greatest chances of colliding with Earth of any known asteroid, with about a 1 in 4,000 chance of impacting the Earth in the year 2880.

    1950DA
    This image is one of several radar views of the asteroid 1950 DA as observed on March 4, 2001 by astronomers using the Arecibo Observatory in Puerto Rico. A new study of asteroid 1950 DA released Aug. 13, 2014 finds that the space rock is actually a rubble pile in space. Credit: S. Ostro (NASA/JPL)

    A study in 2003 suggested that if asteroid 1950 DA smashed into the Atlantic Ocean about 360 miles (580 km) from the United States, the resulting blast could be equal to a 60,000-megaton explosion, or about 3.75 million times stronger than the nuclear bomb dropped on Hiroshima, causing tsunami waves at least 200 feet high (60 meters) to crash against the East Coast.

    Unexpectedly, the scientists found 1950 DA is a porous rubble pile, about half of which is empty space. They also discovered that this loose collection of rocks is spinning faster than the forces of gravity or friction would allow it to remain in one piece, which suggests mysterious forces are helping this clump of debris to stick together.

    “I was expecting to find a high-density metallic asteroid, as such an asteroid wouldn’t require cohesive forces to hold itself together under its fast rotation,” lead study author Ben Rozitis, an astronomer at the University of Tennessee at Knoxville, told Space.com. “Instead we found the opposite!”

    A rock pile in space

    In the past decade, scientists have confirmed that many asteroids are not solid rocks, but are instead cosmic rubble piles made up of jumbles of rocks. Researchers typically suggest that these asteroids stay together due to gravity pulling them into clusters and friction locking them in place.

    Asteroid 1950 DA is covered with sandy particles known as regolith. At the same time, the asteroid spins quickly, completing one revolution every 2.12 hours. The centripetal force the asteroid experiences — the same force that causes the arms of a spinning ice skater to drift outward — should fling its regolith away.

    “We knew from previous work that this asteroid was rotating faster than it should be, and we wanted to know why,” Rozitis said.

    Based on the asteroid’s size, density and shape, in order for centripetal force to not break 1950 DA apart, the researchers estimate the asteroid needs at least 64 pascals of pressure to hold together, similar to the amount of pressure a penny exerts on the palm of a person’s hand. Scientists have previously suggested that cohesive forces other than gravity and friction can help keep rubble-pile asteroids from spinning apart — for instance, van der Waals forces are weak, short-range electric forces that can attract particles together.

    “We found a low-density rubble pile that traditionally would be unable to hold itself together unless cohesive forces were present,” Rozitis said. “It’s exciting because we’ve provided the first evidence that cohesive forces are important for small asteroids, which had only been predicted up until now.”

    These findings could shed light on how disks of gas and dust around newborn stars coalesce into asteroids, comets, rings, moons and planets, researchers say. “Cohesive forces will be present in every asteroid, and not just the fast-spinning ones,” Rozitis said. “It is just easier to observe the effects of cohesive forces in the fast-spinning ones.”

    steroid mining and defense concerns

    In addition, the complexity of the forces holding rubble piles together might complicate government and private missions to visit and mine asteroids, they added.

    “Mining missions intend to visit small asteroids about 10 meters (33 feet) or less in size, as it is thought that they are predominantly solid bodies,” Rozitis said. “However, cohesive forces enable such small asteroids to be rubble piles instead. A small rubble-pile asteroid would be harder to interact with and collect, as it can easily deform or break up when subject to external forces.”

    This work could also inform future strategies to prevent asteroids from impacting Earth.

    “The best way to mitigate an impacting asteroid is to nudge it slightly several years before impact so that it changes course,” Rozitis said. “This can be done by hitting the asteroid with a fast and heavy spacecraft. However, by hitting a fast rotating asteroid held together by cohesive forces, you risk breaking it up into several smaller, hazardous asteroids. Therefore, with such an asteroid, you want to avoid interacting with it directly to prevent it breaking up. An alternative is to use a ‘gravity tractor,’ or a heavy spacecraft placed near the asteroid, which uses the force of gravity to pull the asteroid off course.”

