Scientists say that they have found no evidence of life on a 4-billion-year-old meteorite from Mars that crashed on Earth in 1984, according to a report by The Associated Press.
About 25 years ago, NASA scientists said that the organic compounds on the meteorite seemed to have been left by living things, though other scientists expressed skepticism at the time, reports the AP.
The theory was unraveled throughout the decades, but the Carnegie Institution for Science's team led by Andrew Steele was the latest to debunk the claim.
The compounds that the NASA team believed were caused by living things were actually caused by water that was probably salty or briny and flowed atop the rock for years, Steele explained.
The water that moved through the meteorite's cracks while it was on Mars formed the carbon compounds, which are still seen on the rock, the researchers explained, according to the AP. This same phenomenon occurs on Earth and provides an explanation for methane present in the Martian atmosphere.
The NASA scientists who initially studied the rock said they were "disappointed" by the latest results of the study and that they are staying firm on their 1996 observations, the outlet reports.
"While the data presented incrementally adds to our knowledge of [the meteorite], the interpretation is hardly novel, nor is it supported by the research," Kathie Thomas-Keptra and Simon Clemett, both astro-material researchers at NASA, stated.
"Unsupported speculation does nothing to resolve the conundrum surrounding the origin of organic matter," added the researchers, according to the AP.
Steele said that technological advancements made his team's newer findings possible and he applauded the original researchers, stating that the life hypothesis was "reasonable."
The only way to prove for certain if there had ever been life on Mars, even at a microbial level, is to bring samples to Earth and analyze them, Steele concludes.
This process is currently ongoing as samples that were collected by NASA's Perseverance Mars rover are set to be sent to Earth in the coming decade, though three dozen samples are desired for analysis, the AP notes.