Study suggests Venus could have been wet planet

Researchers are searching for evidence that Venus could once have harbored liquid water like Earth

By Richard Stenger
CNN.com Writer

(CNN) -- Hot, dry Venus might have once been a wet, cool world like Earth and ancient Mars, planetary researchers said this week.

The new evidence comes from a series of experiments documenting the chemical stability of a common mineral that forms in the presence of water at temperatures similar to that of the surface of Venus.

The researched focused on tremolite, a kind of mineral that forms when lava and magma interact with water. Related minerals are thermodynamically unstable and according to theory should decompose rather quickly at high temperatures.

MESSAGE BOARD Stargazing    Did you know? Venus is the second planet from the sun and the sixth-largest. Venus' orbit is the most nearly circular of that of any planet, with an eccentricity of less than 1 percent.

But researchers at the University of Washington in St. Louis determined that tremolite is much more stable than previously thought. It would take about 4 billion years to decompose by half in conditions similar to Venus' blistering surface, where temperatures hover around 870 degrees Fahrenheit (465 degrees C).

The presence of tremolite or some other hydrous mineral on Venus would confirm once and for all whether Venus lost water over time, according to the scientific team.

"We have shown that tremolite can withstand extreme temperatures and remain intact for billions of years. If we can go to Venus and find tremolite, or some other hydrous mineral, then we would have proof that Venus had water in its past," said researcher Natasha Johnson.

Indirect evidence that Venus had water in the past is found in its high ratio of deuterium to hydrogen. Deuterium, a heavier form of hydrogen, can indicate the past presence water.

"We want to know if it is worth our time to go to Venus and look for minerals that have water in them," Johnson added.

Exactly how wet Venus was remains very controversial, according to Jeffrey Kargel of the U.S. Geological Survey:

"Did it have one percent as much water as Earth or more or less? Was it water that Venus was originally endowed with or did late-arriving comets carry it to Venus?"

An image of rocks on Venus' surface taken by the Soviet Venera probe in 1982

The new report by Johnson and her colleague Bruce Fegley Jr. contributes to the theory that Venus still retains water locked in mineral deposits, according to Kargel.

"Water may still exist on Venus," he said. "Johnson made some tongue-in-cheek statements (in the report) about wondering whether we should bring a parka to Venus (but) those statements make a point that Venus does or can have water."

If tremolite or related watery minerals formed on Venus in the past, current technology should be to detect them, the researchers said. Johnson added that a new generation of landers is needed to better study the fog-enshrouded planet.

"It has been about 20 years since we have purposefully placed anything on the venusian surface," she said. "Although it may seem that we have done all that can be done with Venus, we have really only scratched the surface."

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Washington University

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