Tracking the Icy History of Mars from Space
New research using data from the ESA's Mars Express orbiter is revealing a complex history of glacial activity on Mars, with major implications for understanding the planet's climate evolution. Images from the orbiter's High Resolution Stereo Camera show intricate patterns etched into the Martian surface, providing a glimpse into the Red Planet's icy past.
Just as Earth has experienced multiple ice ages over the past 2.5 billion years, Mars too bears the scars of repeated glacial cycles. These climatic shifts were driven by long-term variations in Mars' axial tilt, or obliquity, leading to fluctuating temperatures and the advance and retreat of ice flows across the planet.
"The patterns we see on Mars' surface, known as lineated valley fill and concentric crater fill, are strikingly similar to glacial features on Earth," said Dr. Maria Zuber, a planetary scientist at MIT's Department of Earth, Atmospheric and Planetary Sciences. "This suggests that Mars experienced not just one, but multiple ice ages in its distant past."
Uncovering Martian Glacial Features
The new images from Mars Express focus on a region known as Coloe Fossae, a system of intersecting canyons located between the planet's Northern Lowlands and Southern Highlands. On the floors of these canyons and the numerous craters that dot the landscape, scientists have spotted telltale signs of past glacial activity:
- Lineated Valley Fill (LVF): Swirling patterns of rocky material deposited by advancing and retreating ice flows
- Concentric Crater Fill (CCF): Similar deposits found within impact craters, indicating that glaciers once filled these basins
These features are remarkably similar to glacial till on Earth - a combination of clay, silt, sand, and gravel left behind by retreating glaciers in the form of ridges and elongated mounds.
A Planet-Wide Phenomenon
What makes the Coloe Fossae findings particularly intriguing is the region's location, far from the ice cap in Mars' northern polar region. This suggests that glaciers once extended across much of the planet, advancing from the poles towards the mid-latitudes during colder periods and retreating again during warmer interglacial times.
In fact, scientists have identified LVF and CCF features across Mars' mid-latitudes, hinting at a global history of glacial activity. Dr. Susan Conway, a glacial geomorphologist at the French National Centre for Scientific Research, explains:
"We've found evidence of glacial features not just in Coloe Fossae, but in many regions across the mid-latitudes of Mars. This suggests that the entire planet may have experienced multiple ice ages as its atmosphere gradually thinned over time."
Reconstructing Mars' Climate History
By tracking the flow of ice across the Martian surface, scientists can piece together the planet's geological and environmental history. The presence of multiple glacial periods indicates that Mars once had a thicker atmosphere, capable of supporting liquid water on its surface.
However, as the planet's atmosphere was slowly stripped away by solar wind and cosmic radiation, Mars transitioned from a warmer, wetter world to the cold, dry planet we see today. Studying the timing and extent of these glacial periods can help scientists better understand the mechanisms behind this dramatic climate shift.
The Mars Express findings also have implications for the search for potential habitable environments on the Red Planet. Dr. John Bridges, a planetary scientist at the University of Leicester, notes:
"During these ancient ice ages, the presence of liquid water and a thicker atmosphere could have created conditions more favorable for life as we know it. By identifying regions where glaciers once flowed, we can target future missions to search for signs of past habitability on Mars."
The Future of Martian Glacial Research
As scientists continue to study the glacial history of Mars, new questions arise about the planet's complex climate evolution. Future missions, such as NASA's Perseverance rover and ESA's ExoMars program, will build upon these findings, seeking evidence of past life and further unraveling the mysteries of the Red Planet's icy past.
By combining data from orbital spacecraft, surface rovers, and eventual crewed missions, scientists hope to construct a comprehensive timeline of Mars' glacial epochs, shedding light on the planet's potential for harboring life and informing our understanding of planetary climate change both on Earth and beyond.
