A team of researchers from the United States, UK and Japan has found liquid water and a mix of complex organic compounds in 4.5-billion-year-old salt crystals preserved in two unique meteorites, Zag and Monahans, which separately crashed to Earth in 1998.
Zag/Monahans meteorites and their salt (halite) crystals: (A) diagram showing the lithologies of the Zag and Monahans meteorites, their dark (carbonaceous) clasts, the salt crystals, and the fluid and solid inclusions within the salt crystals; (B) salt crystals hosted in the matrix regions of the Zag meteorite; the arrow marks one of the several salt crystals shown in this photo; (C) a microphotograph showing a salt crystal sampled from the Zag meteorite; (D) salt crystals sampled from the Zag meteorite contained in a pre-sterilized glass ampoule before hot-water extraction. Image credit: Chan et al, doi: 10.1126/sciadv.aao3521.
If life did exist in some form in the early Solar System, salt crystal-containing meteorites raise the ‘possibility of trapping life and/or biomolecules’ within the salt crystals.
“This is really the first time we have found abundant organic matter also associated with liquid water that is really crucial to the origin of life and the origin of complex organic compounds in space,” said lead author Dr. Queenie Chan, a planetary scientist and postdoctoral researcher at the Open University, UK.
“We’re looking at the organic ingredients that can lead to the origin of life, including the amino acids needed to form proteins.”
“It’s like a fly in amber,” added Dr. David Kilcoyne, a scientist at the Department of Energy’s Lawrence Berkeley National Laboratory.
“While the rich deposits of organic remnants recovered from the meteorites don’t provide any proof of life outside of Earth, the meteorites’ encapsulation of rich chemistry is analogous to the preservation of prehistoric insects in solidified sap droplets.”
The researchers also found evidence for Monahans and Zag’s past intermingling and likely parents.
These include Ceres, a dwarf planet that is the largest object in the main asteroid belt, and the asteroid Hebe, a major source of meteorites that fall on Earth.
“We revealed that the organic matter in these meteorites (Monahans smashed into the ground near a children’s basketball game in Texas in March 1998 and Zag hit near Morocco in August 1998) was somewhat similar to that found in primitive meteorites, but contained more oxygen-bearing chemistry,” said Dr. Yoko Kebukawa, from Yokohama National University, Japan.
“Combined with other evidence, the results support the idea that the organic matter originated from a water-rich, or previously water-rich parent body — an ocean world in the early Solar System, possibly Ceres.”
“The similarity of the crystals found in Monahans and Zag suggest that their asteroid hosts may have crossed paths and mixed materials,” Dr. Chan said.
“There are also structural clues of an impact — perhaps by a small asteroid fragment impacting a larger asteroid.”
This opens up many possibilities for how organic matter may be passed from one host to another in space, and scientists may need to rethink the processes that led to the complex suite of organic compounds on these meteorites.
“Things are not as simple as we thought they were,” Dr. Chan said.
“There are also clues, based on the organic chemistry and space observations, that the crystals may have originally been seeded by ice- or water-spewing volcanic activity on Ceres.”
“Everything leads to the conclusion that the origin of life is really possible elsewhere.”
“There is a great range of organic compounds within these meteorites, including a very primitive type of organics that likely represent the early Solar System’s organic composition.”
The study is published in the journal Science Advances.
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Queenie H.S. Chan et al. 2018. Organic matter in extraterrestrial water-bearing salt crystals. Science Advances 4 (1): eaao3521; doi: 10.1126/sciadv.aao3521
