Good Research Paper On The Great White Spots

Introduction

Considered the second largest gas giant, Saturn has strong winds that are much stronger than the winds here on Earth. Moreover, once every thirty Earth years, a strong storm churns in the planet’s atmosphere so great that it creates a bright spot visible to weaker telescopes. In addition, this storm is so massive that its diameter can be larger than Earth’s while leaving a trail of weaker storms that encircles the entire planet. This phenomenon which occurs every one Saturnian year is collectively known as the Great White Spots of Saturn. In this light, this paper aims to provide theories that could explain why the Great White Spots form.
In order to understand the phenomenon, it is important to consider Saturn’s atmosphere because understanding its composition proves to be useful in unlocking the secrets of the Great White Spots. Therefore, this paper includes a detail of Saturn’s atmosphere. The composition and the structure of the atmosphere of Saturn will be discussed.
In addition, the history and documentation of Saturn’s Great White Spots must be examined in order to define the pattern of the spots. From its history, several attributes of the Great White Spots can be concluded, such as where it usually forms. Therefore, a brief history of the Great White Spots will be reported.
It is important to note that since this phenomenon recurs in a certain pattern, studying the development of one of the Great White spots can conclude how all the Great White Spots form and develop. In this case, a well-documented case of one of the Great White Spots will be examined. In particular, the 1990 Great White Spot will be examined. The analysis will provide a detailed information how the Great White Spots develop.
Finally, this paper will explain why insolation and the internal heat of the planet helps in the formation of the Great White Spots.

Saturn's Atmosphere

Considered one of the gas giants, Saturn is composed highly of gases while lacking a solid surface (Redd, 2012). The precise composition of the gas giants is still under debate, however, certain theories present evidences from in-earth from observatories and close-up observations from space programs traveling near Saturn.
As seen through a telescope, Saturn, similar with Jupiter, presents bands in its surface. These bands are caused by convection (Heath, 1995).
Hydrogen predominantly makes up the atmosphere of Saturn. This high concentration of hydrogen is believed to be stuck in the planet's atmosphere in the beginning of its formation. The second most dominant gas in the atmosphere of Saturn is helium. Although helium comprises almost one-fourth of the planet's mass, the atmosphere of Saturn is only 7% helium. The remaining gases in the atmosphere of Saturn constitutes to methane, ammonia, nitrogen, oxygen and water (Redd, 2012; Heath, 1995).
Because of the distance from the Sun, which is almost ten times the distance of the Earth from the sun, Saturn's atmosphere is very cold. Since traces of water exists in the atmosphere, most exist as ice (Redd, 2012).
Moreover, the clouds of the planet is layered with each defined by a certain range of pressure and temperature. The bottom layer of clouds consists of water ice, while a band of ammonia hydrosulfide clouds sit on top of it. Clouds consisting of ammonia ice can be found on the upper layer below a tropospheric band, which the composition is unknown, obscuring everything (The Daily Galaxy, 2013).
In the event where a storm develops, such as in the Great White Spots, the storm initially develops in the bottom water level. The buildup projects the layers upward driven by strong convection underneath the atmosphere, and develops a huge convective tower of clouds. This tower becomes visible that it provides a glimpse to the composition of the atmosphere underneath. Thus, by studying the composition of Saturn’s great storms, results could be an evidence to the composition of Saturn’s atmosphere (The Daily Galaxy, 2013).

History of Great White Spots

Since the invention of telescopes, the storms on giant planets, such as in Jupiter and Saturn, have been observed. However, Jupiter had shown more bands and whirls than Saturn. Still, great storms arose in the atmosphere of Saturn, precisely every thirty years (one Saturnian year). These storms are collectively known as the Great White Spots (Heath and McKim, 1992; Calar Alto Observatory, 2011).
The Great White Spots are storms with tremendous speeds and size that some are observed to cover Saturn's diameter. They occur almost every thirty years or one Saturnian year. However, some weaker storms occur every so often. Furthermore, these storms develop in the northern hemisphere during the strongest insolation (amount of solar energy received) (Heath and McKim, 1992; Calar Alto Observatory, 2011; Hernandez, 2011; The Daily Galaxy, 2013).
The first recorded observation of the Great White Spot was by Asaph Hall in 1876. The Great white Spot was so prominent that it was visible in apertures of around 60 millimeter. The second observation was by Edward Barnard in 1903, then Will Hay in 1933. The succeeding occurrence was in 1960 and 1990. However, a strong storm developed in 2010 can be considered one of the Great White Spots (Heath and McKim, 1992; Hainaut, 1990; Wilkins, 2010).
Mark Kidger described the Great White Spots to be in an alternating manner. The storms develop either in the North Temperate Zone or the Equatorial Zone. The 1876 and 1933 Great White Spots developed in the Equatorial Zone while the 1903 and 1960 Great white Spots Developed in the North Temperate Zone. Moreover, the storms that developed in the North Temperate Zones are less prominent than the storms developed in the Equatorial Zones (Heath and McKim, 1992).
The Great White Spots are storms of tremendous strength occurring every Saturnian year. These storms are so massive that it can cover the entire diameter of the planet (Wilkins, 2010). Even if the differential wind speed in the atmosphere is accounted for, the vertical wind speed in these storms can reach up to 300 miles per hour (The Daily Galaxy, 2013).

