Carbon-based molecules that make up the building blocks of life such as proteins and DNA have been found in meteorites from Mars that have fallen to Earth, raising fierce debate as to whether they are signs of life or contaminants invading the rocks after they landed.
Researchers analyzed 11 martian meteorites, including one that crashed into the Moroccan desert in 2011, and determined organic molecules within these meteorites did originate on Mars.
"Mars apparently has had organic carbon chemistry for a long time," researcher Andrew Steele, a microbiologist at the Carnegie Institution of Washington, told SPACE.com.
However, he said, a biological origin for these organic molecules has been ruled out.
"They formed from volcanic processes," Steele said.
Complex hydrocarbons found in the meteorites were found inside grains of crystallized minerals that formed within cooling volcanic magma, the researchers determined.
"When the minerals crystallized from the magma, they trapped carbon in them, and over time, organic compounds formed within these mineral bottles," Steele said.
Still, he said, it is unknown what other activity might have taken place on Mars after such organic molecules formed.
"We now find that Mars has organic chemistry, and on Earth, organic chemistry led to life, so what is the fate of this material on Mars, the raw material that the building blocks of life are put together from?" Steele said.