observations of molecular ices on interstellar dust grains can be used to constrain the physical conditions that were present when the ice first formed. this has already been done in a limited way using the 3.1 um stretching vibration of the most abundant ice, h_2o (smith et al., 1989, apj 344, 413). however, the other vibrations of h_2o ice can also provide important and unique information. we are proposing to use the iso long wavelength spectrometer (lws) to investigate two key problems relating to the formation of icy mantles and the nature of grain surfaces, by observing the far-infrared translational-mode spectrum of h_2o ice in a small, carefully selected sample of objects. the primary objective of this proposal is to measure the relative strengths of three of the translational mode features in the far-infrared spectrum of h_2o ice; these fall at 44 um, 62 um and 165 um. the 44/62 um peak ratio is indicative of the formation conditions of the ice and can be used to trace the temperature history of the dust, e.g. whether it was initially deposited at low temperatures and then warmed up (as might occur when a protostar forms in a molecular cloud) or whether it was initially deposited at high temperatures and then cooled (as might occur in a circumstellar envelope). on the other hand, the strength or even the presence of the 165 um feature seems to be dependant on the nature of the grain surface. in conjunction with existing and ongoing laboratory work we can use the proposed observations to provide a powerful tool for studying the formation of icy grain mantles and the nature of the surfaces they were formed on.
Instrument
LWS01
Temporal Coverage
1996-10-04T18:42:34Z/1997-08-23T06:03:19Z
Version
1.0
Mission Description
The Infrared Space Observatory (ISO) was the world's first true orbiting infrared observatory. Equipped with four highly-sophisticated and versatile scientific instruments, it was launched by Ariane in November 1995 and provided astronomers world-wide with a facility of unprecedented sensitivity and capabilities for a detailed exploration of the Universe at infrared wavelengths.
European Space Agency, 1998, Formation Of Molecular Ice Mantles On Interstellar Dust Grains And The Nature Of The Grain Surfaces., 1.0, European Space Agency, https://doi.org/10.5270/esa-ui7fkh1
