What kind of erosion is on the moon

Erosion on earth occurs mainly because of the action of wind, water and rain. On the moon, however, there is not atmosphere, so no weather. Instead, tiny dust particles impact the surface of the moon from space. These particles hit the Earth as well, but burn up in the upper atmosphere.

On the moon there is no atmosphere, so they hit the surface. The lack of weather on the moon is the reason erosion is so slow, and we can see features that are millions and even billions of years old. The truth is both the Earth and the Moon have been hit many, many times throughout their long 4. The main difference between the two is that Earth has processes that can erase almost all evidence of past impacts. The Moon does not. Three processes help Earth keep its surface crater free.

The first is called erosion. Earth has weather, water, and plants. These act together to break apart and wear down the ground. Throughout this report we mention and illustrate e. Numerous additional examples could be given. Most of these glass surfaces are rather shiny, yet some are dull, depending on whether they are holohyaline or crystallized See et al.

Such melt drapings represent an independent indicator of impact and might be encountered in the general surface imagery of other planetary surfaces. We now turn to thermal fatigue as a potential agent in eroding and comminuting lunar surface rocks, and especially those on asteroids where thermal cycling appears to be more severe Molaro and Byrne, ; Delbo et al. It is difficult to perform thermal-fatigue experiments because the thermal conductivity of rock is so low.

The penetration of a thermal pulse to a suitable distance into a sample requires time; that time then determines the length of the heat-cool cycle. The deeper the desired penetration depth, the longer the required cycle and, with a realistic experiment taking thousands if not millions of such cycles, the experiment quickly becomes impractical. As a consequence, discussion of the process remains substantially theoretical by necessity, relating the heat-induced stress patterns and gradients to the orientation and distribution of overall strain and, ultimately, the generation and propagation of cracks and fracture systems.

Some of the strain is parallel to the surface and may lead to exfoliation. For example, Lamp et al. They found that during summer months, low-magnitude stresses due to temperature variations over time resulted in thermal-fatigue weathering, producing slow propagation of existing cracks, leading ultimately to flake detachment.

This crack propagation appears to be facilitated through a reduction of fracture toughness. Thermal fatigue seems capable of producing stresses high enough to split rocks in half Molaro et al. The dominant expression of thermal fatigue, however, are stresses and cracks parallel to the illuminated surface, resulting in some form of exfoliation and the production of slab-like fragments. We have demonstrated that this is also a common form of impact-generated fragments e. Indeed, the shapes of collisionally produced fragments can vary enormously, with rock texture and the specific energy of the impactor being major controlling factors.

Given such a great variation, the shapes of impact-produced fragments will almost certainly overlap those produced by thermal fatigue. We thus suggest that fragment shape is not a good criterion for distinguishing between the two processes. Fragments resulting from thermal fatigue should be piled up rather close to their source, as local gravity only will act on them.

In its most general form, the centrosymmetric propagation of an impact-induced shock wave results in stress and strain distributions that differ dramatically from those imparted by thermal fatigue. These differences occur not only in overall geometry, but also in amplitude and strain rate by orders of magnitude. Centrally symmetric deformation features on planetary rock surfaces are thus the most telling evidence for impact.

As illustrated by the lunar-rock collection, most impact features on rocks display circular spall zones or remnants thereof, and rare rocks display radial fracture systems, with or without a glass lined pit in their centers. Thermal fatigue lacks this centrosymmetric property.

As synthesized in Fig. Because a large rock will not equilibrate thermally as readily as a small one, the large rock will build up much higher stresses between its warm surface and cold interior than a small one. Large rocks are thus destroyed more efficiently in the thermal-fatigue scenario. As shown earlier, the independent observations of Basilevsky et al. The observational evidence on the Moon is thus contrary to the size- or mass-dependent predictions of the thermal-fatigue process and supports the impact-erosion scenario.

In contrast, the thermal-fatigue process is a thermal-equilibrium phenomenon that equally affects all local rocks of a given size and composition. One would therefore expect actual survival times to cluster rather closely around some mean value for any population of such rocks. No rock will be destroyed until some critical fracture is produced over some time interval and all rocks should approach the stage of failure after rather similar if not identical exposure times. As a consequence, the distribution curve for the survival times for any specific population of rocks should be strongly peaked and substantially Gaussian for the thermal-fatigue scenario, which is fundamentally different from the exponential curve of impact erosion.

