Gas Density of Lunar Crater Rims: Comet vs. Asteroid Impacts

In summary, the typical gas densities at the lunar crater rim when it is made by a comet and an asteroid are initially very high due to the explosion caused by the impact. However, as the blast spreads out, the energy is transmitted to the soil, resulting in a drop in temperature and condensation of rock and iron vapor. This process is different for comet and asteroid craters due to the presence of an atmosphere. On the Moon, the lack of atmosphere results in fine dust and sand being accelerated more and blown further from the crater, while boulders are left behind. This winnowing effect is not as conspicuous on Earth, Venus, and Mars due to the presence of an atmosphere. The strength of gravity, atmosphere, and surface
  • #1
snorkack
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TL;DR Summary
Properties of vapour driving explosion
I mean - when they form.
What are typical gas densities at lunar crater rim when the crater is made by a comet? An asteroid?

Both a comet and an asteroid, hitting Moon at several km/s, initially heat up to several thousand K, and even asteroid produces some vapour... at hypocentre.

However, by the time a crater rim forms, the blast has spread out a lot. If a crater is 100 km in diametre, then throwing soil 50 km from the centre to the rim requires propelling the soil at 400 m/s... by the time crater rims are formed, the energy of explosion has been transmitted from a small amount of rock moving at several km/s to a large amount of soil moving a few hundred m/s. Which process would be accompanied by drop of temperature - and condensation of rock and iron vapour.

However, cometary ices would NOT be in any hurry to condense!
Does this cause comet craters on Moon to be very different from asteroid craters?
For example... on Earth, Venus and perhaps Mars, air is ahead of soil thrown out of crater. It follows that fine dust and sand in soil are slowed down by air, while boulders continue further, by inertia.

In contrast, on Moon what lies ahead is vacuum, and the steam is behind the soil. It follows that fine dust and sand should be accelerated more and blown further from the crater, while boulders should be left behind.
Are this kind of winnowing effects conspicuous on Moon?
 
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Also by a "typical" object (asteroid, comet)?

The Moon has some atmosphere though, 0.3 nPa so its not vacuum (still better vacuum than most/all man made vaccuums)
 
  • #4
snorkack said:
Summary: Properties of vapour driving explosion

Does this cause comet craters on Moon to be very different from asteroid craters?
For example... on Earth, Venus and perhaps Mars, air is ahead of soil thrown out of crater. It follows that fine dust and sand in soil are slowed down by air, while boulders continue further, by inertia.

In contrast, on Moon what lies ahead is vacuum, and the steam is behind the soil. It follows that fine dust and sand should be accelerated more and blown further from the crater, while boulders should be left behind.
Are this kind of winnowing effects conspicuous on Moon?
Strength of gravity, the presence of an atmosphere, as well as surface material strength would all play a part in the formation of the crater and ejecta. And of course, the yield strength of the incoming celestial body for atmospheric conditions - does the incoming body explode from the pressure wave within resulting from the drag force of the atmosphere somewhere above the surface, or stay relatively intact to produce a hypervelocity impact upon the surface ( in a no, or thin, atmosphere this would be the case ).
Since the mv^2 kinetic energy is huge, the release of that energy is of several atomic bombs strength.
In no atmospheric conditions, ejecta would be following a ballistic path,
In an atmospheric conditions, large ejecta would follow a more ballistic paths but still suffer from atmospheric drag. Smaller ejecta would probably go pyrothechnic-ish ( its ballistic trajectory ( velocity ) greatly reduced due to the atmosphere ) much the same way as from a volcano, and blanket the surrounding area for several crater radii ( I presume. )
 

1. What is the purpose of studying the gas density of lunar crater rims?

The gas density of lunar crater rims can provide valuable information about the type of impact that created the crater. This can help us better understand the history and formation of the Moon, as well as the potential impact hazards for future lunar missions.

2. How does the gas density differ between comet and asteroid impacts on lunar crater rims?

Comet impacts tend to have higher gas densities compared to asteroid impacts due to the high amounts of volatile materials present in comets. This results in a more explosive impact and a larger amount of gas being released into the crater rim.

3. What methods are used to measure the gas density of lunar crater rims?

Scientists use remote sensing techniques such as spectroscopy to measure the gas density of lunar crater rims. This involves analyzing the light reflected off the surface of the Moon to determine the composition and density of gases present in the crater rim.

4. How does the gas density of lunar crater rims vary with the size of the impact?

The gas density of lunar crater rims generally increases with the size of the impact, as larger impacts result in more material being ejected and more gases being released. However, the specific gas density can also vary depending on the composition of the impacting object.

5. What can the gas density of lunar crater rims tell us about the formation of the Moon?

The gas density of lunar crater rims can provide insight into the early conditions of the Moon and the types of objects that have impacted its surface. By studying the gas densities of different craters, scientists can better understand the processes that shaped the Moon and its evolution over time.

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