Accretion of Extraterrestrial Matter Throughout Earth’s History

pp 75-92

Spacecraft Measurements of the Cosmic Dust Flux

  • Herbert A. ZookAffiliated withNASA Johnson Space Center

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Spacecraft measurements of the cosmic dust flux in space have determined the flux of meteoroids as a function of meteoroid mass at 1 AU. The measurements show that the total influx rate of meteoritic material to the entire Earth is about 40,000 tons per year, with nearly all of the meteoritic mass residing in grains with masses between 10−16 kg and 10−4 kg. Less than 25% of this mass is believed to derive from asteroids. Data from the Pioneer 8 and 9 spacecraft gave evidence for a flux of sub-micron grains (now called β meteoroids) leaving the solar system under radiation pressure at the rate of about 10 tons per second. A 1.5 × 10−4 m−2s−1 flux of interstellar grains, with a mean mass around 3 X 10−16 kg, has been found to be passing through the solar system by the Ulysses and Galileo spacecraft. These spacecraft have also sensed dust grains in orbit about Jupiter as well as dust escaping the Jovian system.