What whacked the inner solar system?For the first 700 million years of their existence, the moon and Earth and the other rocky planers took a beating. Space debris Space debris or orbital debris, also called space junk and space waste, are the objects in orbit around Earth created by humans, that no longer serve any useful purpose. hammered these bodies so fiercely that their surfaces were stripped away. Moon samples brought back by the Apollo missions The Apollo missions were a series of space missions, both manned and unmanned, flown by NASA between 1961 and 1975. They culminated with a series of manned moon landings between 1969 and 1972. in the early 1970s confirmed that this violent era ended about 3.85 billion years ago. But researchers haven't known the form of that early debris. A team of planetary scientists has now determined that the culprits were ancient asteroids This is a list of numbered minor planets, nearly all of them asteroids, in sequential order. As of late September 2007 there are 164,612 numbered minor planets, and many more not yet numbered. Most asteroids are ordinary and not particularly noteworthy. rather than comets. The rocks came from the asteroid belt, which lies between the orbits of Mars and Jupiter. They ranged in diameter from about 100 meters to tens of kilometers, assert Robert G. Strom of the University of Arizona (body, education) University of Arizona - The University was founded in 1885 as a Land Grant institution with a three-fold mission of teaching, research and public service. in Tucson and his colleagues in the Sept. 16 Science. From the sizes of the craters, Strom's team determined the diameters of the projectiles that created them. The researchers then analyzed a compilation of recent asteroid surveys that provide the first detailed information on asteroids as small as 1 km in diameter. The scientists then compared the sizes of existing asteroids with the sizes of the projectiles that cratered the moon, Earth, Mars, Venus, and Mercury eons ago. To the team's delight, the mix of sizes was identical to that of asteroids that now reside in the belt. The researchers conclude that an ancient population of belt asteroids did the damage. The cratering record in the inner solar system solar system, the sun and the surrounding planets, natural satellites, dwarf planets, asteroids, meteoroids, and comets that are bound by its gravity. The sun is by far the most massive part of the solar system, containing almost 99.9% of the system's total mass. changed dramatically after the initial violent era and indicates that most of the impactors since then have been near-Earth asteroids Near-Earth asteroids (NEAs) are asteroids whose orbits are close to Earth's orbit. Some NEAs' orbits intersect Earth's so they pose a collision danger. On the other hand, NEAs are most easily accessible for spacecraft from Earth; in fact, some can be reached with much less fuel , less than 20 km across. These asteroids came from the main belt but were long ago nudged into Earth-crossing orbits.--R.C. |
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