Thursday, March 16, 2023

3919 - ASTEROIDS - how close to Earth?

 

-   3919  -  ASTEROIDS  -  how close to Earth?   In 2019, for the first time, scientists have found the building blocks for life on an asteroid in space.   Japanese researchers have discovered more than 20 amino acids on the space rock Ryugu, which is more than 200 million miles from Earth.


------------  3919  -    ASTEROIDS  -  how close to Earth?

-    Scientists made the first-of-its-kind detection by studying samples retrieved from the near-Earth asteroid by the Japan Aerospace Exploration Agency's (JAXA) Hayabusa2 spacecraft, which landed on Ryugu in 2018.

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-   In 2019, the spacecraft collected 0.2 ounce (5.4 grams) from the asteroid's surface and subsurface, stowed it in an airtight container and launched it back to Earth on a fine-tuned trajectory.

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-    Rather than being one large boulder, Ryugu is made up of many small rocks, and the asteroid got its unusual spinning top shape from rapid rotation.

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-    As a carbonaceous, or C-type, asteroid, Ryugu contains a large amount of carbon-rich organic matter, much of which likely originated from the same nebula that gave birth to the sun and the planets of the solar system roughly 4.6 billion years ago. Sample analysis has also suggested that the asteroid harbors water.

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-    The sample collected from Ryugu was sent back to Earth in an airtight container for analysis.  The Ryugu material is the most primitive material in the solar system we have ever studied.

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-    Unlike the organic molecules found on Earth, the pitch-black asteroid samples, which the scientists found only reflect 2% to 3% of the light that hits them, have not been changed by interactions with Earth's environment, giving them a chemical composition much closer to that of the early solar system.

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-   These prebiotic organic molecules can spread throughout the solar system, potentially as interplanetary dust from the Ruygu surface by impact or other causes.

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-    Sample analysis detected 20 amino acid types.  Amino acids are the fundamental building blocks of all proteins and are indispensable prerequisites for the existence of life on our planet.

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-    A 2019 study found organic molecules from space in a group of           3.3-billion-year-old rocks discovered in South Africa, raising the possibility that some of these life-building molecules first came to Earth on comets and asteroids. The Ryugu findings make the evidence that asteroids carry these molecules even stronger.

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-   This means that amino acids could likely be found on other planets and natural satellites, a clue that life could have been born in more places in the universe than previously thought.

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-    The researchers are continuing to analyze Ryugu samples, and more data on the asteroid's formation and its composition will become available soon.

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-    In 2021, NASA's OSIRIS-REx spacecraft collected a rock sample from another diamond-shaped asteroid, named Bennu. When the sample returns to Earth in 2023, signs of organic matter contained within it could provide scientists with important clues into the evolution of the solar system and its materials, alongside how life emerged from them.

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-    NASA's Dawn spacecraft will rendezvoused with the asteroid “Vesta”. Most asteroids, including Vesta, reside in the doughnutlike ring of the main asteroid belt that peppers the space between Mars and Jupiter. Other asteroids whirl in tight circles closer to the sun than the Earth, while a large number of them share planets' orbits.  Some asteroids' orbits take them on planet-crossing swings through the inner solar system.

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-   The biggest asteroid by far is Ceres which explains why it was discovered first and it makes up about a third of the asteroid belt's mass. The object is so hefty that it's the only asteroid that has the gravitational strength to pull itself into a sphere.

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-   On account of this roundness, Ceres is also considered a "dwarf planet," a designation it shares with four other objects in the solar system, including Pluto.

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-    After scoping out Vesta, the Dawn spacecraft will journey on to Ceres, arriving in 2015.  The object is probably the "wettest" asteroid, with large stores of water in its interior as ice, though also possibly as a liquid layer beneath the surface

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-  Baptistina is the name of one of the youngest families of asteroids in the asteroid belt.  Families of asteroids are swarms of objects that share orbital characteristics.

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-     Baptistina and its swarm were spawned some 160 million years ago by a smashup between a 37-mile-wide body body and another object about 106 miles in diameter. That cataclysm created hundreds of large objects, some of which then drifted into a collision course with Earth.

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-   One or several of these rocky shards of shrapnel then plowed into our planet 65 million years ago and helped doom the dinosaurs. The impact gouged out the Chicxulub crater, now buried by the Yucatan peninsula and the Gulf of Mexico.

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-   The 100-million-year Baptistina barrage did not spare the Moon, either. A meteorite scooped out the giant Tycho crater about 109 million years ago.

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-   Many asteroids, believe it or not, have a moon, and some even sport two satellites. Kleopatra has two moons, which were named Alexhelios and Cleoselene earlier this year. The metallic asteroid has an unusual dog-bone shape.

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-    The asteroid is roughly 135 by 58 by 50 miles in length, height and width. Its moons Alexhelios and Cleoselene are, respectively, about 3 miles  and 1.9 miles in diameter.

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-    Like Kleopatra, Hektor is very elongated, with length and width dimensions of approximately 230 by 124 miles. Hektor has a moon as well. Unlike Kleopatra, however, Hektor is not found in the main asteroid belt; instead, the dark, reddish body dominates as the biggest of Trojan asteroids stuck in Jupiter's orbit.

