planets revision 1.pdf

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How are the ages of meteorites determined?

Researchers have aged dated a very important group of meteorites with far greater precision

than previously possible by using a different type of radioactive dating on a particularly

difficult type of specimen to study. Most meteorite dating research has looked at two types of

meteoriteangrites and eucriteswhich contain ample amounts of minerals necessary forthe study. Goodrich and her team opted to investigate ureilites.

The projects radioactive isotope dating methods looked at short-lived radionuclides rather

than the long-lived radionuclides that researchers have studied for years.

Ureilites are the second most abundant group of differentiated meteorites, but they are

particularly enigmatic and are very difficult to date because they dont contain many different

minerals, she said.

Radiometric dating is based on the principle that radioactive elements decay and change into

other elements at a constant rate that can be measured in a laboratory. The basic idea behind

radioactive dating is that if you can measure the ratio of parent to daughter isotopes in a rock

or mineral using a mass spectrometer, which separates isotopes from one another according

to their weight, you can calculate its age.

Short-lived radionuclides are isotopes that decay much faster than the long-lived ones. In

fact, they decay so quickly that any parent atoms that were present at the time the Solar

System formed would have completely changed into daughter isotopes a long time ago, she

said. By measuring the daughter isotopes in several different minerals, it is possible to

determine how much of the parent isotope was in the rock when rock formed, and this value

can be compared to a known value for how much of the parent was present at some specifictime, say at the formation of the Solar System.

The clock suitable for meteorites is the decay of Rudium (87Rb) into Strontium (87Sr), which has a

half life of abiout 49 billion years. The manner in which the age is determined is based on calculating

ratios of these isotopes. The most accurate age of meteorites is determined by- first, assuming that.

meteorites represent an array of nranium-lead systems with eert,ain properties, and by then

computing the age of this array from the observed lead pat,tern. The most. accurate age of t,he

earth is obtained by denlollst.ra~~i~~g that t,he earths urallilln~-lead system belongs to the array of

meteoritic uranium-lead syst,ems.* The following assumptions are made concerning meteorit,es:

they were formed at, the same time: they existed as isolated and closed systems: they originallycontained lead of the same isotopic composition; they contain uranium which has the same isotopic

composition as that in the earth. On the basis of these assumptions various leads might be expected

to evolve as a result of different original U/Pb ,ratios in separate meteorites, and an expression* for

any pair of leads derived from such an array.

how to estimate the age of part of the lunar surface

Meteors do not arrive on the moon at the same rates. Very large meteors that produce the largest

craters are much less common than the smaller bodies producing the smallest craters. That's

because there are far more small bodies in space than large ones. Astronomers can use this fact to

estimate the ages of various surfaces in the solar system by just comparing the number of large


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craters and small craters that they find in a given area. However, in the case of remote planetary

bodies, with little accessibility to their rock samples, the Crater Size Frequency Distribution (CSFD) is

a well developed method for determining surface ages using remote sensing techniques. Planetary

surface age determination method, mostly referred to as Crater Size Frequency Distribution (CSFD)

method, has wide application due to the presence of impact craters which are the dominant

landforms on most of the solid surfaces in our solar system. These impact craters act as a tool to

understand the geological history and various surfaces on different planets to reveal spatial and

temporal variations of the crater-forming projectile flux as a function of time. The Moon is such a

natural laboratory in the entire solar system, which would reveal the history of the inner solar

system so as to understand many basic scientific key issues, not only of the Moon, but also of the

entire solar system.

why jupiter has strong magnetic field

Jupiter has a large, complex, and intense magnetic field that is thought to arise from electrical

currents in the rapidly spinning metallic hydrogen interior. Jupiter's magnetic field is 14 times as

strong as the Earth's, ranging from 4.2 gauss (0.42 mT) at the equator to 10-14 gauss (1.0-1.4 mT) at

the poles, making it the strongest in the Solar System. This field is generated by eddy currents-

swirling movements of conducting materials-within the metallic hydrogen core. The field is

doughnut shaped (toroidal), containing giant versions of the Earth's Van Allen Belts that trap high-

energy charged particles (mostly electrons and protons). Because of the forces associated with the

rapid rotation of Jupiter and its magnetic field, these "belts" are flattened into "plasma sheets" in

the case of Jupiter. The field rotates with the approximately 9 hour rotational period of the planet.

