Zircon crystals from the Jack Hills in Western Australia are the oldest rock fragments ever found. To date, this is the best evidence we have for the earliest stable, habitable surface on the Earth, and we only know about it from studying this incredible mineral. By studying the chemistry of the ancient zircon grains geologists have been able to find clues about the earliest history of the Earth, including the presence of liquid water on the surface by the time that these zircons had formed. We know that these zircons formed in a different rock that was weathered and recycled, and the zircons were incorporated into the younger sandstones and conglomerates, which were then buried and metamorphosed. The rocks that contain the zircons are only ~3.0 billion years old, but some of the zircons are as old as 4.4 billion years. ![]() Specifically, I'm talking about zircons in the Jack Hills sedimentary rocks of Australia. On the Earth, the oldest materials from Earth are zircons that have been incorporated into much younger sandstone. Particularly for the early records of planets, where rocks have generally been metamorphosed, melted, weathered, recycled, or otherwise destroyed by nature and the ravages of time, zircons can still preserve records of the environments they formed in. To a geologist, this is exciting because it means that zircons tend to preserve records of the environments they formed in, even when they're part of a rock that has been extensively altered. The mineral is chemically, physically and thermally robust-meaning that once it's formed, it tends to stick around, and there's not a lot that changes it. Zircons can form in most kinds of igneous rocks, and larger zircons typically form in metamorphic rocks. The story focuses on the study of the mineral zircon, a zirconium silicate mineral (ZrSiO 4). It is noteworthy that previous Martian meteorite research, including work by Steele, has demonstrated that a range of organic molecules can be created by abiotic organic chemistry.The short version is that it challenges our understanding of when Mars could have sustained an environment capable of supporting life-that is, a habitable environment-effectively shortening the window for possible life on Mars. ‘Understanding the processes and sequence of events that shaped this rich organic bounty will reveal new details about Mars’ habitability and potentially about the reactions that could lead to the formation of life,’ said study co-author Andrew Steele from Carnegie, who has studied organic material in Martian meteorites and served on the science teams of the Perseverance and Curiosity rovers. ![]() Greater understanding of the genesis of such organic compounds on Mars can help shed light on whether the planet ever hosted life, and it can also illuminate the geological history of Earth, explained the team that comprised scientists from several institutions including the Technical University of Munich in Germany and the Carnegie Institution for Science in Washington DC. These organic molecules provide new insights about the high-pressure, high-temperature geochemistry that shaped the deep interior of Mars and the researchers point to a connection between the planet’s carbon cycle and its mineral evolution. One of the biggest surprises was the discovery that the Tissint contained an abundance of organic magnesium compounds, which had never been seen before on Mars. The scientists have assembled the most comprehensive catalogue to date of the various organic compounds found in the five Martian meteorites that have been recovered on Earth since 1815, or in any sample retrieved by a Mars rover. ![]() The Tissint meteorite from Mars that was found in Morocco in 2011Īn international team of researchers has found that Martian meteorite Tissint, which landed in Morocco in July 2011, contains a ‘large diversity’ of organic compounds commonly associated with life. Source: © Ludovic Ferriere/Natural History Museum Vienna
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