A rock on Mars has spilled a surprising yellow treasure after Curiosity accidentally broke through its unremarkable exterior.
When the rover rolled the body of 899 kilograms (1,982 pounds) on the fragile piece of minerals in May of last year, the deposit was opened, revealing yellow crystals of elemental sulfur, known as sulfur.
Although sulfates are quite common on Mars, this represented the first sulfur in its pure elemental form found on the red planet.
Related: Curiosity Finds First In Situ Evidence of Carbon Cycle on Ancient Mars
Most excitingly, the Gediz Vallis Channel, where Curiosity found the rock, is littered with objects that look suspiciously like sulfur rock before it was fortuitously crushed – suggesting that, somehow, elemental sulfur may be abundant there in some places.
Watch the video below for a summary:
YouTube thumbnail
“Finding a field of stones made of pure sulfur is like finding an oasis in the desert,” said Curiosity project scientist Ashwin Vasavada of NASA’s Jet Propulsion Laboratory in July 2024.
“It shouldn’t be there, so now we have to explain it. Discovering strange and unexpected things is what makes planetary exploration so exciting.”
Sulphates are salts that form when sulphur, usually in compound form, mixes with other minerals in water.
When the water evaporates, the minerals mix and dry, leaving the sulfates behind.
These sulfate minerals can tell us a lot about Mars, such as the history of its water, and how it has evolved over time.
Pure sulfur, on the other hand, only forms under a very narrow set of conditions, which are not known to have occurred in the region of Mars where Curiosity made its discovery.
There are many things we don’t know about the geological history of Mars, but the discovery of only scads of pure sulfur hanging on the Martian surface suggests that there is something pretty big that we are not aware of.
Win a $10,000 Space Coast Adventure Vacation
Sulphur, it is important to understand, is an essential element for all life. It is usually taken in the form of sulfates, and is used to make two of the essential amino acids that living organisms need to make proteins.
Since we have known about sulfates on Mars for some time, the discovery does not tell us anything new in that area. We have yet to find definite signs of life on Mars, anyway.
But we keep stumbling across the remains of bits and pieces that living organisms find useful, including chemistry, water, and past habitable conditions.
Stuck here on Earth, we are pretty limited in how we can access Mars.
Curiosity’s instruments were able to analyze and identify the sulfur rocks in the Gediz Vallis Channel, but if it hadn’t taken a circuitous route and one open fissure, it could have been a while before we found the sulfur.
The next step will be to understand exactly how, based on what we know about Mars, that sulfur could have been there.
That will take a bit more work, possibly involving some detailed modeling of the geological evolution of Mars.
Meanwhile, Curiosity will continue to collect data on the same.
Related: Mysterious Streaks on the Hills of Mars May Finally Be Solved
The Gediz Vallis channel is an area rich in Martian history, an ancient waterway whose rocks now bear the imprint of the ancient river that once flowed over them, billions of years ago.
Curiosity continues along the channel, to see what other surprises may be waiting around the next rock.
You can follow Curiosity’s adventures at the rover’s science update blog.
And more than five years into its own mission, NASA’s Mars Perseverance rover is still roaming the surface of the red planet, doing what every five-year-old loves to do – stopping to look at every rock in its path.
One of her latest discoveries happens to look surprisingly out of place, prompting scientists to wonder if it could have come from Mars at all.
Related: Life on Mars? NASA’s Stunning Find Is The Best Evidence Yet
On June 19 this year, the six-wheeled explorer set a new record, officially completing the longest road trip by any robot vehicle on another planet.
In one drive, the rover circled 411 meters of the rocky surface of Mars. This may not sound like much, but compared to Curiosity and Opportunity, which is an inch long with a relative snail’s pace, Percy is a demonstration of speed.
The Mars robots really are a marvel. They represent the intrepidity of the human spirit, resilience, and determination. And, of course, our boundless curiosity about the Universe we live in.
An earlier version of this article was published in July 2024.