Millions of miles away, on the surface of Mars, a remote experiment has revealed something shocking about the Red Planet. During the summer months, it seems, oxygen levels in the Martian atmosphere spike to extraordinary levels – and scientists have no idea why. Could this be evidence of biological life? The jury is still out.
For six years, the Curiosity rover has been stationed at a crater on Mars known as Gale. Here, it’s been tasked with learning more about the conditions on the planet. Equipped with a mobile chemistry lab dubbed Sample Analysis at Mars (SAM), the rover has been beaming back data to researchers on Earth. And slowly, we’ve been learning more about the atmosphere of the Red Planet.
Announced in 2019, these mysterious oxygen spikes are just the latest in a number of intriguing discoveries made by Curiosity over the years. Launched from Cape Canaveral in Florida on November 26, 2011, the rover was the fourth NASA vehicle to make its way to the Red Planet. And some eight months later, it finally arrived.
On August 6, 2012, Curiosity touched down at Gale crater, a depression stretching for some 96 miles across the surface of Mars. Approximately the same dimensions as an SUV, the rover was tasked with exploring the atmospheric conditions on the Red Planet. And through these observations, researchers hoped to learn more about the possibility of alien life.
As experts from NASA have explained, Curiosity had four primary objectives. As well as searching for signs of life on Mars, the rover would also carry out preparatory work for future manned missions. And in order to do so, it would study the climate and geology of the Red Planet.
Amazingly, it would be just six months before the first breakthrough was announced. In February 2013 NASA revealed that Curiosity had successfully drilled into Martian rock. And even though the agency had landed rovers on the planet in the past, this was the first time that such a feat had been accomplished.
Drilling a hole 0.6 inches wide by 2.5 inches deep, Curiosity collected powdered rock from just below the surface of Mars. Then, the substance was transferred to SAM, as well as a Chemistry and Mineralogy instrument – otherwise known as CheMin – for analysis. Just under a month later, the results were in.
According to NASA, the experiment detected a mixture of chemicals including phosphorus, nitrogen, sulfur, hydrogen, carbon and oxygen present in the sample. In short, the Martian rock contained some of the main ingredients required for biological life. And from this data, researchers were able to conclude that organisms may once have thrived on the Red Planet.
In a statement released in 2013, NASA scientist Michael Meyer explained the significance of the discovery. “A fundamental question for this mission is whether Mars could have supported a habitable environment,” he said. “From what we know now, the answer is yes.” But if life really did exist on Mars in the past, what would it have looked like? And could it still be there today?
On Mars, the samples came from an area of Gale crater known as Yellowknife Bay. And according to the data collected by Curiosity, this region was once either a riverbed or a lake that alternated between wet and dry. In the past, researchers believe, this environment could have provided the ideal conditions for microbes to thrive.
The California Institute of Technology’s John Grotzinger explained more in a statement. He said, “We have characterized a very ancient but strangely new ‘gray Mars’ where conditions were once favorable to life. Curiosity is on a mission of discovery and exploration, and as a team we feel there are many more exciting discoveries ahead of us in the months and years to come.”
Clearly, Grotzinger wasn’t wrong. In fact, by the time that the discovery was made public, Curiosity had already proved itself an invaluable research tool. Initially scheduled to last just two years, the mission was extended by NASA in December 2012. And as time passed, the rover continued to deliver earth-shattering results.
In December 2014 NASA announced another discovery. According to researchers, Curiosity had detected methane in the Martian atmosphere – and that wasn’t all. Apparently, the gas – which may indicate the presence of organic life – was present in drastically fluctuating levels throughout the year.
Although it’s possible that the methane detected on Mars could have been from inorganic sources, the data was exciting for those holding out hope for alien life. And for years, Curiosity continued to take measurements from the Gale Crater, hoping to get to the bottom of the mystery. Then, in June 2019 another discovery was revealed.
According to NASA, it’s normal for the amounts of methane present on Mars to vary from season to season. From a low of 0.24 parts per billion per unit volume – or ppbv for short – in winter, it has been known to rise to 0.65 ppbv during the warmer months. However, in the summer of 2019 researchers detected a huge surge in concentrations.
Interestingly, this wasn’t the only time that methane levels on Mars have surged to unusual levels. Back in June 2013 – just a couple of months after NASA determined that the planet may once have supported life – concentrations of the gas rose to about 6 or 7 ppbv. And later that year, another peak occurred.
On this occasion, researchers believe that the surge in methane levels lasted until around the beginning of 2014. But just like the earlier peak, the concentration did not exceed 7 ppbv. And for the next five years, there were seemingly no extraordinary measurements other than the typical fluctuation between the seasons.
However, in June 2019 Curiosity documented the biggest surge in methane levels yet, reaching a staggering 21 ppbv. For context, that’s over 30 times higher than the normal concentration. But what did it mean? Might this unusual activity be evidence at last that something is living and breathing on Mars?
On Earth, methane is typically generated by organic life. And so, many have predicted that the presence of the gas on other planets might be indicative of similar activity. However, experts are currently unsure whether Curiosity’s observations were the result of organic life or a different process altogether.
NASA’s Paul Mahaffy elaborated in a statement in 2019. As he put it, “With our current measurements, we have no way of telling if the methane source is biology or geology, or even ancient or modern.” Bizarrely, within a week, levels had dropped back to almost normal once more – leaving researchers clueless as to what could have been the cause.
