Comets And Deep Fried Ice Cream: the Tasty Similarities

MmmMmm deep-fried ice cream; you ever have it? Cold creamy goodness wrapped in a warm flaky fried shell - the alliteration alone is enough to make my mouth water (what can I say? I'm a writer!) Now an expert at NASA is saying that while comets might not taste as good, they are just like the delicious dessert in terms of formation.

The recent and historic close encounter between the European Space Agency's Rosetta spacecraft and comet 67P/Churyumov-Gerasimenko recently confirmed astronomers' longstanding suspicions that comets have cold, but soft interiors. And that's despite boasting a crunchy outer shell - one tough enough for the Philae lander to audibly bounce off of.

"A comet is like deep fried ice cream," Murthy Gudipati, of NASA's Jet Propulsion Laboratory in Pasadena, Calif., reiterated in a recent statement. "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."

Gudipati and several of his colleagues recently used an icebox-like cryostat instrument nicknamed Himalaya to show how the fresh and fluffy ice of a newborn comet will gradually crystallize and harden as it draws closer to the Sun in a wide, elliptical spiral, just like 67P's own path.

The Himalaya data was recently published in the The Journal of Physical Chemistry.(Scroll to read on...)

It's important to note that in normal Earth conditions, we would never see the amorphous "fluffy" ice that makes up a comet. That's because no where on Earth, even in the Himalayas, is cold enough to flash freeze molecules in their initially chaotic state, trapping even polycyclic aromatic hydrocarbons - ice infused with organics (dust) from the Universe. Even the fluffiest of snow on Earth is actually a loose clump of tiny ice crystals.

Gudipati, who obviously loves his food similes, said amorphous ice is a lot like cotton candy.

However, as the comet's "cotton candy" exterior warms near the Sun, water-ice crystals start to form. The surface becomes denser and more ordered, and the trapped hydrocarbons are freed to race to the comet's surface. The result is a crunchy comet crust sprinkled with organics, with an amorphous ice interior - the "ice cream" of our fried ice cream example - just below.

"It's beautiful to think about how far we have come in our understanding of comets," Gudipati added. "Future missions designed to bring cold samples of comets back to Earth could allow us to fully unravel their secrets."

When that time comes, however, they might want to use some new similes. We wouldn't want a hungry researcher "taste-testing" the samples, after all.

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