Editing Solar System (section)

===Mass and Composition Distribution===
[[File:Solar_system_mass_distribution_ppm_chart.svg|thumb|Solar system mass distribution]]
The Solar System’s mass and the way its parts are spread out tell us a lot about how it formed and changed over time. Most of the Solar System’s [[mass]], about 99.86%, is in the [[Sun]], which is a huge ball made mostly of [[hydrogen]] and [[helium]]. The Sun’s gravity controls the movement of all the planets, asteroids, comets, and space dust. It’s incredibly massive, weighing about 1.989 × 10³⁰ kilograms. This huge mass creates a strong gravitational pull that keeps everything else in the Solar System in [[orbit]], and it also helps determine how things spin and move.<ref>{{Cite web|date=2023-05-31|title=Sun - NASA Science|url=https://science.nasa.gov/sun/|access-date=2025-07-15|language=en-US}}</ref><ref>{{Cite web|title=Sun Fact Sheet|url=https://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html|access-date=2025-07-15|website=nssdc.gsfc.nasa.gov|archive-date=1998-02-22|archive-url=https://web.archive.org/web/19980222081658/https://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html|url-status=dead}}</ref> Only about 0.14% of the Solar System’s total mass is in everything else, like the eight [[planet]]s, [[dwarf planet]]s, [[Natural satellite|moon]]s, [[asteroid]]s, objects in the [[Kuiper Belt]], and the [[Oort cloud|Oort Cloud]].<ref>{{Cite web|date=2023-07-20|title=Chapter 1: The Solar System - NASA Science|url=https://science.nasa.gov/learn/basics-of-space-flight/chapter1-1/|access-date=2025-07-15|language=en-US}}</ref> Out of this small portion, more than 70% is found in [[Jupiter]], the largest planet. Jupiter weighs about 1.9 × 10²⁷ kilograms, which is 318 times heavier than [[Earth]].<ref>{{Cite web|title=Jupiter |url=https://www.dlr.de/en/research-and-transfer/projects-and-missions/juice/jupiter-gas-giant-and-ringed-planet/jupiter|access-date=2025-07-15|website=www.dlr.de|language=en}}</ref> Because of its size, Jupiter has a very strong gravitational pull. It affects the movement of asteroids, helps keep the orbits of other planets stable, and played a big role in clearing out leftover space rocks when the Solar System was still forming.<ref>{{Cite web|date=2023-05-31|title=Jupiter|url=https://science.nasa.gov/jupiter/|access-date=2025-07-15|language=en-US}}</ref>

The [[giant planet]]s, [[Jupiter]], [[Saturn]], [[Uranus]], and [[Neptune]], make up about 99% of the total mass of all the planets in the Solar System. This shows that the Solar System has a bimodal structure, meaning most of the mass is in these large [[Gas giant|gas]] and [[ice giant]]s, not the smaller rocky planets closer to the Sun.<ref>{{Cite book|url=https://nap.nationalacademies.org/read/13117/chapter/10|title=Read "Vision and Voyages for Planetary Science in the Decade 2013-2022" at NAP.edu|language=en}}</ref> Saturn is the second largest planet, with a mass about 95 times that of Earth. Like Jupiter, it is mostly made of hydrogen and helium, but Saturn has more ices and heavier elements deep inside.<ref>{{Cite web|date=2023-05-31|title=Saturn|url=https://science.nasa.gov/saturn/|access-date=2025-07-15|language=en-US}}</ref> Uranus and Neptune are called ice giants. They also have atmospheres made of hydrogen and helium, but inside they have a lot of [[water]], [[ammonia]], and [[Methane|methane ices]]. Each of them has a mass between 14 and 17 times the mass of Earth.<ref>{{Cite web|title=Uranus/Neptune|url=https://pages.uoregon.edu/jschombe/ast121/lectures/lec20.html#:~:text=Neptune%20is%2017%20times%20the,could%20contain%20nearly%2060%20Earths.|access-date=2025-07-15|website=pages.uoregon.edu}}</ref>

On the other hand, the [[Terrestrial planet|terrestrial (rocky) planet]]s, [[Mercury (planet)|Mercury]], [[Venus]], [[Earth]], and [[Mars]], have only a tiny amount of the Solar System’s mass. Earth makes up more than half of the total mass of these four rocky planets because it’s the biggest and densest. These inner planets are made mostly of [[Silicate|silicate rock]] and [[metal]], with common elements like [[iron]], [[oxygen]], [[silicon]], and [[magnesium]].<ref name=":1" /> They do not have much hydrogen or helium because, when the Solar System was forming, the area close to the Sun was too hot for light gases to stick around. The Sun’s heat pushed those gases away, so only heavier materials like rock and metal were left behind to form the inner planets.<ref>{{Cite web|title=Planets and How They Formed|url=https://lco.global/spacebook/solar-system/planets-and-how-they-formed/|access-date=2025-07-15|website=lco.global|language=en}}</ref>

