Podcast Summary: Short Wave — "An Icy Mystery: What Are Lake Stars?"

Podcast: Short Wave (NPR)
Episode Title: An Icy Mystery: What Are Lake Stars?
Air Date: March 13, 2026
Hosts: Regina Barber
Guest Expert: Victor Tsai, Geophysicist, Brown University

Overview

In this enlightening and playfully-scientific episode, host Regina Barber explores the mysterious patterns known as "lake stars" alongside geophysicist Victor Tsai. What starts as NPR producer Burley McCoy’s fascination (and concern) with odd star-shaped ice patterns on her local frozen lake spirals into an investigation of the physics behind lake stars, their DIY recreation, and their uncanny resemblance to massive formations on Europa, Jupiter’s icy moon. The episode also addresses important questions about ice safety, all in under 15 minutes.

Key Discussion Points & Insights

1. The Mystery on the Lake (00:20–00:50)

• Burley McCoy discovers star-shaped, spidery patterns in the ice on her local frozen lake.
  • "They were black and branching and they kind of just made me nervous because I spent a lot of time on the ice and I hadn't seen them before and I didn't know what they were." — Burley McCoy (00:37)

2. Introducing the Expert: What Are Lake Stars? (00:57–02:26)

• Lake Stars Defined:
  • Victor Tsai explains: “They're actually quite common, but you need a particular set of circumstances to happen.” (00:57)
  • Lake stars emerge when snow covers a thin ice sheet over a lake, and a hole in the ice allows relatively warm lake water to seep up, melting slushy paths in a star-shaped pattern.
  • “If a small hole forms on the underside of that ice, that allows warm lake water to seep up through that hole and then melt through this slushy snow layer and eventually form these star patterns.” — Victor Tsai (02:43)

3. Lab Science: Recreating Lake Stars (03:08–06:06)

• Laboratory Lake Stars:

  • Without winter ice for field studies, Tsai devised an experiment with a kitchen blender to make slush in a cold lab.
  • “I purchased a blender... I found that playing around with different blender settings, I could make a slush that was similar to what we observe.” — Victor Tsai (03:31)
  • Experiment involved slowly dripping just-above-freezing water onto the slush to mimic lake conditions.
  • Key procedural insight: It’s all about slowly dripping water—"like a leaky faucet"—to see branching, star-like patterns instead of just a melted puddle or a 'snake' channel. (04:39, 06:52)

• DIY Lake Stars at Home:

  • Listeners encouraged to try the experiment at home using a blender to make slush and drip cold (but not too warm) water over it.
    • “You can do exactly what I did. Take a kitchen blender, form some slush, place it on a flat surface, and then try to pour some slightly warm water through that slush pattern.” — Victor Tsai (05:08)
  • Patience is key—too much or too warm water destroys the pattern.

4. Earth to Space: Lake Stars and Europa (06:58–10:11)

• Jupiter's Moon Europa:

  • There is a "spider" or "star-like" formation on Europa—a mile-wide feature resembling lake stars.
  • Europa's icy surface and hidden ocean make these features tantalizing.
  • Tsai’s group found that the same physics explaining Earth’s lake stars might explain Europa’s spider:
    • “This same theory that we could use to explain lake stars on Earth could approximately make a feature that looks like what's observed on Europa.” — Victor Tsai (08:22)
  • Physical experiments: Similar slushy setups used in the lab to model these extraterrestrial patterns. (08:55)

• Significance for Space Exploration:

  • If Europa’s spider patterns are made by water closer to the surface, that could shape future missions.
  • "If it’s 40km thick, that ain’t happening. But yeah, if it’s right near the surface, then yeah, maybe we can get in there." — Regina Barber (10:48)
  • "If we really want to have a better chance of knowing whether or not there is life in that water down there, the easiest way to do it is to really drill there and sample it and see what's there." — Victor Tsai (10:26)

5. Practical Takeaway: Are Lake Stars Safe? (10:53–12:14)

• Ice Safety:
  • Recent lake stars = thin, risky ice—stay off!
  • “If a lake star had recently formed, then it would be very not safe. ...But in many cases you get very thick ice forming afterwards that preserves the lake stars. ...Most of the cases where people have observed them are in cases where there's thicker ice.” — Victor Tsai (11:23–12:06)
  • General advice: If you see a lake star, wait a few days—the ice may become safer after thickening.

Notable Quotes & Memorable Moments

• “It wouldn't be a star, it'd be a snake.” — Regina Barber (06:52)
• “I purchased a blender... playing around with different blender settings and things like that, I could make a slush that was similar to what we observe.” — Victor Tsai (03:31)
• “That's a very big lake star.” — Regina Barber, on Europa’s kilometer-sized feature (08:01)
• “If we really want to have a better chance of knowing whether or not there is life in that water down there, the easiest way to do it is to really drill there and sample it and see what's there.” — Victor Tsai (10:26)

Important Timestamps

• 00:37: Discovery of mysterious ice patterns
• 02:32: Explanation of how lake stars form
• 03:31: DIY approach using a blender for slush
• 05:08: How to try making lake stars at home
• 06:52: Explanation of the "snake" vs "star" formation
• 07:20: Linking lake stars to Europa’s spider features
• 09:17: Why this matters for understanding Europa
• 11:23: Advice on ice safety around lake stars

Final Thoughts

This episode offers a delightful blend of curiosity-driven storytelling, practical DIY science, and a cosmic perspective—showing how a seemingly small icy mystery from Earth might hold clues for distant moons. It’s engaging, accessible, and leaves listeners with both knowledge and wonder, along with real-world safety advice for winter lake exploration.