More information: Ablation zone.

In glaciology and meteorology, ablation - the opposite of accumulation - refers to all processes that remove snow, ice or water from a glacier or snowfield. Ablation refers to the melting of snow or ice run off from the glacier, evaporation, sublimation, calving or erosive removal of snow by wind. Air temperature is usually the dominant factor in ablation, with precipitation exerting a secondary control. In a temperate climate, during the ablation season, ablation rates are typically around 2 mm/h.[4]​ When solar radiation is the dominant cause of snow ablation (for example, if air temperatures are low under clear skies), characteristic ablation textures such as "suncups" and "penitentes" may appear on the snow surface. (glaciology)")".[5]​.

Ablation can refer to both the processes of ice and snow removal and the amount of ice and snow removed.

Debris-covered glaciers have also been shown to greatly influence the ablation process. On top of glaciers there may be a thin layer of debris that intensifies the ablation process beneath the ice. The debris-covered portions of an ablating glacier fall into three categories: ice cliffs, lagoons, and debris. These three sections allow scientists to measure the heat digested by the debris-covered area and calculate it. The calculations depend on the surface area and the net amounts of heat absorbed in relation to the entire debris covered areas. These types of calculations are carried out on several glaciers to understand and analyze future melting patterns.[6]​.

The moraine (glacial debris) moves by natural processes that allow the downslope movement of materials in the body of the glacier. It is observed that if the slope of a glacier is too high, the debris will continue to move along the glacier to a further location. The sizes and locations of glaciers vary around the world, so depending on climate and physical geography the varieties of debris may differ. The size and magnitude of the debris depends on the area of ​​the glacier and can vary from dust-sized fragments to house-sized blocks.[7]​.

Many experiments have been done to demonstrate the effect of debris on the surface of glaciers. Yoshiyuki Fujii, a professor at the National Polar Research Institute, designed an experiment that showed that the rate of ablation was accelerated under a thin layer of debris and delayed under a thick layer, compared to that of a natural snow surface.[8] This science is significant because of the importance of long-term water resource availability and evaluating the response of glaciers to climate change. The availability of natural resources is one of the main drivers of the research carried out in relation to the ablation process and the general study of glaciers.[9]​.

Main article: laser ablation").

Laser ablation is greatly affected by the nature of the material and its ability to absorb energy, so the wavelength of the ablation laser must have a minimum absorption depth. Although these lasers may average low power, they can offer peak intensity and fluence given by:.

while the maximum power is:.

Superficial ablation of the cornea for various types of refractive eye surgery is now common, using an excimer laser system (LASIK and LASEK). Since the cornea does not grow back, the laser is used to reshape the refractive properties of the cornea to correct refractive errors such as astigmatism, nearsightedness, and farsightedness. Laser ablation is also used to remove part of the uterine wall in women with menstruation problems and adenomyosis, in a process called endometrial ablation.

Recently, researchers have demonstrated an effective technique for ablating subsurface tumors with minimal thermal damage to surrounding healthy tissue, using a focused laser beam from an ultrashort-pulse diode laser source.[10]​.

Antifouling paints and other related coatings are commonly used to prevent the accumulation of microorganisms and other animals, such as barnacles, on the lower hull surfaces of recreational, commercial, and military marine vessels. Ablative paints are often used to prevent dilution or deactivation of the antifouling agent. Over time, the paint slowly breaks down in the water, revealing fresh antifouling compounds on the surface. Engineering of antifouling agents and ablation rate can produce long-lasting protection against the harmful effects of biofouling.

In medicine, ablation is the removal of a piece of biological tissue "Tissue (biology)"), usually by surgery. Superficial skin ablation (dermabrasion), also called resurfacing because it induces regeneration, can be performed using chemicals (chemoablation), laser (laser ablation), freezing (cryoablation), or electricity (fulguration). Its purpose is to eliminate skin spots, aged skin, wrinkles, rejuvenating it. Superficial ablation is also used in otorhinolaryngology for various types of surgery, such as snoring surgery. Radiofrequency ablation (RFA) is a method of removing aberrant tissue from inside the body through minimally invasive procedures. It is used to cure various cardiac arrhythmias such as supraventricular tachycardia, Wolff-Parkinson-White (WPW) syndrome, ventricular tachycardia and, more recently, as a treatment for atrial fibrillation. The term is often used in the context of laser ablation, a process in which a laser dissolves the molecular bonds of a material. For a laser to ablate tissues, the power density or fluence must be high, since otherwise thermocoagulation occurs"), which is nothing more than the thermal vaporization of tissues.

Rotablation") is a type of arterial cleansing that involves inserting a tiny, diamond-tipped, drill-shaped device into the affected artery to remove fatty deposits or plaque. The procedure is used in the treatment of coronary heart disease to restore blood flow.

