What is one proposed model of outgassing from 'Oumuamua?

• A. Solar radiation causing sublimation of water ice.
• B. The direct conversion of nitrogen or carbon monoxide from a solid to a gaseous state without becoming liquid.
• C. Random fragmentation into smaller icy chunks.
• D. Emission of argon gas from the interior.

Answer: (B)

The idea being tested is how outgassing can propel a small body in space. A proposed model for outgassing on 'Oumuamua is that very volatile ices—specifically nitrogen or carbon monoxide—subside directly from solid to gas, bypassing a liquid phase. This sublimation can produce a gas jet that pushes the object, providing the observed non-gravitational acceleration without needing a visible dust coma or tail. CO and N2 sublimate at very low temperatures, so this can happen even far from the Sun, where water ice wouldn’t sublimate as readily and would be more likely to produce a noticeable coma. In contrast, sublimation of water ice near the Sun would likely create a detectable coma, fragmentation isn’t a neat match to the measured acceleration, and argon emission would not naturally account for the thrust observed.