The Moon’s Poles Have “Wandered” Over Billions of Years

A gravity map of the Moon with (left) and without (right) many craters. Credit: Smith, et al

Until 1959, humans had only seen one side of the Moon. The Moon is tidally locked with Earth, and so we can only see one side from the Earth’s surface. It took the soviet Luna 3 spacecraft to capture a blurry image for humans to get their first glimpse of the lunar far side. Because of this, many people imagine that the Moon has always been this way. But as a recent study shows, that isn’t quite true.

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It’s Been Constantly Raining Meteors on Mars for 600 Million Years. Earth too.

An impact crater on Mars. Image Credit: NASA

New research shows that Mars has faced a constant rain of meteors during the last 600 million years. This finding contradicts previous research showing that the impact rate has varied, with prominent activity spikes. Why would anyone care how often meteors rained down on Mars, a planet that’s been dead for billions of years?

Because whatever Mars was subjected to, Earth was also likely subjected to.

Who wouldn’t want to know our planet’s history?

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The Moon was Pummeled Even Harder by Asteroids Than it Looks

The Full Moon. Our view of the Moon is dominated by the large volcanic mares, and the especially dramatic Tycho Crater. Image Credit: By Gregory H. Revera - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=11901243

The Moon’s pitted surface tells a tale of repeated impacts over a long period of time. While Earth’s active geology erases most evidence of impacts, the Moon has no mechanism that can do the same. So there it sits, stark evidence of an impact-rich past.

The visible record of lunar cratering is used to understand Earth’s formation and history since periods of frequent impacts would affect both bodies similarly. But something’s wrong in our understanding of the Moon’s history. Impact crater dating, asteroid dynamics, lunar samples, impact basin-forming simulations, and lunar evolution modelling all suggest there’s some missing evidence from the Moon’s earliest impacts.

New research says that there were even more large, basin-forming impacts than we think. Scientists think that some of those impacts left crater imprints that are nearly invisible.

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Rock Almost Rolled Into This Crater on the Moon… Almost

Credit: NASA/GSFC/Arizona State University

The history of the Moon is a tale told by geology, apparent in its rocks, craters, and other surface features. For centuries, astronomers have studied the Moon from afar and for the past few decades, it has been visited by countless robotic missions. Between 1969 and 1972, a total of twelve astronauts walked on its surface, conducted lunar science, and brought samples of lunar rock back to Earth for study.

These efforts have taught us a lot about the things that have shaped the lunar surface, be they one-off events like the massive impact that formed the Shakleton crater to things that happened regularly throughout its 4.51 billion-year history. For instance, scientists recently discovered something unusual about the Antoniadi crater: a large boulder was perched on the rim of a smaller crater within after rolling about 1000 meters (1093 yards) downhill.

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