Cookin’ Up a Comet

Manchester Science Festival is rapidly approaching, and we are busy planning and preparing our activities for the Meteorite Day on Monday 29th October.

Some of the equipment and ingredients needed to make a comet in the lab – dry ice, Coca-Cola, hammer, mixing bowl, hair dryer, etc.

One of the things we want to show visitors is a “real” comet, based on NASA’s Cookin’ Up a Comet. And in the name of science, we thought we should try it out ourselves first! So this morning we gathered together all the necessary ingredients and equipment, and had a go at making our very own comet in the lab.

The dry ice needs to be mixed with sand, water and Coca-Cola.

Our comet, straight out of the mixing bowl

Comets are often described as big, dirty snowballs. They are primarily made up of mixtures of dust, rocks, ice, frozen carbon dioxide and ammonia. They have irregular shapes, and can be 1000’s of metres across. Our comet wasn’t quite that big! It was more like 20cm across. But the materials we used to make it are representative of those in a real comet.

Comets spend much of their time in the cold, frozen, outer regions of our Solar System. But occasionally their orbits bring them close to the sun. The heat from the sun causes the volatile material to change into gases. These gases escape from the snowball (or nucleus), taking some of the dust with them.  The escaping gases and dust are known as the coma, and are illuminated by the Sun when the comet passes through the inner solar system, making it visible from Earth. A comet also has a tail, which always points away from the Sun.

As the comet warmed up we could see jets of gas coming off it as the dry ice (solid carbon dioxide) turns into gas.

In January 2004 NASA’s Stardust Mission flew through the coma of Comet Wild 2, and collected some of the dust and other material coming off the comet. Those samples were returned to Earth in January 2006 for scientific analysis. We are in the process of developing a technique to analyse the xenon in the cometary material…

If you’d like to see this in action for yourself, please come along to the Meteorite Day at the Manchester Museum on Monday 29th October. We’ll be there from 11 am till 4 pm, with lots of activities and fun for all the family.


About Sarah Crowther

I'm a Post Doc in the Isotope Geochemistry and Cosmochemistry group. I study xenon isotope ratios using the RELAX mass spectrometer, to try to learn more about the origins and evolution of our solar system. I look at a wide range of samples from solar wind returned by NASA's Genesis mission to zircons (some of the oldest known terrestrial rocks), from meteorites to presolar grains.
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2 Responses to Cookin’ Up a Comet

  1. Ilavenil says:

    Hi, Did you get a tail when you used the hairdryer? I am not able to get one, though the comet came out perfectly.

    • Sarah Crowther says:

      Hi Ilavenil,
      No we didn’t really get a very good tail either. You could see the carbon dioxide subliming, but not enough to make a tail.
      We didn’t use any ammonia, and wondered if that might have contributed to the lack of a tail? We will try with ammonia next time…

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