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-    These rocks lurk in what are known as the L4 and L5 Lagrangian points two of the five zones in an orbit where the gravity of two bodies ( Jupiter and the Sun) balances out. L4 and L5 lie ahead and behind, respectively of Jupiter.

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-   Themis, a large main belt asteroid, stands out as the first and only asteroid known thus far to have ice on its surface.  In 2009, observations in infrared light confirmed the presence of this ice, as well as carbon-containing, or organic, molecules.

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-    These characteristics make Themis and similar bodies called main belt comets good candidates for having delivered water and carbon some of the ingredients of life to the surface of a young, hot, dried-out Earth some four billion years ago.

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-    Named after a Celtic god, Toutatis is one of the oddest asteroids. Instead of rotating in an orderly fashion about an axis, the double-lobed object chaotically tumbles. This unpredictable movement partially derives from Toutatis being composed of two bodies barely in contact with each other and from the influences of both Earth and Jupiter's gravity.

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-    Toutatis' path through the solar system has it sweep close to Earth, but because the asteroid's orbit is chaotic, its exact path and how close it might come to us centuries from now cannot be well predicted.

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-  Like some other asteroids, Toutatis is said to be a like a "rubble pile" fragments of rock that have gravitational come back together after a collision, but left many gaps between them.

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-   Toutatis has made some close shaves to Earth, and passed within 1,000,000 miles of Earth, or about four Moon distances, back in 2004. Yet some rocks have made notably closer passes, and the one that has most alarmed astronomers and the public alike is Apophis.

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-    Discovered in 2004 and named after the Greek word for the evil Egyptian god of darkness, Apophis will return to the neighborhood in 2029. At the time, scientists calculated that its impacting Earth on that future pass were as high as 1 in 40, but subsequent measurements have now relegated that possibility to almost nil .

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-   Panic peaked in December 2004, and Apophis achieved a ranking of 4 on the Torino scale, the 10-point scale that rates the risk of an object colliding with Earth (10 being an unquestioned apocalypse). Although Apophis is now deemed a 0 for its 2029 pass, it will zoom a mere 18,600 miles above Earth's surface.

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-   A number of these other so-called Near Earth Objects, or NEOs, have yet to be cataloged. Yet some that have pose no threat, and benignly share Earth's orbit. At least four examples exist of asteroids that follow Earth in horseshoe-shaped orbits; a new one, designated 2010 SO16, was found earlier this year.

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-    An experiment to bounce a radio signal off an asteroid on Dec. 27 will serve as a test for probing a larger asteroid that in 2029 will pass closer to Earth than the many geostationary satellites that orbit our planet.

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-    Astronomers will transmit radio signals to asteroid 2010 XC15, which could be about 500 feet across. The University of New Mexico Long Wavelength Array near Socorro, New Mexico, and the Owens Valley Radio Observatory Long Wavelength Array near Bishop, California, will receive the signal.

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-     Longer wavelengths can penetrate the interior of an object much better than the radio wavelengths used for communication.   Knowing more about an asteroid’s interior, especially of an asteroid large enough to cause major damage on Earth, is important for determining how to defend against it.

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-    If you know the distribution of mass, you can make an impactor more effective, because you’ll know where to hit the asteroid a little better.  Those radar-imaging programs use signals of short wavelengths, which bounce off the surface and provide high-quality external images but don’t penetrate an object.

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-   HAARP will transmit a continually chirping signal to asteroid 2010 XC15 at slightly above and below 9.6 megahertz.  The chirp will repeat at two-second intervals. The asteroid will be twice as far from Earth as the moon is.

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-    The test on 2010 XC15 is yet another step toward the globally anticipated 2029 encounter with asteroid Apophis. It follows tests in January and October in which the moon was the target of a HAARP signal bounce.

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-    Apophis was discovered in 2004 and will make its closest approach to Earth on April 13, 2029, when it comes within 20,000 miles. Geostationary satellites orbit Earth at about 23,000 miles. The asteroid, estimated to be about 1,100 feet across, was initially thought to pose a risk to Earth in 2068.

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-     NASA says an automobile-sized asteroid hits Earth’s atmosphere about once a year, creating a fireball and burning up before reaching the surface. About every 2,000 years a meteoroid the size of a football field hits Earth. Those can cause a lot of damage. And as for wiping out civilization, NASA says an object large enough to do that strikes the planet once every few million years.

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-   NASA first successfully redirected an asteroid on September, 26, 2022 when its Double Asteroid Redirection Test mission, or DART, collided with Dimorphos. That asteroid is an orbiting moonlet of the larger Didymos asteroid.  The DART collision altered the moonlet’s orbit time by 32 minutes.

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-  The December 27 test could reveal great potential for the use of asteroid sensing by long wavelength radio signals. Approximately 80 known near-Earth asteroids passed between the moon and Earth in 2019, most of them small and discovered near closest approach.

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                   March 16, 2023        ASTREROIDS   - how close to Earth?        3919                                                                                                                         

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