The satellites Amalthea, Io, Europa, and Ganymede all orbit through this region; they are affected by

it and in turn affect the magnetic field and charged-particle belts

Describe the process of convection in planetary interiors

Mantle convection is the slow creeping motion of Earth's rocky mantle caused by convection

currents carrying heat from the interior of the Earth to the surface.[3] The Earth's surface

lithosphere, which rides atop the asthenosphere (the two components of the upper mantle), is

divided into a number of plates that are continuously being created and consumed at their opposite

plate boundaries. Accretion occurs as mantle is added to the growing edges of a plate, usually

associated with seafloor spreading. This hot added material cools down by conduction and

convection of heat. At the consumption edges of the plate, the material has thermally contracted to

become dense, and it sinks under its own weight in the process of subduction at an ocean trench.

Compare and contrast the atmosphere of the terrestrial planets, the Earth, Mars, and Venus

In ipad ref atmosphere of venus, earth, and mars a critical comparison

What are the processes that dominate the atmospheres of the gas giants?

Jupiter's Atmosphere

The atmosphere merges with the underlying liquid hydrogen layers with no solid surface being

present. The atmospheric features are the result of coloration by trace chemicals containing P and Sand a complex pattern of circulation. Belts are darker appearing regions where material has cooled


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and is sinking while zones are comprised of warmer that is rising on a convective air flow. These

regions get stretched all around Jupiter due to its rapid rotation rate. The velocities of gas in the

belts and zones are similar to the jet stream velocities on Earth. Turbulence at the boundaries

between belts and zones leads to the formation of large, whirlpool-like storms analogous to

hurricanes on Earth. The Great Red Spot is an example of such a storm. Storms can persist for years

on Jupiter because, unlike hurricanes on Earth, there are no continental land masses to disrupt the

flow causing the storm.

The atmosphere of Jupiter lacks a clear lower boundary and gradually transitions into the fluid

interior of the planet.[2] From lowest to highest, the atmospheric layers are the troposphere,

stratosphere, thermosphere and exosphere. Each layer has characteristic temperature gradients.[3]

The lowest layer, the troposphere, has a complicated system of clouds and hazes, comprising layers

of ammonia, ammonium hydrosulfide and water.[4] The upper ammonia clouds visible at Jupiter's

surface are organized in a dozen zonal bands parallel to the equator and are bounded by powerful

zonal atmospheric flows (winds) known as jets. The bands alternate in color: the dark bands are

called belts, while light ones are called zones. Zones, which are colder than belts, correspond to

upwellings, while belts mark descending air.[5] The zones' lighter color is believed to result from

ammonia ice; what gives the belts their darker colors is not known with certainty.[5] The origins of

the banded structure and jets are not well understood, though two models exist. The shallow model

holds that they are surface phenomena overlaying a stable interior. In the deep model, the bands

and jets are just surface manifestations of deep circulation in Jupiter's mantle of molecular hydrogen,

which is organized in a number of cylinders.[6]

The Jovian atmosphere shows a wide range of active phenomena, including band instabilities,

vortices (cyclones and anticyclones), storms and lightning.[7] The vortices reveal themselves as large

red, white or brown spots (ovals). The largest two spots are the Great Red Spot (GRS)[8] and Oval

BA,[9] which is also red. These two and most of the other large spots are anticyclonic. Smaller

anticyclones tend to be white. Vortices are thought to be relatively shallow structures with depths

not exceeding several hundred kilometers. Located in the southern hemisphere, the GRS is the

largest known vortex in the Solar System. It could engulf several Earths and has existed for at least

three hundred years. Oval BA, south of GRS, is a red spot a third the size of GRS that formed in 2000

from the merging of three white ovals.[10]

Jupiter has powerful storms, always accompanied by lightning strikes. The storms are a result of

moist convection in the atmosphere connected to the evaporation and condensation of water. They

are sites of strong upward motion of the air, which leads to the formation of bright and dense clouds.

