Nearly three decades ago, the Allan Hills 84001 meteorite - a rock formation that formed on Mars about 4 billion years ago was declared by NASA to contain traces of life attesting to the existence of life on the Red Planet. This statement immediately caused fierce controversy in the scientific world, questions related to extraterrestrial life were constantly raised. After many years, when things seemed to have gone into the past, recently, a research paper in the journal Science once again brought this issue back.

Meteorite origin and controversy over signs of extraterrestrial life

The Allan Hills meteorite 84001 (abbreviated ALH84001) was formed on Mars during the tumultuous Noachian period. The meteorite was thrown into space by a giant collision about 17 million years ago and landed on Earth about 13,000 years ago. The meteorite is named after the place where it was found - Allan Hills in Antarctica. ALH84001 weighs about 1.94 kg and is one of the oldest meteorites ever found.

In 1996, a group of NASA scientists shocked the world when they declared worm-shaped carbonate blocks on meteorites to be fossils, and this was the first evidence of extraterrestrial life. This statement made many scientists around the world doubtful. They began to put forward other theories to explain the above carbonates, such as volcanic activity, space collisions or traces of currents, etc. Most scientists consider that there is no evidence of life on ALH84001, but the debate continues after more than a quarter of a century.

New study disproves NASA claims

Until recently, an article in the journal Science once again offered evidence that the features seen on the meteorite were unrelated to life. The new paper argues that the organic molecules found on meteorites were formed from slow and steady interactions caused by groundwater sifting through cracked rocks. This new study was led by astrophysicist Andrew Steele from the Carnegie Institution for Science.

In fact, it is impossible to confirm a place with life just because it contains organic matter. Organic molecules usually include carbon, hydrogen, oxygen, nitrogen, and sulfur. They are usually related to biological processes, but can also arise from abiotic processes, otherwise known as “Abiotic Organic Chemistry”.

The new paper also reminds us: "The probe has found complex organic molecules in ancient rocks on the Martian surface, as well as methane in the Martian atmosphere today."

"It's not clear what process created these organics, both biotic and abiotic," explains Steele, a member of NASA's Perseverance and Curiosity probe science team.

The new study is not just an attempt to disprove NASA's claim that ALH84001 contains Martian fossils. The study also talks about early conditions on Mars and Earth, how these conditions underpinned life, and why Mars exhibited the features we see today, such as presence of methane gas. "The search for life on Mars is not just an attempt to answer questions about alien life ," Steele said. It is also related to the early Earth environment and indicates the origin of life on Earth'.

Steele and his colleagues used nanoscale microscopy, spectroscopy, and isotope analysis to study the meteorite. From this, they concluded, organic molecules were formed as a result of the interaction between water (possibly seawater) and basalt.

The paper states that one of two geochemical processes can lead to organic synthesis: solidification and carbonization. During solidification, igneous rocks rich in iron or magnesium interact with flowing water, producing hydrogen. Meanwhile, with carbonation, acidic water containing dissolved carbon dioxide interacts with the rock, creating carbonate salts.

It is not yet known exactly what process leads to organic synthesis, nor the exact sequence of this phenomenon. But the scientists assert that the reactions that produce organic matter from the reduction of CO2 and the abiotic processes that cause the carbon-rich compound have been going on for a very long time.

NASA decided not to compromise

Despite these arguments, according to The Guardian, the scientists behind the 1996 study were not convinced by the new paper. They say that it offers nothing new and that this interpretation is not supported by any evidence.

The debate thus still rages on. Just relying on a tiny meteorite won't confirm that there is life on Mars. So, the best option right now is to wait for the mission to bring samples from Mars to Earth. Fortunately, this mission has been carried out. NASA's Perseverance probe is currently collecting and storing surface samples for a mission to bring samples to Earth, which could be completed in the early 2030s.
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