Mars clays may have volcanic source
Deposits didn’t need flowing water to form, new research suggests
By Erin Wayman
Ancient clay deposits on Mars may not indicate that the Red Planet was originally a warm, wet place, as scientists have thought. Instead of needing liquid water to form, many of Mars’ 4-billion-year-old clays could have originated from cooling lava, researchers report online September 9 in Nature Geoscience.
Clays are widely scattered across Mars’ oldest terrain, dating to the Noachian period 4.1 billion to 3.7 billion years ago. When the Mars Express and Mars Reconnaissance Orbiter discovered these minerals from orbit several years ago, geologists assumed the clays were a result of large bodies of water weathering and altering Mars’ basalt surface. But last year, some researchers suggested that underground hydrothermal activity provided the water that is necessary to form the clays (SN: 12/3/11, p. 5).
Now there’s another suggestion: Crystallizing lava may have contained tiny pockets where water could react with other chemicals to make small amounts of iron- and magnesium-rich clay. No additional water flowing on the surface or belowground would be needed. So early Mars could have been a largely cold, dry world.