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Re: Great Siberian Explosion
Hello again!
> It has been reported that they are dirty snowballs of
> water, amonium, dirt, etc. What else is there? - dona
Some Halley data:
Coma: 10 tons/s water vapor production
Dust: 3.1 t/s (production rate at closest approach)
Ions: C+ H+ O+ S+ He+ H2O+ H3O+ CO+ OH+
Dust: C H O N Mg Si Fe
NATURE, No. 6067, 15-21 May 1986:
Neutral gas and dust:
In the internal part of the coma (< 500 km from the nucleus), H2O and
CO2 were identified by their infrared spectra. CO2 is probably the
second most abundant species after H2O in the set of parent molecules.
Many secondary species (such as OH, C2, CH, CN, NH) were revealed by
numerous spectra.
The spectra can be classified into three different groups:
(1) spectra of particles with an elemental composition reminiscent of
type C1 carbonaceous chondrites (C, O, Na, Mg, Si, Ca, Fe);
(2) spectra that differ from group (1) spectra by the presence of
considerable carbon (12C and 13C) and nitrogen; and
(3) spectra of H2O or H2O/CO2-clathrate ice (clathrate = resembling a
lattice framework).
Spectroscopic study of comet Halley by the Vega 2 spectrometer:
The spectrometer aboard the Vega 2 spacecraft recorded infrared and
visible spectra near the nucleus of comet Halley. Spectra at a distance
of 300 km from the nucleus the H2O and OH bands, the latter excited by
dissociation of a parent molecule. The dust particle density is 0.35 g
cm-3, typical of fluffy particles of interplanetary dust. The ratio of
the production rates of C2, C3 and CN to that of OH are close to those
of comet Bradfield 1979. The OH production rate contrasts strongly with
the water vapour production rate obtained from the H2O band and may
indicate the existence of parents of OH other than H2O.
Near-ultraviolet and visible spectrophotometry from Vega 2:
The emission from dust (the continuum) is as intense as that of the
gases. The most prominent emissions are the usual ones; that is, OH, NH,
CN, CH, C2, C3, NH2. A feature that is present with variable intensity
can probably be attributed to the S2 molecule, as already observed in
comet IRAS-Araki-Alcock.
Best wishes,
Bernd
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