A key chemical ingredient for life may have been more abundant on early Mars than on early Earth, researchers say.
The nutrient in question, phosphate, serves as the backbone of DNA and is also an essential part of the molecules cells use for energy and membranes. Scientists think it was also critical to reactions that led to the origin of life on Earth.
Mars is rich in phosphate, five to 10 times more so than Earth, based on analysis of meteorites from Mars that crash-landed on Earth as well as scans of the Red Planet's surface by NASA's Spirit and Opportunity rovers. This detail adds to speculation about whether or not Mars once had life, and whether or not it still might. [The Search for Life on Mars (Photo Timeline)]
However, just because phosphate is present does not mean it is necessarily available for use in chemical reactions for life. For instance, the minerals that hold phosphate on Earth dissolve very slowly, limiting its availability in watery environments, which scientists think may have posed a roadblock to the emergence of life on Earth.
Gauging the hurdles for life
To learn more about hurdles any life on Mars could have faced when it came to phosphate, planetary geochemist Christopher Adcock at the University of Nevada at Las Vegas and his colleagues examined how the phosphate-loaded minerals thought to be most common on Mars dissolved across a range of acidity levels.
The researchers found the dominant phosphate-loaded minerals on Mars are distinctly more soluble, and thus release more phosphate into water, than those most common on Earth.
"One hurdle to the origin of life on Earth was limited available phosphate within environments," Adcock told Space.com. "Our results suggest such a hurdle may not be as significant when looking at the possibility of life arising on Mars."
The experimental findings suggest phosphate is released as much as 45 times faster during interactions between water and rock on Mars than on Earth. All in all, phosphate concentrations in wet environments on early Mars may have been twice those of early Earth.
"It's exciting whenever you find evidence that has positive implications for the possibility of life outside of Earth," Adcock said.
Did life start on Mars?
Some researchers have even suggested that life on Earth may have begun on Mars, hitchhiking to Earth aboard meteorites blasted off the Red Planet by cosmic impacts.
These synthetic crystals of the calcium phosphate mineral whitlockite are similar to those used to produce the extraterrestrial mineral merrillite. If life ever arose on Mars, merrillite may have been a major source of biologically required phosphate. Largest crystals are about 1 millimeter wide.
"I don't think our results have any direct bearing on the theory that terrestrial life may have begun first on Mars, other than that our results suggest phosphate for potential biologic reactions may have been more available on Mars — that the 'phosphate problem' may not have been as significant there," Adcock said.
The researchers are now modeling how Martian rocks high in phosphate might break down chemically to further understand how the chemical moves on Mars "and the implications for potential past or present life there," Adcock said.
"We haven't discovered life on Mars, nor have we presented evidence that it existed there," Adcock cautioned. "However, we have shown that one potential roadblock for life to arise on Mars may not be such a roadblock after all."
Adcock and his colleagues Elisabeth Hausrath and Paul Forster detailed their findings online Sept. 1 in the journal Nature Geoscience.
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First published September 1 2013, 11:52 AM