Curiosity crossed the Gediz Vallis canal and passed over a rock that opened and revealed crystals of pure yellow sulfur.
![Image of a pile of rocks on Mars. The soil surrounding the rocks is terracotta-colored, and the rocks in the center of the image have yellow crystals on the edges.](https://www.astronomy.com/uploads/2024/07/Sulfur-crystals-on-Mars-1200x676.jpeg)
The sulfur crystals, as observed on May 30, are elemental sulfur, or pure sulfur. Curiosity determined what the crystals were made of. Credit: NASA/JPL-Caltech/MSSS
NASA's Curiosity rover made an unexpected discovery that one scientist compared to finding an “oasis in the desert.”
On May 30, Curiosity passed through the Gediz Vallis channel and over a rock that split open and revealed crystals of pure yellow sulfur. These crystals, according to a NASA Press ReleaseThey are a first for the region and raise questions about the geological history of Mars.
“Finding a field of stones made of pure sulfur is like finding an oasis in the desert,” Ashwin Vasavada, Curiosity’s project scientist at NASA’s Jet Propulsion Laboratory, said in the statement. “It shouldn’t be there, so now we have to explain it. Discovering strange and unexpected things is what makes planetary exploration so exciting.”
The Gediz Valley Canal and sulfur
![](https://www.astronomy.com/uploads/2024/07/Curiosity-rover_view_of_Gediz_Vallis-1200x434.jpg)
Experts knew about the Gediz Vallis channel long before NASA sent a rover there. Flowing water and debris likely created the region, which carved out part of Mount Sharp. Piles of debris around the area suggest floods and landslides carried it there at some point. The flowing water likely carried smoother stones.
Related: Where did the water on Mars go?
Among the debris, Curiosity captured images of jagged rocks surrounded by a white halo. Scientists suspect that dry avalanches brought these rocks there and that their white halos formed after they absorbed water from the area. The channel is in a sulfate-rich region. Previous sulfate readings have been a mix of sulfur and other minerals. In this region, the Curiosity rover captured images of a field of several pure sulfur boulders and drilled its 41st rock sample.
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