Intriguing images captured by NASA’s Mars Reconnaissance Orbiter (MRO) reveal unique ridges carved into the martian landscape, indicating that ice once flowed vigorously across the surface of the red planet. These discoveries provide further evidence that Mars was once a water-rich world, with conditions potentially suitable for microbial life.
Orbiter Discovers Distinctive Ridges
On December 15, 2023, scientists published striking images gathered by the MRO spacecraft showing long sinuous ridges spanning nearly a kilometer in length across the martian mid-latitudes [1]. These ridges have a distinctive shape that researchers have never before seen on Mars or any other planetary body [2]. Their winding, intertwining patterns resemble braided streams on Earth, indicating they were carved by flowing material.
Sinuous ridges captured by the Mars Reconnaissance Orbiter [1]
The ridges lie atop a region of Mars called Arcadia Planitia, roughly 1,000 kilometers from the site where NASA’s Perseverance rover landed in 2021. Their winding shapes indicate fluid flows hundreds of meters wide once coursed over the area. According to the research team, led by planetary scientist Dr. Candice Hansen, the patterns provide unambiguous evidence that large amounts of ice sculpted the landscape ~100 million to 200 million years ago [3].
Wet History on Mars
These latest findings add to a growing body of evidence that Mars had a watery past. Rivers, lakes, and even oceans likely covered parts of its surface billions of years ago. As Mars grew colder and drier over geological timescales, much of that surface water froze. Vast deposits of water ice remain locked away under Red Planet sands and soils even today [4].
The newly discovered ridges required large, rapid flows of ice or icy slurries to sculpt the landscape so dramatically. Their winding, interwoven shapes resemble terrestrial features carved by fluid flows exceeding 10 meters per second (over 20 miles per hour). On Earth, such quickly moving fluids include rivers swollen with rainfall or meltwater from glaciers and ice sheets.
Comparison between martian ridges and terrestrial ice flows [5]
To generate such rapid ice movements on modern Mars, which sees little rainfall and peak daily temperatures averaging -20°C (-4°F) globally, scientists propose transient warm periods or briny ice melts as likely causes. Late-stage flows of now-vanished glaciers may have also carved the long sinuous ridges.
Implications for Past Habitability
These latest findings have profound implications for understanding Mars’ ancient climate and potential to host life. Flowing water is an essential ingredient for life, at least as we know it. If ice was dynamic enough to sculpt kilometers-long ridges rapidly, then Mars likely had surface conditions compatible with possible prebiotic chemistry and microbial organisms at various points in its past.
The orientation of the ridges indicates the ice flow direction was guided by local geography and slopes, as flowing liquids are but unconsolidated glacial ice is not. This suggests Mars’ climate swings drove large-scale freezing and thawing of ice sheets. Dramatic climate variations like this imply the planet was fundamentally different billions of years ago—likely warmer with a much thicker atmosphere than the harsh, arid freeze-dried world encountered by rovers today.
The ridges themselves lie too far north of Jezero Crater to have formed the remarkable river delta deposits NASA’s Perseverance rover currently explores. However, the ice movements do underscore just how profoundly wet and dynamic Mars’ early climate was overall. As researchers continue piecing together evidence of ancient environments sculpted by flowing liquid water, a living world long lost in time comes further into focus.
Mars Exploration Continues
The Mars Reconnaissance Orbiter launched in 2005 and continues revealing new insights over 18 years into its planned mission. The durable spacecraft’s high-resolution imaging spectrometer and weather-monitoring instruments spot dynamic phenomena on Mars daily—everything from dust devils swirling through Gale Crater to icy clouds gathering over volcanoes.
Meanwhile NASA’s Perseverance rover has collected over a dozen rock core samples so far containing signs of past microbial life from Jezero Crater’s ancient lakebed. A future Mars Sample Return mission will collect these cached specimens and bring them to Earth by the early 2030s for more intensive study. Scientists hope these preserved geological materials from an alien shoreline will at last confirm whether microscopic Martian life ever existed, fulfilling a decades-long quest to unearth signatures of biology beyond our own planet.
Together with international and commercial satellites probing Mars from orbit and China’s Zhurong rover exploring Utopia Planitia, humanity’s investigation of Mars continues apace. As teams pour over the wealth of images and data streaming back to answer fundamental questions about planetary evolution and the origins of life itself, more surprises likely await just over the horizon—or beneath the sands—of Earth’s little red neighbor three doors down.
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