The storms form mainly in belt regions. The lightning strikes on Jupiter are more powerful than

those on Earth. However, there are fewer of them, and the average levels of lightning activity are

comparable to those on Earth

Lobate scarps


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Lobate= having or resembling lobes

Scarp= cliff Global tectonic feature Named Rupes from Latin for cliff All named after ships Large,

curved cliffs-Really large!Interpreted as thrust faults

Characteristics of Lobate Scarps

-section

GRABEN

A graben is a down-dropped block of the earth's crust resulting from extension, or pulling, of the

crust.

Yardangs


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A yardang is a streamlined hill carved from bedrock or any consolidated or semiconsolidated

material by the dual action of wind abrasion, dust and sand, and deflation.[1] Yardangs become

elongated features typically three or more times longer than wide, and when viewed from above,

resemble the hull of a boat. Facing the wind is a steep, blunt face that gradually gets lower and

narrower toward the lee end.[2] Yardangs are formed by wind erosion, typically of an originally flat

surface formed from areas of harder and softer material. The soft material is eroded and removed

by the wind, and the harder material remains. The resulting pattern of yardangs is therefore acombination of the original rock distribution, and the fluid mechanics of the air flow and resulting

pattern of erosion.They can also be attributed to the past pluvial processes i.e. their formation.this

can be as a result of ephemoral river that eroded eroded the plateaus

Lava tubes

Lava tubes are natural conduits through which lava travels beneath the surface of a lava flow,

expelled by a volcano during an eruption. They can be actively draining lava from a source, or can be

extinct, meaning the lava flow has ceased and the rock has cooled and left a long, cave-like channel.

Lava tubes are likely to exist on previously or currently geologically active planets or moons,

including the Earth.

Lava tubes are a type of lava cave formed when an active low-viscosity lava flow develops a

continuous and hard crust, which thickens and forms a roof above the still-flowing lava stream.[1]

Tubes form in one of two ways: by the crusting over of lava channels, and from pahoehoe flows

where the lava is moving under the surface.

Lava usually leaves the point of eruption in channels. These channels tend to stay very hot as their

surroundings cool. This means they slowly develop walls around them as the surrounding lava cools

and/or as the channel melts its way deeper. These channels can get deep enough to crust over,


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forming an insulating tube that keeps the lava molten and serves as a conduit for the flowing lava.

These types of lava tubes tend to be closer to the lava eruption point.

Further away from the eruption point, lava can flow in an unchanneled, fanlike manner as it leaves

its source, which is usually another lava tube leading back to the eruption point. Called pahoehoe

flows, these areas of surface-moving lava cool, forming either a smooth or rough, ropy surface. The

lava continues to flow this way until it begins to block its source. At this point, the subsurface lava is

still hot enough to break out at a point, and from this point the lava begins as a new "source". Lava

flows from the previous source to this breakout point as the surrounding lava of the pahoehoe flow

cools. This forms an underground channel that becomes a lava tube.

self compression of the interior of a planet: ie the increase is in density caused by the density

caused by the pressure of the overlying material.

