Asteroid regolith formed by thermal fatigue

[Waspie_Dwarf]

French, American team finds regolith of small asteroids formed by thermal fatigue

Boulder, Colo. — April 2, 2014 — The centimeter-sized fragments and smaller particles that make up the regolith — the layer of loose, unconsolidated rock and dust — of small asteroids is formed by temperature cycling that breaks down rock in a process called thermal fatigue, according to a paper published today in the Nature Advance Online Publication.

Previous studies suggested that the regolith of asteroids one kilometer wide and smaller was made from material falling to the surface after impacts and from boulders that were pulverized by micrometeoroid impacts. Recent laboratory experiments and impact modeling conducted by a team of researchers from Observatoire de la Côte d’Azur, Hopkins Extreme Materials Institute at Johns Hopkins University, Institut Supérieur de l’Aéronautique et de l’Espace and Southwest Research Institute (SwRI) have shown that the debris from large impacts reaches escape velocities and breaks free from the gravitational pull of these asteroids, indicating this mechanism is not the dominant process for regolith creation.

Read more...

[Peter B]

Presumably the same process would be acting on the Moon too.

Although given the Moon has higher gravity than asteroids, that would suggest it would attract proportionately more micrometeors.

[taniwha]

Presumably the same process would be acting on the Moon too.

Although given the Moon has higher gravity than asteroids, that would suggest it would attract proportionately more micrometeors.

Yes it would attract more micrometeors but would the moon also suffer from thermal fatigue? I think the main point of the research is to propose that the metallic elements in asteroids can stress and crack due to thermal fatigue. So, instead of being shiny and polished they infact tumble through space decaying day after day (asteroid days are many times faster than Earth days) and combined with solar radiation eventually an asteroid would break down to be a micrometeor itself, or even lesser.

Presumably the process slows the further from the sun they are, I wouldnt be suprised if other forces could then take hold, such as ice fatigue or hydrogen embrittlement. Perhaps these were tested for too but we have to wait a few days more to find out.

[Waspie_Dwarf]

Presumably the same process would be acting on the Moon too.

This process would be much slower on the Moon. The Moon rotates, with respect to the Sun, once ever 28 days roughly. Small asteroids are rotating in only a few hours, so the cycle of heating and cooling occurs much more frequently.

[Waspie_Dwarf]

I think the main point of the research is to propose that the metallic elements in asteroids can stress and crack due to thermal fatigue.

The article makes no mention of metallic elements, that is pure invention from you.

The main point of the research is to explain how small asteroids have a layer of regolith when impact debris would reach escape velocity.

[taniwha]

The article makes no mention of metallic elements, that is pure invention from you.

The main point of the research is to explain how small asteroids have a layer of regolith when impact debris would reach escape velocity.

We will wait and see but it is likely I am right, considering the metallic composition of space rock, and without having to re read your links I seem to remember that that is exactly what was inferred by suggesting the major accumulation of regolith was due to fissures developing, and eroding the asteroid due to thermal fatigue rather than from micro impacts. Micro-tectonics if you will.

[Waspie_Dwarf]

We will wait and see but it is likely I am right, considering the metallic composition of space rock,

I don't have to wait and see. This line alone is enough to show that you don't know what you are talking about. Composition of "space rock":

C-type, carbonaceous asteroids comprise 75% of the population

S-type, silicaceous asteroids comprise 17% of the population

M-type metallic asteroids comprise just 8% of the population.

Since the article refers to small asteroids in general and makes no reference to any particular asteroid type the injection of facts is rather damaging to your guess work I'm afraid.

and without having to re read your links I seem to remember

May I respectfully suggest that you do re-read it before making any more wildly inaccurate guesses.

that that is exactly what was inferred by suggesting the major accumulation of regolith was due to fissures developing, and eroding the asteroid due to thermal fatigue rather than from micro impacts. Micro-tectonics if you will.

How does that infer anything to do with metallic elements? A rhetorichal question really as the anser is "it doesn't". I repeat, when it comes to metallic elements, "that is pure invention from you".

Edited April 5, 2014 by Waspie_Dwarf

[taniwha]

I don't have to wait and see. This line alone is enough to show that you don't know what you are talking about. Composition of "space rock":

C-type, carbonaceous asteroids comprise 75% of the population

S-type, silicaceous asteroids comprise 17% of the population

M-type metallic asteroids comprise just 8% of the population.

Since the article refers to small asteroids in general and makes no reference to any particular asteroid type the injection of facts is rather damaging to your guess work I'm afraid.

May I respectfully suggest that you do re-read it before making any more wildly inaccurate guesses.

How does that infer anything to do with metallic elements? A rhetorichal question really as the anser is "it doesn't". I repeat, when it comes to metallic elements, "that is pure invention from you".

If its a guess its a well weighted one. The types of asteroid that were lab tested were 1cm C type and S type. You should know that even C type asteroids are partly composed of metals that are present in all asteroids. How else would thermal fatigue work if not within the elemental metals? And like I have also suggested ice fatigue and hydrogen embrittlement might also contribute to the erosion. I would be prepared to say it is a fact more than a suggestion.

You can read more about the lab test here

http://www.abc.net.au/science/articles/2014/04/03/3976092.htm