The researchers contend that, like geological processes on Earth, water once moved downward, carrying away some of the elements as it flowed downward into the ground.

They specifically compared this process on Mars with the process that happened in the Atacama Desert, in Chile.

The Amundson team concentrated on sulfate deposits on Mars and in the Atacama Desert, along with Antarctica, of Earth.

Amundson states, "The Atacama Desert and the dry valleys of Antarctica are where Earth meets Mars. I would argue that Mars has more in common geochemically with these climate extremes on Earth than these sites have in common with the rest of our planet." [UC Berkeley News]

The team compared sulfate (an ester or a salt of sulfuric acid) on Earth, which is found in Earth’s oceans and its atmosphere. It is also found in rain falling on the ground. Sulfate typically does not remain on the ground, but flows downward into the ground.

However, because it is less soluble (less dissolvable) than chlorides (any compound of chloride and another element), for instance, one would expect that sulfates to move downward less distances than chlorides.

Thus, the way sulfate accumulates in the soil on Earth is similar, according to these researchers, to the distribution of sulfate on Mars.

Amundson states, "Sulfates tend to be less soluble in water than chlorides, so if water is moving up through evaporation, we would expect to find chlorides at the surface and sulfates below that. But when water is moving downward, there's a complete reversal of that where the chlorides move downward and sulfates stay closer to the surface. There have been weak but long-term atmospheric cycles that not only add dust and salt but periodic liquid water to the soil surface that move the salts downward." [UC Berkeley News]

Amundson’s team suggests that the history of Mars may be similar to processes at work on Earth.

He states, "It seems very logical that a dry, arid planet like Mars with the same bedrock geology as many places on Earth would have some of the same hydrological and geological processes operating that occur in our deserts here on Earth. Our study suggests that Mars isn't a planet where things have behaved radically different from Earth, and that we should look to regions like the Atacama Desert for further insight into Martian climate history." [UC Berkeley News]

Scientists are not generally convinced yet that the geology and atmosphere of Earth can be used to analyze Mars, and vice versa. However, the Amundson study does add evidence that, indeed, the Earth and Mars may be similar to each other—at least in some respects—and futher studies would seem to be indicated to learn more about the parallels with Earth and Mars.

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Atmosphere  Earth  Mars  Science  Water  William Atkins