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https://www.sciencealert.com/curiosity-cracked-open-a-rock-on-mars-and-discovered-a-big-surprise

Curiosity Cracked Open a Rock on Mars And Discovered a Big Surprise
Space
09 March 2025
ByMichelle Starr

An accident on Mars revealed the surprising contents of an otherwise
unremarkable rock. (NASA/JPL-Caltech/MSSS)
A rock on Mars spilled a surprising yellow treasure after Curiosity
accidentally cracked through its unremarkable exterior.

When the rover rolled its 899-kilogram (1,982-pound) body over the rock
in May last year, the rock broke open, revealing yellow crystals of
elemental sulfur: brimstone.


Although sulfates are fairly common on Mars, this represents the first
time sulfur has been found on the red planet in its pure elemental form.

What's even more exciting is that the Gediz Vallis Channel, where
Curiosity found the rock, is littered with rocks that look suspiciously
similar to the sulfur rock before it got fortuitously crushed –
suggesting that, somehow, elemental
sulfur may be abundant there in some places.

Gediz Vallis Mars
Gediz Vallis channel beyond the ridge, with surrounding sulfate-bearing
unit. (NASA/JPL-Caltech/ESA/University of Arizona/JHUAPL/MSSS/USGS
Astrogeology Science Center)
"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.

"It shouldn't be there, so now we have to explain it. Discovering
strange and unexpected things is what makes planetary exploration so
exciting."

Sulfates are salts that form when sulfur, usually in compound form,
mixes with other minerals in water.

When the water evaporates, the minerals mix and dry out, leaving the
sulfates behind.

These sulfate minerals can tell us a lot about Mars, such as its water
history, and how it has weathered 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, to be fair, a lot of things we don't know about the
geological history of Mars, but the discovery of scads of pure sulfur
just hanging about on the Martian surface suggests that there's
something pretty big that we're not aware of.

Sulfur, it's important to understand, is an essential element for all
life. It's usually taken up in the form of sulfates, and used to make
two of the essential amino acids living organisms need to make proteins.

Since we've known about sulfates on Mars for some time, the discovery
doesn't tell us anything new in that area. We're yet to find any signs
of life on Mars, anyway.

But we do keep stumbling across the remains of bits and pieces that
living organisms would find useful, including chemistry, water, and past
habitable conditions.

Stuck here on Earth, we're fairly limited in how we can access Mars.
Curiosity's instruments were able to analyze and identify the sulfurous
rocks in the Gediz Vallis Channel, but if it hadn't taken a route that
rolled over and cracked one open, it could have been sometime until we
found the sulfur.

The next step will be to figure out exactly how, based on what we know
about Mars, that sulfur may have come to be there.

That's going to take a bit more work, possibly involving some detailed
modeling of Mars's geological evolution.