Detection of 4He in stratospheric particles gives evidence of extraterrestrial origin

Abstract

Whipple predicted the existence of micrometeorites, small interplanetary particles which enter the Earth's atmosphere without being melted by frictional heating. During the past 2 yr, large numbers of micrometre sized stratospheric particles have been collected which are believed to be extraterrestrial, because their elemental compositions closely match those of primitive meteorites. We report here the detection of large concentrations of 4He in some of the particles. This not only suggests an exposure to solar wind, but also indicates that these particles are true micrometeorites in the sense that they were not strongly heated by entry into the atmosphere. Strong heating would have caused much of the helium to escape.

3He, 20,21,22Ne, 14C, 10Be, 26Al, and 36Cl in magnetic fractions of cosmic dust from Greenland and Antarctica

“…Rajan et al (1977) began studies that provided evidence of cosmogenic noble gas isotopes in cosmic dust. This result was confirmed by Hudson et al (1980) and demonstrated independently by Ozima et al (1984).…”

Noble gases in diamonds: Occurrences of solarlike helium and neon

“…Solar wind-saturated cosmic dust with a diameter less than 10 11m contains 0. 1 em• STP /g of He [Rajan et al, 1977] presumed to have the solar He ratio because elemental patterns of the noble gases in dust particles measured by Hudson et al [ 1981] are solar.…”

Solar Wind Noble Gases in Micrometeorites

“…The first report concerning noble gas (2008) and Benkert et al (1993), respectively. compositions of IDPs is that by Rajan et al (1977). They detected very high concentrations of 4 He ranging from 0.002 to 0.25 cm 3 STP/g in ten stratospheric particles collected by NASA U-2 aircraft and asserted that the particles were extraterrestrial and that some or all of them were exposed to solar wind for at least 10-100 years.…”