- 3667 - METEORS - life building blocks? Friday, August 12, 2022. The asteroid, “2015 FF“, has an estimated diameter between 42 and 92 feet, or about the body length of an adult blue whale, and it will zoom past the Earth at 20,512 mph.
--------------------- 3667 - METEORS - life building blocks?
- A "potentially hazardous" asteroid the size of a blue whale is set to zip past Earth . At its closest approach, the asteroid traveling at around than 27 times the speed of sound will come within about 2.67 million miles of Earth, a little more than eight times the average distance between Earth and the moon.
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- Space objects that comes within 120 million miles of Earth as a "near-Earth object" and any fast-moving object within 4.65 million miles is categorized as "potentially hazardous."
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- Once the objects are flagged, astronomers closely monitor them, looking for any deviation from their predicted trajectories, such as an unexpected bounce off another asteroid, that could put them on a devastating collision course with Earth.
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- NASA knows the location and orbit of roughly 28,000 asteroids, which it maps with the Asteroid Terrestrial-impact Last Alert System (ATLAS), an array of four telescopes capable of performing a complete scan of the entire night sky once every 24 hours.
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- Since ATLAS came online in 2017, it has detected more than 700 near-Earth asteroids and 66 comets. Two of the asteroids detected by ATLAS actually hit Earth, one exploding off the southern coast of Puerto Rico and the other landing near the border of Botswana and South Africa.
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- In March 2021, a bowling ball-sized meteor exploded over Vermont with the force of 440 pounds of TNT. Those fireworks have nothing on the most explosive recent meteor event, which occurred near the central Russian city of Chelyabinsk in 2013. As the Chelyabinsk meteor struck the atmosphere, it generated a blast roughly equal to around 400 to 500 kilotons of TNT, or 26 to 33 times the energy released by the Hiroshima bomb. Fireballs rained down over the city and its environs, damaging buildings, smashing windows and injuring approximately 1,200 people.
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- If astronomers were to ever spy an asteroid careening straight toward our planet, space agencies around the world are already working on possible ways to deflect the object. On November 24, 2021, NASA launched a spacecraft as a part of its Double Asteroid Redirection Test (DART) mission, which plans to redirect the non-hazardous asteroid Dimorphos by ramming it off course in autumn 2022.
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- China is also in the early planning stages of an asteroid-redirect mission. By slamming “23 Long March 5” rockets into the asteroid Bennu, the country hopes to divert the space rock from a potentially catastrophic impact with Earth.
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- Every year, millions of rocky shards from outer space burn up in Earth's atmosphere, many briefly flaring and appearing in the sky as "shooting stars." But how many survive their high-speed plunges to strike the ground?
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- Rocks from space that land on Earth are known as “meteorites“. Giant impacts, such as the one that likely ended the reign of the dinosaurs about 66 million years ago, caused by an asteroid or comet measuring about 6 miles across, are extraordinarily rare. Instead, most rocks that fall to Earth are very small, and relatively few survive their fiery plummet through Earth's atmosphere.
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- Scientists estimate that fewer than 10,000 meteorites collide into Earth's land or water, which is a drop in the bucket compared with the moon, which doesn't have an atmosphere and gets hit by varying sizes of space rocks: about 11 to 1,100 tons the mass of about 5.5 cars of space rock dust per day, and about 33,000 pingpong-ball-sized space rock collisions yearly.
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- The space rocks that typically end up as meteorites are known as “meteoroids” , small asteroids. These range in size from boulders measuring about 3 feet wide down to micrometeoroids the size of dust grains.
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- Meteoroids are generally fragments of asteroids or comets. However, some may be debris blasted off planets or moons. For example, there are more than 300 known meteorites that originated as pieces of Mars.
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- As meteoroids plow through Earth's atmosphere, they burn up from air friction and produce streaks of light across the sky: these flaming, falling rocks are called “meteors“. Thousands of meteors blaze across Earth's sky each day, but most of these happen over the oceans and uninhabited regions, and a good many are masked by daylight.