Rocks exposed at the surfaces of atmosphereless planetary bodies erode by a number of processes, such as sputtering, impact, thermal fatigue, and possibly others. Hypervelocity impact is characterized by the production of a high-pressure shock wave that propagates quasi-spherically into the target; this stress wave deposits sufficient energy to vaporize, melt, and fracture parts of any target rock.

The centrosymmetric geometry, the amplitude of the stress wave, and the associated strain rates are not duplicated by any other geologic process. Examples and effects of these phenomena can be found throughout the lunar regolith, an extraordinarily dynamic sediment Costello et al.

Heiken et al. On the basis of lunar-surface observations, returned Apollo samples, and laboratory experiments, we have attempted in this report to develop criteria by which we can recognize impact as a process that can erode surface rocks.

We emphasize macroscopic criteria that can assist in the interpretation of planetary surface images, including:. In many cases it will be impractical to distinguish among different processes, as they can generate similar products. Such ambiguous factors are the detailed shapes of rock fragments, the gradual rounding of rocks exposed at the surface, and the differential erosion of matrix and clasts, resulting in knobby surfaces of breccia boulders. Identification of specific erosional processes also strongly depends on the spatial resolution of remotely obtained imagery or other information from spacecraft targeted to diverse planetary objects.

For example, the information gleaned about the impact process solely from the interpretation of Apollo surface photography is minor compared to that extracted from detailed analysis of returned rocks and soils. In the absence of landers with such capabilities, however, only sample-return missions could unequivocally reveal the significance of small-scale impacts in the erosion of surface rocks and the overall evolution of regoliths on the Moon and other airless bodies. While we favor impact as the dominant macroscopic, erosive process on the Moon, we expect that thermal fatigue would also be a contributing factor, especially on asteroids.

A major goal for the community going forward is to develop criteria by which we can recognize the effects of thermal fatigue and to compare these to the impact criteria that we have advanced in this analysis. It is also very possible that the two processes complement each other.

Regions permanently shielded from sunlight at the poles of the Moon are essentially at constant, albeit low, temperatures Williams et al. Investigation of boulders, rocks, and soils from such permanently shadowed regions — either remotely or in the terrestrial laboratory — will reveal the effects of impact only, as all processes related to thermal cycling should be absent.

We look forward to these developments and their application to our understanding of regolith evolution in the Solar System. This is a review article that is the outgrowth of earlier papers by this group of authors on the subject of impact erosion and rock survival times, the latter senior authored by A.

Basilevsky, who was thus a natural to come along. The present paper was substantially written by Friedrich Horz and Mark Cintala, due to their experience with Apollo rocks and experimental craters in dense rocks.

James Head contributed examples of terrestrial erosion by thermal fatigue. All 4 authors participated in the iteration of this paper.

This review article was motivated by the ever increasing prominence of thermal fatigue-related proposals that presumably shaped the surfaces and their rocks of asteroids Bennu and Ryuga as revealed by the recent OSIRIS REX and Hyabusa 2 missions.

The paper points out that the evidence used in support of thermal fatigue processes is compatible also with impact in many cases. There is obviously lots of overlap between the two processes, and we encourage our colleagues to develop a list of diagnostic criteria for thermal fatigue, as we have done here for impact.

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. We appreciate the skill and dedication with which R.

Montes, F. Cardenas, and the late G. Haynes conducted many experiments mentioned in this paper. Emily S, Costello and an anonymous reviewer provided helpful comments. National Center for Biotechnology Information , U. Planet Space Sci. Published online Sep Basilevsky , b James W. Head , c and Mark J. Cintala d. Alexander T. James W. Mark J. Author information Article notes Copyright and License information Disclaimer.

Elsevier hereby grants permission to make all its COVIDrelated research that is available on the COVID resource centre - including this research content - immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source.

Associated Data Supplementary Materials Multimedia component 1. Abstract This report summarizes observations of returned Apollo rocks and soils, lunar surface images, orbital observations, and experimental impacts related to the erosion and comminution of rocks exposed at the lunar surface. Keywords: Planetary regoliths, Crater-morphology, Thermal fatigue, Particle abrasion, Collisional fragmentation, Rock erosion.

