A Representation of an Interstellar Ice Grain

Since there is far more hydrogen than anything else the condition of the hydrogen determines what the ice mantles will look like. So, if the hydrogen is atomic then it will add to the less abundant elements (like C, O, and N) making reduced compounds like water (H2O), methane (CH4), methanol (CH3OH), and ammonia (NH3).

If the hydrogen is molecular then the C, O and N have a chance to react with one another forming molecules like CO, N2, and O2. Once these ice mantles are exposed to radiation all kinds of reactions occur.

Comparisons between the infrared absorption bands seen through the telescope and measured in the laboratory have been used to constrain the composition of these clouds. As a result IR astronomers now know the composition of clouds many light years away. Please follow these links for a representation how this is done, and for more technical details) about IR spectroscopy.


Go to the Astrochemistry Home PageGo to the SETI InstituteGo to the NASA Astrobiology InstituteGo to the Ames Space Science DivisionGo to the NASA Ames Research CenterGo to NASA

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