Humans on Mars will need oxygen, and Mars’ atmosphere is pretty anemic when it comes to the life-sustaining element. NASA’s Perseverance rover successfully extracted oxygen from CO2 in Mars’ atmosphere, but there are other ways to acquire it. There seem to be vast amounts of water buried under the Martian surface, and oxygen in the water is just waiting to be set free from its bonds with hydrogen.
On Earth, that’s no problem. Just run an electrical current through water, and you get oxygen. But Mars won’t give up its oxygen so easily.
NASA’s Perseverance rover extracted oxygen from CO2 in Mars’ atmosphere, another first for the mission. It was an exciting achievement since future human visitors to Mars will need it to breathe and to create rocket fuel. But a team of Chinese scientists are developing a different approach.
They’ve shared their results in a paper titled “Automated synthesis of oxygen-producing catalysts from Martian meteorites by a robotic AI chemist.” It’s published in Nature Synthesis, and the lead authors are from the Key Laboratory of Precision and Intelligent Chemistry at the University of Science and Technology of China, Hefei, China.
“Oxygen supply must be the top priority for any human activity on Mars because rocket propellants and life support systems consume substantial amounts of oxygen, which cannot be replenished from the Martian atmosphere,” the authors write. (NASA scientists might disagree with that statement.)
Instead, Chinese researchers think that solar energy can be used to produce oxygen from Martian water. But it won’t be the simple electrolysis from science class. Instead, they intend to employ catalysts.
Simple electrolysis faces barriers that limit its potential and productivity. The oxygen evolution reaction is a bottleneck in electrolysis, and scientists sometimes call electrolysis “sluggish.” On Earth, scientists know which catalysts can overcome the bottleneck. But conditions are different on Mars than they are on Earth. Scientists can’t just transpose methods that work on Earth onto Mars. The trick is finding the appropriate catalysts available on Mars. Scientists call them oxygen evolution reaction (OER) catalysts.
Here’s the problem: there are over three million possible catalysts on Mars. How can scientists work through all those possibilities when the communication delay between Mars and Earth can be up to 20 minutes long? It’s not practical.
This is another situation where robotics and AI can solve a problem, according to the research team.
“Here we demonstrate a robotic artificial-intelligence chemist for automated synthesis and intelligent optimization of catalysts for the oxygen evolution reaction from Martian meteorites,” the researchers explain. “The entire process, including Martian ore pretreatment, catalyst synthesis, characterization, testing and, most importantly, the search for the optimal catalyst formula, is performed without human intervention.”
China doesn’t have a functioning spacecraft on Mars that can do some of this work. Fortunately, nature has delivered samples of Mars to Earth in the form of meteorites. The researchers used small amounts of five types of Martian meteorites as feedstock in their automated system.
To illustrate how effective this fully automated, robotic AI system is, the researchers calculated how long it would take for humans to complete the same tasks using typical ‘trial and error’ methods.
The trial and error method is difficult because of what researchers call chemical space or material space. There are a confounding number of variables that need to be tested, and they occupy an enormous chemical space. “Designing a catalyst from a given list of elements requires the exploration of a vast chemical space,” the researchers explain, “which poses a daunting task using the conventional ‘trial-and-error’ paradigm.”
With the five Martian meteorites as feedstocks, there are an estimated 3,764,376 potential catalysts. That creates lifetimes of work for human scientists. “Finding the optimal formula would require 2,000?years of human labour to finish such a screening, where each complete experiment takes 5?hours, at least,” the researchers write.
Robotic chemistry has made serious advances in recent years, something the researchers say can be leveraged for use on Mars. They point to research by Cooper et al. in 2020. In that effort, a team of researchers used a mobile robot to tackle the chemical space and search for improved photocatalysts for hydrogen production from water. “The robot operated autonomously over eight days, performing 688 experiments within a ten-variable experimental space,” Cooper and his colleagues wrote in 2020. That’s 86 experiments per day.
With this new research, which the researchers call a ‘proof of concept study,’ the trend for robotic/AI chemistry takes another step.
It started with the AI. “Within six weeks, the AI chemist built a predictive model by learning from nearly 30,000 theoretical datasets and 243 experimental datasets,” the researchers explain. Eventually, the system delivered an exceptional catalyst made up of several metals. The material catalyzed the oxygen evolution reaction—the bottleneck in the electrolysis of oxygen from water—for 550,000 seconds (about 153 hours.) Furthermore, the catalyst was effective at -37 C, a typical surface temperature on Mars.
“Our study provides a demonstration that an advanced AI chemist can, without human intervention, synthesize OER catalysts on Mars from local ores,” the authors claim. This is an impressive development. The fact that it’s all done in situ is also compelling.
“The established protocol and system, which are generic and adaptive, are expected to advance automated material discovery and synthesis of chemicals for the occupation and exploration of extraterrestrial planets,” they conclude. But what’s next?
China’s next mission to Mars could be a sample return endeavour, according to the China National Space Administration. That mission will be Tianwen 3, the third in the Tianwen line, and China hopes to beat NASA/ESA to the punch by returning a sample to Earth in 2031.
It seems unlikely that China can also shoehorn a robotic/AI chemistry experiment into a sample return mission, but you never know. The CNSA is ambitious and eager to measure up to NASA’s record of success.
If they can, it’ll be an extremely impressive feat and a big leap forward in Mars exploration.