A NASA’s Indian origin scientist has used an icebox-like instrument nicknamed ‘Himalaya’ to show how fluffy ice on the surface of a comet would crystallise and harden as the comet heads toward the Sun and warms up.
As the water-ice crystals form, becoming denser and more ordered, other molecules containing carbon would be thrown up to the comet’s surface, resulting in a crunchy comet crust with organic dust, said NASA in a statement.
“A comet is like deep fried ice cream. The crust is made of crystalline ice, while the interior is colder and more porous. The organics are like a final layer of chocolate on top,” explained Murthy Gudipati of NASA’s Jet Propulsion Laboratory in Pasadena, California.
Though it is known already that comets have soft interiors and seemingly hard crusts, the new study, by Gudipati and Antti Lignell, post-doctoral scholar at the California Institute of Technology, put together a model of crystallising comet crust for a deeper study.
The experiments began with amorphous or porous ice — the proposed composition of the chilliest of comets and icy moons, in which water vapour molecules are flash-frozen at extremely cold temperatures of around minus 243 degrees Celsius.
Gudipati and his team used their Himalaya to slowly warm their amorphous ice mixtures to minus 123 degrees Celsius, creating similar weather conditions a comet would face as it journeys toward the sun, sort of like Han Solo in the Star Wars movie “The Empire Strikes Back.”
The ice had been infused with certain organics called polycyclic aromatic hydrocarbons (PAHs) which are seen everywhere in deep space, said the researchers. “What we saw in the lab – a crystalline comet crust with organics on top – matches what has been suggested from observations in space,” Gudipati said.
“Deep-fried ice cream is really the perfect analogy, because the interior of the comets should still be very cold and contain the more porous, amorphous ice,” he pointed out.
In view of new results from the Rosetta mission, it is known that asteroids may have been the primary carriers of life’s ingredients. Gudipati said comets are capsules containing clues not only to our planet’s history but to the birth of our entire solar system.
The study appeared in the Journal of Physical Chemistry.