Around 100 million years after the formation of the solar system, a Mars-sized object dubbed Theia slammed into the Earth and created the Moon. We now have a better idea as to where this wayward object came from.<\/p>\n
In a study<\/a> published today in the journal Science, researchers\u00a0investigated the isotopic fingerprints<\/a>\u2014the ratio of isotopes, or versions, of elements in a material\u2014of iron in rocks from the Moon, Earth, and meteorites<\/a> (meteoroids that reach the ground). Their results bolster the theory that the impactor was born in the inner solar system and closer to the Sun than where Earth originated.<\/p>\n Their findings suggest that Theia\u2014lurking in the inner solar system\u2014eventually drifted outward and collided with the proto-Earth around 4.5 billion years ago, a violent impact that shattered both bodies and led to the formation of the Moon.<\/p>\n Whence came Theia? <\/p>\n Most computer models simulating the creation of the Moon indicate that our favorite satellite is largely made of material originally belonging to Theia. So if Theia had a different isotopic fingerprint than Earth, the Moon should, too. This matters because isotopic differences can shed light on a planetary body\u2019s origin in the solar system.<\/p>\n Previous analyses of lunar rocks, however, showed that Earth and the Moon have almost indistinguishable isotopic compositions across numerous elements. This \u201clack of measurable isotopic differences and uncertainty over which process caused this have prevented a determination of Theia\u2019s formation region,\u201d the researchers explained. The team included Timo Hopp, a geoscientist from the Max Planck Institute for Solar System Research.<\/p>\n As such, the team carried out new high-precision isotope analyses of iron in lunar samples and terrestrial rocks, as well as meteorites from isotopic reservoirs (parts of the solar system with distinct isotopic compositions) that may have birthed Theia and Earth. This approach revealed, once again, that the isotopic makeup of our planet and the Moon are identical to each other. However, the researchers also found that this makeup aligns with that of non-carbonaceous meteorites\u2014materials that researchers believe originated in the inner solar system.<\/p>\n In other words, both the Moon and Earth likely formed in the inner solar system. But this evidence on its own wasn\u2019t enough to confidently pinpoint Theia\u2019s origins.<\/p>\n Sunnier than Earth <\/p>\n \u201cCombining our results with those for other elements, we performed mass balance calculations for Theia and proto-\u00adEarth,\u201d the researchers explained in the study. Simply put, mass balance calculations enabled the researchers to use Earth\u2019s current isotopic composition to figure out what the planet and Theia\u2019s original isotopic signatures were before the catastrophic collision.<\/p>\n \u201cWe found that all of Theia and most of Earth\u2019s other constituent materials [the ones that aren\u2019t from Theia] originated from the inner Solar System,\u201d they added. What\u2019s more, \u201cour calculations suggest that Theia might have formed closer to the Sun than Earth did.\u201d<\/p>\n While this might all feel far from daily life, the study ultimately sheds light on astronomical dynamics that likely played a role in making Earth the life-nurturing planet it is today\u2014and put a Moon in our skies to inspire countless romantic poets and songwriters.<\/p>\n