The relatively high average density and low mass of Mercury indicates an unusual bulk compositionand thus provides an important constraint for the initial temperature of the solar nebula, the degree ofradial mixing, and the extent of condensation and evaporation [e.g. 4]. The high iron content ofmercury could be the result of chemical and thermal gradients in the solar nebula or partial removal ofthe silicate portion of a differentiated planet by giant impact or vaporization. These hypotheseslead to different predications, by numerous authors, of the bulk chemistry of Mercury, particularlythe abundance of volatile elements. Little is directly known of Mercurys composition and internalstructure, however its high average density suggests a high metal to silicate ratio. Remote sensingsuggests low FeO in the crust [5-8] and mantle [9]. The presence of an intrinsic magnetic field,possibly generated by a hydromagnetic dynamo, has led many researchers to postulate that Mercuryhas a molten outer core, thus demanding an alloying element, possibly sulfur, to lower the meltingtemperature [e.g. 10-11]. Sodium and potassium are present in the exosphere of Mercury, but it is not

clear if their source is endogenic or exogenic [12]. Volatiles in the exosphere together with the intrinsicmagnetic field demand consideration of a range of volatile abundances for Mercury.

Methods: We model Mercurys interior under adiabatic self-compression using the Adams-

Williamson equation with the second order Birch- Murnaghan finite strain equation of state (EOS) to

estimate its decompressed density. We assume the thermal profile is adiabatic except for a thermal

boundary layer at the core mantle boundary, modeled as a temperature

difference between the adiabats for the core and the mantle extrapolated to zero pressure.

Earths magnetic field

Earth's magnetic field (also known as the geomagnetic field) is the magnetic field that extends from

the Earth's inner core to where it meets the solar wind, a stream of energetic particles emanatingfrom the Sun. Its magnitude at the Earth's surface ranges from 25 to 65 T (0.25 to 0.65 G). It is


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approximately the field of a magnetic dipole tilted at an angle of 11 degrees with respect to the

rotational axisas if there were a bar magnet placed at that angle at the center of the Earth.

However, unlike the field of a bar magnet, Earth's field changes over time because it is generated by

the motion of molten iron alloys in the Earth's outer core (the geodynamo).

The Magnetic North Pole wanders, but slowly enough that a simple compass remains useful fornavigation. At random intervals (averaging several hundred thousand years) the Earth's field

reverses (the north and south geomagnetic poles change places with each other). These reversals

leave a record in rocks that allow paleomagnetists to calculate past motions of continents and ocean

floors as a result of plate tectonics.

The region above the ionosphere, and extending several tens of thousands of kilometers into space,

is called the magnetosphere. This region protects the Earth from cosmic rays that would strip away

the upper atmosphere, including the ozone layer that protects the earth from harmful ultraviolet

radiation.

The Earth is largely protected from the solar wind, a stream of energetic charged particles

emanating from the Sun, by its magnetic field, which deflects most of the charged particles. Theseparticles would strip away the ozone layer, which protects the Earth from harmful ultraviolet rays.[3]

Calculations of the loss of carbon dioxide from the atmosphere of Mars, resulting from scavenging of

ions by the solar wind, are consistent with a near-total loss of its atmosphere since the magnetic

field of Mars turned off.[4]

The polarity of the Earth's magnetic field is recorded in sedimentary rocks. Reversals of the field are

detectable as "stripes" centered on mid-ocean ridges where the sea floor is spreading, while the

stability of the geomagnetic poles between reversals allows paleomagnetists to track the past

motion of continents (the study of past magnetic field is known as paleomagnetism).[5] Reversals

also provide the basis for magnetostratigraphy, a way of dating rocks and sediments.[6] The field

also magnetizes the crust; magnetic anomalies can be used to search for ores.[7]

Humans have used compasses for direction finding since the 11th century A.D. and for navigation

since the 12th century.[8]

A magnetosphere is the area of space near an astronomical object in which charged particles are

controlled by that object's magnetic field.[1][2] Near the surface of the object, the magnetic field

lines resemble those of an ideal magnetic dipole. Farther away from the surface, the field lines are

significantly distorted by external currents, such as the solar wind.[3][4] When speaking about the

Earth, magnetosphere is typically used to refer to the outer layer of the ionosphere,[3] although

some sources consider the ionosphere and magnetosphere to be separated.


