4583 - MOON SAMPLES - from 50 years ago? - Samples collected from the surface of the moon by the crew of Apollo 16 more than 50 years ago have helped scientists reconstruct billions of years of lunar history. New analysis of a distinct set of lunar breccias have never been scrutinized in detail before.
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- MOON SAMPLES
- from 50 years ago?
-
- Astronauts John Young, Charles Duke and Ken
Mattingly brought more than 95 kilogram of samples from the moon back to Earth
after their mission to the moon's Descartes highlands in 1972.
-
- Among those samples were "regolith
breccias," which form when moon dust is fused into rock by asteroid
impacts. Once fused into a rock, these breccias preserve the geochemical
composition of the regolith at the moment of its formation, which can be
carefully analyzed for clues about how and when they were created.
-
- The moon's distinctive, heavily cratered
appearance is the result of countless collisions with asteroids since its
formation around 4.5 billion years ago. Over such extensive history, the matter
of what happened and when it happened quickly becomes complicated.
-
- Sophisticated analytical mass spectrometry
techniques were used to analyze the makeup of gases trapped in smaller chip
samples, known as soil-like breccias. These samples, which were among those
raked from the moon's surface by the Apollo 16 crew, had never been subjected
to mass spectrometry before.
-
- Mass spectrometry, which identifies
molecules in samples and quantifies their relative abundance, can help us
determine how much time the samples spent exposed on or near the moon's
surface. That helps give us a clearer idea of the history of impacts on this
particular area of the moon.
-
- This helped advance scientists'
understanding of how the surface of the moon has been changed by the solar wind
and violently blasted by asteroids over the course of more than 2 billion
years.
-
- Over the course of the samples' time on the
surface of the moon as regolith, they were exposed to varying amounts of solar
wind, charged particles flowing from the sun which also carry traces of noble
gases like argon and xenon, which built up on the outer layers of their mineral
grains for millions of years before they were struck by an asteroid.
-
- The moon's history is the Earth's history
too. The record of asteroid bombardments
etched on its face and under its surface can help us understand the conditions
of the early solar system which formed our planet as well as its closest
neighbor.
-
- Unlike the Earth, however, the moon's
history is locked in geological time capsules on its surface, untouched by
plate tectonics or erosion, which allows us to use cutting-edge technology like
mass spectrometry to unlock their secrets.
-
- Previous research had analyzed the traces
of noble gases within larger fragments of the Apollo 16 breccia samples,
helping researchers separate the samples into two groups, "ancient,"
aged between 3.8 and 2.4 billion years old, and "young," which were
formed between 2.5 and 1.7 billion years ago.
-
- NASA provided the researchers with 11 moon
samples for analysis. Nine of the samples revealed a wide range of exposure
ages, from 2.5 billion years ago to less than 1 billion. This suggests they are
made up of lunar soil from an area which has had a varied history of impacts,
where some were exposed to the solar wind for billions of years, while others
were dredged up to the surface by more recent impacts.
-
- The team also found that two of the samples
had much lower concentrations of noble gases, suggesting they were formed much
more recently, and were perhaps exposed to solar wind for less than 1 million
years. The team suggest that the impact which formed the nearby South Ray
crater might have been the source of that sample.
-
- This study establishes for the first time
that soil-like breccias are their own distinct category, with their own
histories to share. Combined with analysis of the ancient and young rocks
recovered by Apollo 16, we can build a much more complete picture of the
history of this part of the moon during the early solar system, where heavier
impacts on the lunar surface in its first billion years or so gave way to less
intense periods from 2 billion years ago.
-
- The research could also help inform ongoing
efforts to send future missions to the moon in the near future, like NASA's
Artemis program, which plans to establish long-term human lunar habitats.
-
- One of the challenges of establishing
long-term habitats for humans on the moon is making decisions about how we can
use the natural resources which await future missions so they don't have to
carry everything they'll need with them from Earth. Studies like this add to our knowledge base
about where useful elements like noble gases can be found in the lunar
regolith, and how abundant they might be.
-
- It's remarkable to think that the samples
Apollo 16 brought back more than half a century ago still have secrets to
reveal about the moon's history, and that they could yet help shape how we
explore the solar system in the decades to come.
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October 21, 2024 4583
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--------------------- --- Tuesday, October 22,
2024
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