The Great Salt Lakes of Mars

The Cosmic Companion
Oct 22 · 4 min read

Mars may have once been home to large salt lakes similar to those found in South America, a new study reveals. So, where did they go?

A selfie taken of Curiosity on Mars. This mosaic photo is created from 92 separate images taken by the Martian rover. Image credit:

Massive salty lakes may have once dotted the Martian landscape, a new study from Texas A&M reveals. Examining the geological terrain of Gale Crater on Mars also revealed the Red Planet experienced wet and dry periods which could have been a prime mover of the environment on that world.

Gale Crater stretches 158 kilometers (95 miles) across, and has been explored by the Curiosity rover since 2012 as part of NASA’s Mars Science Laboratory (MSL) mission. This sizable geological feature was formed 3.6 billion years ago when a massive body impacted the surface of the Red Planet.

“Since then, its geological terrains have recorded the history of Mars, and studies have shown Gale Crater reveals signs that liquid water was present over its history, which is a key ingredient of microbial life as we know it,” Marion Nachon, a postdoctoral research associate in the Department of Geology and Geophysics at Texas A&M, said.

A flat, red rock, surrounded by darker crust.
A flat, red rock, surrounded by darker crust.
“Old Soaker,” a rock slab on the surface of Mars, which may have been formed three billion years ago, as mud hardened as the climate of Mars became hotter and dryer. Image credit: NASA/JPL-Caltech/MSSS

Researchers believe the ancient salt lakes on Mars were much like those found in South America, especially those found in the Altiplano region near the border between Bolivia and Peru. There, rivers and streams running off mountains send water into a basin, rather than to an ocean or sea. Geologists studying Mars believe Gale Crater once had a similar environment.

A dry, flat plain with a shallow body of water.
A dry, flat plain with a shallow body of water.
The Quisquiro salt flat in Altiplano, Chile. Image credit: Maksym Bocharov

“Gale Crater is the ancient remnant of a massive impact. Sediment carried by water and wind eventually filled in the crater floor, layer by layer. After the sediment hardened, wind carved the layered rock into the towering Mount Sharp,” NASA reports.

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AN illustration of a car-sized robot on wheels and tracks traveling on Mars
AN illustration of a car-sized robot on wheels and tracks traveling on Mars
An artist’s concept of the Curiosity rover traveling along the Martian surface. Image credit: NASA/JPL

Since 2012, the Curiosity Mars Rover has explored Gale Crater and surrounding regions, utilizing 17 instruments in an effort to learn if the environment there is, or was ever, capable of supporting life.

Curiosity recently found an ancient oasis on the Red Planet, and the findings lend evidence to the idea that Gale Crater was once dotted by small ponds.

“This latest clue may be a sign of findings to come as Curiosity heads toward a region called the “sulfate-bearing unit,” which is expected to have formed in an even drier environment. It represents a stark difference from lower down the mountain, where Curiosity discovered evidence of persistent freshwater lakes,” NASA reported in October 2019.

Studies of Gale Crater suggest that basin experienced at least one major drought and recovery prior to the final drying out period that forever altered the climate of Mars. It is also possible that water in Gale Crater sat in several separate lakes, which evaporated at different rates.

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“There is every reason to think that in the coming years Mars and its mysteries will become increasingly familiar to the inhabitants of the Planet Earth.”
― Carl Sagan, Pale Blue Dot: A Vision of the Human Future in Space

A self-portrait of the Curiosity rover on Mars, taken at Rocknest, where the robotic explorer first entered Gale Crater. Image credit: NASA/JPL-Caltech/MSSS

Several mysteries of these ancient salt lakes on Mars remain, researchers explain. Not the least of these is discovering how long these ancient salty lakes existed on the surface of Mars before they disappeared.

“During these drying periods, salt ponds eventually formed. It is difficult to say exactly how large these ponds were, but the lake in Gale Crater was present for long periods of time — from at least hundreds of years to perhaps tens of thousands of years,” Nachon describes.

Another puzzle concerns exactly what happened to the lakes, as the surface of Mars developed an arid, desert environment. One idea is that Mars lost its protective magnetic field, allowing the solar wind and radiation to strip the Red Planet of its atmosphere over millions of years.

With an atmosphere becoming thinner, the pressure at the surface became lesser, and the conditions for liquid water to be stable at the surface were not fulfilled anymore. So liquid water became unsustainable and evaporated,” Nachon explained.

A guided video tour of Gale Crater. Credit: NASA Jet Propulsion Laboratory

These new findings provide a chance for researchers to examine the wet-and-dry cycles of ancient Mars, but it also opens up more detailed information about the local geology, and the chance that ancient life once took a foothold in the region.

“They also tell us about the types of chemical elements (in this case sulfur, a key ingredient for life) that were available in the liquid water present at the surface at the time, and about the type of environmental fluctuations Mars life would have had to cope with, if it ever existed.”

This study is detailed in the journal Nature Geoscience.

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The Cosmic Companion

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Writing about space since I was 10, still not Carl Sagan. Mailing List/Podcast: https://thecosmiccompanion.substack.com

The Cosmic Companion

Exploring the wonders of the Cosmos, one mystery at a time

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