Evidence of ancient lakes, rivers found in clay Martian soil

William Atkins
Thursday, 17 July 2008 20:48

Science - Space

The second study was published in the June 2, 2008 issue of the journal Nature Geosciences. The title of the article is “Clay minerals in delta deposits and organic preservation potential on Mars.”

Its authors are: Bethany L. Ehlmann, John F. Mustard, Caleb I. Fassett, Samuel C. Schon, James W. Head III, David J. Des Marais, John A. Grant, and Scott L. Murchie.

The study researches the clay-rich sedimentary deposits found in a crater lake within the northern hemisphere of Mars.

Approximately 25 miles (45 kilometers) in diameter, Jezero Crater was filled with water billions of years ago when rivers took water from the highlands and into this crater formed by one of the impacts.

CRISM team member Bethany Ehlmann, from the Department of Geological Sciences, Brown University (Providence, Rhode Island), states, “The distribution of clays inside the ancient lakebed shows that standing water must have persisted for thousands of years. Clays are wonderful at trapping and preserving organic matter, so if life ever existed in this region, there's a chance of its chemistry being preserved in the delta."

The team identified three principal classes of water-related minerals dating to the early Noachian period (which occurred 4.6 to 3.8 billion years ago on Mars, the earlier era of the planet and the approximate time when the solar system was formed).

The classes are aluminum-phyllosilicates, hydrated silica or opal, and iron/magnesium-phyllosilicates.

What is important about these three classes of minerals, according to their paper, is that the differences in the minerals suggest several water-based processes were used to create them.

They conclude in the abstract to their paper, “We find that the two deltas and the lowest observed stratigraphic layer within the crater host iron–magnesium smectite clay. Jezero crater holds sediments that record multiple episodes of aqueous activity on early Mars. We suggest that this depositional setting and the smectite mineralogy make these deltaic deposits well suited for the sequestration and preservation of organic material.”

Read more about these discoveries, and look at images of the discoveries, at the NASA MRO website “NASA Spacecraft Shows Diverse, Wet Environments on Ancient Mars.”

The NASA Jet Propulsion Laboratory website for MRO is found at: http://marsprogram.jpl.nasa.gov/mro/.