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---------------------- 2250 - Asteroids visits and impacts
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- We have several spacecrafts visiting asteroids right now. January, 2019. This Review will summarize the current visits and then get into the history even some that are evident on the Earth and on the Moon.
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- Hayabusa I spacecraft visited the asteroid Itokawa in 2005. It returned with only 2,000 grains of asteroid dust. This time Hayabusa II reached asteroid Ryugu on June 27, 2019 with hope of collecting many more samples.. Ryugu’s mission is to blow up a crater and recover a good amount subsurface samples to return to Earth.
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- Another space craft OSIRIS-Rex is visiting the asteroid Bennu. Its mission is to bring back samples by 2023.
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- Both of these asteroids have so little gravity that even sunlight can change their orbits. The goal is to pick up samples and keep them pristine during their return trip to Earth for laboratory analysis.
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- The purpose of this analysis is to learn more about the origin of the solar system, the origin of the planets, and the origin of life itself? Science already has thousands of samples of asteroids that have reached the surface of Earth. Hundreds fall each year. But, all of these have been coated with the Earth’s atmosphere and burned from ground landings.
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- Pristine samples would tell science what it was like 4,600,000,000 years ago. Could these carbon-rich asteroids carry the raw ingredients for life? The organic compounds in the asteroid would hopefully not be contaminated.
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- Asteroid Ryugu is only 880 meters across and asteroid Bennu is only 510 meters across. The slightest pressure on their surfaces will push them off course in their trajectory.
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- Even the smallest grains that have already been returned, particles only 50 micrometers across have significantly improved the science for asteroids.. The OSIRIR mission plans to collect up to 2,000 grams of dust samples. Hayabusa II plan on collecting 100 milligrams at three different locations.
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- Much more science will occur beyond returned surface samples. Bennu will be analyzed by 3 cameras, a laser altimeter, and 3 spectrometers. Hayabusa will fire a 2 kilogram projectile into Ryugu’s surface, then collecting the debris.
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- Bennu asteroid has visited with near Earth passes in 1999, 2005, and 2011. So, radio telescopes have already mapped the surface shape, but less of the details needed for a good landing. This data was enough to allow calculations on how much sunlight alone is affecting the asteroid’s orbit.
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- Asteroids rumble through space absorbing sunlight on one surface then re-emitting heat later when the surface is not facing the Sun. That radiating heat alone is enough to change the asteroid’s orbit. Calculations on this data have determined that Bennu has a 1 in 2,000 chance of hitting the Earth in 2200.
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- We will see what these missions can tell us there is a lot more to learn. I won’t be here.
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- There is another asteroid , Oumuamua, that has been studied since October , 2017. Science has been trying to define its trajectory studying the affects of sunlight photons, friction like forces, and magnetic interactions with the solar wind. Or, the trajectories can also be influenced by venting gas and dust from the surface.
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- The sunlight can sublimate ices trapped just below the surface turning the solid ice directly into gas. This out gassing can in turn generate a tiny amount of thrust. The path being traced has already concluded that Oumaumau is from outside our solar system. And, it will leave us after passing through.
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- Spacecraft have studied some 24 asteroids to date. Halley’s Comet has had 5 spacecraft visits in 1986. The closest approach to Halley was 850 miles. The Deep Impact spacecraft visited Tempel 1 in 2005 then coasted by Comet Halley in 2010 to within 430 miles pf its surface.
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- Europe’s Rosetta spacecraft visited Comet 67P in 2014. It orbited the comet and deployed a lander , Philae in November to it surface. The lander’s batteries only lasted for 64 hours. But, it did manage to discover organic molecules in the comet’s atmosphere. It discovered a magnetic field on the comet and temperatures ranging from
-292 F to -229. The comet is not quit a rock and not quit an iceberg.
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- Science is also studying the asteroid impacts on our Moon to better understand the history of impacts on Earth. Even closer to home the comet exploding over Chelyabinsk, Russia, in 2013, was 65 feet in diameter.
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- Asteroid Duende , 100 feet in diameter, passed between the Earth and the Moon, missing us by only 17,000 miles. It was estimated to weigh 130,000 tons.
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- Some 10,000 years ago the Barringer Meteor Crater impact occurred in Arizona. It was 300,000 ton asteroid traveling at 29,000 miles per hour. Its impact was equivalent to an explosion of 2,500,000 tons of TNT.
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- Asteroids are mostly rock and metal. Comets are mostly composed of water, hydrogen cyanide, carbon monoxide, ammonia, and methane.
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- To date the Hayabusa I is the only spacecraft so far to return a sample of a asteroid back to Earth for a pure sample analysis. The asteroid Itokawa that it visited is basically a rubble pile of stone and metal.
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- The Dawn spacecraft visited the asteroid Ceres in 2015 which has since been
re- designated as a Dwarf Planet orbiting the Sun every 4.6 years. Dawn then visited asteroid Vesta that had a 326 mile diameter. Request separate Reviews to learn more about Ceres and Vesta.
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-------------------------- Other Reviews available.
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- 2226 - Asteroid Ryugu.
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- 2203 - Asteroid Bennu.
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- 2044 - Asteroid Oumaumau, this Review lists eleven more reviews about asteroids.
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- 1923 - In 2017 50 asteroids passed between us and the Moon.
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- 1193 - About the Chicxulub Crater in the Yucatan, Mexico.
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- 937 - Spinning Asteroid, teacher’s lesson plan.
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- January 29, 2019
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-------------------------- Wednesday, January 30, 2019 --------------------------
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