Development of Great White Spots

The storms in Saturn resemble the thunderstorms here in the Earth. The development of the thunderstorms here in the Earth is primarily driven by the upward convective push of air and water vapor high in the atmosphere (The Daily Galaxy, 2013). In the case of the Great White Storms, the air underneath the “surface” are projected high in the atmosphere. However, the Great White Spots are much massive than the thunderstorms in the Earth. For comparison, the clouds on Great White Spots can have depths of 200 kilometers (The Daily Galaxy, 2013).
The Great White Spots develop either on the North Temperate Zone or the Equatorial Zone, however, all of them was observed to be just a "white spot" in the surface of the atmosphere (Hainaut, 1990). For further understanding on the formation of the Great White Spots, let us examine the formation of the 1990 Great White Spot.
On September 25, 1990, astronomers at the Las Cruces Observatory located in New Mexico, USA observed a white spot at +12-degrees of the northern hemisphere of Saturn. The formation of the storm is so rapid that within a week, it grew in size to about 20,000 kilometers (Hainaut, 1990). The rotation period of the spot was observed to be about 10 hours and 17 minutes. This reading was thought to be slower than the rotation of the surrounding atmosphere. Moreover, the spot was brighter than the rest of the Equatorial Zone. Kidger suggested that the storm initially developed deep in the atmosphere because of the observation that the spot faded near the limb then reappeared (Heath and McKim, 1992).
In addition, the observations showed a rapid expansion in length and width. The Great White Spot was seen only within a range in the northern Equatorial Zone, but by October 1, the storm covered the entire width of the Equatorial Zone (Heath and McKim, 1992).
The brightness of the spot decreased from October 2 to October 5 while the expansion proceeded. This observation suggests that the material that is being pushed upward was being dispersed into the zone without being replaced. In addition, the continuous expansion resulted in the loss of sharpness of the spot's edges. The length of the storm was around 27,000 kilometers on October 2, while it increased to about 49,000 kilometers by October 4 (Heath and McKim, 1992).
Furthermore, the spot began to form its "tail". Occasionally, massive storms like the Great White Spots develop a head and a tail. The tail is a result of the winds left behind by the head. In the case of the 1990 Great White Spot, the tail was first observed on October 1, but it was more prominent on October 2 (Heath and McKim, 1992).
The development of the storm continued and by October 10, the length of the storm covered half of the planet's diameter. By October 23, it encircled the entire planet and is visible as a bright band (Hainaut, 1990).

The Cause of the Great White Spots

There are several ideas why the Great White Spots emerge and why it emerges every 30 Earth years. The most accepted theory, however, presents further irregularities. For the purpose of defining what causes the Great White Spots on the atmosphere of Saturn, it is best to examine the evidences that are apparent in the early formation as well as the recurring pattern of the Great White Spots.
First, it is established that the Great White spots occur every thirty Earth years, or one Saturnian year. However, some data suggests a more accurate representation of the occurrence of the Great White Spots. According to Heath and McKim (1992), the interval between two Great White Spots emerging within the same zone (i.e. the 1933 and 1960 Great White Spots in the Equatorial Zone) is 57 Earth years. This constitutes to the idea that Great White Spots emerge within a certain "season". Thus, by examining the data from various studies, it can be concluded that the Great White Spots emerge in the early summer of the Saturnian season, or when Saturn is within its ecliptic longitude range of 290- to 315-degrees.
It is important to note that the early summer season of Saturn suggests the greatest insolation (the amount of solar energy received) during the entire Saturnian year. Since the Great White Spots occur every one Saturnian year, it can be concluded that insolation could be a factor in the formation of the Great White Spots. However, insolation cannot answer why the storms consist of certain composition.
The Great White Spots consist predominantly of water and ammonia ice as well as a third component believed to be ammonia hydrosulfide. Thus, it can be concluded that the storm developed underneath the surface of the atmosphere. Recall that the atmosphere of Saturn is layered, and that the layers below the surface of the atmosphere are composed of water ice, ammonia hydrosulfide and ammonia ice. Therefore, the storms developed underneath the visible layer of the atmosphere (Hernandez, 2011; The Daily Galaxy, 2013; Wilkins, 2010).
It is important to note that if the heat from the sun cannot reach the water ice layer of the atmosphere of Saturn. Moreover, scientists have determined that the clouds on the storms have depths of about 200 kilometers. Hence, Saturn's internal heat must have helped in forming the storm (Hernandez, 2011; The Daily Galaxy, 2013; Wilkins, 2010; Calar Alto Observatory, 2011).

Documentation

Summary
In summary, the Great White Spots are storms of tremendous strength and size. The storms form as a small spot within either the North Temperate Zone or the Equatorial Zone of Saturn’s atmosphere. The formation phase continues until the storm becomes stationary encircling the entire planet. Within one week, the storm could grow into an enormous and strong storm. The tail of the storm develops with smaller storms. These storms occur every thirty years or one Saturnian year. This pattern suggests that insolation could be a factor in the formation of the storms. However, the composition of the storm, which is highly composed of water and ammonia ice as well as a third component believed to be ammonia hydrosulfide, points out that the storm developed in the lower layer of the atmosphere. Moreover, scientists have determined that the clouds of the storm have depths of about 200 kilometers making it possible that the internal heat of the planet may have helped in forming the storm. Lastly, in order to fully understand the cause of the Great White Spots, certain information must be obtained first which could be from in-Earth or close-up observations.

References:

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Heath, Alan W. (1995). Saturn 1992. Journal of the British Astronomical Association, 105(2), 75-81. Print. 18 February 2015.
Heath, A. W. and McKim, R. J. (1992) Saturn 1990: The Great White Spot. Journal of the British Astronomical Association, 102(4), 210-219. Print. 18 February 2015.
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