Open a meteorite that landed on Earth from it Mars It yielded an unexpected treasure.
Hidden inside a piece of rock, scientists found a few grains of garnet, a mineral that had never before been found in a Martian sample.
This little spot raises some huge questions.
On Earth, agate often forms under conditions involving extreme heat, pressure, or chemical change. The correct set of conditions for garnets on Mars has not been determined.
So this meteorite, preserved in the collection of the Royal Ontario Museum, has some explaining to do.
Did agate form inside it on Mars? If so, what process produced it, and when?
If not, where did it come from and how did it reach Mars?
“This discovery will expand our knowledge of possible geological processes on this planet.” Planetary geologist Tanya Kiesovsky says From Brock University in Canada.
“This new type of garnet-bearing rock could give us clues about how Mars changed throughout its history and new insights into ancient environments that could have formed garnet and related minerals.”
When we think of garnet, we tend to think of the highly valuable mineral due to its deep blood red color.
The Martian version doesn’t look like that.
Like many minerals, agate doesn’t always look the way we expect. In particular, one form of iron-rich garnet known as com.andradite It is often greenish-yellow in color, much like other minerals often found in meteorites, and does not stand out in the same way.
For this reason, researchers almost missed their discovery.
“This little fragment of the meteorite looked really interesting, and its chemistry was a little strange.” Kizowski says.
“At first, we assumed it was a mineral called pyroxene, which is very common, but then we decided to take a second look.”
Follow-up analyzes confirmed that the mineral was andradite. Only a few grains were found in a small piece of rock measuring about 0.8 x 0.5 mm in size, which is smaller than a poppy seed.
The meteorite is named NOAA 8171is already of great interest to planetary scientists.
It consists of Basaltic Brescia – A type of rock that forms when magma cools and solidifies around other mineral blobs.
Its composition is somewhat similar to a fruit cake, where the basalt is a dough cake, and other mineral impurities are fruits and nuts.
Between the basalt and its inclusions, NWA 8171 has a lot to say about the geology of Mars, from ancient magma flows to any information that may be trapped within the grains.
This is what makes the discovery of garnets in NWA 8171 so exciting – because these minerals tell particularly fascinating stories.
Agate keeps excellent records of past geological processes, preserving unique snapshots of the temperature and pressure conditions under which it formed. They can also be used to date the timeline of these instances, and often contain traces of other minerals that can reveal the chemistry of their formation environment.
Researchers don’t yet know what that formation environment looked like, whether it involved an unusual type of magma not yet found on Mars, or whether the process was a metamorphic process.
“Agate is a classic example of a mineral often found in metamorphic rocks on Earth. The metamorphic process transforms igneous or sedimentary rocks into a new form through exposure to intense heat, high pressure, or hot fluids.” Kiesowski explains.
“On Mars, the heat and pressure needed to produce garnet through metamorphism could be the result of a meteorite hitting the Martian surface, magma rising into the Martian crust, or both.”
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Researchers also cannot rule out the possibility that garnet did not form on Mars.
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Some of the chemistry of the agate-bearing piece seems Martian.
But because NWA 8171 is a breccia containing multiple types of material, the piece could still theoretically have originated elsewhere and landed on Mars before being incorporated into the breccia.
To check this, the next step would be to look at the isotope ratios in the mineral. If they are similar to the isotope ratios of other Martian minerals, that would indicate that garnet formed there, which in turn would shed new light on the red planet’s deep geological history.
“The results add a fascinating new dimension to our understanding of the geology of Mars.” says planetary scientist James Darling from the University of Portsmouth in the United Kingdom, “opening an exciting new window on the evolution of our planetary neighbour.”
The results are detailed in Geochemical Perspectives Letters.
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