Spaceborne ultraviolet 251–384 nm spectroscopy of a meteor during the 1997 Leonid shower

Abstract

Abstract-We used the ultraviolet to visible spectrometers onboard the midcourse space experiment to obtain the first ultraviolet spectral measurements ofa bright meteor during the 1997 Leonid shower. The meteor was most likely a Leonid with a brightness of about -2 magnitude at 100 km altitude. In the region between 251 and 310 nm, the two strongest emission lines are from neutral and ionized magnesium. Ionized Ca lines, indicative of a hot T = 10 000 K plasma, are not detected. The Mg and Mg" line intensity ratio alone does not yield the ionization temperature, which can be determined only by assuming the electron density. A typical air plasma temperature of T = 4400 K would imply a very high electron density: n e = 2.2 x 10 18 m-3, but at chondritic abundances ofFe/Mg and Si/Mg =1.For a more reasonable local-thermodynamic-equilibrium (LTE) air plasma electron density, the Mg and Mg! line ratio implies a less than chondritic Fe/Mg = 0.06 abundance ratio and a cool non-LTE T= 2830 K ionization temperature for the ablation vapor plasma. The present observations do not permit a choice between these alternatives. The new data provide also the first spectral confirmation of the presence of molecular OR and NO emission in meteor spectra.

Hydrogen Emission in Meteors as a Potential Marker for the Exogenous Delivery of Organics and Water

“…It is not known if they contain water bound to minerals (see discussion in Jenniskens et al, 2004c). On the other hand, OH A-X (0,0) emission at 310 nm has previously been identified in meteor spectra, including those of Leonids (Harvey, 1977;Abe et al, 2002;Jenniskens et al, 2002). We did not find ground-state OH X 2 P Meinel band emission in Leonid spectra, providing support to the hypothesis that the OH originates from the dissociation of water (Jenniskens et al, 2004c).…”

“…Such continuous production of water molecules in the plasma may, in fact, account for the OH ARX emission at 310 nm (Harvey, 1977;Abe et al, 2002;Jenniskens et al, 2002). However, this would imply that much of the hydrogen in the mesopause is not in the form of molecular hydrogen, but rather in the form of hydrates.…”

Quantitative meteor spectroscopy: Elemental abundances

“…Borovicka (1994b) has proposed that a high temperature component is responsible, with an excitation temperature in the range T = 10,000-15,000 K. The idea being that this high temperature component accounts for a small fraction of emitting plasma and is almost completely ionized. Jenniskens et al (2002) has proposed that this hot component could be the cascade phase following the initial collision of air molecules with meteoric atoms and solids. Once the molecules have come to rest with respect to ambient air molecules, the plasma is still hot and would radiate the warm emission.…”

Physical and chemical properties of meteoroids as deduced from observations

“…His resolution in the 388 nm region was, however, lower than that of . The ultraviolet band of OH at 308 nm was tentatively detected by Jenniskens et al (2002) and Abe et al (2005). Russell et al (2000) detected CO, CO 2 , H 2 O and probably CH 4 in the mid-infrared spectrum of a meteor train several minutes after the fireball passage.…”