Synthesizing the 'Stuff' of Comets

Here's a simple way to produce something only seen in nature in the deep reaches of interstellar space ...

We started out with a two-liter (2 L) beaker of liquid nitrogen (N₂) boiling at a temperature of 321 degrees Fahrenheit below zero (i.e., -321 °F) as shown in the photo below. This beaker is essentially filled with liquid air since most of Earth's atmosphere is composed of nitrogen gas. The condensation you see on the external sides of the beaker is a mixture of frozen water vapor (i.e., ice) and liquid oxygen (which starts to condense at temperatures greater than that of nitrogen).

 

Initial 2 L Beaker of Liquid Nitrogen at -321 °F

 

The liquid nitrogen was then transferred into a smaller 500 mL beaker and placed inside a vacuum chamber as shown in the two photos below. Make note of the vigorous boiling action occurring inside the beaker.  

  

Liquid Nitrogen Boiling in a Vacuum		Close-up of Boiling Action

  

It took approximately 90 minutes under the application of a vacuum for the temperature to transition the mere -26 degrees Fahrenheit from boiling liquid nitrogen (-321 °F) to solid {frozen} nitrogen gas (-346 °F), with the length of the process being solely a function of the small two-stage 3 CFM vacuum pump being used in the lab. The entire process is shown in the time-lapse video below where we have compressed the 90 minute process into two-minutes (this is a large video, you might have to wait a minute for it to fully load).

Time Lapse Video of Nitrogen Gas Freezing into a Solid  

Initially we observe a rapid boiling of the liquid nitrogen with significant condensation vapor present. After the liquid level drops to about 50% of the initial 500 mL volume, the rate of boiling slows down considerably and the liquid is within a few degrees of the freezing point. Once the liquid nitrogen reaches the freezing point, we can see rapid 'ice' crystal formation and the remaining liquid freezes within a couple of minutes. The condensation observed is frost {water ice} forming on the outside of the vacuum bell jar, which can be seen in the first photo below. The second photo shows the finished product, instant 'comet stuff'.

 

Photo of the Frozen Vacuum Bell Jar		Frozen Nitrogen Gas at -346 °F

Outside of a laboratory setting, solid nitrogen is only predominately seen in interstellar space within comet fragments and within the craters of asteroids. It is a transient substance for once we remove the applied vacuum, it rapidly melts back to liquid nitrogen and from there to its gaseous state. The sample shown in the above photo is held in place at a temperature of 114 degrees Fahrenheit above absolute zero (absolute zero is approximately -460 °F)