What do cheetahs, ladybugs, and  a lake in Canada have in common?

And no, this isn’t the setup to a bad joke. The answer is that all three  sport a striking pattern of spots.

But while the animals wear  their stylish spots year-round, Canada’s Spotted Lake only pulls  out its polka dots for the summer. And as some of these are many meters  across and have a variety of colors, they make quite the fashion statement! But while Spotted Lake might look  unique, it has actually some competition.

There are several other lakes that share the necessary characteristics  for these stunning spots. Even some on other planets. [♪ INTRO] This polka-dot lake is in Canada,  specifically in British Columbia. And for most of the year, Spotted  Lake doesn’t look spotted at all.

The lake only gets its signature  makeover in the summertime. It’s isolated from other waterways,  and it’s also pretty shallow. So in the warmer months, in a place  with a relatively dry climate, a lot of the water in the lake just…evaporates.

The lack of rain makes the  water level drop low enough that patterns on the lakebed start to appear. These patterns are pools of mineral-dense “brine”, the source of the stunning spots  visible in the photos of the lake. The brine pools are super salty,  and when the water level falls, they get covered in a crust of salt that  forms a shell over the whole lake bed.

The salty crust solidifies over the  mud in between the pools as well, making bridges through the polka dotted landscape. But where do the spots underneath the  lake come from in the first place, and how are they so colorful? Well, turns out it’s a delicate  balance of geology and chemistry that makes this lake such a fashion icon.

Spotted Lake is an alkaline  saline lake, meaning it has a high concentration of salts that are very basic. And as the water evaporates in the summertime, the water becomes so salty  that it’s more like a brine. That brine is denser than water, causing  it to settle on the bottom of the lake.

And as more and more water evaporates, eventually each puddle of brine is surrounded by solid salt rings that form  bridges between the pools. And to be clear, this isn’t  table salt we’re talking about. The most common salts in Spotted  Lake are magnesium sulfate, sodium sulfate, and sodium carbonate.

These salts are a lot of what  gives the spots their color, so each brine pool’s unique composition  plays a role in its appearance. Magnesium and sodium salts make up most of the white crusts on the pools’ surface. Meanwhile, some of the other striking  hues come from different concentrations of magnesium salts, silicates, and  other minerals in each pool, many of which formed the aptly-named  greenstone that lies underneath the lake.

On top of that, there’s some microscopic  life that can impact the color. Even though a briny lake sounds  like a horrible place to live, there are algae and microbes that can  contribute to the hues of some pools. Layers of bacterial biofilm known as  “microbial mats” can form in the lake, and give some of the brine pools  a green, black, or purple sheen.

And these brine pools aren’t  just pretty, they’re also useful. The mineral-rich pools once made Spotted Lake a prime site for mining metals  like magnesium and calcium. Early surveys of the area  around Spotted Lake noted the potential for industrial use of its metals.

Magnesium mined from the lake bed was even used to make ammunition during World War I. But since then, the lake has been  protected from industrial use and public intervention, and it’s now under the  stewardship of the Syilx First Nations people. They’ve revered Spotted Lake  as a sacred site for centuries, and historically used it as a  medicine lake with healing properties.

In 2001, the Syilx reclaimed the land around Spotted Lake to preserve the cultural site. But it isn’t the only lake on  Earth with this mineral makeup. Similar saline lakes stretch across  Canada and the pacific northwest.

This region has a semi-arid climate,  which produces just the right conditions to make all of the lakes tend to  evaporate in the summer, leaving behind mineral deposits in pools and producing  that otherworldly polka-dot effect. And I don’t just mean otherworldly  as a figure of speech. The Spotted Lake might have a twin…on Mars.

Or at least, it had a twin…a  few billion years ago. But don’t worry, its mineral deposits  don’t look a day over one million. Martian samples found deposits of minerals  very similar to those in Spotted Lake, including magnesium and  sodium salts and silicates.

An eagle-eyed undergraduate named  Kevin Cannon made this connection as a geology student back in 2012,  as one of many scientists who have noticed that the hydrogeology of  Earth and Mars have a lot in common. So Earth lakes could be used to study  ancient Mars lakes that have dried up, based on the composition  of their mineral deposits. Studying these lakes could  give scientists a peek into the history of Mars using what’s in our own backyard.

So if you’re ever up in British Columbia  in the summer, see if you can spot the Spotted Lake at its most fashionable. But  don’t be too *salty* if it out-dresses you. [♪ OUTRO]