- 3851 - ASTEROIDS - history of the Universe? - The history of the solar system is encoded in asteroids, the planetary crumbs left over from its birth over 4.5 billion years ago. NASA is trying to bring back a sample from Bennu, a carbonaceous asteroid.
--------------- 3851 - ASTEROIDS - history of the Universe?
- Asteroid samples are how we analyze
meteorites and debris from asteroids and other planetary bodies that fall to
Earth. NASA’s Artemis missions will
also return lunar samples.
-
- The OSIRIS-REx mission was designed to
return 60 grams, over 2 ounces, of surface material from asteroid Bennu. The
mission team estimates that it’s collected quite a bit more than that. Science team members, who are spread all
over the world, will be allotted 25% of the total mass collected.
-
- We want to be sure we can look at the
samples at multiple scales, from something you can see in the palm of your
hand, all the way down to the atomic level.
To do this, we need extremely sophisticated instrumentation.
-
- This includes a focused-ion-beam scanning
electron microscope, transmission electron microscope, an electron microprobe
laboratory and scanning electron microscopes. A “NanoSIMS” instrument for measuring
chemical elements in a sample is scheduled to arrive in June.
-
- The first in a line of sample probing tools
is the light microscope, familiar to many and used for centuries. It helps
scientists visualize samples several hundred nanometers to micrometers in size,
about the scale of bacteria and cells.
-
- Visible light microscopes are not able to
‘sniff out’ the chemical makeup of a sample, but they provide us with images,
which might reveal textures and some information on its microstructure.
-
- The scanning electron microscope, or SEM,
and electron microprobe are used for analyzing samples at a slightly smaller
scale. An electron microprobe, also known as an electron probe microanalyzer,
is similar to a scanning electron microscope, but offers the added capability
of revealing clues about the sample’s chemical composition.
-
- The microprobe allows us to image and map
out the chemical heterogeneity in a sample in two dimensions at the micrometer
scale, less than half the length of an average-sized bacterial cell.
-
- The SEM can do the same thing, although not
quite the same level of precision. Both can image and give us compositional
information at the microscale, and both are critical in analysis of the sample
from Bennu.
-
- The NanoSIMS instrument measures the
chemical elements in a sample, which is important for understanding the origins
of the material. Unlike the SEM or microprobe, the NanoSIMS can reveal the
isotopic composition of a sample. Isotopes are different varieties of chemical
elements.
-
- The isotopic composition of a planetary
material can tell us something about its origins and history that the elemental
information alone may not. The NanoSIMS
also lets us measure trace elements, which are present in extremely small
amounts, at the scale of tens of a nanometer.
-
- The transmission electron microscope
operates at the smallest scales, allowing scientists to see individual
atoms. A magnifying glass just won’t
cut it for the high-tech “detectives” .
-
- The history of the solar system is encoded
in asteroids left over from its birth over 4.5 billion years ago. In addition to asteroid samples, scientists
analyze meteorites and debris from asteroids and other planetary bodies that
fall to Earth.
-
- NASA’s Artemis missions will return lunar
samples. The Comet Astrobiology
Exploration Sample Return, or CAESAR mission, would return a sample from a
comet.
-
- The university-led OSIRIS-REx mission was
designed to return 60 grams, a little over 2 ounces, of surface material from
asteroid Bennu.
-
- The microprobe is used to image and map out
the chemical heterogeneity in a sample in two dimensions at the micrometer
scale, less than half the length of an average-sized bacterial cell. Compositional information at the microscale
will tell us where in the sample we might want to probe further using NanoSIMS
or TEM.
-
- In 2021,
team used this tool, combined with quantum mechanics, chemical
thermodynamics and astrophysical modeling, to reconstruct the origin journey of
a dust grain through the nascent solar system.
-
January 28, 2022 ASTEROIDS -
history of the Universe?
3851
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--------------------- --- Monday, January 30, 2023 ---------------------------
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