A GLOBAL WARM STORY, TOLD IN NANO-SIZED CRYSTALS
A new study published in Science reveals that ancient Mars experienced long-lasting warm and wet conditions deep underground, even as the planet’s surface climate turned cold.
The Data from the Red Planet
NASA's Curiosity rover drilled 20 samples from different elevations within Gale Crater. Using the Chemistry and Mineralogy (CheMin) instrument—which employs X-ray diffraction—the rover analyzed the mineral composition and crystal structure of each sample.
Key Findings: A Tale of Two Elevations
- Crystal Size Variation: Hematite crystallites from higher (younger) elevations measured less than 10 nanometers in size. In contrast, those from lower (older) elevations reached up to 65 nanometers.
- Mineral Composition: The mineral goethite was detected in samples from higher elevations but was completely absent from lower-elevation samples.
- Formation Conditions: According to NASA researcher Tanya Peretyazhko, the presence of goethite and smaller crystals in upper layers indicates formation under colder conditions with limited water. The absence of goethite and the presence of larger crystals in lower layers indicates formation under warmer conditions with long-standing water.
"What we found was that warm and wet conditions were present for extended periods in buried rocks, despite Mars' climate becoming colder." — Tanya Peretyazhko, Planetary Scientist, NASA Johnson Space Center
Duration of Water Activity
The findings suggest that warm groundwater may have persisted in the deepest layers of Gale Crater for up to 4.7 million years.
Scientific Context
Iron oxides like hematite form only in the presence of water. This study demonstrates that the size and structure of hematite crystals can serve as reliable markers of past climate conditions.
What the Researchers Say
"With CheMin’s X-ray diffraction patterns, we can look at the hematite crystal’s size and dimensions, information that can’t be gathered from satellite analysis." — Tom Bristow, Principal Investigator of CheMin, NASA Ames
"It doesn’t just tell you there is hematite. One can use the data to extract the size and shape of the hematite crystallites and the presence of other related minerals." — Ashwin Vasavada, Curiosity Project Scientist, NASA JPL
The Bigger Picture
The study underscores that buried rocks on ancient Mars could have supported habitability—if other essential factors were present—even as the planet's surface became increasingly inhospitable.