Introduction An unconsolidated, global surface deposit of debris typically a few meters thick, the lunar regolith is the result of impact-cratering processes that extend over scales from sub-micrometers to kilometers e. Open in a separate window. Rock erosion by abrasion Impact is a stochastic process, and the size, spatial distribution and formation times of the regolith-forming craters are random.

Rock erosion by collisional fragmentation As discussed above, there is a finite probability that any surface rock might suffer an impact sufficiently energetic to fragment and thus destroy it.

Rock erosion models and lunar surface observations Cratering experiments using dense, crystalline rocks as targets establish the relationships between the kinetic energy and momentum of a projectile and the volume of the resulting crater, and thus of displaced crater mass.

Generation of fine-grained regoliths The ultimate and final product of the impact-triggered erosion process is the generation of a fine-grained regolith matrix. Discussion 7. Erosion by impact This report attempts to summarize how the impact process erodes and comminutes rocks on the lunar surface, and it develops criteria by which the impact process might be distinguished from other erosive agents, such as thermal fatigue.

Implications for thermal fatigue We now turn to thermal fatigue as a potential agent in eroding and comminuting lunar surface rocks, and especially those on asteroids where thermal cycling appears to be more severe Molaro and Byrne, ; Delbo et al. Conclusions Rocks exposed at the surfaces of atmosphereless planetary bodies erode by a number of processes, such as sputtering, impact, thermal fatigue, and possibly others. We emphasize macroscopic criteria that can assist in the interpretation of planetary surface images, including: 1.

Author statement Re. Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements We appreciate the skill and dedication with which R. Appendix A. References Ashworth D. Lunar surface micr-erosion related to interplanetary dust particle distributions. Space Res. Lunar and Planet. Abstract Lunar Sci. On the evolution of small lunar craters; pp. Survival Times of meter-sized boulders on the surface of the Moon. Space Sci. Survival times of meter-sized boulders on the surface of airless bodies.

Cosmic-ray exposure history of North Ray and South Ray material; pp. Experimental impacts into chondritic targets, part 1: disruption of an L6 chondrite by multiple impacts. Meteoritics Planet Sci. An experimental evaluation of the mineral specific comminution. Cratering flow fields: implications for the excavation and transient expansion stages of crater formation; pp. Lunar surface dynamics: some general conclusions and new results from Apollo 16 and 17; pp.

The mixing of the lunar regolith: viral updates to a canonical model. On collisional disruption: experimental results and scaling laws. Thermal fatigue as the origin of regolith on small asteroids. There is no weather on the Moon as we Earthlings define weather as there is no atmosphere and no liquid water.

When the Moon was young, erosion was mainly due to impacts from comets, asteroids and meteorites and volcanism.

Today the main causes of erosion are micro-meteorites, the solar wind, moonquakes and degradation of rocks by the temperature change as the surface alternately heats up and cools down.

The term Lunar Swirls describes unusual sinuously-shaped features on the lunar surface. They have been described as looking like the swirls on the top of a mug of coffee when cream is poured in and slightly stirred! The following image shows an example of a lunar swirl in Oceanus Procellarum and is the largest and longest swirl on the near side. All the lunar swirls found so far appear to be associated with magnetic anomalies on the lunar surface but their formation is still a bit of a mystery.

At the resolution of current data, the swirls appear to overprint the topography on which they lie, indicating that they are quite thin or a surface manifestation of an underlying phenomenon that is manipulating normal surface processes.

Swirls on the maria are characterized by strong albedo contrasts and complex, sinuous morphology, whereas those on highland terrain may be less prominent and exhibit simpler shapes such as single loops or diffuse bright spots. Two of the swirls on the far side of the Moon are directly opposite the centres of two large near side impact basins, Mare Imbrium and Mare Orientale, so there appears to be some connection with a large impact causing a swirl to appear on the opposite side of the Moon.

If the original impacts that formed the near side impact basins also somehow caused the magnetic domains on the antipodes to form with swirls above them then these swirls are very old. This is one of the many mysteries of lunar swirls.