A perspective view of two valley glaciers (labeled A and B) in Batson Crater on Mars. The winding valleys radiating from Glacier A have been eroded by meltwater from the glacier. These glaciers likely filled the valleys deeper in the past. Image credit: Murray Lab at Caltech and Alan Howard/PSI
A new paper The study, published in Icarus, describes, maps and dates how glaciers and glacial meltwater have shaped the northeastern edge of the Hellas Basin on Mars over the past 3 billion years. The work was authored in part by Alan Howard, a senior scientist at PSI, and Alexander Morgan, a research scientist.
Before beginning the research, the team was intrigued by the dramatic features in the Hellas Basin, particularly in and around Batson Crater, which they believed might indicate a history of disintegrating glaciers. Until now, these features had not been adequately described and characterized as glacial.
Glaciers leave their mark on a landscape in many ways. On Earth, glaciers mainly grind away the underlying rock as they slowly flow downhill. On Mars, however, where gravity is weaker, the physical processes that lead to this behavior require thicker ice. The team therefore argues that during a time when Mars was warmer, it is more likely that meltwater shaped the landscape as it flowed under and out of glaciers.
The team also wanted to understand how the landforms would differ if they had been formed by glacial meltwater rather than rain – which probably didn’t occur at the time – or seasonal snowmelt – which is more likely, Howard said. They found that in many cases, glacial meltwater did not form clearly defined valleys branching out like a tree, but rather shallow valleys that interlock like a latticework, yet flow in a dominant direction down the crater slopes.
Location map of the study region with named craters and the extent of geomorphological mapping (white border). Unless otherwise indicated, north is at the top in all figures. The “*” at 83°E, 29°S indicates the regional location and the inset shows the location relative to the global topography (scale from 21,000 m to -8,000 m). Image and elevation sources for all figures are listed in the Supplementary Figures, Table S1. – Ikarus
“Water flowing beneath glaciers is often under pressure and can seek multiple flow paths, while surface water tends to remain trapped in glacier-eroded valleys,” Howard said. “These landforms are the most compelling argument that this area is covered by deep ice and runoff.”
Glaciers on Mars wax and wane as the tilt of its axis changes dramatically over long periods of time. It’s likely that this area was cold when it was at its steepest tilt, but warmest, creating glacial meltwater.
“We often think of Mars as having an early warm and wet period with lots of erosion, as opposed to a more recent cold and dry period when the surface was quite inactive,” Morgan said. “This study highlights the complexity of Martian landscapes during the more recent cold and dry period, with large glaciers playing a significant role in shaping the terrain.”
Today, small glaciers can still be found poleward of the 30th parallel, but the team assumes that there was a much more extensive glaciation during the Amazonian period, which began three billion years ago and was climatically comparable to today.
“Even though we can see things on Mars with a resolution of five meters per pixel, there is still so much mystery,” Howard said. “We will probably look for similar signatures in other regions as we see in this particular region. The limitation of remote observations is actually what attracted me to Mars. You have to be a good detective to put together a convincing story of the past.”
Howard and Morgan’s work was funded by grants 80NSSC18K1476 from NASA’s Mars Data Analysis Program, a subprogram of the University of Colorado, and 80NSSC19K1221, a subprogram of the Smithsonian Institution.
Glacial sculpture of a Martian crater landscape on the northeastern flank of the Hellas Basin, Icarus (open access)
Astrobiology, Astrogeology,
