This article was originally published on Conversation. (Opens in a new tab) Post contributed this article to Space.com Expert voices: editorial and perspectives.
Joshua Davis (Opens in a new tab)Professor of Earth and Atmospheric Sciences, University of Quebec in Montreal (UQAM)
Margaret Lantinck (Opens in a new tab)Postdoctoral Research Associate, Department of Earth Sciences, University of Wisconsin-Madison
Looking at the moon in the night sky, you would never imagine it slowly moving away from earth. But we know the opposite. In 1969, NASA Apollo Missions Installation of reflective panels on the surface of the moon. They showed that the moon It is It is currently moving 3.8 cm away from Earth each year. (Opens in a new tab).
If we take the moon’s current stagnation rate and put it back in time, we end up with A collision between the Earth and the Moon about 1.5 billion years ago (Opens in a new tab). However, the moon formed About 4.5 billion years ago (Opens in a new tab)meaning that the current rate of recession is poor evidence of the past.
With our research colleagues from University of Utrecht (Opens in a new tab) and the University of Geneva (Opens in a new tab)We’ve used a range of techniques to try to get information about our solar system’s distant past.
We recently discovered the perfect place to reveal the long-term history of our waning moon. It is not the study of the moon itself, but of the Reading signals in ancient rock layers on Earth (Opens in a new tab).
about: How did the moon form?
Reading between lessons
in the beauty Karigeni National Park (Opens in a new tab) In Western Australia, some gorges cut through rhythmically layered sediments 2.5 billion years old. These deposits are striated iron formations, consisting of distinct formations Layers of iron and silica-rich minerals (Opens in a new tab) They were deposited on a large scale at the bottom of the ocean and are now found in the oldest parts of the earth’s crust.
Cliff’s window Chutes Geoffrey (Opens in a new tab) Show how layers of reddish-brown iron formation just under a meter thick alternate, at regular intervals, with darker, thinner horizons.
Dark struts are made of a softer type of rock that is more susceptible to erosion. A closer look at the bumps reveals a smaller, even contrast. The rocky surfaces, polished by the waters of the seasonal rivers that cross the valley, reveal alternating white, red and bluish gray layers.
In 1972, Australian geologist AF Trendall raised the question of the origin of Various scales for periodic and recurring patterns (Opens in a new tab) Visible in these ancient rock layers. He suggested the patterns could be linked to past climate changes caused by so-called “Milankovitch cycles”.
Periodic weather changes
Milankovitch cycles describe how small periodic changes in the shape of the Earth’s orbit and the direction of its axis It affects the distribution of sunlight that the Earth receives (Opens in a 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. These differences exert a strong control over our climate over long periods.
The main examples of the effect of the Milankovitch climate effect in the past are the appearance of Quite cold (Opens in a new tab) or hot periods (Opens in a new tab)next to wet (Opens in a new tab) Or dry regional climatic conditions.
These climatic changes have significantly altered the conditions on the Earth’s surface, such as The size of the lakes (Opens in a new tab). They are the interpretation of Periodic greening of the Saharan desert (Opens in a new tab) And the Low oxygen levels in the deep ocean (Opens in a new tab). The Milankovitch cycles also influenced Migration and evolution of plants and animals (Opens in a new tab) including special species (Opens in a new tab).
The signatures of these changes can be read Periodic changes in sedimentary rocks (Opens in a new tab).
recorded oscillation
The distance between the Earth and the Moon is directly related to the frequency of one of the Milankovitch cycles – climate cycle cycle (Opens in a new tab). This cycle results from the preliminary motion (vibration) or change in direction of the Earth’s axis of rotation over time. The duration of this cycle is currently around 21,000 years, but this period would have been shorter in the past when the moon was closer to a terrain.
This means that if we can first find the Milankovitch cycles in the ancient sediments, then find the Earth’s oscillation signal and determine its period, we can estimate the distance between the Earth and the Moon at the time the sediments have been filed.
Our previous research has shown that Milankovitch cycles can also be Preserved in the old iron banded formation in South Africa (Opens in a new tab)thus supporting Trendall’s theory.
The banded iron formations were probably in Australia deposited in the same ocean (Opens in a new tab) Like the rocks of South Africa, about 2.5 billion years ago. However, the periodic variations of Australian rocks are better exposed, allowing us to study the variations at a much higher resolution.
Our analysis of Australian Band Iron Formation has shown that the rocks contain multiple scales of periodic variations that repeat at approximately 4 and 33 inches (10 and 85 cm intervals). Combining these thicknesses with the rate at which the sediments were deposited, we find that these periodic changes occurred approximately every 11,000 years and 100,000 years.
Therefore, our analysis suggested that the 11,000-year cycle observed in the rocks is likely related to a climatic introductory cycle, having a much shorter period than the current 21,000 years. Then we used this forward reference to Calculate the distance between the Earth and the Moon 2.46 billion years ago (Opens in a new tab).
We found that the Moon was approaching the Earth about 37,280 miles (60,000 km) at that time (this distance is about 1.5 times the distance). Circumference of the Earth). This would make the length of the day much shorter than it is now, by around 17 hours instead of the current 24 hours.
Understand the dynamics of the solar system
Astronomical research has provided models for Shaping our solar system (Opens in a new tab)And the Notes for current conditions (Opens in a new tab).
Our study and Some research by others (Opens in a new tab) This is one of the only ways to get real data on the evolution of our solar system, and it will take Future models of the Earth-Moon system (Opens in a new tab).
It is truly amazing that the past dynamics of the solar system can be determined by small differences in ancient sedimentary rocks. However, there is one important data point that does not give us a complete understanding of the evolution of the Earth-Moon system.
We now need more reliable data and new modeling methods to track the moon’s evolution over time. And our research team has already started searching for the next set of rocks that could help us uncover more clues to the history of the solar system.
This article was republished from Conversation (Opens in a new tab) Under Creative Commons license. Read it article original (Opens in a new tab).
Follow all Expert Voices issues and discussions – and join the discussion – on Facebook and Twitter. The opinions expressed are those of the author and do not necessarily reflect those of the publisher.