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- Most of Earth's detected meteors "come from the meteor showers associated with the dust released by comets. Meteor showers do not produce meteorites, as the meteoroids in such showers are typically too fragile to survive the fall to the ground. From 2007 to to 2018, there were 95 reports of meteorites falling to Earth, averaging a rate of about 7.9 reports per year.
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- It's impossible to know for sure how many meteorites fall into the ocean and sink to the bottom undetected. However, 29% of Earth's surface is covered by land. Urban areas, in which about 55% of people live, cover about 0.44% of land.
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- There are probably about 6,100 meteorite falls per year over the entire Earth, and about 1,800 over the land.
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- Space rocks measuring about 33 feet wide are expected to enter Earth's atmosphere every six to 10 years. A rock big enough to generate an explosion like that of the 1908 Tunguska event in Russia happens about every 500 years. A major cosmic impact from a rock about 3,280 feet wide is estimated to happen every 300,000 to 500,000 years, whereas a collision like the one that ended the Cretaceous period and obliterated the dinosaurs might take place once in 100 million to 200 million years.
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- Three meteorites contain the molecular building blocks of DNA and its cousin RNA, scientists recently discovered. This discovery supports the idea that, some four billion years ago, a barrage of meteorites may have delivered the molecular ingredients needed to jump-start the emergence of the earliest life on Earth.
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- A class of compounds known as “pyrimidines“, appeared in "extremely low concentrations" in the meteorites. Components of DNA and RNA have been found in meteorites before.
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- Specifically, such space rocks have been found to contain nucleobases, the nitrogen-containing compounds that serve as the "letters" in the genetic code of our DNA and RNA. Nucleobases come in five primary flavors — adenine (A), thymine (T), guanine (G), cytosine (C) and uracil (U) — but previously, only A, G and U had ever been identified in meteorites.
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- Scientists reported finding all five nucleobases inside carbon-rich meteorites. This included trace amounts of all three pyrimidines: cytosine, uracil and thymine. The detection of cytosine is of surprise, because cytosine is relatively unstable and likely to react with water.
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- In lab settings, scientists have recreated the chemical conditions of interstellar space where immense clouds of gas and dust measure about 10 Kelvins or minus 441.67 degrees Fahrenheit and the parent asteroids of meteorites can be found. Through these experiments, researchers synthesized thymine, cytosine and the other primary nucleo-bases, suggesting that all of these compounds could theoretically be detectable in meteorites.
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- Hydrocarbons and the building blocks of proteins (amino acids) had been identified in the three meteorites. They detected an elusive molecule called “hexamethylenetetramine” (HMT), which is thought to be an important precursor to organic molecules.
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- Researchers used a technique called “high-performance liquid chromatography“, which involved using pressurized water to separate the meteorite samples into their component parts. In this way, the team extracted the nucleobases from each sample and then analyzed the bases using mass spectrometry, a technique that revealed the chemical makeup of the material in fine detail. This method "enabled us to detect nucleobases with very low concentrations, as low as parts per trillions.
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- The analysis revealed that all of the meteorites carried adenine and guanine. The Murchison samples also contained uracil, while the other meteorites carried at least one uracil isomer, meaning a compound that contains the same number and types of atoms as uracil but in a different spatial arrangement.
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- In addition, samples carried thymine, and thymine isomers. All of the meteorites contained cytosine, along with various isomers of the compound.
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- By comparing the diversity of nucleobases found in the meteorite against that found in the soil, the team concluded that the compounds in the space rock formed in space. Because of this, they expect that the nucleobases "contributed to the emergence of genetic properties for the earliest life on Earth. However, there's still some uncertainty.
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- Astronomers plan to hunt for nucleobases in material collected directly from asteroids, rather than from meteorites on Earth. This could minimize the issue of Earth-born contaminants. The Japanese spacecraft Hayabusa2 recently brought the asteroid Ryugu down to Earth. NASA's OSIRIS-REx probe is due to touch down with samples of the near-Earth asteroid Bennu in 2023.
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- We may still learn if the ingredients for life on Earth were delivered by meteors.
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August 30, 2022 METEORS - life building block ? 3663
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