Earth

=== Formation ===
{{Further|Early Earth|Hadean}}
[[File:The Mysterious Case of the Disappearing Dust.jpg|thumb|upright=1.3|A 2012 artistic impression of the early [[Solar System]]'s [[protoplanetary disk]] from which Earth and other Solar System bodies were formed|center]]

The oldest material found in the [[Solar System]] is dated to {{val|4.5682|0.0002|0.0004}} [[Gigaannum|Ga]] (billion years) ago.<ref name=bouvier_wadhwa2010 /> By {{val|4.54|0.04|u=Ga}} the primordial Earth had formed.<ref name="age_earth1" /> The bodies in [[Formation and evolution of the Solar System|the Solar System formed and evolved]] with the Sun. In theory, a [[solar nebula]] partitions a volume out of a [[molecular cloud]] by gravitational collapse, which begins to spin and flatten into a [[circumstellar disk]], and then the planets grow out of that disk with the Sun. A nebula contains gas, ice grains, and [[Cosmic dust|dust]] (including [[primordial nuclide]]s). According to [[nebular theory]], [[planetesimal]]s formed by [[accretion (astrophysics)|accretion]], with the primordial Earth being estimated as likely taking anywhere from 70 to 100 million years to form.<ref>{{cite journal|url=https://ntrs.nasa.gov/citations/20180002991|title=Ag Isotopic Evolution of the Mantle During Accretion: New Constraints from Pd and Ag Metal–Silicate Partitioning|journal=Differentiation: Building the Internal Architecture of Planets|last1=Righter|first1=K.|first2=M.|last2=Schonbachler|date=7 May 2018|volume=2084|page=4034|bibcode=2018LPICo2084.4034R|access-date=25 October 2020}}</ref>

Estimates of the age of the Moon range from 4.5 Ga to significantly younger.<ref>{{Cite journal|last1=Tartèse|first1=Romain|last2=Anand|first2=Mahesh|last3=Gattacceca|first3=Jérôme|last4=Joy|first4=Katherine H.|author-link4=Katherine Joy|last5=Mortimer|first5=James I.|last6=Pernet-Fisher|first6=John F.|last7=Russell|first7=Sara|author7-link=Sara Russell|last8=Snape|first8=Joshua F.|last9=Weiss|first9=Benjamin P.|date=2019|title=Constraining the Evolutionary History of the Moon and the Inner Solar System: A Case for New Returned Lunar Samples|journal=Space Science Reviews|language=en|volume=215|issue=8|page=54|doi=10.1007/s11214-019-0622-x|bibcode=2019SSRv..215...54T|issn=1572-9672|doi-access=free}}</ref> A [[giant impact hypothesis|leading hypothesis]] is that it was formed by accretion from material loosed from Earth after a [[Mars]]-sized object with about 10% of Earth's mass, named [[Theia (planet)|Theia]], collided with Earth.<ref name=reilly20091022 /> It hit Earth with a glancing blow and some of its mass merged with Earth.<ref name="canup_asphaug2001b" /><ref>{{cite journal|title=On the origin and composition of Theia: Constraints from new models of the Giant Impact|journal=Icarus|last1=Meier|first1=M. M. M.|last2=Reufer|first2=A.|last3=Wieler|first3=R.|date=4 August 2014|volume=242|page=5|doi=10.1016/j.icarus.2014.08.003|arxiv=1410.3819|bibcode=2014Icar..242..316M|s2cid=119226112}}</ref> Between approximately 4.1 and {{val|3.8|u=Ga}}, numerous [[Impact event|asteroid impacts]] during the [[Late Heavy Bombardment]] caused significant changes to the greater surface environment of the Moon and, by inference, to that of Earth.<ref>{{cite book|title=Encyclopedia of Astrobiology|first1=Philippe|last1= Claeys|first2=Alessandro|last2=Morbidelli|author-link2=Alessandro Morbidelli (astronomer)|editor-first1=Muriel|editor-last1= Gargaud|editor-first2=Prof Ricardo|editor-last2=Amils|editor-first3= José Cernicharo|editor-last3= Quintanilla|editor-first4= Henderson James (Jim) |editor-last4= Cleaves II|editor-first5=William M.|editor-last5=Irvine|editor-first6= Prof Daniele L.|editor-last6= Pinti|editor-first7= Michel|editor-last7= Viso|year= 2011|publisher=Springer Berlin Heidelberg|pages=909–912|doi=10.1007/978-3-642-11274-4_869|chapter=Late Heavy Bombardment|isbn= 978-3-642-11271-3}}</ref>