    Future research can investigate fast-spinning asteroids of different compositions, “as the cohesive forces involved might vary with asteroid composition,” Rozitis said.

    Rozitis and his colleagues Eric MacLennan and Joshua Emery detailed their research in the Aug. 14 edition of the journal Nature

    In addition, the complexity of the forces holding rubble piles together might complicate government and private missions to visit and mine asteroids, they added.

    “Mining missions intend to visit small asteroids about 10 meters (33 feet) or less in size, as it is thought that they are predominantly solid bodies,” Rozitis said. “However, cohesive forces enable such small asteroids to be rubble piles instead. A small rubble-pile asteroid would be harder to interact with and collect, as it can easily deform or break up when subject to external forces.”

    This work could also inform future strategies to prevent asteroids from impacting Earth.

    “The best way to mitigate an impacting asteroid is to nudge it slightly several years before impact so that it changes course,” Rozitis said. “This can be done by hitting the asteroid with a fast and heavy spacecraft. However, by hitting a fast rotating asteroid held together by cohesive forces, you risk breaking it up into several smaller, hazardous asteroids. Therefore, with such an asteroid, you want to avoid interacting with it directly to prevent it breaking up. An alternative is to use a ‘gravity tractor,’ or a heavy spacecraft placed near the asteroid, which uses the force of gravity to pull the asteroid off course.”

    Future research can investigate fast-spinning asteroids of different compositions, “as the cohesive forces involved might vary with asteroid composition,” Rozitis said.

    Rozitis and his colleagues Eric MacLennan and Joshua Emery detailed their research in the Aug. 14 edition of the journal Nature.

    See the full article here.

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  • richardmitnick 7:15 pm on June 19, 2014 Permalink | Reply
    Tags: Asteroids, , , , ,   

    From NASA/Spitzer: “Spitzer Spies an Odd, Tiny Asteroid” 



    Spitzer

    06.19.14
    No Writer Credit

    Astronomers using NASA’s Spitzer Space Telescope have measured the size of an asteroid candidate for NASA’s Asteroid Redirect Mission (ARM), a proposed spacecraft concept to capture either a small asteroid, or a boulder from an asteroid. The near-Earth asteroid, called 2011 MD, was found to be roughly 20 feet (6 meters) in size, and its structure appears to contain a lot of empty space, perhaps resembling a pile of rubble. Spitzer’s infrared vision was key to sizing up the asteroid.

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    2011 MD

    NASA Asteroid Redirect Mission
    NASA ARM spacecraft

    “From its perch up in space, Spitzer can use its heat-sensitive infrared vision to spy asteroids and get better estimates of their sizes,” said Michael Mommert of Northern Arizona University, Flagstaff, lead author of a new study appearing today, June 19, in the Astrophysical Journal Letters. David Trilling, also of Northern Arizona University, leads the team of astronomers.

    The Spitzer results confirm that asteroid 2011 MD has characteristics suitable for the ARM proposal, elevating it to the “valid candidate” level. Valid candidates are those asteroids with the right size, mass and rotation rate to be feasibly captured by the robotic spacecraft. Two other valid candidates have been identified so far. (The proposal to capture a boulder from an asteroid involves a different set of criteria.) NASA continues to search for and find new potential candidates using its ground-based asteroid survey programs.

    Prior to the Spitzer study, the size of 2011 MD was only very roughly known. It had been observed in visible light, but an asteroid’s size cannot be determined solely from visible-light measurements. In visible light alone, for example, a white snowball in space could look just as bright as a dark mountain of cosmic rock. The objects may differ in size but reflect the same amount of sunlight, appearing equally bright.

    Infrared light, on the other hand, is a better indicator of an object’s true size. This is because an object’s infrared glow depends largely on its temperature, not its reflectivity.

