In a surprising turn of events, NASA’s Curiosity rover has uncovered one of the most remarkable findings of its mission on Mars: rocks made of pure sulfur. This discovery was purely serendipitous, resulting from the rover accidentally driving over a rock and revealing yellowish-green crystals, never before seen on the Martian surface.
The Initial Discovery
Ashwin Vasavada, the Curiosity project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, expressed his astonishment: “I think it’s the strangest find of the whole mission and the most unexpected.” This discovery was indeed fortunate, as not every rock on Mars contains such interesting elements.
The Curiosity team had been keen to explore the Gediz Vallis channel, a winding groove that appears to have been formed 3 billion years ago by a combination of flowing water and debris. This channel cuts through part of the 3-mile-tall Mount Sharp, which Curiosity has been climbing since 2014. The team had noticed white stones from a distance and wanted a closer look, which led to the accidental crushing of the sulfur-containing rock.
The Discovery Process
On May 30, the Curiosity team examined a mosaic captured by the rover’s cameras and noticed a crushed rock in the rover’s tracks. Closer inspection revealed the “mind-blowing” find: yellowish-green crystals indicating the presence of pure sulfur. This was a significant departure from previous discoveries on Mars, where sulfates (salts containing sulfur formed when water evaporates) were found. These included bright white calcium sulfate or gypsum, which are hard-water deposits left behind by ancient groundwater flows.
“No one had pure sulfur on their bingo card,” Vasavada commented. The sulfur rocks displayed a “beautiful, translucent and crystalline texture,” typically hidden by Mars’ sandblasting environment, which weathered the rocks to blend with the planet’s orange surface.
Analyzing the Sulfur
The Curiosity rover’s instruments analyzed the crushed rock, confirming it was composed of pure sulfur. This finding is particularly intriguing because on Earth, pure sulfur is usually found in hydrothermal vents or volcanic regions, suggesting a complex geological history for the Martian rocks.
This discovery echoes a significant finding by NASA’s Spirit rover, which, while dragging a broken wheel, uncovered nearly pure silica soil. Silica on Earth often indicates the presence of hot springs or steam vents, which could have supported microbial life. Similarly, the sulfur discovery on Mars raises questions about the planet’s geological and possibly biological past.
Geological Context
As Curiosity explored Gediz Vallis channel, it sent back images of a flat area, about half the size of a football field, scattered with bright white rocks. Initially thought to be debris transported by water from higher up the mountain, further investigation suggested these rocks formed in situ. However, Curiosity couldn’t drill into the brittle rocks, so the team turned to analyzing nearby bedrock.
Pure sulfur formation on Earth typically involves volcanic processes or hot/cold springs, each associated with different minerals. The team sampled a large rock from the channel, nicknamed “Mammoth Lakes,” which revealed an unprecedented variety of minerals, adding complexity to the Martian geological narrative.
Mars’ Dynamic History
Since landing in 2012, Curiosity has climbed 2,600 feet up Mount Sharp, which stands in the center of Gale Crater, an ancient lake bed. Each layer of Mount Sharp provides a glimpse into Mars’ history, revealing transitions from wet to dry periods. The Gediz Vallis channel, formed well after the mountain, has intrigued scientists due to its mix of water and debris-carved features.
Curiosity’s analysis suggests that both water flows and landslides contributed to the channel’s formation. Rounded river rocks indicate water transport, while angular rocks suggest dry avalanches. Water likely soaked into the debris, causing chemical reactions that left halo patterns on some rocks.
The Importance of Sulfur
The discovery of pure sulfur is a significant milestone. It could point to past volcanic activity or hydrothermal conditions, both of which are important for understanding Mars’ potential to support life. The sulfur rocks provide insights into the planet’s chemical environment and geological processes, adding to the narrative of Mars as a dynamic planet with a complex history.
Curiosity’s Ongoing Mission
Curiosity continues to explore the Gediz Vallis channel, searching for more geological surprises. Despite 12 years of wear and tear, including mechanical issues and wheel damage, the rover remains in good health. Vasavada emphasized the importance of making the most of Curiosity’s remaining operational time, given the wealth of scientific data the rover has already collected.
In conclusion, the accidental discovery of pure sulfur on Mars by the Curiosity rover highlights the unpredictable and exciting nature of space exploration. This finding not only enriches our understanding of Mars’ geological history but also underscores the potential for discovering conditions that might have once supported life on the red planet. As Curiosity continues its journey, scientists remain hopeful for more groundbreaking discoveries that will shed light on Mars’ mysterious past.