Ashwin Vasavada, a NASA scientist involved with Curiosity, spoke about this occurrence in a statement. “The methane mystery continues,” he said. “We’re more motivated than ever to keep measuring and put our brains together to figure out how methane behaves in the Martian atmosphere.” And while experts have yet to get to the bottom of this phenomenon, they hope that its secrets will one day be revealed.
With so much that’s still unknown about the atmosphere on Mars, observations such as these could be key to unlocking its secrets. And if we ever do uncover evidence of alien life, the science of gases and microbes could be exactly where we find it. Interestingly, just five months after the massive methane spike, another bizarre anomaly on the Red Planet was revealed.
On November 12, 2019, a team of researchers from NASA and other institutions published the results of a study in the Journal of Geophysical Research: Planets. In it, they explained that they had observed another gas behaving in an unexpected manner on Mars. And this time it was oxygen, rather than methane, that was the culprit.
According to data collected by Curiosity, oxygen levels on Mars spiked to extraordinary levels during the planet’s spring and summer months. In fact, they went up by a staggering 400 parts per million – around 30 percent higher than what researchers were expecting. But what could have caused this inexplicable surge?
On Mars, molecular oxygen is created when the sun’s rays meet both water vapor and carbon dioxide on the planet’s surface, breaking the substances apart. And according to experts, it can linger on the Red Planet for a decade or more. In total, these molecules are believed to make up around 0.13 percent of the Martian atmosphere.
Previously, however, researchers believed that the molecular oxygen on Mars behaved in a stable manner, just like the planet’s other nonreactive gases. And before Curiosity came along, there was no reason to challenge this theory. But then, the Mars rover recorded some surprising information which brought existing presumptions into question.
According to the data collected by Curiosity, Mars’ oxygen was far from fixed and stable. Indeed, not only did the levels differ widely from season to season, the researchers discovered, they also experienced irregular spikes from year to year. Understandably, the team were left somewhat baffled by these latest findings.
“When we first saw it, my first reaction was, this is totally bizarre,” the University of Michigan’s Sushil Atreya told National Geographic in 2019. Strangely, the results appeared to indicate that something on Mars was producing large amounts of oxygen during the warmer season. And when temperatures dropped, it seems, an unknown process was causing those same molecules to deplete.
On Earth, of course, fluctuating oxygen levels can sometimes be explained by the presence of biological life. As such, this discovery has generated a lot of excitement within certain circles of people interested in the Red Planet. But could Curiosity’s latest findings really be the evidence that we’ve been waiting for?
Of course, the team were keen to explore all possible explanations before considering the prospect of alien life. Could the oxygen spikes, for example, be the result of sunlight hitting water vapor and carbon dioxide in the normal fashion? According to their research, this process occurs far too slowly to account for the unexpected results.
So, what else might explain the data? Some have suggested that perchlorates, a type of toxic salt found on Mars, could be responsible. Apparently, these could theoretically be broken down by radiation – a reaction that would release oxygen into the atmosphere. However, this process is likely too slow to cause the seasonal spikes observed by Curiosity.
As an alternative explanation, some pointed to hydrogen peroxide, a substance that is also produced when sunlight hits water vapor and carbon dioxide on Mars. According to experts, it’s possible that this gas could seep into the soil, making its way as far as 10 feet beneath the surface. And there, it’s proposed, it could be stored for as long as 10 million years.
However, experts have pointed out that these underground oxygen reserves are not nearly large enough to account for the mysterious surge. Stumped, the team looked to the results of earlier missions for clues. In the 1970s NASA’s Viking landers were able to generate oxygen from Martian soil simply by raising its humidity. Could the warmer climate in spring and summer be creating a similar effect?
Again, this theory was soon shot down. According to reports, the Viking experiments were performed at temperatures of 50 °F. In other words, in conditions generally much warmer than the surface of Mars. Moreover, this wouldn’t explain how the substance continued to spike on a regular basis, with no apparent source of renewal.
Apparently, the team were so puzzled that they even considered the possibility that their data was flawed. However, people such as NASA’s Paul Niles remain confident in the accuracy of the results. “I think they’ve done their due diligence,” he told Scientific American in 2019. “I don’t see any reason to have any doubt in the oxygen measurements.”
To further complicate matters, the team observed that the phenomenon appeared to mimic the methane spikes previously detected on Mars. And while the latter began their peak later in the year – and reached similar annual levels – the correlation between the two raises further questions. Is this proof that an unknown process is causing these strange reactions?
Speaking to National Geographic, NASA’s Melissa Trainer said, “That’s a whole new part of the mystery. We find it extremely intriguing, and we’re very interested to figure out if there’s a true correlation between the two. They both potentially could have a source at the surface, [but] it’s not clear that they have the same source.”
So, what does all of this mean in the search for alien life? Although oxygen spikes can be the result of organic processes on Earth, there’s no guarantee that things are the same on Mars. Speaking to the Scientific American, Newcastle University’s Jon Telling explained, “It’s almost certainly going to be a non-biological chemical reaction.”
Meanwhile, Trainer did not dismiss the idea of a biological source outright. She did, however, point out that researchers would be reluctant to accept such a conclusion. “People in the community like to say that it will be the explanation of last resort, because that would be so monumental” she told Scientific American.
For now at least, the mystery remains unsolved. However, in July 2020 NASA hopes to launch its Mars 2020 rover, with the aim of bringing soil samples back to Earth. Meanwhile, the joint European and Russian mission ExoMars plans to drill up to six feet beneath the surface of the Red Planet – deeper than anyone has gone before. Might these future experiments shed more light on the strange atmosphere of this alien world?