A meteorite that originated on Mars billions of years ago reveals details of ancient impact events on the red planet. Some minerals from the Martian crust were oxidized in the meteorite, suggesting the presence of water during the impact that formed the meteorite. This discovery helps fill a gap in knowledge about the role of water in planetary formation.
There is a long-standing question in planetary science about how water on Earth, Mars, and other large bodies (such as the Moon) originated. One hypothesis suggests that it came from asteroids and comets after they formed. But some planetary researchers believe that water may be just one of many substances that naturally occur during planetary formation. A new analysis of an ancient Martian meteorite supports the second hypothesis.
A few years ago, a pair of dark meteorites were discovered in the Sahara Desert. They were named NWA 7034 and NWA 7533, NWA for Northwest Africa and the numbers are the order in which the meteorites were officially recognized by the Meteoritical Society, an international planetary science organization. Analysis indicates that these meteorites are new types of Martian meteorites, a mixture of different rock fragments.
The earliest fragments on Mars were formed 4.4 billion years ago, making them the oldest known Martian meteorites. Stones like these are rare and can fetch up to $10,000 per gram. Recently, an international research team involving Takashi Mikouchi, a professor at the University of Tokyo, obtained 50 grams of NWA 7533 for analysis.
"I study the minerals in Martian meteorites to understand how Mars was formed and how its crust and mantle evolved. This is the first time I've investigated this particular meteorite, known as Black Beauty because of its dark color." Mikouchi said, "We performed four different spectroscopic analyses on samples from NWA 7533 and used methods to detect chemical fingerprints. These results have led our team to some exciting conclusions."
Planetary scientists know that there has been water on Mars for at least 3.7 billion years. But judging from the mineral composition of the meteorites, Mikouchi and his team deduce that there was probably water much earlier, about 4.4 billion years ago.
"Pyroclastic debris or fragments in meteorites are formed by magma, usually from collisions and oxidation," Mikouchi said. "Such oxidation could have occurred if an impact 4.4 billion years ago melted part of the Martian crust and water was present on or in the Martian crust. Our analysis also suggests that such an impact would have released large amounts of hydrogen, which would have caused Mars to warm at a time when it already had a thick layer of carbon dioxide isolating its atmosphere."
If water existed on Mars earlier than we thought, it would mean that water may have been a natural byproduct of some process early in the planet's formation. This discovery could help researchers answer the question of where water came from, which in turn could influence theories of the origin of life and the search for extraterrestrial life.
Article source: phys-org
