Although Mars is known for being a dry and desolate desert, its landscape hasn’t always been so hostile. Rivers and lakes were once present on the Red Planet before it began to dry up somewhere around 3 billion years ago. The latest research has explored evidence from this distant chapter of Mars’ past, revealing ancient sources of water in the Gale crater region that evaporated and left behind wave ripples.
Researchers have investigated these geological clues in a recent study published in the journal Science Advances. They concluded that the presence of wave ripples formed 3.7 billion years ago indicates that Mars’ climate was warm and dense enough to maintain bodies of water not covered by ice, and therefore open to the Martian air.
"The discovery of wave ripples is an important advance for Mars paleoclimate science," said John Grotzinger, geology professor at Caltech and a principal investigator of the study, in a statement. "We have been searching for these features since the Opportunity and Spirit landers began their missions in 2004."
Discovering the Ripples
The ripples were first discovered in 2022 as NASA’s Curiosity traversed through Mars’ Gale crater, an 96-mile-wide (154 km) impact basin that had been filled with lakes and streams billions of years ago.
Researchers found one set of ripples in an area called the Prow outcrop, which used to contain wind-blown dunes; another set of ripples was found in the nearby Amapari Marker Band (AMB), a layer of rock likely tied to a 2-meter-deep ancient lake that previously existed. The AMB ripples occurred slightly later in Mars’ history than the Prow outcrop ripples, suggesting that the atmospheric conditions for both ripple formations occurred at multiple points in time.
Read More: Life on Mars May Have Evolved Like a Nice Risotto – Not Too Moist and Not Too Dry
Evidence of a Shallow Lake
In the new study, the ripples were analyzed in computer models to determine the size of the lake and where they originated. The ripples themselves were only 6 millimeters high and spaced 4 centimeters to 5 centimeters apart, conveying that the movement of small waves formed them. This led the researchers to deduce that the lake was shallow, at less than about 2 meters deep.
The researchers assert that the ripples represent wind blowing on open water. Some studies in the past have advanced the possibility of ice-covered lakes on Mars, but the AMB and Prow outcrop ripples distinctly show evidence of ice-free bodies of water.
"Earlier missions, beginning with Opportunity in 2004, discovered ripples formed by water flowing across the surface of ancient Mars, but it was uncertain if that water ever pooled to form lakes or shallow seas. The Curiosity rover discovered evidence for long-lived ancient lakes in 2014, and now 10 years later Curiosity has discovered ancient lakes that were free of ice, offering an important insight into the planet's early climate," said Grotzinger.
Why Did Mars Dry Up?
The study of the AMB and Prow outcrop ripples has helped to fill in a murky part of Mars’ history going back billions of years. Scientists aren’t certain, however, about the exact details surrounding the transition of the planet’s climate from wet to dry. Billions of years ago, Mars was also warmer than it is now — the median surface temperature of Mars today is around negative 85 degrees Fahrenheit (negative 65 degrees Celsius).
The climate of ancient Mars struck a balance that allowed water to exist; in particular, the late Noachian period (about 4.1 billion years to 3.5 billion years ago) is thought to have been a time when Mars was potentially habitable, even having rainfall that caused erosion.
The most common interpretation for Mars’ transition to a dry climate is that intense solar wind stripped a significant amount of carbon dioxide (which also kept the planet warm) from the atmosphere, making it much thinner. A 2024 study in Nature Geoscience also claimed that the drying period was not one single transformation, but seven fluctuating climate transitions that may have even allowed water to exist periodically after 3 billion years ago.
Although a consensus on the climatic mysteries of Mars hasn’t yet been solidified, scientists are still hard at work trying to find any signs of life that may have once existed on the planet.
Read More: 5 Martian Mysteries That Have Scientists Scratching Their Heads
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
Science Advances. Wave ripples formed in ancient, ice-free lakes in Gale crater, Mars
NASA. Long lived ice-covered Hesperian lakes in Gale Crater, Mars
NASA. NASA-Funded Study Extends Period When Mars Could Have Supported Life
Nature. Geological evidence for multiple climate transitions on Early Mars
Jack Knudson is an assistant editor at Discover with a strong interest in environmental science and history. Before joining Discover in 2023, he studied journalism at the Scripps College of Communication at Ohio University and previously interned at Recycling Today magazine.
