Is there life on Mars? Whether it’s the pursuit of little green men or sources of water, Mars exploration holds a particular fascination both within and outside the scientific community. President Trump’s announcement last week directing the Pentagon to create a sixth branch of the military called Space Force further demonstrates how society can’t escape its innate curiosity of space and the final frontier. This appeal toward the red planet has led to new studies on the climate and geology of Mars, particularly as improvements in satellite data enhance our ability to understand our neighboring planet.
A recent study from a team of scientists led by Jacob Adler of Arizona State University explored a unique area of scientific interest on Mars called Hypanis Valles. Considered a potential landing site for NASA’s Mars 2020 rover and ESA’s ExoMars 2018 rover mission, Hypanis is a large, fan-shaped sedimentary deposit on Mars approximately 150 meters tall and 60 kilometers wide. It has been hypothesized whether a major lobe of Hypanis Vallis could be home to a rock glacier. Adler’s team used satellite images to rule out that option. Instead, they found compelling evidence that these layered, fine-grained deposits were a massive delta.
Because of the lack of high-enough resolution satellite data until recently, scientists were uncertain of which landforms composed Hypanis. For the major lobe of Hypanis, the main candidates were a delta, mudflow, or alluvial fan. For the second, dubbed northern lobe, which the team hypothesized was formed by a different mechanism than the major lobe, one of the main landforms considered was a rock glacier. Interpreting the geomorphology and silt compositions, Adler and his team determined both lobes appear to be of deltaic origin and the largest yet found on Mars.
The paper uses the definition of a delta as a “fan-shaped sedimentary deposit formed when fluvial transport reaches a larger body of standing water.” The team explored three hypotheses before determining the delta hypothesis was the most plausible.
Located in the large Xanthe Terra region along the equator of the red planet, Hypanis appears to have existed for over 3.6 billion years, the product of a large lake or sea once spanning the area. The study explored the geological story of Hypanis and used the most recent high-resolution images and data collected on the region to characterize the deposit in greater detail.
Kenneth Tanaka, a scientist and cartographer recently retired from the United States Geological Survey, told GlacierHub that the team compiled a strong argument for a deltaic origin for these layered, fine-grained deposits occurring at the mouth of Hypanis Valles by using the latest and best imaging datasets available from spacecrafts orbiting Mars
The study supports that the ancient layered material was deposited by a large body of water on the surface of Mars. Adler told GlacierHub that a striking fact from the study was the sheer size of the deltaic structure on Mars. As potentially the largest delta on Mars, Hypanis doesn’t compete with the largest ones on Earth and is only slightly smaller than the Colorado River delta. But for the dusty red planet, it is remarkable.
“Its gently dipping layers were surprisingly continuous for many kilometers, implying deposition in a calm environment,” Adler said. “If it were indeed once a delta, then there would have been a large lake or sea spanning this area of Mars.”
A delta origin seems most likely. But what all options had in common was that a large body of water over 4 billion years old was in place to shape the Hypanis region. When Hypanis formed, scientists believe rivers and oceans may have covered Mars and shaped the planet’s geography and climate. But over time, the atmosphere thinned, and the surface dried as water was sequestered to the polar caps or in the soil, or lost to space. To explain how something as strongly associated with water as a delta could be found on a planet so dry, the team describes how “the ancient deltaic deposit we observe today was largely untouched by subsequent catastrophic outflows, and its surface has only been moderately reshaped by over 3 billion years of aeolian [wind-blown] erosion.”
Although the possibility of Hypanis being a rock glacier was ultimately ruled out, glaciers on Mars are a part in understanding the planet.
“Glaciers on Mars can tell us about the climate history of the planet and could be a great water resource for future astronauts to utilize,” Adler told GlacierHub. He also explained the basic characteristics of Martian glaciers. For one thing, unlike the striking white and blue images of glaciers on Earth, red dust and debris bury the ice on Mars, making Martian glaciers difficult to identify. Additionally, as noted above, Martian features can remain for immensely long periods on Mars.
What’s the significance of all of this? Identifying these structures remains critical to our understanding of water on Mars and whether life may have once existed on the planet. Fortunately, the identification of Martian glaciers appears to be getting easier, as evidenced with this recent study.
According to another author of the article, Peter Fawdon, “the incredible level of detail that can be seen in the HiRISE [High-Resolution Imaging Science Experiment] image of the area” is surprising. With the new data, more studies on the geomorphology and geological context of Hypanis are in the works and expected for publication in the near future. Other potential deltas across the planet could also be analyzed in a similar manner. A more thorough understanding of the delta may suggest that Hypanis Vallis could once again become the target of a future Mars mission, a space force or otherwise.