Asger Risom
A new study suggests that long-chain organic molecules discovered by NASA’s Curiosity rover on Mars are difficult to explain using known non-biological processes alone, though researchers stop short of claiming evidence of life.
NASA scientists are increasingly struggling to explain a remarkable discovery made by the Curiosity rover on Mars without at least considering the possibility of ancient life.
Last year, Curiosity drilled into what is believed to be an ancient lake bed and detected long-chain organic molecules known as alkanes.
On Earth, such molecules can derive from fatty acids — key components of cell membranes — making them chemically intriguing in the search for life.
While the finding was never presented as proof of biology, new research suggests that purely non-biological explanations may be running thin.
Radiation modeling complicates abiotic theories
In a recent study published in Astrobiology, a team led by Alexander Pavlov of NASA’s Goddard Space Flight Center examined how millions of years of radiation exposure would have altered these molecules after Mars lost much of its atmosphere.
Mars has been bombarded by cosmic radiation for billions of years, which tends to degrade complex organic compounds.
The researchers calculated how 80 million years of radiation would affect long-chain alkanes and used that data to estimate how abundant the molecules must have originally been.
Their conclusion: the initial concentration would have needed to be significantly higher than previously assumed.
Known non-life sources fall short
Scientists have long considered several abiotic — or non-biological — sources for organic molecules on Mars. Carbon-rich meteorites and interplanetary dust particles could have delivered such compounds to the planet’s surface.
Additionally, ancient atmospheric chemistry may have helped organics accumulate billions of years ago.
However, Pavlov and his colleagues found that even when combining these known mechanisms, they could not fully account for the inferred original abundance of the alkanes.
“We argue that such high concentrations of long-chain alkanes are inconsistent with a few known abiotic sources of organic molecules on ancient Mars,” the researchers wrote.
This does not amount to evidence of life — but it does narrow the range of comfortable non-biological explanations.
Caution remains central
The researchers were careful not to overstate their findings. Unknown chemical processes may still exist that could explain the data without invoking biology.
“We agree with Carl Sagan’s claim that extraordinary claims require extraordinary evidence,” they wrote, emphasizing that any confirmed detection of life beyond Earth would require multiple independent lines of evidence.
Mars was once home to rivers, lakes, and possibly oceans, making it one of the most promising places in the solar system to search for past life.
The presence of long-chain organic molecules adds another compelling piece to that puzzle — but not a final answer.
For now, the mystery deepens. NASA may not be declaring life on Mars, but scientists are finding it increasingly difficult to rule it out entirely.
Sources: Futurism; Astrobiology