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http://cseligman.com/text/planets/internalpressure.htm

Earths Magnetoshpere
http://cseligman.com/text/planets/internalpressure.htmhttp://cseligman.com/text/planets/internalpressure.htmhttp://cseligman.com/text/planets/internalpressure.htm


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Uranus Magnetoshere


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Saturn


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Magnetosphere,

The magnetosphere is the region of space surrounding a planet that houses the dynamo. Earths

dynamo system consists of the planet, its radiation belts, magnetic field, ring current, and the planet

itself. The dynamo gets its energy supply from the solar wind, which comes from the sun. The

magnetosphere is distorted by the incoming solar wind on Earth's daylight side like the head of a

teardrop. It is stretched out on the night-side like the tail of a teardrop. The magnetic field is near

the center of the magnetosphere and is locked with the planet in its rotation. Together the magnetic

field and the planet form the core of the dynamo system. They are locked together and make a

complete turn every twenty-four hours.

http://chandra.harvard.edu/photo/2005/earth/earth_mag_auro_illustration_nolabel.jpgData and measurements from many space missions show that the Earth's magnetosphere is blown

out of shape by the solar wind to form the teardrop shape. The head of the drop extends only about

10 Earth radii, or about 65,000 kilometers (40,000 miles) "upwind" toward the Sun. The tail stretches

away in the direction opposite the Sun, reaching beyond the Moon's orbit to a distance of 600,000

kilometers (370,000 miles) from the Earth.

Understanding the Dynamo

The dynamo, which is a power generator, can be simple or complex. The simplest type of dynamo is

a battery. A battery produces current that flows in only one direction and aligns the compass needle

with the magnetic axes. The alternator is a more complex form of a dynamo. It generates

alternating current that flows in both directions. Alternating current does not align the compassneedle because the current flow changes direction about sixty times a second. The compass needle


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simply does not have time to move every time the current changes direction. When conducting

experiments to investigate the magnetic field, it is better to use a battery or a direct current

generator (dynamo system) because of the need for a steady flow of current in one direction.

http://svs.gsfc.nasa.gov/stories/magnetosphere_20020509/images/mag3copy.jpg

Dynamo Systems

Each planet in our solar system is part of a larger dynamo system. Five of the dynamo systems are

fully developed and produce large magnetic fields, which protect the planets atmosphere. These

planets are Earth, Jupiter, Saturn, Uranus and Neptune.

The current flow around a planet is contained within a narrow passage called ring current, which is

generally inline with the plane of the sun and the magnetic equator.

Current Flow and Field Strength

Since current flowing through a conductor, such as a copper wire, produces a magnetic field, the

strength of the magnetic field will be determined by the strength of the current flow. If there is a

strong current flow, there will be a strong magnetic field. If there is a weak current flow, there will

be a weak magnetic field. If there is no current flow, there will be no magnetic field.

https://reader009.{domain}/reader009/html5/0412/5ace4db5d64c5/5ace4dbd29654.jpgThe Straight Wire

When current is flowing through a straight wire, the magnetic lines of force will be in the shape of

circles surrounding the wire when looking at the wire from the end. The lines of force will be the

strongest close to the wire. The lines of force will be weaker furthest from the wire.

The Direction of Current Flow Guides the Compass Needle

When a compass needle is positioned next to a current-carrying conductor, the needle will line up

perpendicular to the wire. If the current is moving from west to east, the compass needle will point

north and south. If the current is flowing from north to south, the compass needle will turn 180

degrees and point east and west. This means that the direction of the current flow will determine

which way the compass needle points.

The Moving Poles

Earths magnetic North Pole moves 100 meters each day. It will not be in the same place it was

yesterday, and it will be found somewhere else tomorrow. Some scientists are still trying to figure

out what causes the movement, as they ask the following questions: Is the magnetic axis moving

relatively to the planet, or is the planet moving relatively to the magnetic axis? We now know that

the planet is moving because the magnetic axis is relatively fixed.

