Mars arguably illustrates a worst-case scenario for our planetary future. As with the Red Planet, will deserts one day engulf the Earth? The barren Martian landscape evokes a vision of a planet-wide mass extinction, after all. But it may also hold secrets about our primordial origins too. In fact, once upon a time, Mars was covered with water. And the findings of a groundbreaking new study suggest that the planet was even more Earth-like than previously thought.
Scientific knowledge about our solar system has grown exponentially over the past 60 years. This is due in no small part to the work of the National Aeronautics and Space Administration (NASA). Established in 1958, NASA not only launches manned space flights, but it also develops robotic spacecraft and sophisticated measuring instruments. These include orbital telescopes, for observing and exploring distant regions of outer space.
In the 1970s NASA’s Viking program successfully landed two probes on Mars. This gave the world its first close-up glimpse of the Red Planet’s ominous, dust-filled surface. The probes – designed to analyze Mars’ physical composition – also took samples of the planet’s atmosphere and soil. Then, in 1993, NASA created the Mars Exploration Program (MEP) to further enhance our knowledge. This program deployed a range of rovers, landers and orbital crafts to fulfill its missions.
So in November 2011 NASA launched the Mars Space Laboratory (MSL) from Cape Canaveral. The MSL spacecraft then spent nine months traveling 350 million miles across the solar system. Then, upon reaching Mars, it deployed Curiosity – a large robotic rover. And in August 2012 Curiosity successfully touched down on the planet’s surface inside Gale Crater.
Curiosity had several mission objectives. Firstly, it aimed to study the planet’s climate and geological composition. It would also analyze how water may have influenced its geography and determine its suitability for human habitation and exploration. In fact, it would search the planet for evidence that it may once have been able to support organic life. The mission was only intended to last two years, but in 2012 NASA extended it until further notice.
Then in June 2018 the journal Science published the results of two groundbreaking studies. One concerned the presence of organic molecules that Curiosity had identified in the soil. The other provided new details about the atmosphere’s methane content. Both studies gave exciting new insights into the planet’s ancient landscape – and also suggested that Mars may once have supported life.
Specifically, Curiosity found organic molecules within sedimentary material at the bottom of a three-billion-year-old lake bed. The compounds included benzene, toluene and thiophene as well as small carbon chains – such as butene and propane. The quantities of these organic materials are around 100 times greater than those previously observed there.
To collect the molecules, Curiosity drilled into the lake bed. This allowed it to retrieve a sample of ancient sedimentary rock known as mudstone. The sample was then placed inside Curiosity’s onboard oven, which raises the temperature to between 932 and 1508 °F. The heat increase subsequently caused the organic molecules within the sample to vaporize. And from this, Curiosity was then able to detect and identify them.
Curiosity also measured the variation in methane levels in the Martian atmosphere over a period of nearly six years. The measurements indicate that methane levels increase during the planet’s summer and decrease in the winter. However, the source of the methane is unclear. It could, for instance, be coming from an organic source on the planet’s surface or an underground reservoir.
Chris Webster, one of the Science paper’s main authors and a researcher at NASA’s Jet Propulsion Laboratory, said the results were obtained thanks to Curiosity’s durability. “This is the first time we’ve seen something repeatable in the methane story,” he said. “This is all possible because of Curiosity’s longevity. The long duration has allowed us to see the patterns in this seasonal ‘breathing.’”
Meanwhile, the discovery of organic molecules in the planet’s rocks – as well as fluctuations in its atmospheric methane – has profound implications for our understanding of Mars. It could be that both phenomena are a sign of endemic carbon-based life forms, past or present. Indeed, the findings represent strong evidence of extraterrestrial life.
Speaking to The Guardian in June 2018, Kirsten Siebach, a self-professed “life-on-Mars sceptic” and geologist at Rice University, found the results encouraging. “These molecules could have been part of life, but they could also have been food for life,” she said. “To know that the water really was full of organic molecules really opens up the different ways that life could have existed on Mars.”
And according to Inge Loes ten Kate of the University of Utrecht in the Netherlands, the discoveries represent an astrobiology breakthrough. “The question of whether life might have originated or existed on Mars is a lot more opportune now that we know that organic molecules were present on its surface at the time,” she wrote in a companion article for Science.
Yet the scientific definition of “organic” is actually quite different to the common definition. Colloquially, organic means biological or living. Scientifically, though, “organic” refers to any compound that contains hydrogen and carbon – such as methane. So, by this definition, organic compounds are not necessarily biological; some are wholly or partly synthetic, such as plastics.
The presence of these organic compounds on Mars could therefore indicate biological life. Or they could be the result of other less exciting phenomena. In fact, no one knows the true source of the molecules. Natural processes, such as volcanic activity, may have created them. Alternatively, they may have arrived on the planet via a comet or a meteor.
But biogeochemist Jennifer Eigenbrode, who works at Maryland’s NASA’s Goddard Space Flight Center, still thinks the findings are promising. “The amazing consistency of the material makes me think we have a slam-dunk signal for organics on Mars,” she told The Guardian in June 2018. “It is not telling us that life was there, but it is saying that everything organisms really needed to live in that kind of environment, all of that was there.”
Ashwin Vasavada, a scientist working on Curiosity, argues that it’s now increasingly probable that NASA could uncover conclusive evidence of biological life. “The chances of being able to find signs of ancient life with future missions, if life was ever present, just went up,” he told The Independent in June 2018.
These days, NASA’s InSight lander, which touched down on Mars in November 2018, represents the agency’s latest effort to explore the planet. Its mission is to analyze the internal structure of Mars, including its core, mantle and crust. NASA will then be able to determine if Mars is “geologically active,” like Earth.
In 2020 NASA also intends to dispatch a new rover to the planet. Its specific goal will be to identify evidence of ancient microbes. This rover will have the capability of creating a cache of samples that can be later picked up by another craft and returned to Earth, where they can be thoroughly analyzed in laboratories that are too large to attach to a mobile unit.
Speaking to The Independent, associate administrator for NASA’s Science Mission Directorate Thomas Zurbuchen expressed hope for the future. “With these new findings, Mars is telling us to stay the course and keep searching for evidence of life,” he said. “I’m confident that our ongoing and planned missions will unlock even more breathtaking discoveries on the Red Planet.”