The Martian meteorite found in the 80s with organic molecules contains no signs of life, but it helps us understand the early Earth

Of all the “rocks” on the planet —which are not exactly few— ALH84001 It is probably one of the most famous and one that has given scientists the most headaches. The reason, very simple: it is not of this world. Allan Hills 84001, which is its full name, is a fragment of a Martian meteorite located in Antarctica almost four decades ago, in December 1984, by a team from the ambitious Ansmet program.

Weighing 1.93 kilos, the boulder has been intriguing researchers for years because of a peculiarity: the presence of organic molecules. To the disappointment of ufologists, however, a new study has just concluded that they are not signs of life, but the result of chemical reactions between water and rocks on the Red Planet around 4 billion years ago. Of course, the finding can help us better understand early Earth and its geochemical processes.

The key: the interaction between water and rock

In an article published in Science, a group of researchers led by Andrew Steele, from the Carnegie Institution (USA) concludes that the molecules are not linked to a biological process, but rather to abiotic chemistry, to interactions between water and rock not unlike those found on Earth. For their analysis, the team resorted to techniques such as nanoscale imaging, isotope analysis and spectroscopy, with which they identified two geochemical processes: serpentinization and carbonization, in both cases marked by the interrelation of rocks and water.

“We examined the carbonates and silicates in the Martian meteorite Allan Hills 84001 using nanoscale analysis to characterize the nature of water-rock reactions on early Mars. We found complex refractory organic material associated with mineral assemblages that were formed by carbonation and serpentinization reactions of minerals. The organic molecules are collated with nanophase magnetite; both were formed in situ during water-rock interactions on Mars”, details the team of researchers in their article. “Two potentially distinct mechanisms of abiotic organic synthesis operated on early Mars during the late Noachian period, 3.9 to 4.1 billion years ago”.

The study sheds light on the origin of ALH84001, a debate that has been ongoing among experts for decades and has captured public interest. In 1996, even the then president of the United States, Bill Clinton, even went on television to announce that just a few days before a team from NASA and Stanford University had made public —curiously, also through Science— that the meteorite could yield evidence of past life on the Red Planet. “If the discovery is confirmed, it will surely be one of the most surprising about our universe science has ever done. Its implications are far-reaching”, Clinton stressed.

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Since then, scientists have put on the table different explanations for the mysterious organic chemicals of Allan Hills 84001. When it comes to proposing answers, they have pointed to the possibility of ancient life on Mars, but also abiotic factors, such as volcanic activity and cosmic impacts. Another hypothesis pointed to that the rock was contaminated when it hit the Earth, which occurred, it is believed, during a meteor shower 13,000 years ago.

“The debate over this meteorite polarized the community many years ago, but I think a lot of that polarization has eased over the years,” Andrew Steele acknowledges to Space.com: “I hope this document inspire discussion again in a positive way”.

Analysis of a meteorite suggests the existence of a gigantic asteroid wandering through the Solar System

In their article they recall that Mars rovers have found complex organic molecules in ancient rocks exposed on the planet’s surface and methane in the atmosphere. “It is not clear what processes produced the organic compounds, with proposals that include both biotic and abiotic sources”, the study abounds, which settles that the tests with ALH 84001 “demonstrate that the abiotic production of organic molecules operated on Mars 4,000 million years ago. years”.

The work of Steele’s team could go beyond the Allan Hills or even the Red Planet and also shed light on the origins of the building blocks of life on Earth itself, billions of years ago. The investigations – Steele details in statements to Space.com – also provides information on “how some important building blocks for life on early Earth and they are occurring elsewhere in our solar system.” Geological reactions such as those detected in ALH 84001 offer a valuable signal for the study of Mars and could help to better understand Enceladus, the moon of Saturn.

Images | NASA-JSC and USGS

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