    From the new Spitzer data, the team was able to measure the size of asteroid 2011 MD. When the infrared and visible-light observations were combined, the asteroid’s density and mass could also be measured. The density of 2011 MD is remarkably low — about the same as water, which agrees with a separate analysis of observations taken in 2011. Since rock is about three times more dense than water, this implies that about two-thirds of the asteroid must be empty space.

    What does an asteroid with that much empty space look like? The team doesn’t know, but proposes two possible solutions: it might be a collection of loosely bound rocks, like a fleet of flying boulders, or a solid rock with surrounding fine debris.

    A similar “rubble-pile” type of composition was also found for asteroid 2009 BD, another valid candidate for ARM. Trilling and colleagues used Spitzer to help pin down the size of that asteroid to roughly 10 to 13 feet (3 or 4 meters).

    In both studies, Spitzer stared at the asteroids for about 20 hours. Such long observations are scheduled more often in Spitzer’s “warm” mission, a phase that began in 2009 when the spacecraft ran out of coolant, as planned. Spitzer, which still has two infrared channels that operate without coolant, now specializes in longer, targeted observing campaigns.

    “With Spitzer, we have been able to get some of the first measurements of the sizes and compositions of tiny asteroids,” said Trilling. “So far, we’ve looked at two asteroids and found both of them to be really weird — not at all like the one solid rock that we expected. We’re scratching our heads.”

    The team says the small asteroids probably formed as a result of collisions between larger asteroids, but they do not understand how their unusual structures could have come about. They plan to use Spitzer in the future to study more of the tiny asteroids, both as possible targets for asteroid space missions, and for a better understanding of the many asteroid denizens making up our solar system.

    Other authors of the Spitzer paper are: D. Farnocchia, P. Chodas and S. R. Chesley of NASA’s Jet Propulsion Laboratory, Pasadena, California; J. L. Hora, G. G. Fazio and H.A. Smith of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts; M. Mueller of the SRON Netherlands Institute for Space Research, Netherlands; and A. W. Harris of the DLR Institute for Planetary Research, Germany.

    JPL manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA.

    Through its Asteroid Initiative, NASA is developing a first-ever mission to identify, capture and redirect a near-Earth asteroid to a stable orbit around the moon with a robotic spacecraft. Astronauts aboard an Orion spacecraft, launched by a Space Launch System rocket, will explore the asteroid in the 2020s, returning to Earth with samples. Experience in human spaceflight beyond low-Earth orbit through this Asteroid Redirect Mission will help NASA test new systems and capabilities needed to support future human missions to Mars. The Initiative also includes an Asteroid Grand Challenge, which is seeking the best ideas to find all asteroid threats to human populations and accelerate the work NASA already is doing for planetary defense.

    JPL manages the Near-Earth Object Program Office for NASA’s Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena.

    See the full article here.

    The Spitzer Space Telescope is a NASA mission managed by the Jet Propulsion Laboratory located on the campus of the California Institute of Technology and part of NASA’s Infrared Processing and Analysis Center.
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  • richardmitnick 8:20 am on June 13, 2014 Permalink | Reply
    Tags: Asteroids, , , , ,   

    From SETI Institute: “Life on the Billionth Rock from the Sun” 


    SETI Institute

    Undated
    Seth Shostak, Senior Astronomer, Director, Center for SETI Research

    I’ve always regarded asteroids as somewhat like dinosaurs: mildly interesting and faintly dangerous. But I’m now thinking that they might be a profitable real estate investment.

    ast

    As any astronomer (including this one) will tell you, asteroids hold the answer to a perennial puzzle about the formation of planets. In particular, how do specks of senseless debris organize themselves into balls of rock and vapor – a few of which could be homes for life?

    That’s why we should study asteroids, from the science point of view. But a recent talk by Marc Rayman, chief engineer for NASA’s Dawn mission, impressed me with the many other reasons to be interested in these primordial rocks.

