New from the University of Arizona suggests an unlikely connection between the Lower Colorado River Basin and the planet Mars.
It鈥檚 a link that spans 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鈥檚 the intriguing or because it鈥檚 one of the points of light in the night sky, but the planet Mars has always in the Earthling imagination. We long to know the Red Planet better, while simultaneously fearing what we might find.
鈥淚t鈥檚 extremely important because it's the most Earth-like of other planets,鈥� said Scott Hubbard, a retired Stanford University astronautics professor who was the first director of NASA鈥檚 Mars Program director from 2000-2001 and went on to lead the Agency鈥檚 Ames Research Center for several years. 鈥淗umanity has been fascinated by this little red dot in the sky for thousands of years.
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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 鈥� most of her research has focused on the 鈥� a few years ago, she became fascinated by of the Red Planet.
The Martian landscape 鈥� full of branching, twisting 鈥� was distinctive and stuck in her mind. And that's why she noticed something interesting looking down at Arizona鈥檚 from her airplane window.
鈥淚 thought, 鈥榦h, this Santa Cruz River system looks exactly the same to the Martian Valleys,鈥欌�� she said. 鈥淭hey both have tree-like, branching river systems.鈥�
That observation sparked a big idea that eventually made its way into her dissertation.
鈥淚 realized that there could be a connection between the Earth鈥檚 river systems and the Mars valley networks,鈥� she said. 鈥淭hey share similar characteristics. Which indicates that they could have a similar climate.鈥�
Where鈥檚 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鈥檚 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鈥檚 a reason. Despite its fiery color, Mars is a .
鈥淢ars today has a very thin atmosphere. It's like Earth at 100,000 feet,鈥� Hubbard said. 鈥淚t's mostly carbon dioxide.鈥�
There is , and certainly no flooding rivers, on the Red Planet. As far as scientists currently know, the planet鈥檚 surface is of liquid water: all of it is frozen solid at the surface in large .
But the Martian valleys in Lin鈥檚 hypothesis were formed of years ago, when the solar system was much younger. Back then, widespread on Mars constantly spewed atmosphere-forming gasses, keeping the planet warm. During Mars鈥檚 Noachian and Hesperian , ranging from 3 to 4 billion years ago, liquid water was . Ji鈥檚 research suggests flash flooding was common, just like in the valleys of the Lower Colorado River Basin.
鈥淲e inferred that the valley network on Mars was also formed by high intensity rainfall and a very quick flow process,鈥� 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.
鈥淲e used machine learning to connect the Earth's climates and its landforms,鈥� she said. 鈥淭hen 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.鈥�
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鈥檚 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 of geologic layers, ice age , and , not to mention ecosystem processes 鈥� interacting with the landscape, and the presence or absence of deep-rooted .
鈥淚t鈥檚 a really complex interplay of different factors that have different time scales,鈥� Abbot said. 鈥淎nd the morphology that you see is the combination of all of those.鈥�
He says that complexity makes it hard to compare the two planets in a straightforward way.
鈥淚t's really tough to get down to the real nitty gritty of what climate regime on Earth matches the climate regime on Mars,鈥� he said. 鈥淚'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.鈥�
Abbott has not read Ji鈥檚 dissertation, but he does see the promise of her approach of using sophisticated computer modeling to cut through some of that complexity.
鈥淓xploring 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,鈥� he said. 鈥淭hat's where it can be a real advantage and move our understanding forward beyond what it was before.鈥�
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?
鈥淲hat 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?鈥� Hubbard said. 鈥淚t 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.鈥�
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.
鈥淯nderstanding how the climate evolved over time would tell us a lot about, if life did form, where it might be today.鈥�
This story was produced by 萝莉少女 in partnership with The Water Desk at the University of Colorado Boulder鈥檚 Center for Environmental Journalism.
