Researchers throw more light on 1.2bn-yr-old Mars meteorite
A team of scientists from various institutions, including the Universities Space Research Association (USRA) have found that the martian meteorite discovered in Algeria is 1.27 billion years old.
[A different Mars meteorite found in Northwest Africa, known as 7635, is a shergottite believed to be around 2.5 billion years old. (Image credit: Mohammed Hmani)]
Washington: A team of scientists from various institutions, including the Universities Space Research Association (USRA) have found that the martian meteorite discovered in Algeria is 1.27 billion years old.
The scientists further established that the meteorite - called Northwest Africa (NWA) 13441 and physically found in Algeria in 2019, originated from a previously unsampled, pristine source on Mars.
Dr. Robert Willie Nicklas of Universities Space Research Association's Lunar and Planetary Institute, who was part of the team, used high-precision isotopic techniques to date the sample to approximately 1.273 billion years ago, making it the first such discovery of its kind.
Dr. Nicklas conceived the study, secured the meteorite sample, and supervised Boston College graduate student and lead author Dylan Seal throughout the isotopic analyses and preparation of the manuscript.
Because rocks from Mars reach Earth only when impacts eject them from the planet's surface, researchers have access to a relatively limited collection of approximately 400 martian meteorites for the study published in the journal Geochimica et Cosmochimica Acta.
Dated samples from the most common group of igneous martian rocks, the shergottites, are almost entirely geologically young, less than 600 million years old.
Between that point in time and the next oldest characterized shergottites, dating back 2.4 billion years, there is an approximately 1.8-billion-year gap in understanding the geology and history of Mars, a period for which no shergottite samples exist to provide information about geological activity on Mars. And that makes the research more challenging.
"We were fortunate to have access to such an unusual shergottite. This study demonstrates that the diverse collection of Martian meteorites, many of which remain undated, continues to provide valuable insights into the geologic history of the Red Planet", Dr. Nicklas stated.
According to Dr. Seal, Mars formed very quickly, less than approximately 5 million years after the birth of the solar system, and it does not have plate tectonics like Earth, allowing these early-formed compositions to remain pristine.
In addition to its age of 1.27 billion years, its chondritic initial isotope composition was equally surprising, providing important new boundaries on the processes that occurred in the very early solar system as Mars formed.
The work will be continued by Seal during his postdoctoral fellowship at the Carnegie Institution in Washington September, and it will extend martian meteorite isotope research in several new and exciting directions.
The researchers further said that the meteorite helped answer questions about a huge gap in the Martian geologic record: a span of time between 600 million years ago and 2.4 billion years ago.
NWA 13441 was surprising to researchers in two ways. The first was its composition. While it is a shergottite, the space rock also contains isotopes (element types) of a rare-Earth metal called neodymium. Neodymium is usually found in chrondrites, another kind of meteorite made up of unmelted rocks, and chondrites were common in the solar system when it was formed 4.56 billion years ago.
"This blended composition of shergottite and chrondrite suggests deeper parts of Mars have remained relatively untouched since the planet was formed", Ethan Baxter, Boston College Earth and Environmental Sciences Professor and co-author of the study, said.
The research team included lead author Dylan M. Seal (Boston College), along with co-authors Melody Z. Chen (Boston College), Robert W. Nicklas (Lunar and Planetary Institute), Ethan F. Baxter (Boston College), James M.D. Day (Scripps Institution of Oceanography), Ben G. Rider-Stokes (The Open University), Anthony B. Love (Appalachian State University), and James Malley (The Open University).
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