    An obvious one is well known: they’re dangerous. Asteroids are nature’s kamikazes, cruising the solar system at tens of thousands of miles per hour. They could take out a city or worse. Last year, a house-sized rock lit up the skies above the Russian city of Chelyabinsk, providing a nice example of why this menace is more than hysterical paranoia.

    It’s a threat to take seriously, and the first step in giving humanity a chance against these peripatetic impactors is to find as many as we can. Reconnaissance is first, defense is second.

    Apollo astronaut Rusty Schweickart and his B612 Foundation are working on the problem. They hope to boost the inventory of known Earth-threatening asteroids from ten thousand to about a million. That would give us a handle on many of the smaller rocks that – while not on the scale of the asteroid that wiped out the dinosaurs – could still toast Cincinnati. Know your enemy.

    But there’s another aspect of asteroids that warrants our attention: They could be an insurance policy for our long-term survival.

    That bizarre notion ultimately derives from the fact that the Earth is a ball. Somewhere in your mathematical upbringing, you may have learned that a sphere has the minimum surface area for its volume. Put another way, by shaping stuff into a ball you get the least amount of acreage per cubic foot of material. The Earth would have more surface area if it were, for example, a cube – although this would present a driving hazard at the edges.

    So if exploiting natural resources is what your society does, then living on a ball is a bummer. Most of the good stuff sits unreachable and largely useless, hunkered down in the planet’s unseen core.

    Dicing up your world could help. Imagine cutting our planet in two, and then rolling up each half. Two balls instead of one, and you’d gain 26 percent in surface area, allowing more room for shopping malls. But why stop there? Cut each of those balls in half, and you gain another 26 percent. Et cetera and ad infinitum.

    It’s conceivable that subdividing the Earth in this way won’t get approval from the Environmental Protection Agency, but no matter. Nature has done this for you – producing millions of small balls (and an assortment of other shapes) called asteroids. They’re the left-over building blocks of a failed planet just outside the orbit of Mars. This world never got built, thanks to endless interference by Jupiter’s gravitational field.

    These rocks are a resource. The fact that they’re in small chunks makes mining them as appealing as cat videos. And at least two companies are considering doing just that. The consequences could be mind-boggling. According to John Lewis, chief scientist for Deep Space Industries, if humanity can improve its recycling efforts, then ores smelted out of just the nearest asteroids will supply the needs of 80 billion of us until that distant day on which the Sun dies.

    That sure beats the slow and inevitable impoverishment that will be our fate if we confine mining to our own back yards (or preferably someone else’s back yard). The asteroids aren’t so much a renewable resource as an endless one.

    But wait; there’s more.

    Some of the small bodies in the solar system could be our future homes. No, not so much the asteroids–to begin with, they’re going to have the look and feel of an open pit mining operation, as Lewis notes. Maybe that’s not the best neighborhood for raising your great-grandkids. And in addition to their distasteful Virginia City ambience, they’re also lacking in the light elements that are necessary for food and life in general. These rocks are a hard place.

    But in the dim outer pickets of the solar system – beyond Neptune, and up to tens of thousands of times farther than the asteroid belt – is the bulk of the solar system’s colossal collection of ice balls. Depending on how far out you go, these are referred to either as Kuiper belt objects, or comets of the Oort cloud.

    They have water and the light elements that are missing from the asteroids. And thanks to being small, I figure they collectively have a billion times as much acreage as Earth.

    True, there’s not much sunlight where the comets are, but physicist Freeman Dyson has suggested that big, easily built mirrors could shine a little light on cometary colonies.

    It may all sound far out and fantastic. But if you step back from your day-to-day headaches for a moment, and ponder our species’ long-term prospects, well, small is beautiful.

    So while many consider rocks in the sky to be like sharks, cruising the solar system and occasionally wreaking havoc and destruction, I see them as both a mother lode and a future home. Anyone want to float me a loan?

    See the full article here.

    SETI Institute – 189 Bernardo Ave., Suite 100
    Mountain View, CA 94043
    Phone 650.961.6633 – Fax 650-961-7099
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