APOD: A Spherule from the Earths Moon (2010 Jan 10)

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APOD: A Spherule from the Earths Moon (2010 Jan 10)

Post by APOD Robot » Sun Jan 10, 2010 4:56 am

Image A Spherule from the Earths Moon

Explanation: How did this spherule come to be on the Moon? When a meteorite strikes the Moon, the energy of the impact melts some of the splattering rock, a fraction of which might cool into tiny glass beads. Many of these glass beads were present in lunar soil samples returned to Earth by the Apollo missions. Pictured above is one such glass spherule that measures only a quarter of a millimeter across. This spherule is particularly interesting because it has been victim to an even smaller impact. A miniature crater is visible on the upper left, surrounded by a fragmented area caused by the shockwaves of the small impact. By dating many of these impacts, astronomers can estimate the history of cratering on our Moon.


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Re: A Spherule from the Earths Moon (2010 Jan 10)

Post by neufer » Sun Jan 10, 2010 12:29 pm

Image
Art Neuendorffer

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Re: A Spherule from the Earths Moon (2010 Jan 10)

Post by iamlucky13 » Mon Jan 11, 2010 6:57 am

The idea of a microscopic impact crater on a dust grain that itself is for all practical purposes microscopic is fascinating.

Great choice for an APOD.
"Any man whose errors take ten years to correct is quite a man." ~J. Robert Oppenheimer (speaking about Albert Einstein)

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Re: A Spherule from the Earths Moon (2010 Jan 10)

Post by DavidLeodis » Tue Jan 12, 2010 8:27 pm

What is that circular like thing at about the middle of the image? I wonder if it may be a result of the scanning electron microscope but I would be grateful if someone could tell me what it is. Thanks.

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Re: APOD: A Spherule from the Earths Moon (2010 Jan 10)

Post by orin stepanek » Mon Dec 23, 2019 12:44 pm

Is this similar to the ones on Mars! :?
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Re: APOD: A Spherule from the Earths Moon (2010 Jan 10)

Post by neufer » Mon Dec 23, 2019 5:36 pm

orin stepanek wrote: Mon Dec 23, 2019 12:44 pm
Is this similar to the ones on Mars! :?
  • Only in that they are both roundish.
Martian blueberries are 10 times larger and consist mostly of opaque balls of iron oxide.
https://en.wikipedia.org/wiki/Martian_spherules wrote:
<<Martian spherules (also known as blueberries due to their blue hue in false-color images released by NASA) are the abundant spherical hematite inclusions discovered by the Mars rover Opportunity at Meridiani Planum on the planet Mars. The Mars Global Surveyor Thermal Emission Spectrometer (TES) first detected “crystalline hematite (α‐Fe2O3)” within Sinus Meridiani from orbit. The presence of hematite was confirmed after the Opportunity rover landed in Meridiani Planum. The moniker "blueberries" was coined by the original science team due to the hematite appearing blue relative to the surrounding media in the "natural color RGB images" analyzed.

The JPL team found many fragmented blueberries and suggested the fracturing occurred after spherule formation. They believe the fracturing either be from meteoric impacts, or the “same process” that “fractured the outcrop.” However, the team note this would not explain the presence of the smallest hematite spherules detected. The smallest are close to perfectly spherical and therefore cannot be explained by fracturing or erosion.

"A number of straightforward geological processes can yield round shapes," says Hap McSween. These include accretion under water, meteor impacts, or volcanic eruptions. The principal investigator, Steve Squyres, indicates they could alternately be concretions, or accumulated material, formed by minerals coming out of solution as water diffused through rock.

Researchers at NASA’s Jet Propulsion Laboratory studied all the soil environments observed by Opportunity, and therefore studied the blueberries from Eagle Crater to Endurance (crater). They found that in a sample of 696 blueberries, disregarding any non-spherical blueberries from the sample, the blueberries average major axis to be about 2.87 mm. They also discovered blueberries that are found within soils are typically smaller than blueberries found in the outcrops. They noted the size of the blueberries tends to decrease with decreasing latitude.

Researchers from the University of Utah have explored the similarities between the blueberries and spherical concretions discovered within “Jurassic Navajo Sandstone” in southern Utah. They have concluded Mars must have had previous ground water activity to form the blueberries. However, they do note the spherules are more spherical in the Martian sample due to the lack of “joints, fractures, faults, or other preferential fluid paths,” unlike the Utah sample. A team of researchers from Japan studied the spherules found in Utah as well as spherules that were later discovered in Mongolia, in the Gobi. They found evidence that the concretions found in these locations are first formed as “spherical calcite concretions” in sandstone. Acidic water rich in iron then dissolve the calcite leaving behind the iron rich (hematite) spherule. This leads to the conclusion that the blueberries may have formed early in Mars’s history when the atmosphere was more dense by the same process.>>
https://en.wikipedia.org/wiki/Navajo_Sandstone#Iron_oxide_concretions wrote:
<<The Navajo Sandstone is also well known among rockhounds for its hundreds of thousands of iron oxide concretions. Informally, they are called "Moqui marbles" and are believed to represent an extension of Hopi Native American traditions regarding ancestor worship ("moqui" translates to "the dead" in the Hopi language). Thousands of these concretions weather out of outcrops of the Navajo Sandstone within south-central and southeastern Utah.

The abundant concretions found in the Navajo Sandstone consist of sandstone cemented together by hematite (Fe2O3), and goethite (FeOOH). The iron forming these concretions came from the breakdown of iron-bearing silicate minerals by weathering to form iron oxide coatings on other grains. During later diagenesis of the Navajo Sandstone while deeply buried, reducing fluids, likely hydrocarbons, dissolved these coatings. When the reducing fluids containing dissolved iron mixed with oxidizing groundwater, they and the dissolved iron were oxidized. This caused the iron to precipitate out as hematite and goethite concretions found in the Navajo Sandstone. Evidence suggests that microbial metabolism may have contributed to the formation of some of these concretions. These concretions are regarded as terrestrial analogues of the hematite spherules, called alternately Martian "blueberries" or more technically Martian spherules, which the Opportunity rover found at Meridiani Planum on Mars.

The iron oxide concretions found in the Navajo Sandstone exhibit a wide variety of sizes and shapes. Their shape ranges from spheres to discs; buttons; spiked balls; cylindrical hollow pipe-like forms; and other odd shapes. Although many of these concretions are fused together like soap bubbles, many more also occur as isolated concretions, which range in diameter from the size of peas to baseballs.>>
Art Neuendorffer

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