This article was originally published at: Speech. (opens in new tab) The publication contributed the article to Space.com. Expert Voices: Op-Ed & Insights.
Joshua Davies (opens in new tab)Professor of earth and atmospheric sciences, Université du Québec à Montréal (UQAM)
Margriet Lantinck (opens in new tab)Postdoctoral Fellow, Department of Earth Sciences, University of Wisconsin-Madison
When you look at the moon in the night sky, you can never imagine it slowly moving away from Earth. But we know otherwise. NASA in 1969 Apollo missions placed reflective panels on the moon. These have shown that moon is is is currently moving 3.8 cm away from Earth each year (opens in new tab).
If we take the moon’s current recession rate and project it back in time, we’ll eventually come to a conclusion. Collision of Earth and Moon 1.5 billion years ago (opens in new tab). But the moon was formed about 4.5 billion years ago (opens in new tab)means that the current recession rate is a weak guide for the past.
with our researchers Utrecht University (opens in new tab) and University of Geneva (opens in new tab)We use a combination of techniques to try and learn about the distant past of our solar system.
We recently discovered the perfect place to uncover the long-term history of our waning moon. And this is not from studying the moon itself, Reading signals in ancient rock layers on Earth (opens in new tab).
Related: How was the moon formed?
Reading between layers
well Karijini National Park (opens in new tab) In Western Australia, some gorges cut 2.5 billion years of rhythmically layered sediments. These sediments are banded iron formations. mineral layers rich in iron and silica (opens in new tab) it was once widely deposited on the ocean floor and is now found in the oldest parts of the earth’s crust.
Cliff exposures Joffre Falls (opens in new tab) show how reddish-brown layers of iron formation just under one meter are replaced at regular intervals by darker, thinner horizons.
Darker ranges consist of a softer type of rock that is more susceptible to erosion. A closer look at the protrusions reveals the presence of an additional regular, smaller-scale variation. Polished by the seasonal river waters flowing through the gorge, the rock surfaces reveal a pattern of alternating layers of white, reddish and bluish gray.
In 1972, Australian geologist AF Trendall raised the question about the origin of the earth. different scales of circular, repetitive patterns (opens in new tab) this can be seen in ancient rock layers. He suggested that the models could relate to past changes in climate triggered by so-called “Milankovitch cycles.”
Cyclic climate changes
Milankovitch cycles describe how small, periodic changes in the shape of the Earth’s orbit and the orientation of its axis are. Influencing the distribution of sunlight received by the Earth (opens in new tab) over the years.
Currently, the dominant Milankovitch cycles change every 400,000 years, 100,000 years, 41,000 years, and 21,000 years. It exerts strong control over these variations. our climate over long periods of time.
Important examples of the past impact of Milankovitch climate forcing are: extreme cold (opens in new tab) horse hot periods (opens in new tab)together this (opens in new tab) or drier regional climatic conditions.
These climate changes significantly altered the conditions on the Earth’s surface, for example size of lakes (opens in new tab). They explain it Periodic greening of the Sahara desert (opens in new tab) and low oxygen levels in the deep ocean (opens in new tab). Milankovitch cycles also influenced. migration and evolution of flora and fauna (opens in new tab) including ours own kind (opens in new tab).
And the signatures of these changes can be read through. cyclic changes in sedimentary rocks (opens in new tab).
Recorded wobbles
The distance between the earth and the moon is directly related to the frequency of one of the Milankovitch cycles – climatic precession cycle (opens in new tab). This cycle is caused by the movement (wobble) or changing directions of the Earth’s axis of rotation over time. This cycle currently has a duration of ~21,000 years, but this period would have been shorter in the past when the moon was closer. Soil.
This means that if we can first find Milankovitch cycles in ancient sediments and then find a signal of the Earth’s wobble and determine its period, we can estimate the distance between the Earth and the moon at the time the sediments were deposited.
Our previous research has shown that Milankovitch cycles can happen. Preserved in an ancient banded iron formation in South Africa (opens in new tab)thus supporting Trendall’s theory.
Banded iron formations in Australia are likely accumulated in the same ocean (opens in new tab) Like the South African rocks, about 2.5 billion years ago. However, cyclic variations in Australian rocks are better exposed, allowing us to study variations at much higher resolution.
Our analysis of the Australian banded iron formation showed that the rocks contain multiple repeating scales of cyclic variation, about 4 and 33 inches (10 and 85 cm apart). Combining these thicknesses with the rate at which sediments were deposited, we found that these cyclical changes occur approximately every 11,000 years and every 100,000 years.
Therefore, our analysis suggested that the 11,000 cycles observed in the rocks are likely related to the climatic precession cycle, which has a much shorter duration than the current ~21,000 years. We then used this precession signal. Calculate the distance between earth and moon 2.46 billion years ago (opens in new tab).
We found that the Moon is about 37,280 miles (60,000 kilometers) closer to Earth (about 1.5 times that of Earth). circumference of the world). This would make the length of a day much shorter than it is now, roughly 17 hours rather than the current 24 hours.
Understanding solar system dynamics
It provided models for astronomy research. formation of our solar system (opens in new tab)and observations of current conditions (opens in new tab).
Our work and some research by others (opens in new tab) represents one of the only methods of obtaining real data on the evolution of our solar system and will be very important to us. Future models of the earth-moon system (opens in new tab).
It is quite surprising that past solar system dynamics can be determined from small variations in ancient sedimentary rocks. However, one important data point does not provide us with a full understanding of the evolution of the Earth-moon system.
We now need other reliable data and new modeling approaches to track the evolution of the moon over time. And our research team is already looking for the next group of rocks that could help us uncover more clues about the history of the solar system.
This article has been republished from: Speech (opens in new tab) Under Creative Commons license. To read original article (opens in new tab).
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