As the fragment falls through the atmosphere, it is heated and some of the material is vaporized. Explain how you could determine the composition of this hot vaporized material from the light it emits.
Asteroid fragments cannot be approached too closely; hence spectral analyses are all remote based.
Several important components of asteroids can be detected from the emission spectrum in the near UV till the IR region. Some common diagnostic absorption features that are detectable from the spectra in this region are due to i) ice of H2O and CO2, ii) presence of iron from characteristic bands of iron bearing minerals pyroxene, olivine and plagioclase.
X-Ray Spectroscopy and Gamma Ray Spectroscopy are two important techniques commonly used for characterization of elemental composition of asteroids.
“When highly energetic radiation or particles fall upon the asteroid's surface materials, each type of atom in these materials responds by emitting radiation in a characteristic frequency. These characteristic frequencies then identify the atoms that are present in the surface soils. X-rays from the sun provide the incident radiation for the x-ray spectrometer. High-speed atomic nuclei (cosmic rays) from space are responsible for inducing the high frequency radiation measured by the gamma ray spectrometer.”
X-rays provide information on the light elements, Mg, Al and Si.
Gamma ray spectroscopy is useful for detecting K and U abundances and for determining elemental ratios such as Fe/Si and Mg/Si. Often the X-ray spectroscope is coupled with an alpha emitter (curium) which bombards the vaporized surface materials with alpha particles and emits characteristic X-ray spectra that is highly useful for detecting the presence and abundances of light elements like C, N, O, F, Na.
Altogether, these remote spectroscopic techniques can analyze the emitted light for detecting as well as measuring abundances of many of the elements expected to be present in the surface of the asteroids and thus make substantial contribution to chemical analysis of such bodies.
Than you so much. Your explanation was very clear to understand.