Clay Studies Alter View of Early Mars Environment

July 18, 2007
Clay Studies Alter View ...

A study of the thermodynamics of clays found on Mars suggests that little carbon dioxide could have been present during their formation, which contradicts a popular theory of the early Martian atmosphere and will send researchers looking for other explanations for clay formation.

Vincent Chevrier of the University of Arkansas and François Poulet and Jean-Pierre Bibring of the Université Paris-Sud in Orsay, France, reported their findings in the journal Nature.

Gullies, valleys and clay formations found on Mars seem to point to a wet past for the Red Planet. Almost all clays formed on earth do so in the presence of water or under extremely humid conditions. These clay remnants of ancient Mars had previously led scientists to hypothesize that the earliest era on the planet, the Noachian period, had a carbon-dioxide-rich atmosphere that created a warm, wet surface with liquid water -- ideal for creating clays.

Chevrier used thermodynamic calculations to examine possible historic conditions on the planet. These calculations look at the equilibrium conditions of the clay deposits on Mars with respect to different relevant other mineral phases -- carbonates, sulfates, iron oxides -- to extrapolate the surface environment at the time of their formation. He made the assumption that the clays would form on the surface of Mars in the presence of liquid water as they do on Earth.

In a carbon-dioxide-rich environment, clay formation would be accompanied by carbonate formation, but current studies of Mars have found no such compounds. Chevrier's calculations show that, given current conditions, the carbon dioxide pressure would have been low in the Noachian atmosphere.

"If you had a thick atmosphere of carbon dioxide, you should have abundant carbonates," Chevrier said. "So far no one has seen even a grain of carbonate."

Despite this evidence that carbon dioxide did not provide a warm, wet atmosphere, it is possible that other greenhouse gases, such as methane, helped create the ancient conditions that shaped modern-day Mars. It also is possible that impacts generated heat and energy that could have warmed the Mars surface, creating liquid water. However, both of these hypotheses present their own enigmas: If methane was present, where did it go? And how do you relate impacts to the formation of clays? On Mars, thousands of square kilometers are covered by clay deposits up to 100 meters thick - not the hallmark of a single impact event.

Another possibility is that some of these chemicals - the carbonates and the methane - may be present deep below the surface of Mars. To address the question of the underground presence of these materials will require a Mars rover with a probe. Until then, the history of the early Martian atmosphere remains an enigma.

"Thermodynamics can give you the conditions, but not the process," Chevrier said.

Source: University of Arkansas

Explore further: Mars Curiosity celebrates sol 2,000

Related Stories

Mars Curiosity celebrates sol 2,000

March 23, 2018

NASA's Mars Curiosity rover just hit a new milestone: its two-thousandth Martian day, or sol, on the Red Planet. An image mosaic taken by the rover in January offers a preview of what comes next.

Mystery solved for mega-avalanches in Tibet

January 23, 2018

An international scientific effort determined the cause of a highly unusual and deadly glacier avalanche in Tibet in 2016, a new Nature Geoscience paper says.

Recommended for you

Studying dwarf galaxies to get the big picture

April 23, 2018

EPFL scientists have completed the fastidious task of analyzing 27 dwarf galaxies in detail, identifying the conditions under which they were formed and how they've since evolved. These small-scale galaxies are perfect for ...

NASA engineers dream big with small spacecraft

April 20, 2018

Many of NASA's most iconic spacecraft towered over the engineers who built them: think Voyagers 1 and 2, Cassini or Galileo—all large machines that could measure up to a school bus.

Unveiling the secrets of the Milky Way galaxy

April 20, 2018

A multinational team of astronomers involving the University of Adelaide has catalogued over 70 sources of very high energy gamma rays, including 16 previously undiscovered ones, in a survey of the Milky Way using gamma ray ...

Where is the universe's missing matter?

April 19, 2018

Astronomers using ESA's XMM-Newton space observatory have probed the gas-filled haloes around galaxies in a quest to find 'missing' matter thought to reside there, but have come up empty-handed – so where is it?

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

out7x
1 / 5 (1) Dec 06, 2007
The CO2 atmosphere would have escaped due to insufficient gravity. Carbonates form in shallow seas. Clay formation is from weathering. These are two separate processes.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.