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If you’re trying to figure out when the genesis of life happened on Earth, maybe you should try searching for evidence on the Moon.
That seems to make no sense, though. Isn’t the Moon just a piece of dead rock with nothing alive crawling on it (except the astronauts who will land there if Artemis 2 goes as planned) and no proof of ever having hosted life? Turns out objects in space don’t necessarily need to be inhabited or even habitable to reveal what happened in the fiery post-Big Bang violence that endured for hundreds of millions of years. A new study insists that lunar impacts from a cosmic era straight out of Dante’s Inferno can help us understand when life started to emerge on Earth.
A mountain in the middle of Yerkes Crater, found in the Mare Crisium impact basin (below), is believed to be “where future robotic and/or human missions could confidently add a key missing piece to the puzzle of the combined issues of early Earth-Moon bombardment and the emergence of life,” said Dan Moriarty, a NASA postdoctoral program fellow at Goddard Space Flight Center, and colleagues in the soon-to-be-published study.
Fun fact: Mare Crisium means “sea of crises.” Pretty appropriate for the remnants of an ancient lunar collision.
That era of spewing lava and epic crashes that occurred 4.1 to 3.8 billion years ago is known as Late Heavy Bombardment (LHB). It was during this period that the surfaces of the Earth, Moon and other objects in our solar system experienced an unusually high rate of impacts.
Scientists also believe that the first microbial Earthlings started creeping around at that time. Impact basins could be hiding the answer to whether the stuff of life, like amino acids, were carried over by comets, asteroids, and anything else whizzing around and slamming into our planet. The problem is that Earth’s largest impact basins have been trampled and overgrown by life, drowned by flowing water, and altered by geological phenomena.
The Moon, however, didn’t see all this action. Volcanic eruptions and massive lava flows definitely happened, covering up some basins and parts of basins, but there are still exposed areas left, including Mare Crisium, especially that mountain in Yerkes Crater (located in Mare Crisium), which is high enough not to have had its surface — and any impact dust that settled on it — disturbed by seas of molten rock. The Moon’s impact basins were preserved because it was so much more chill than Earth after the LHB.
“The formation of those large basins melted lots of rock which then cooled; by collecting those rocks on future missions and figuring out how old they are, we can determine the timing of when large basins formed on the Moon, and by extension, on Earth,” Moriarty said.
We need to unearth material that can shed light on the age of Mare Crisium (at least as close to its exact age as possible) in order to potentially find out when life started on Earth. Four billion years ago is only a hazy estimate. The ideal find would be rock that contains amino acids and other ingredients necessary for abiogenesis, the theoretical emergence of early life-forms from inorganic substances.
Scientists will need to learn when most lunar impacts happened in order to come to a conclusion about when it was most likely that things that crashed into Earth and the Moon brought over the elements of life. These kind of specimens are what we’re relying on Moon-traversing robots and eventually astronauts to bring back to Earth, so they can be investigated.
Apollo missions samples unfortunately couldn’t tell us these secrets. We’re counting on you, Artemis.
(via AGU Pubs)