Clear evidence of liquid water on Mars

 Discovery of Clear evidence of liquid water on Mars     

Curiosity Rover uncovers 3.7-Billion-Year-Old Ripples which suggest Mars once had Ice-Free Lakes. Ancient ripples suggest a warmer, wetter past for the Red Planet that supported open water on its surface. The existence of water on Mars has long been a subject of curiosity and debate. A recently published study presents compelling evidence of ancient “wave ripples” in rocks that were shaped by Martian water and winds billions of years ago. These ripples, imprinted on the Martian surface, speak to a time when shallow bodies of water were open to the Martian air. In the dusty, rust-coloured expanse of Gale Crater on Mars, NASA’s Curiosity rover has uncovered a ghostly echo of a long-lost world. Etched into the rock are tiny undulations, ripples frozen in time, preserved for billions of years. These ripples, scientists say, are the telltale marks of waves that once lapped the shores of an ancient Martian lake. The discovery offers some of the strongest evidence yet that Mars was once a planet of liquid water, not just ice. The ripples, formed 3.7 billion years ago, suggest that the Red Planet’s climate during that time was warm and dense enough to support liquid water exposed to the atmosphere. This hints that Mars may have been habitable for longer than previously thought.

The importance of these ripples cannot be overemphasized as they provide clear evidence of the existence of a standing body of water on Mars approximately 3.7 billion years ago. This profound discovery paints a picture of a time when the Martian climate was seemingly warm enough to support liquid bodies water, not just frozen ice fields, that were open to the air. “The shape of the ripples could only have been formed under water that was open to the atmosphere and acted upon by wind,” observed Claire Mondro, a postdoctoral scholar from The California Institute of Technology (CalTech) and the study’s first author. The notion that Mars once harboured liquid water on its surface is almost unanimous among scientists. Evidence includes ancient river valleys, dried-up lakebeds, and mineral deposits like clays and sulphates which form in the presence of water. Additionally, the presence of hematite, a mineral that often forms in water, and the detection of hydrated minerals further support the idea that Mars had a watery past. Dr. Michael Lamb, a geology professor at Caltech, painstakingly created computer models based on these ripples to estimate the size of the ancient Martian lake. Lamb’s extensive experience in studying sediment, water and atmosphere interactions on Earth lent credibility to this model. The ripples, a mere 6 mm's high and spaced 4 to 5 cm's apart suggest the existence of a shallow lake, no deeper than about 2m (6.5 ft). Mondro’s observations lend further weight to these inferences. “Extending the length of time that liquid water was present extends the possibilities for microbial habitability later into Mars’s history,” she pointed out. However, whether any of this water was ever in liquid form while exposed to the atmosphere is less clear.

Discovering that Mars once had liquid water is a game-changer for our understanding of the planet and the broader possibilities of life beyond Earth. Water is a fundamental ingredient for life as we know it, so finding evidence of past liquid water raises exciting questions about whether Mars could have supported microbial life. Beyond the search for life, knowing that Mars had liquid water has practical implications for future human missions. Water is a crucial resource for astronauts, not only for drinking but also for producing oxygen and even rocket fuel. If remnants of ancient water sources or ice deposits exist on Mars, they could be tapped into to support long-term human habitation and exploration. The ripples were found in two distinct rock formations within Gale Crater, a 96-mile-wide basin that Curiosity has been exploring since 2012. One set of ripples, located in an area called the Prow outcrop, lies within what was once a field of wind-blown sand dunes. The other, found in the sulfate-rich Amapari Marker Band, points to the presence of a shallow lake. Both sets of ripples are small, but their implications are enormous. These marvellous ripples went unnoticed until NASA’s Curiosity rover documented them in 2022 during its expedition across the Gale Crater region of Mars, a region that was once home to wind-blown dunes. 

A nearby band of rock, the Amapari Marker Band, hinted at the existence of another lake, approximately 6.5 feet (2 meters) deep, that formed slightly later in Mars’s history than the previous one. “The discovery of wave ripples is an important advance for Mars paleoclimate science,” noted John Grotzinger, the Harold Brown Professor of Geology at Caltech. “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,” added Grotzinger, a former project scientist for Curiosity’s Mars Science Laboratory (MSL) mission. It seems we are just scratching the surface of understanding the red planet’s past, and with each discovery, we inch closer to unravelling the mysteries of Mars and its potential for supporting life.

“The shape of the ripples could only have been formed under water that was open to the atmosphere and acted upon by wind,” says Claire Mondro, a postdoctoral scholar at Caltech and lead author of the study. “This means the water wasn’t frozen. It was liquid, and it was exposed to the air.” The discovery of these ancient ripples offers a crucial glimpse into Mars’s climate history, providing scientists with valuable data to reconstruct the environmental conditions that existed billions of years ago. The ripples’ size and spacing suggest the lake was shallow, less than 2m deep. But what’s most striking is their age: 3.7 billion years old. This places them in a period when Mars was thought to be drying out, losing its water to space. The discovery suggests that pockets of liquid water persisted longer than scientists had assumed, potentially extending the window of habitability for microbial life. The presence of liquid water suggests that Mars once had a significantly thicker atmosphere that was capable of sustaining warmer temperatures. Over time, the planet’s climate underwent drastic changes, leading to the loss of surface water and the thinning of its atmosphere.

Understanding these transitions is key to determining how long Mars could have supported habitable conditions and whether it might have once harboured microbial life. Scientists believe that further exploration of ripple formations could shed light on the duration and stability of these ancient lakes, helping to piece together the timeline of Mars’ environmental shifts. The findings from Curiosity’s observations could play a pivotal role in shaping the objectives of upcoming Mars missions. Future rovers and landers, equipped with more advanced instruments, may focus on analysing ripple formations in greater detail, searching for chemical signatures that indicate past life-supporting conditions. The Perseverance rover, currently exploring Jezero Crater, has already been tasked with collecting samples that might contain traces of ancient microbial activity. These efforts align with NASA’s long-term goal of bringing Martian samples back to Earth for comprehensive laboratory analysis. Many models have previously suggested that water on the planet’s surface would have been locked under thick ice, given the faintness of the young Sun and Mars’s greater distance from it. However, these ripples would beg to differ. Mars seemed to have had open water on its surface and may have supported these conditions for quite some time. The Prow ripples formed earlier than those in the Amapari Marker Band, suggesting that conditions suitable for liquid water occurred multiple times — or lasted for an extended period. This raises the possibility that Mars’ climate oscillated between wet and dry phases, rather than undergoing a single, irreversible drying event. “At the time of ripple formation, climate conditions must have supported ice-free liquid water on the surface of Mars,” the study states.

What This Means for Life on Mars?

John Grotzinger, a geologist at Caltech and former project scientist for the Curiosity mission, calls the discovery a “game-changer” for Mars paleoclimate science. “We’ve been searching for these features since the Opportunity and Spirit missions began in 2004,” he says. “Earlier missions found evidence of flowing water, but it was unclear if that water ever pooled into lakes or seas. Now, we have proof of ice-free lakes.” Liquid water is a key ingredient for life as we know it, and the presence of open water increases the chances that microbial life could have thrived. “Extending the length of time that liquid water was present extends the possibilities for microbial habitability later into Mars’ history,” Mondro says. While scientists have yet to present any solid proof of ancient life on Mars, the new findings have painted a picture of a planet that was once far more Earth-like. Gale Crater, for instance, is thought to have been a large lake system which persisted for millions of years. The ripple evidence on Mars is also encouraging for future crewed missions, as understanding past water sources could help identify potential locations for human exploration and resource utilization.