Microwave ablation (MWA) is similar to RFA but with higher frequencies of electromagnetic radiation.

High-intensity focused ultrasound (HIFU) ablation removes tissue from inside the body non-invasively.

Bone marrow ablation is a process in which human bone marrow cells are removed in preparation for a bone marrow transplant. It is performed using high-intensity chemotherapy and total body irradiation. As such, it has nothing to do with the vaporization techniques described in the rest of this article.

Brain tissue ablation") is used to treat certain neurological disorders, particularly Parkinson's disease, and sometimes also psychiatric disorders.

Recently, some researchers have reported satisfactory results with genetic ablation. Specifically, genetic ablation is potentially a much more effective method for eliminating unwanted cells, such as tumor cells, since a large number of animals lacking specific cells could be generated. Genetically ablated lines can be maintained for an extended period and shared with the research community. Researchers at Columbia University report pooled reconstituted caspases from C. elegans and humans, which maintain a high degree of target specificity. The genetic ablation techniques described could be useful in the fight against cancer.[11]​.

Fire retardants and firestop products can be ablative in nature. This can mean endothermic materials, or simply materials that are sacrificial and “wear out” over time while exposed to fire, such as silicone firestop products. If exposed to fire or heat for long enough, these products char, crumble, and disappear. The idea is to put enough of this material in the path of the fire so that a level of fire resistance rating can be maintained, as demonstrated in a fire test. Ablative materials usually have a high concentration of organic matter that fire reduces to ashes. In the case of silicone, organic rubber") surrounds very finely divided silica powder (up to 380 m² combined surface area of ​​all dust particles per gram of this powder. When organic rubber is exposed to fire, it turns to ash and leaves behind the silica powder "Silicon(IV) Oxide") with which the product was started.

Protoplanetary disks are rotating circumstellar disks of dense gas and dust that surround young, newly formed stars. Shortly after star formation, stars often have leftover surrounding material that is still gravitationally bound to them, forming primitive disks that orbit the star's equator, somewhat like the rings of Saturn. This occurs because the decreasing radius of the protostellar material during formation increases the angular momentum, meaning that this remaining material becomes a circumstellar disk. flattened around the star. This circumstellar disk can eventually become what is known as a protoplanetary disk: a disk of gas, dust, ice and other materials from which planetary systems can form. In these disks, matter in orbit begins to accumulate in the colder midplane of the disk from grains of dust and ice that stick together. These small accumulations grow from pebbles to rocks, to baby planets, called planetesimals, then protoplanets, and finally, complete planets.[12]​.

As massive stars are thought to play a role in actively triggering star formation (by introducing gravitational instabilities, among other factors),[13] it is plausible that younger, smaller stars with disks live relatively close to older, more massive stars. Observations have already confirmed that this is the case in some clusters, such as Trapezium.[14] Since massive stars tend to collapse at the end of their lives through supernovae, research is underway into what role the shock wave from such an explosion, and the resulting supernova remnant (SNR), would play if it occurred in the line of fire of a protoplanetary disk. According to computer simulations, an SNR colliding with a protoplanetary disk would cause significant ablation of the disk, and this ablation would tear away a significant amount of protoplanetary material from the disk, but would not necessarily destroy the disk completely.[15] This is an important point because a disk that survives such an interaction with enough material left over to form a planetary system could inherit altered disk chemistry from the SNR, which could have effects on planetary systems that form. later.

Main article: atmospheric reentry § Ablative.

In spacecraft design, ablation is used to both cool and protect mechanical parts and/or payloads that would otherwise be damaged by extremely high temperatures. Two main applications are "heat shields" for spacecraft entering a planetary atmosphere from space and the cooling of rocket engine nozzles. Some examples are the Apollo Command and Service Module, which protected astronauts from the heat of atmospheric reentry, and the Kestrel second-stage rocket engine, designed for exclusive use in a space vacuum environment as heat convection is not possible.

In a basic sense, the ablative material is designed so that, instead of heat being transmitted to the spacecraft structure, only the outer surface of the material bears most of the heating effect. The outer surface chars and burns, but very slowly, gradually revealing new protective material. The heat is carried away from the spacecraft by gases generated by the ablation process and never penetrates the surface material, so the metal structures and other sensitive structures they protect remain at a safe temperature. As the surface burns up and disperses into space, the remaining solid material continues to insulate the spacecraft from continued heat and superheated gases. The thickness of the ablative layer is calculated to be sufficient to survive the heat you will encounter on your mission.

There is an entire branch of space research dedicated to the search for new flame retardant materials to achieve the best ablative performance; This feature is critical to protecting spacecraft occupants and payload from otherwise excessive thermal loading. The same technology is used in some passive fire protection applications, in some cases by the same suppliers, who offer different versions of these fire retardant products, some for aerospace protection and others for structural fire protection.

