In 1976, NASA’s Viking mission successfully landed the first spacecraft on Mars. When the mission began sending images from the surface of Mars to Earth, scientists noticed long dark streaks on crater walls and rocks. To this day, some researchers have speculated that these strange geographic features are the result of water flow – but a recent study suggests otherwise.
Planetary scientists from Brown University and the University of Bern have used artificial intelligence to discover that the mysterious Martian streaks are most likely the result of wind and dust, not water flow. Their findings have important implications for future Mars exploration, as well as for humanity’s ongoing search for habitable environments and life beyond Earth.
Some of the slope bands are long-lasting, while others – the so-called recurring slope lines (RSLs) – are more ephemeral, appearing consistently in the same locations during the hottest times of the year on Mars. Although Mars is generally dry and cold (with temperatures as low as -225 degrees Fahrenheit, or -153 degrees Celsius), small amounts of water from potential ice, underground springs, or moisture can mix with enough salt to become a liquid and flow down a slope. Since water is a key ingredient for life on Earth, such formations could also represent habitable regions on the Red Planet. But some researchers are not convinced of this, arguing that these features could instead have been created by dry processes.
To address this question, the researchers trained the algorithm on a dataset of confirmed observations of streaks on slopes, as detailed in a study published Monday in the journal Nature Communications. They then used the algorithm to scan more than 86,000 high-resolution satellite images and mapped the Martian slope streaks.
“Once we had this global map, we were able to compare it with databases and catalogs of other factors such as temperature, wind speed, hydration, landslide activity, and others,” said Valentin Bickel, a co-author of the study and a member of the Center for Space and Habitability at the University of Bern, in a statement to Brown University. “We could then look for correlations in hundreds of thousands of cases to better understand the conditions under which these features form.”
Simply put, their results do not link slope streaks and RSL to features that indicate the presence of liquid or even frost. Instead, the researchers found that both slope streaks and RSL tend to develop in areas with high wind speeds and dust deposition. In other words, they are likely caused by a dry process in which layers of dust slide abruptly downhill under the influence of external forces.
Instead of viewing these results as another setback in the search for extraterrestrial life, the planetary scientists explain that the study still has implications for future Mars exploration. If their study had supported the theory that the streaks on the slopes were caused by water, and that some form of life might exist in the region as a result, NASA would have actually avoided the area for the time being. That’s because scientists fear that spacecraft and rovers could still contain Earthly life, such as microbes, that could contaminate the Martian habitat and interfere with our search for Martian life.
“This is the advantage of a big data approach,” explained Adomas Valantinas, another co-author of the study, a planetary scientist at Brown University who specializes in Martian geology. “It helps us rule some hypotheses out of orbit before we even send spacecraft to explore.”
For an industry that seems obsessed with finding water on Mars, this study is a reminder that not every scientific breakthrough has to be about extraterrestrial life.
