UNB Co-Authors Confirm the First Native Sulfur Ever Found on Mars

Two University of New Brunswick researchers are on the author list of a Science cover story that settles a first for Mars: the bright stones NASA's Curiosity rover found in Gale crater are native, elemental sulfur — not the sulfate salts the rover has been tasting for more than a decade.

UNB's newsroom posted the campus angle August 21, the day after Washington University in St. Louis flagged the paper as the cover of the August 20 issue. The study is S. J. VanBommel et al., "A native sulfur deposit in Gale crater, Mars". Twenty-three authors sit on it, from NASA, the Canadian Space Agency, the University of Guelph, and WashU among others. UNB's Dr. Lucy Thompson and Dr. Catherine O'Connell-Cooper are the pair who operate the rover's Alpha Particle X-Ray Spectrometer — APXS — from the Planetary and Space Science Centre.

This is the Mars follow-up UNB previewed when it wrote about Artemis II tracking and the Curiosity science team. The earlier piece promised a deeper look at Thompson and O'Connell-Cooper's geology. The sulfur paper is that look.

Sulfate was the default. This was not.

Until now, almost every sulfur detection on Mars had been a compound: sulfates and sulfides, the salts that record evaporated water. Thompson, who was a scientific lead on Curiosity's Gediz Vallis campaign — a canyon cut through the layered slopes of Mount Sharp inside Gale crater — put the surprise in one line:

"All the sulfur that we'd found had pretty much been present as sulfate. So it was really unusual and surprising and exciting to find elemental sulfur."

APXS is a Canadian-built, funded, managed, and operated instrument on the rover's arm. The UNB pair help pick geological targets, work the instrument with the rest of the mission, and read the spectra it sends home. In Gediz Vallis the rover rolled into a field of light-toned stones that did not match the neighbourhood. The spectrometer said they were sulfur in its elemental form.

WashU's Scott VanBommel, a Canadian researcher and former Guelph graduate student, is the paper's lead author and co-led the analysis with Jeff Berger at NASA Johnson Space Center. Their write-up dates the stones to roughly three billion years ago. The Science abstract's working model: magmatic vapor cooled in the near-surface cryosphere, then native sulfur was released by decompression as Gediz Vallis eroded. UNB's campus summary adds that the deposit was later trapped under debris-flow and avalanche material and exposed again by erosion.

The stones are clean enough that the team argues they formed in place. VanBommel told WashU that if they had been hauled in from elsewhere they would be smashed or full of debris. Curiosity, which weighs less than 750 pounds in Martian gravity, crushed chunks just by driving over them.

Why a Fredericton lab is on a Mars cover

PASSC opened in 2001 as Canada's first dedicated planetary-science centre. It has been on Curiosity's APXS team since the rover landed in 2012. That is the same pipeline UNB sketched for its Earth Station work on Artemis II: a small campus that keeps showing up on instruments other countries paid to fly.

Native sulfur on Earth usually means high heat — fumaroles — or microbes. The paper's authors do not see either in this corner of Gale crater. What they do see is a dry, chemically quiet interval long enough to leave fist-sized sulfur stones sitting unoxidized for billions of years. That is a constraint on how late Gale crater stayed wet, written in an element New Brunswick researchers have been measuring from Fredericton for fourteen years.

Sources

• UNB researchers contribute to discovery of native sulfur on Mars — UNB Newsroom (Aug 21, 2026) — Thompson and O'Connell-Cooper roles, APXS, Gediz Vallis, Thompson quote, 23-author team
• A native sulfur deposit in Gale crater, Mars — Science (doi:10.1126/science.adu5501) — VanBommel et al.; in-place deposit; magmatic-vapor / cryosphere model
• Pristine sulfur preserves a snapshot of ancient Mars — WashU EEPS (Aug 20, 2026) — Science cover; ~3 billion years; VanBommel and Berger quotes
• Planetary and Space Science Centre — UNB — PASSC mandate and NASA / CSA instrument work
• When the First Canadian Flew to the Moon, Fredericton Was Listening — NB Tech News — prior UNB NASA / Curiosity coverage