One theory suggests that composition of the volatiles from volcanic gases was more oxidized. Both are volatiles, so engine residues simply evaporate. These diamonds probably formed in kimberlite magma and sampled the volatiles. Most of the remaining sulfurous volatiles are then removed by low-pressure evaporation. The instrument also measured organic volatiles, such as methane, down to 10 ppb. It also promotes flavor development through frictional heat, release of volatiles and acids, and oxidation. Inside this radius, the dust must consist of silicate grains that lack volatiles. The "ice" may be water, methane, ammonia, or other volatiles, alone or in combination. Successful development of synthetic fruit volatiles has led to increased control of codling moths. They are also used for experiments of reaction kinetics, volatiles and thermodynamics. Thus, the acquired preference for male-derived volatiles reveals an olfactory-vomeronasal associative learning. There are fewer flames, due to reduced volatiles but a generally higher ash content. Some of these spiders are attracted to the smell of volatiles in gasoline. Comets can also run out of volatiles. Volatiles released from the skin can also be detected.