More information: Ablation zone.

In glaciology and meteorology, ablation - the opposite of accumulation - refers to all processes that remove snow, ice or water from a glacier or snowfield. Ablation refers to the melting of snow or ice run off from the glacier, evaporation, sublimation, calving or erosive removal of snow by wind. Air temperature is usually the dominant factor in ablation, with precipitation exerting a secondary control. In a temperate climate, during the ablation season, ablation rates are typically around 2 mm/h.[4]​ When solar radiation is the dominant cause of snow ablation (for example, if air temperatures are low under clear skies), characteristic ablation textures such as "suncups" and "penitentes" may appear on the snow surface. (glaciology)")".[5]​.

Ablation can refer to both the processes of ice and snow removal and the amount of ice and snow removed.

Debris-covered glaciers have also been shown to greatly influence the ablation process. On top of glaciers there may be a thin layer of debris that intensifies the ablation process beneath the ice. The debris-covered portions of an ablating glacier fall into three categories: ice cliffs, lagoons, and debris. These three sections allow scientists to measure the heat digested by the debris-covered area and calculate it. The calculations depend on the surface area and the net amounts of heat absorbed in relation to the entire debris covered areas. These types of calculations are carried out on several glaciers to understand and analyze future melting patterns.[6]​.

The moraine (glacial debris) moves by natural processes that allow the downslope movement of materials in the body of the glacier. It is observed that if the slope of a glacier is too high, the debris will continue to move along the glacier to a further location. The sizes and locations of glaciers vary around the world, so depending on climate and physical geography the varieties of debris may differ. The size and magnitude of the debris depends on the area of ​​the glacier and can vary from dust-sized fragments to house-sized blocks.[7]​.

Many experiments have been done to demonstrate the effect of debris on the surface of glaciers. Yoshiyuki Fujii, a professor at the National Polar Research Institute, designed an experiment that showed that the rate of ablation was accelerated under a thin layer of debris and delayed under a thick layer, compared to that of a natural snow surface.[8] This science is significant because of the importance of long-term water resource availability and evaluating the response of glaciers to climate change. The availability of natural resources is one of the main drivers of the research carried out in relation to the ablation process and the general study of glaciers.[9]​.

Main article: laser ablation").

Laser ablation is greatly affected by the nature of the material and its ability to absorb energy, so the wavelength of the ablation laser must have a minimum absorption depth. Although these lasers may average low power, they can offer peak intensity and fluence given by:.

while the maximum power is:.

Superficial ablation of the cornea for various types of refractive eye surgery is now common, using an excimer laser system (LASIK and LASEK). Since the cornea does not grow back, the laser is used to reshape the refractive properties of the cornea to correct refractive errors such as astigmatism, nearsightedness, and farsightedness. Laser ablation is also used to remove part of the uterine wall in women with menstruation problems and adenomyosis, in a process called endometrial ablation.

Recently, researchers have demonstrated an effective technique for ablating subsurface tumors with minimal thermal damage to surrounding healthy tissue, using a focused laser beam from an ultrashort-pulse diode laser source.[10]​.

Antifouling paints and other related coatings are commonly used to prevent the accumulation of microorganisms and other animals, such as barnacles, on the lower hull surfaces of recreational, commercial, and military marine vessels. Ablative paints are often used to prevent dilution or deactivation of the antifouling agent. Over time, the paint slowly breaks down in the water, revealing fresh antifouling compounds on the surface. Engineering of antifouling agents and ablation rate can produce long-lasting protection against the harmful effects of biofouling.

In medicine, ablation is the removal of a piece of biological tissue "Tissue (biology)"), usually by surgery. Superficial skin ablation (dermabrasion), also called resurfacing because it induces regeneration, can be performed using chemicals (chemoablation), laser (laser ablation), freezing (cryoablation), or electricity (fulguration). Its purpose is to eliminate skin spots, aged skin, wrinkles, rejuvenating it. Superficial ablation is also used in otorhinolaryngology for various types of surgery, such as snoring surgery. Radiofrequency ablation (RFA) is a method of removing aberrant tissue from inside the body through minimally invasive procedures. It is used to cure various cardiac arrhythmias such as supraventricular tachycardia, Wolff-Parkinson-White (WPW) syndrome, ventricular tachycardia and, more recently, as a treatment for atrial fibrillation. The term is often used in the context of laser ablation, a process in which a laser dissolves the molecular bonds of a material. For a laser to ablate tissues, the power density or fluence must be high, since otherwise thermocoagulation occurs"), which is nothing more than the thermal vaporization of tissues.

Rotablation") is a type of arterial cleansing that involves inserting a tiny, diamond-tipped, drill-shaped device into the affected artery to remove fatty deposits or plaque. The procedure is used in the treatment of coronary heart disease to restore blood flow.