Besides the major planets, the Solar System has many smaller objects. Even though these objects have only a small amount of mass compared to the planets, they are very important for helping scientists understand how the planets formed. One group of these small objects is the [[asteroid belt]], which is found between Mars and Jupiter. The asteroid belt has less than 4% of the Moon’s mass, but it contains materials that were part of the early building blocks of the rocky planets. The biggest object in the belt is [[Ceres (dwarf planet)|Ceres]], which is about 940 kilometers wide. Ceres makes up about one-third of the asteroid belt’s total mass and is made mostly of [[rock]] and [[Ice|water ice]].<ref>{{Cite journal|last=Krasinsky|first=G|date=2002|title=Hidden Mass in the Asteroid Belt|url=https://linkinghub.elsevier.com/retrieve/pii/S0019103502968375|journal=Icarus|language=en|volume=158|issue=1|pages=98–105|doi=10.1006/icar.2002.6837}}</ref><ref>{{Cite journal|last1=Pitjeva|first1=E. V.|last2=Pitjev|first2=N. P.|date=2018|title=Masses of the Main Asteroid Belt and the Kuiper Belt from the Motions of Planets and Spacecraft|url=http://link.springer.com/10.1134/S1063773718090050|journal=Astronomy Letters|language=en|volume=44|issue=8–9|pages=554–566|doi=10.1134/S1063773718090050|arxiv=1811.05191 |issn=1063-7737}}</ref> Farther away from the Sun is the Kuiper Belt, which holds thousands of icy objects. Some of the best-known are [[Pluto (dwarf planet)|Pluto]], [[Eris (dwarf planet)|Eris]], [[Haumea (dwarf planet)|Haumea]], and [[Makemake (dwarf planet)|Makemake]]. These objects are much smaller than the giant planets, but their mix of rock and ices like [[methane]], [[nitrogen]], and [[carbon monoxide]] helps scientists learn about the chemistry of the early outer Solar System. The total mass of the Kuiper Belt is only a small fraction of Earth’s mass, between 0.01 and 0.1 times the mass of Earth, because over billions of years, much of its mass was lost in space due to collisions and gravitational forces.<ref>{{Cite journal|last1=Romanishin|first1=W.|last2=Tegler|first2=S. C.|last3=Rettig|first3=T. W.|last4=Consolmagno|first4=G.|last5=Botthof|first5=B.|date=2001-10-09|title=1998 SM165: A large Kuiper belt object with an irregular shape|journal=Proceedings of the National Academy of Sciences|volume=98|issue=21|pages=11863–11866|doi=10.1073/pnas.211147998 |pmid=11572937 |pmc=59815 |doi-access=free }}</ref><ref>{{Cite journal|last1=Pitjeva|first1=E. V.|last2=Pitjev|first2=N. P.|date=2018|title=Masses of the Main Asteroid Belt and the Kuiper Belt from the Motions of Planets and Spacecraft|url=http://link.springer.com/10.1134/S1063773718090050|journal=Astronomy Letters|language=en|volume=44|issue=8–9|pages=554–566|doi=10.1134/S1063773718090050|arxiv=1811.05191 |issn=1063-7737}}</ref><ref name=":17" />

Even farther out is the [[Oort cloud|Oort Cloud]], which scientists think is a huge, round shell of icy objects surrounding the Solar System. It is believed to contain trillions of comets made mostly of water ice, [[carbon dioxide]] ice, and other frozen gases. The total mass of the Oort Cloud is not known for sure, but it might be several times the mass of Earth. It stretches as far as 100,000 [[Astronomical unit|astronomical units (AU)]] from the Sun (1 AU is the distance from Earth to the Sun). The Oort Cloud is thought to be the source of [[Comet|long-period comet]]s, comets that take hundreds or thousands of years to orbit the Sun and sometimes come close enough to be seen from Earth.<ref name=":6" />

[[Natural satellite|Moon]]s and [[Planetary ring|ring]]s around planets add a little bit of mass to the Solar System, but not very much compared to the planets. For example, [[Moon|Earth’s Moon]] is the fifth largest moon in the Solar System. It is pretty big compared to Earth, with a mass that is about 1.2% of Earth’s mass. The Moon is mostly made of [[Silicate|silicate rock]], which is similar to the material found in [[Earth's crust|Earth’s crust]] and [[Earth's mantle|mantle]].<ref>{{Cite web|date=2017-11-15|title=Moon Facts - NASA Science|url=https://science.nasa.gov/moon/facts/|access-date=2025-07-16|language=en-US}}</ref> The outer planets have some very large moons too, like [[Ganymede (moon)|Ganymede]], [[Titan (moon)|Titan]], [[Callisto (moon)|Callisto]], and [[Io (moon)|Io]]. These moons are made of a mix of rock and ice. Some of them, like [[Europa (moon)|Europa]] and [[Enceladus (moon)|Enceladus]], even have [[ocean]]s beneath their icy surfaces, which shows that there are many different kinds of icy, possibly habitable places beyond Earth.<ref name=":16" />

The types of [[Chemical element|element]]s found in different parts of the Solar System also tell us a lot about how it formed. These elements were created in earlier generations of [[star]]s and then spread out into [[Outer space|space]]. In the outer Solar System, there are more volatile elements (which are lighter and can turn into gas easily), while the inner Solar System has more refractory materials (which are heavier and can stay solid at high [[temperature]]s). This difference shows how temperature, [[sunlight]], and the movement of planets affected where different materials could collect and form planets.<ref>{{Cite book|title=Encyclopedia of the solar system|url=https://archive.org/details/encyclopediaofso0000unse_m9q5|date=2014|publisher=Elsevier|isbn=978-0-12-415845-0|editor-last=Spohn|editor-first=Tilman|edition=3rd|location=Amsterdam ; Boston|editor-last2=Breuer|editor-first2=Doris|editor-last3=Johnson|editor-first3=T. V.}}</ref>