Ancient micrometeoroids carried specks of stardust, water to asteroid 4
Vesta
Researchers wonder: Could they have delivered water to the early Earth?


Date:
June 9, 2020
Source:
Washington University in St. Louis
Summary:
Researchers have studied presolar materials that landed on a
planet-like body. Their findings may help solve the mystery:
where did all the water on Earth come from?


FULL STORY ==========================================================================
The formation of our solar system was a messy affair. Most of the
material that existed before its formation -- material formed around
other, long-dead stars - - was vaporized, then recondensed into new
materials. But some grains of that material, formed before the sun's
birth, still persist.


========================================================================== These "stardust" grains arrived on Earth inside primitive meteorites. New Washington University in St. Louis research led by Nan Liu, an assistant research professor in physics and the Laboratory for Space Sciences
in Arts & Sciences, shows that stardust was also delivered to another planet-like body in the solar system, asteroid 4 Vesta, by micrometeoroids
that also carried water.

The research was published in the journal Geochimica et Cosmochimica Acta.

"Like our Earth," Liu said, "Vesta has a core, a mantle and crust,"
features that formed as the materials melted, differentiated and coalesced
into a single planet-like object. And like Earth, Vesta is also pummeled
by micrometeoroids.

The brightest asteroid in the night sky, Vesta orbits the sun in the
asteroid belt between Mars and Jupiter.

Liu, along with Lionel Vacher, a postdoctoral researcher, and Ryan
Ogliore, assistant professor of physics, studied samples of the Kapoeta meteorite for this research. Kapoeta fell to Earth in 1942 in what is
now South Sudan, landing on a road in front of a British convoy during
World War II. NASA's Dawn mission to asteroid Vesta established a link
between Vesta and the howardites, eucrites and diogenites, groups of
meteorites found on Earth.

The research team focused on small, dark inclusions in Kapoeta that seemed
out of place, like pieces of clay in lava rock. "They look completely
different from surrounding material," Liu said. They turned out to be microscopic meteoroids, less than 100 microns across (smaller than the thickness of a human hair), that landed on Vesta's surface.



==========================================================================
Liu used the university's mass-spectrometer microscope, the NanoSIMS,
to search the inclusions for presolar material. Because stardust has
a very different isotopic composition from material that formed within
the solar system, it jumped out at her under the microscope.

The stardust in asteroid Vesta is a unique record of ancient, galactic
material delivered long ago to a body far from Earth. The researchers
postulate that the micrometeoroids arrived at Vesta after the violent
impacts of the Late Heavy Bombardment, about 3.5 billion years ago.

Vacher and Ogliore measured the chemical compositions of the
micrometeoroids to understand in what type of environment they
formed. They recognized minerals and textures that were linked to
interactions between rock and water from melted ice.

One of the big questions is: How did water get on Earth? "We need a
mechanism to bring ice from the outer solar system, where the temperature
is low," Vacher said. "This research shows that you can transport small micrometeoroids that contain ice to dry bodies that formed without water."
The ancient record of these micrometeoroids impacting Earth has been
erased by weather and plate tectonics. The micrometeoroid record from
asteroid Vesta may help to explain how water was delivered to the
young Earth.



==========================================================================
"If icy micrometeoroids delivered water to the inner solar system when
the Earth was still forming, this could be one way that the Earth ended
up with enough water to support life," Ogliore said. "Habitable planets
around other stars may have acquired their water through similar means."
More analyses are needed to determine the when and the where. "Our next measurements will constrain when this wet material was delivered to
Vesta, and where it came from: an icy asteroid, a comet or some other
exotic source," Ogliore said.

Take a trip to 4 Vesta You can zoom in on Kapoeta thanks to Ryan Ogliore, assistant professor of physics. He worked to develop techniques to
visualize objects from the micrometer to the millimeter scale -- that's
a factor of 1,000. "It's like he took a puzzle with 1,000 pieces, but
Ryan is doing the same puzzle with 10,000 pieces," said Lionel Vacher,
research assistant.


========================================================================== Story Source: Materials provided by
Washington_University_in_St._Louis. Original written by Brandie
Jefferson. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Nan Liu, Ryan C. Ogliore, Lionel G. Vacher. NanoSIMS isotopic
investigation of xenolithic carbonaceous clasts from the kapoeta
howardite. Geochimica et Cosmochimica Acta, 2020; DOI: 10.1016/
j.gca.2020.05.026 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200609161936.htm

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