Microwave ablation (MWA) is similar to RFA but with higher frequencies of electromagnetic radiation.

High-intensity focused ultrasound (HIFU) ablation removes tissue from inside the body non-invasively.

Bone marrow ablation is a process in which human bone marrow cells are removed in preparation for a bone marrow transplant. It is performed using high-intensity chemotherapy and total body irradiation. As such, it has nothing to do with the vaporization techniques described in the rest of this article.

Brain tissue ablation") is used to treat certain neurological disorders, particularly Parkinson's disease, and sometimes also psychiatric disorders.

Recently, some researchers have reported satisfactory results with genetic ablation. Specifically, genetic ablation is potentially a much more effective method for eliminating unwanted cells, such as tumor cells, since a large number of animals lacking specific cells could be generated. Genetically ablated lines can be maintained for an extended period and shared with the research community. Researchers at Columbia University report pooled reconstituted caspases from C. elegans and humans, which maintain a high degree of target specificity. The genetic ablation techniques described could be useful in the fight against cancer.[11]​.

Fire retardants and firestop products can be ablative in nature. This can mean endothermic materials, or simply materials that are sacrificial and “wear out” over time while exposed to fire, such as silicone firestop products. If exposed to fire or heat for long enough, these products char, crumble, and disappear. The idea is to put enough of this material in the path of the fire so that a level of fire resistance rating can be maintained, as demonstrated in a fire test. Ablative materials usually have a high concentration of organic matter that fire reduces to ashes. In the case of silicone, organic rubber") surrounds very finely divided silica powder (up to 380 m² combined surface area of ​​all dust particles per gram of this powder. When organic rubber is exposed to fire, it turns to ash and leaves behind the silica powder "Silicon(IV) Oxide") with which the product was started.

Protoplanetary disks are rotating circumstellar disks of dense gas and dust that surround young, newly formed stars. Shortly after star formation, stars often have leftover surrounding material that is still gravitationally bound to them, forming primitive disks that orbit the star's equator, somewhat like the rings of Saturn. This occurs because the decreasing radius of the protostellar material during formation increases the angular momentum, meaning that this remaining material becomes a circumstellar disk. flattened around the star. This circumstellar disk can eventually become what is known as a protoplanetary disk: a disk of gas, dust, ice and other materials from which planetary systems can form. In these disks, matter in orbit begins to accumulate in the colder midplane of the disk from grains of dust and ice that stick together. These small accumulations grow from pebbles to rocks, to baby planets, called planetesimals, then protoplanets, and finally, complete planets.[12]​.

As massive stars are thought to play a role in actively triggering star formation (by introducing gravitational instabilities, among other factors),[13] it is plausible that younger, smaller stars with disks live relatively close to older, more massive stars. Observations have already confirmed that this is the case in some clusters, such as Trapezium.[14] Since massive stars tend to collapse at the end of their lives through supernovae, research is underway into what role the shock wave from such an explosion, and the resulting supernova remnant (SNR), would play if it occurred in the line of fire of a protoplanetary disk. According to computer simulations, an SNR colliding with a protoplanetary disk would cause significant ablation of the disk, and this ablation would tear away a significant amount of protoplanetary material from the disk, but would not necessarily destroy the disk completely.[15] This is an important point because a disk that survives such an interaction with enough material left over to form a planetary system could inherit altered disk chemistry from the SNR, which could have effects on planetary systems that form. later.

Main article: atmospheric reentry § Ablative.

In spacecraft design, ablation is used to both cool and protect mechanical parts and/or payloads that would otherwise be damaged by extremely high temperatures. Two main applications are "heat shields" for spacecraft entering a planetary atmosphere from space and the cooling of rocket engine nozzles. Some examples are the Apollo Command and Service Module, which protected astronauts from the heat of atmospheric reentry, and the Kestrel second-stage rocket engine, designed for exclusive use in a space vacuum environment as heat convection is not possible.

In a basic sense, the ablative material is designed so that, instead of heat being transmitted to the spacecraft structure, only the outer surface of the material bears most of the heating effect. The outer surface chars and burns, but very slowly, gradually revealing new protective material. The heat is carried away from the spacecraft by gases generated by the ablation process and never penetrates the surface material, so the metal structures and other sensitive structures they protect remain at a safe temperature. As the surface burns up and disperses into space, the remaining solid material continues to insulate the spacecraft from continued heat and superheated gases. The thickness of the ablative layer is calculated to be sufficient to survive the heat you will encounter on your mission.

There is an entire branch of space research dedicated to the search for new flame retardant materials to achieve the best ablative performance; This feature is critical to protecting spacecraft occupants and payload from otherwise excessive thermal loading. The same technology is used in some passive fire protection applications, in some cases by the same suppliers, who offer different versions of these fire retardant products, some for aerospace protection and others for structural fire protection.