Why are compounds such as ammonia most common in the outer solar system?

Answer 1

Although this question is controversial, scientists have found somewhat more ammonia, water, sulfur dioxide, and many other nitrates and hydrocarbons to be found in the outer solar system. Here's my theory. Such compounds tend to break down at higher temperatures and have high vapor pressures at low temperatures. Either solar wind gets to these compounds and breaks them into their elements or their isn't enough atmospheric pressure and gravity to keep them from drifting into space as they become gasses. Earth and Venus somewhat (although mainly CO2, Sulfur Dioxide and sulfuric acid) are exceptions because they have at least one of these : sufficient gravity , sufficient magnetic fields to keep solar wind out, and/or enough atmospheric pressure so that the molecules will keep an affinity for each other and solar wind will not blast it into space. Earth and Venus are not known to have as much because in theory, in the creation of the solar system, many of these molecules were destroyed and we never gained them back. However in the outer solar system, the elements in the original nebula were warm enough to react after a previous star supernovaed but when the sun formed these compound cooled very quickly and many of these bodies in the outer solar system were affected by solar wind. Mostly, these compounds stayed locked up in many solid objects at any where from 20 K to 100 K which is substantially cold and they are extremely stable solids. The reason we see them appear as liquids and gasses at some point is because of either inter-tidal forces between the gas giants and these small bodies, or one tends to be exposed to a more intense sun on an elliptical path into the more inner solar system. Basically to sum it up, these compounds are more stable where it is colder and their is higher atmospheric pressure and their is less solar radiation.

Answer 2

Compounds like ammonia are common in the outer solar system because the colder temperatures allow for them to exist in a solid state or as ices. Additionally, these compounds were more abundant in the outer regions during the early formation of the solar system.