More evidence of water on early Mars provided by ancient volcanic blast

Washington - In a new study, a team of researchers is attempting to learn more about the past atmospheric conditions of Mars by analyzing two unlikely sources – ancient volcanic eruptions and surface observations by the planet’s rover Spirit.

The atmosphere of Mars is less than 1 percent the density of Earth’s. It’s one of the reasons liquid water covers much of our planet but cannot exist on the Red Planet.

As more research points toward the possibility of water on early Mars, scientists have increased their studies on the density of its atmosphere billions of years ago.

The new findings, by Josef Dufek from Georgia Tech Assistant, provide more evidence that early Mars was saturated with water and that its atmosphere was considerably thicker, at least 20 times more dense, than it is today.

“Atmospheric pressure has likely played a role in developing almost all Mars’ surface features,” Dufek said.

“The planet’s climate, the physical state of water on its surface and the potential for life are all influenced by atmospheric conditions,” he said.

Dufek’s first research tool was a rock fragment propelled into the Martian atmosphere during a volcanic eruption roughly 3.5 billion years ago. The deposit landed in the volcanic sediment, created a divot (or bomb sag), eventually solidified and remains in the same location today.

Dufek’s next tool was the Mars rover. In 2007, Spirit landed at that site, known as Home Plate, and took a closer look at the imbedded fragment. Dufek and his collaborators at the University of California-Berkeley received enough data to determine the size, depth and shape of the bomb sag.

The researchers then went to the lab to create bomb sags of their own. They created beds of sand using grains the same size as those observed by Spirit. The team propelled particles of varying materials (glass, rock and steel) at different speeds into dry, damp and saturated sand beds before comparing the divots with the bomb sag on Mars.

No matter the type of particle, the saturated beds consistently produced impact craters similar in shape to the Martian bomb sag.

By varying the propulsion speeds, Dufek’s team also determined that the lab particles must hit the sand at a speed of less than 40 meters per second to create similar penetration depths.

In order for something to move through Mars’ atmosphere at that peak velocity, the pressure would have to be a minimum of 20 times more dense than current conditions, which suggests that early Mars must have had a thicker atmosphere.

“Our study is consistent with growing research that early Mars was at least a transiently watery world with a much denser atmosphere than we see today.

“We were only able to study one bomb sag at one location on the Red Planet. We hope to do future tests on other samples based on observations by the next rover, Curiosity,” Dufek added.

The study has been published the journal Geophysical Research Letters.