Reassessing the Moon’s birthday and subsequent start of life on Earth
Scientists have recently reevaluated the Moon’s birthday, moving it back to around 4.51 billion years ago. As a mostly inert satellite, adding a few million years here and there doesn’t necessarily change our view of the Moon’s nature or origin. On the other hand, because that origin is so closely entwined with the Earth, knowing when it happened may have important implications for events closer to home, right down to when life as we know it started making inroads on our planet.
New look at old evidence
The new evidence for the Moon’s advanced age comes from zircon crystals that were gathered by astronauts during the Apollo 14 mission in 1971. The crystals were originally formed in the interior of the Moon, crushed into sand by erosion and other events, then distributed among other bits of rocks and soil. The crystals had been studied in the past, but this new research corrected for damage that would have been caused by cosmic rays from the Sun, giving us a more accurate assessment of their age. The Moon’s earlier formation is now thought to have been very early in the history of the Earth, coming only 68 million years after the solar system as a whole really coalesced.
This ties into life, because the Moon’s birth would have killed everything on Earth in the process. The massive impact of Mars-sized object that essentially tore the Moon out of the Earth would have surely wiped out any and everything, so if that world-shattering event happened earlier, it means there’s more time in Earth’s history that would have been safe for life to get started. A later origin would have essentially made the Moon’s birth a giant reset button for anything that might have been growing on our young planet.
Life’s increasingly-long timeline
As fragile and mysterious as life’s origins seem, there may be evidence that it began tenaciously populating the Earth as soon, and often, as possible. A layer of oxidized minerals from 2.4 billion years ago may be evidence of an early version of cyanobacteria. The oxygen-belching bacteria seemed to be holding a trial run for a later replay of this same pattern that eventually resulted in the complex cells we know today, but this early build-up apparently didn’t take. The oxidation layer abruptly dropped off only 400 million years later.
More direct evidence for even earlier life may have recently been found in Canada. Tiny imprints of what may be the oldest microbes we know of have been dated to be between 3.7 and 4.3 billion years old. That later date is pushing rather close to the Moon’s new birthday, indicating that life not only got started quickly after the Moon’s formation, but also that it probably hasn’t been interrupted by outside forces on such a scale since then.
Source: The Moon Is Probably Older Than We Thought — and Life Could Be Too by Irene Klotz, Seeker
