Word of the Month: Ice!

Word of the Month is a new column from amateur astronomer Scott Levine looking at how a single concept can tell us about the workings of the Universe, with a quick sketch to outline his thoughts.

This month, Scott explores how ice is a phenomenon found throughout our Solar System.

Scott's sketch: Ice water keeps us cool on Earth during the hotter months, but finding ice elsewhere in the Solar System can be a major discovery that changes our understanding of a moon or a planet.
Credit: Scott Levine


Ice? But it’s summer!

Most of us don’t spend a lot of time thinking about ice unless we’re also thinking about skating and sledding, maybe in festively ugly sweaters. What better way to keep cool, though?

Here on Earth, we usually think of ice as frozen water. It’s plentiful, fairly easy to come by, and it comes in a surprising number of different forms; icicles, snowflakes, tasty desserts.

But that’s not all. As robotic probes travel out into the Solar System and better telescopes let us peer deeper into its farthest corners, we’ve learned about different types of ice at other places.

We’ve seen snows of sulphur dioxide on Jupiter’s moon Io. Methane snow falls on Saturn’s moon Titan and also on Pluto. There’s ammonia ice in the atmospheres of the Solar System’s giant planets.

And there are mountains of water ice floating in a slushy-icy sea of nitrogen on Pluto, presumably splashing over the rails on ships full of vacationing office workers.

We’re even finding more and more water ice in comets, moons, Saturn’s rings; seemingly everywhere we look.

An image of the Cthulhu region on Pluto, showing bright surface material on its highest peaks. NASA scientists believe this may be methane ice that has condensed from Pluto’s atmosphere.


Ices are substances we usually think of as being a liquid or gas that has been frozen, brought to their solid form by cold temperatures.

It’s pretty easy to see a similarity between dry ice (frozen carbon dioxide) and water ice. They’re different from my wooden chair and the linoleum kitchen tiles it’s sitting on, which aren’t crystalline or in any real danger of liquefying.

I imagine very few people would offer their friends a refreshing glass of chair after a linoleum snowball fight.

We might not spend a lot of time thinking about ice but it’s everywhere and it’s amazing.

Maybe have another look while it melts away in your glass on one of these warm summer afternoons.


About the author

Scott Levine is a dad and astronomy lover who stares at the sky over his family’s home north of New York City. You can read more of his light-hearted look at astronomy at Scott’s Sky Watch.


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