New research from the University of Arizona suggests an unlikely connection between the Lower Colorado River Basin and the planet Mars.
It’s a link that spans 140 million miles through the cold, dark vacuum of outer space and billions of years through the eons, allowing scientists to use similarities between the two landscapes to learn about the ancient Martian climate.
Maybe it’s the intriguing red color, or because it’s one of the brightest points of light in the night sky, but the planet Mars has always loomed large in the Earthling imagination. We long to know the Red Planet better, while simultaneously fearing what we might find.
“It’s extremely important because it's the most Earth-like of other planets,” said Scott Hubbard, a retired Stanford University astronautics professor who was the first director of NASA’s Mars Program director from 2000-2001 and went on to lead the Agency’s Ames Research Center for several years. “Humanity has been fascinated by this little red dot in the sky for thousands of years.
That little red dot has preoccupied hydrologist Lin Ji for years. While the University of Arizona researcher and freshly minted PhD is usually more solidly grounded on Earth – most of her research has focused on the Lower Colorado River Basin – a few years ago, she became fascinated by satellite images of the Red Planet.
The Martian landscape – full of branching, twisting valley networks – was distinctive and stuck in her mind. And that's why she noticed something interesting looking down at Arizona’s Santa Cruz River from her airplane window.
“I thought, ‘oh, this Santa Cruz River system looks exactly the same to the Martian Valleys,’” she said. “They both have tree-like, branching river systems.”
That observation sparked a big idea that eventually made its way into her dissertation.
“I realized that there could be a connection between the Earth’s river systems and the Mars valley networks,” she said. “They share similar characteristics. Which indicates that they could have a similar climate.”
Where’s the Martian water?
For the canyons of the Lower Colorado River Basin, that would be an arid climate. Rain in the region is rare but when it does come, it’s heavy, leading to flash flooding so powerful it can carve entire landscapes.
If that doesn't sound anything like the Mars we know and love today, there’s a reason. Despite its fiery color, Mars is a cold planet.
“Mars today has a very thin atmosphere. It's like Earth at 100,000 feet,” Hubbard said. “It's mostly carbon dioxide.”
There is no rain, and certainly no flooding rivers, on the Red Planet. As far as scientists currently know, the planet’s surface is mostly devoid of liquid water: all of it is frozen solid at the surface in large polar ice caps.
But the Martian valleys in Lin’s hypothesis were formed several billions of years ago, when the solar system was much younger. Back then, widespread volcanic activity on Mars constantly spewed atmosphere-forming gasses, keeping the planet warm. During Mars’s Noachian and Hesperian Periods, ranging from 3 to 4 billion years ago, liquid water was plentiful. Ji’s research suggests flash flooding was common, just like in the valleys of the Lower Colorado River Basin.
“We inferred that the valley network on Mars was also formed by high intensity rainfall and a very quick flow process,” Ji said.
To prove her hypothesis that the climate of ancient Mars corresponded to that of the Lower Colorado River Basin, Ji used machine learning, a type of artificial intelligence that learns from complex datasets. She trained her model on a very broad sample of earthly landforms from across the globe, enabling it to correlate certain climate zones with specific qualities of valley geomorphology. Then, she turned the model towards Mars.
“We used machine learning to connect the Earth's climates and its landforms,” she said. “Then we switched this to Mars. We compared the Martian valleys to those in different climatic regions on Earth to help inform what the climate might have been on early Mars.”
That process found a close match between the Martian landscapes and the arid climate of the Lower Colorado region, which produced notable geologic wonders such as the Grand Canyon.
Not by flash flooding alone
But river basins aren't shaped by flash flooding alone.
While the speed and volume of a valley’s central river is the driving force, there are many overlapping forces that are also important, according to University of Colorado Boulder geologist Lon Abbott: the structures of geologic layers, ice age cycles, plate tectonics and earthquakes, not to mention ecosystem processes – animals interacting with the landscape, and the presence or absence of deep-rooted vegetation.
“It’s a really complex interplay of different factors that have different time scales,” Abbot said. “And the morphology that you see is the combination of all of those.”
He says that complexity makes it hard to compare the two planets in a straightforward way.
“It's really tough to get down to the real nitty gritty of what climate regime on Earth matches the climate regime on Mars,” he said. “I'm not sure that we could argue with confidence that 3. 5 billion years ago Mars was more similar to the climate that we see today in the Lower Colorado River Basin.”
Abbott has not read Ji’s dissertation, but he does see the promise of her approach of using sophisticated computer modeling to cut through some of that complexity.
“Exploring machine learning is allowing you to run through a set of complex feedbacks more efficiently than we've been able to do in the past,” he said. “That's where it can be a real advantage and move our understanding forward beyond what it was before.”
The big question
And if Ji is right about the Martian climate, that information could help resolve one of humanity's all-time biggest obsessions: is there life on Mars?
“What we would certainly know is: was Mars habitable? Was it an environment that if life emerged, it would be able to live long and prosper?” Hubbard said. “It may be that as Mars cooled and as ice began to form, that some amount of that surface water found its way underneath. And if life formed, it could still be there.”
So, if Mars does still harbor life, it turns out this research connecting the Colorado River to that distant planet just might help scientists anticipate where that life still exists, making it the key to a successful mission, Hubbard said.
“Understanding how the climate evolved over time would tell us a lot about, if life did form, where it might be today.”
This story was produced by KUNC in partnership with The Water Desk at the University of Colorado Boulder’s Center for Environmental Journalism.
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