If life ever arose on Mars, merrillite may have been a major source of biologically required phosphate. Largest crystal are ~1mm.
Credit: C. T. Adcock / University of Nevada Las Vegas
A trio of researchers at the University of Nevada has found that phosphate found in minerals on Mars, is far more soluble than it is in natural Earth minerals.
In their paper published in the journal Nature Geoscience, the researchers describe how they synthesized mineral types found on Mars and then tested how well they dissolved in water releasing phosphate as compared to samples from natural Earth minerals.
Most scientists agree that phosphate is a key ingredient for life. Put another way, they believe that life couldn't have evolved without it.
For that reason, scientists have been studying ways in which minerals that contain phosphate could have broken down to allow the phosphate to escape.
Such studies have thus far found that minerals that hold phosphate on Earth are not very soluble—they don't break down easily when soaked in sea water.
That has led to what Earth scientists call "the phosphate problem." How did life get started on Earth if there wasn't enough phosphate around when life was first beginning?
Some have suggested the answer is that it didn't, instead, it started on another planet, such as Mars, and made its way here via meteorites.
Prior research has already shown that Mars has much more phosphate than does Earth. In this new effort, the team in Nevada looked at minerals that exist on Mars to see if they might be more soluble in water as well.
Lacking samples from Mars to test, the researchers synthesized chlorapatite and merrillite in their lab—two common phosphate bearing minerals found on the Red Planet.
They then soaked samples in several tubs, each with a different pH level for varying amounts of time. As they did so, they measured how much phosphate made its way into the water and how long it took.
In analyzing their results, the researchers found that more phosphate made its way into the water with both types of minerals and they did so at a faster rate than minerals that contain phosphate found naturally on Earth.
In some cases, they report that the Mars rocks released phosphate up to 45 percent faster than Earth rocks.
The findings by the team don't prove that life began on Mars and migrated to Earth—after all, scientists have yet to prove life ever existed Mars. But it does add some credence to the argument that perhaps life did start somewhere other than our home planet, which if true, might mean it's still out there waiting for us to discover it.
More information: Readily available phosphate from minerals in early aqueous environments on Mars, Nature Geoscience (2013) DOI: 10.1038/ngeo1923
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