The Moving Planet

The compass needle always points to the magnetic North Pole but it does not always point to the

same location on the ground. Since the magnetic axis is fixed relatively to the magnetic equator, the

entire magnetic field would have to move each day along with the magnetic North Pole. Since we

know that the magnetic axis stays aligned with equator, the magnetic axis does not move away from


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the planet, but the planet moves away from the magnetic axis. This means that each day the planet

moves away from the magnetic axis by 100 meters. The North and South poles are not moving

beneath the surface of the planet. The planet is constantly moving away from and around the

magnetic axis. The movement of the poles was once attributed to the shifting of a dynamo beneath

the surface of the planet. Now it is understood that there is no dynamo within the planet and that

the planet moves around the magnetic axis. The magnetic axis is stationary except for rotation, whilethe planet wobbles when it moves around like a ball placed unevenly on a shaft.

The Dynamo System

The magnetic field, radiation belts, and planet are all components of the dynamo system. The

radiation belts cannot exist without the planet. The magnetic field cannot exist without the radiation

belts. The radiation belts cannot exist without the magnetic field. They were formed as a single unit

and will die together as a single unit.

http://image.gsfc.nasa.gov/poetry/magnetism/magnetosphere3.gif

Solar Wind and Ring Current

The dynamo system does not fuel itself. It is fueled by charged particles from the sun. The solar

wind brings in the charged particles. The magnetic fields lines of force capture the charged particles

and funnel them into the dynamo system. The particles are moved down the lines of force toward

the North and South Poles. The movement of the charged particle down the lines of force is part of

the process that produces the electric current, which is called ring current. Ring current gets its

name because the current flows in a ring pattern as it moves around the planet. Also, the radiation

belts are in the shape of ovals or rings. On Earth, the compass needle always lines up perpendicular

to the flow of ring current and parallel to the magnetic axis.

The Magnetic Fields Fuel

The magnetic field has the intensity it does because the dynamo system is able to trap large

amounts of charged particles, from the sun and other areas in space. It uses the particles as fuel

when they flow through the dynamo system. As new particles come into the system, the used ones

are expelled.

http://svs.gsfc.nasa.gov/stories/magnetosphere_20020509/images/mag2copy.jpg

Ring Current

Ring current is like a vast invisible river where currents flow without resistance. Positively charged

particles flow westward and negatively charged particles flow eastward like cars in opposite lanes of

a freeway. It is a very dynamic process. The flow of particles is so thick that they appear to occupy

the same space. Other particles from the magneto tail ride the fields lines down to the polar-regions

and create the beautiful aurora in Earths atmosphere.

Ring current extends from about 8,000 kilometers to nearly 30,000 kilometers from the surface and

occupies nearly the same zone as the much more energetic Van Allen belts. Ring current particles

carry energy. It is not a complete equatorial ring like Saturns rings and its strength increases and

decreases with the activity in the magneto tail region. It is always at its strongest on the night-side of

the Earth.

The Unsteady Flow


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We know that the current flowing in the dynamo system will affect the compass needle in the same

way that the current flowing from a battery will affect the compass needle. However, there is a big

difference between the current flow in a battery and that in the radiation belts. The current flow

from a battery has a constant strength. That found in the radiation belts is not constant. The

strength of the current in the radiation belts changes because of the different quantities of charged

particles coming from the sun. Some of the charged particles that make up the radiation belts comefrom outside the solar system and are known as cosmic rays.

A Protective Barrier

The magnetic field extends out into space and helps protect the earth from radiation by forming a

protective barrier called a bow shock. The barrier deflects the charged particles toward the North

and South Poles and protects the planet from direct bombardment.

Jupiter magnetosphere


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Mars Magnetosphere


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Venus Magnetosphere

Neptune magnetosphere


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