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Learning objectives

By the end of this section, you will be able to:

  • Provide an overview of the composition of the giant planets
  • Chronicle the robotic exploration of the outer solar system
  • Summarize the missions sent to orbit the gas giants

The giant planets hold most of the mass in our planetary system. Jupiter alone exceeds the mass of all the other planets combined ( [link] ). The material available to build these planets can be divided into three classes by what they are made of: “gases,” “ices,” and “rocks” (see [link] ). The “gases” are primarily hydrogen and helium, the most abundant elements in the universe. The way it is used here, the term “ices” refers to composition only and not whether a substance is actually in a solid state. “Ices” means compounds that form from the next most abundant elements: oxygen, carbon, and nitrogen. Common ices are water, methane, and ammonia, but ices may also include carbon monoxide, carbon dioxide, and others. “Rocks” are even less abundant than ices, and include everything else: magnesium, silicon, iron, and so on.

Jupiter.

Photograph of Jupiter. Taken from the Cassini spacecraft, the alternating light and dark cloud bands are visible over the entire planet. The Great Red Spot is at lower right. Also seen is the shadow of the moon Europa at lower left.
The Cassini spacecraft imaged Jupiter on its way to Saturn in 2012. The giant storm system called the Great Red Spot is visible to the lower right. The dark spot to the lower left is the shadow of Jupiter’s moon Europa. (credit: modification of work by NASA/JPL)
Abundances in the Outer Solar System
Type of Material Name Approximate % (by Mass)
Gas Hydrogen (H 2 ) 75
Gas Helium (He) 24
Ice Water (H 2 O) 0.6
Ice Methane (CH 4 ) 0.4
Ice Ammonia (NH 3 ) 0.1
Rock Magnesium (Mg), iron (Fe), silicon (Si) 0.3

In the outer solar system, gases dominate the two largest planets, Jupiter and Saturn , hence their nickname “gas giants.” Uranus and Neptune are called “ice giants” because their interiors contain far more of the “ice” component than their larger cousins. The chemistry for all four giant planet atmospheres is dominated by hydrogen. This hydrogen caused the chemistry of the outer solar system to become reducing, meaning that other elements tend to combine with hydrogen first. In the early solar system, most of the oxygen combined with hydrogen to make H 2 O and was thus unavailable to form the kinds of oxidized compounds with other elements that are more familiar to us in the inner solar system (such as CO 2 ). As a result, the compounds detected in the atmosphere of the giant planets are mostly hydrogen-based gases such as methane (CH 4 ) and ammonia (NH 3 ), or more complex hydrocarbons (combinations of hydrogen and carbon) such as ethane (C 2 H 6 ) and acetylene (C 2 H 2 ).

Exploration of the outer solar system so far

Eight spacecraft, seven from the United States and one from Europe, have penetrated beyond the asteroid belt into the realm of the giants. [link] summarizes the spacecraft missions to the outer solar system.

Missions to the Giant Planets
Planet Spacecraft Both the Ulysses and the New Horizons spacecraft (designed to study the Sun and Pluto, respectively) flew past Jupiter for a gravity boost (gaining energy by “stealing” a little bit from the giant planet’s rotation). Encounter Date Type
Jupiter Pioneer 10 December 1973 Flyby
Pioneer 11 December 1974 Flyby
Voyager 1 March 1979 Flyby
Voyager 2 July 1979 Flyby
Ulysses February 1992 Flyby during gravity assist
Galileo December 1995 Orbiter and probe
Cassini December 2002 Flyby
New Horizons February 2007 Flyby during gravity assist
Juno July 2016 Orbiter
Saturn Pioneer 11 September 1979 Flyby
Voyager 1 November 1980 Flyby
Voyager 2 August 1981 Flyby
Cassini July 2004 (Saturn orbit injection 2000) Orbiter
Uranus Voyager 2 January 1986 Flyby
Neptune Voyager 2 August 1989 Flyby

Questions & Answers

how does Neisseria cause meningitis
Nyibol Reply
what is microbiologist
Muhammad Reply
what is errata
Muhammad
is the branch of biology that deals with the study of microorganisms.
Ntefuni Reply
What is microbiology
Mercy Reply
studies of microbes
Louisiaste
when we takee the specimen which lumbar,spin,
Ziyad Reply
How bacteria create energy to survive?
Muhamad Reply
Bacteria doesn't produce energy they are dependent upon their substrate in case of lack of nutrients they are able to make spores which helps them to sustain in harsh environments
_Adnan
But not all bacteria make spores, l mean Eukaryotic cells have Mitochondria which acts as powerhouse for them, since bacteria don't have it, what is the substitution for it?
Muhamad
they make spores
Louisiaste
what is sporadic nd endemic, epidemic
Aminu Reply
the significance of food webs for disease transmission
Abreham
food webs brings about an infection as an individual depends on number of diseased foods or carriers dully.
Mark
explain assimilatory nitrate reduction
Esinniobiwa Reply
Assimilatory nitrate reduction is a process that occurs in some microorganisms, such as bacteria and archaea, in which nitrate (NO3-) is reduced to nitrite (NO2-), and then further reduced to ammonia (NH3).
Elkana
This process is called assimilatory nitrate reduction because the nitrogen that is produced is incorporated in the cells of microorganisms where it can be used in the synthesis of amino acids and other nitrogen products
Elkana
Examples of thermophilic organisms
Shu Reply
Give Examples of thermophilic organisms
Shu
advantages of normal Flora to the host
Micheal Reply
Prevent foreign microbes to the host
Abubakar
they provide healthier benefits to their hosts
ayesha
They are friends to host only when Host immune system is strong and become enemies when the host immune system is weakened . very bad relationship!
Mark
what is cell
faisal Reply
cell is the smallest unit of life
Fauziya
cell is the smallest unit of life
Akanni
ok
Innocent
cell is the structural and functional unit of life
Hasan
is the fundamental units of Life
Musa
what are emergency diseases
Micheal Reply
There are nothing like emergency disease but there are some common medical emergency which can occur simultaneously like Bleeding,heart attack,Breathing difficulties,severe pain heart stock.Hope you will get my point .Have a nice day ❣️
_Adnan
define infection ,prevention and control
Innocent
I think infection prevention and control is the avoidance of all things we do that gives out break of infections and promotion of health practices that promote life
Lubega
Heyy Lubega hussein where are u from?
_Adnan
en français
Adama
which site have a normal flora
ESTHER Reply
Many sites of the body have it Skin Nasal cavity Oral cavity Gastro intestinal tract
Safaa
skin
Asiina
skin,Oral,Nasal,GIt
Sadik
How can Commensal can Bacteria change into pathogen?
Sadik
How can Commensal Bacteria change into pathogen?
Sadik
all
Tesfaye
by fussion
Asiina
what are the advantages of normal Flora to the host
Micheal
what are the ways of control and prevention of nosocomial infection in the hospital
Micheal
what is inflammation
Shelly Reply
part of a tissue or an organ being wounded or bruised.
Wilfred
what term is used to name and classify microorganisms?
Micheal Reply
Binomial nomenclature
adeolu
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Source:  OpenStax, Astronomy. OpenStax CNX. Apr 12, 2017 Download for free at http://cnx.org/content/col11992/1.13
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