The Alan Hills meteorite is a part of Mars history. It came from Mars and meteorite hunters. It is thought to be one of the oldest pieces of rock to come from Mars.
In 1996 a team of researchers said they found evidence of life in a meteorite.
Did they?
The Alan Hills meteorite is part of Mars lore. Twelve years after it was discovered, a team of scientists claim to have found evidence of fossils in the meteorite.
The carbonate globules are similar in size and texture to some of the carbonate precipitates. Many of the observed features, including the PAHs, could be explained by the formation of the globules by biogenic processes. The PAHs, carbonate globules, and their associated secondary mineral phases and textures could be fossils from a past martian biota.
It was huge news that it was controversial. It was so huge that Bill Clinton was able to make a speech about it. Clinton was circumspect when he said that the discovery should continue to be reviewed. It must be confirmed by other scientists.
The strange, organic-seeming morphologies inside the meteorite were not biological in origin according to other scientists.
What made them?
The images of the meteorite showed structures that looked like living structures. The image is from NASA.
There are a lot of false positives when it comes to fossils. geological structures can mimic organic structures. Scientists interpreted the Alan Hills meteorite as evidence of life in 1994. A host of geological processes can produce structures that look organic. These structures are called chemical gardens by scientists.
These images show carbonate-silica biomorphs that are not biological. The image on the left shows structures that look like they are biological. The image on the right shows the blown-up area on the left, which appears to be a branching, flowering organisms. The image is from the Florida State University.
The images could easily be assumed to be organic. The idea that they could be biological had to be looked into. They are geological, and now we know they are not biological.
A team of researchers took a deeper look at the structures in ALH84001. They wanted to understand the geological processes that created them and learn something new about Earth and Mars.
The paper is titled "Organic synthesis associated with serpentinization and carbonation on early Mars." The lead author of the paper is Andrew Steele. Steele is a Senior Staff Scientist at Carnegie University.
Life doesn't come directly from interactions between water and rock. Habitability on both Earth and Mars is likely to be a result of those interactions. They produce organic molecule and create mineralogical diversity. The scientists who found evidence of life in the meteorite were wrong.
The search for life on Mars is more than just an answer to the question.
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Andrew Steele is the lead author.
A deeper understanding of geological interactions is gaining importance now that the Perseverance Rover is on Mars. Perseverance is trying to find evidence of life in the Jezero crater. Scientists are better able to understand the evidence Perseverance gathers by understanding the geological interactions and the false positives they can create. The meteorite from Alan Hills can play a role.
Steele said in a press release that analyzing the origin of the meteorite's minerals can reveal both the geochemical processes occurring early in Earth's history and Mars' potential for habitability. Steele is a member of both the Perseverance and Curiosity rovers' science teams and has researched organic material in Martian meteorites.
Mars rovers have found organic compounds. Methane can have a biological source, and both rovers and orbiters have detected it. Living processes are associated with organic compounds containing carbon, oxygen, hydrogen, nitrogen, sulphur, and other elements. Non-biological processes can also produce them. Abiotic organic chemistry is what those processes are called. The organic carbon in the Alan Hills meteorite raises a question: What process produced it?
There are different answers to the question, including volcanic activity, hydrological exposure, and impact events on Mars. The living processes are a hypothetical answer. They could have been created by ancient Martian life.
The Allan Hills meteorite was provided by NASA.
New investigative techniques are at the disposal of scientists. One of them is using technology. In 1994, researchers weren't able to study the Alan Hills meteorite because of the lack of scale images. The researchers used a variety of methods to deepen their understanding of ALH84001.
The meteorite underwent two types of interactions.
serpentinization is a name that brings organic activity to mind. serpentinization is not related to chemistry. It happens when rocks with iron or magnesium interact with water. The minerals of the rocks are changed by serpentinization. The rocks absorb a lot of water and destroy their initial structure.
The second process is called oxidation. Carbonation is the chemical reaction of carbon dioxide to give carbonates, bicarbonates, and carbonic acid. The reaction between rocks and water with dissolved CO2 is called carbonation.
The results show that the processes occurred quickly. They weren't able to determine if they happened at the same time or at different times. The paper states that they find complex organic material associated with mineral assemblages. During water-rock interactions on Mars, the organic molecule are colocated with the magnetite.
During the Late Noachian period, these reactions occurred on Mars. The Late Noachian was a period of intense impacts on Mars, and the planet likely had extensive surface water. It coincides with the rise of Life on Earth. The search for evidence of life is done on the surface geology from this time. The Perseverance Rover is looking for something that dates from the Noachian period.
The Perseverance Rover searches for evidence of ancient life in the region around Jezero Crater. The Noachian Period was a time when surface water was plentiful. The image is from the ESA/DLR/FU CC BY-SA 3.0 IGO.
The results are in line with recent developments. The carbonates in ALH84001 were formed during a period of surface water evaporation.
The mineralogical features caused by serpentinization are rare in Martian meteorites. Scientists have found evidence of both processes on the planet's surface, as well as other younger meteorites. The Alan Hills meteorite is the first evidence of both processes.
Steele has found organic compounds in other meteorites and on Mars with the SAM instrument. Scientists are pretty sure that the abiotic processes have been working on Mars for a long time.
The presence of them indicates that Martian geology supplied some of the necessary materials for life.
Steele said that these geological reactions are responsible for a pool of organic carbon compounds from which life could have evolved and represent a background signal that must be taken into consideration when searching for evidence of past life on Mars.
The results go beyond Mars. They tell us about Earth and the moon.
An artist's impression of the Enceladus. The ice grains were detected by the Cassini spacecraft. The image is from NASA/JPL.
If these reactions happened on ancient Mars, they must have happened on ancient Earth and could explain the results we have seen from the moon Enceladus. This type of organic synthesis requires a brine that contains dissolved carbon dioxide to be released into the air. The search for life on Mars is more than just an answer to the question. It addresses the question of where we came from.
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