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The Moon's Magnetosphere Used to be Twice as Strong as the Earth's – Universe Today



For decades, scientists have held that the Earth-Moon system formed as a result of a collision between Earth and a Mars-sized object roughly 4.5 billion years ago. Known as the Giant Impact Hypothesis, this theory explains why Earth and the Moon are similar in structure and composition. Interestingly enough, scientists have also determined that during its early history, the Moon had a magnetosphere – much like Earth does today.

However, a new study led by researchers at MIT (with support provided by NASA) indicates that at one time, the Moon’s magnetic field may have actually been stronger than Earth’s. They were also able to place tighter constraints on when this field petered out, claiming it would have happened about 1 billion years ago. These findings have helped resolve the mystery of what mechanism powered the Moon’s magnetic field over time.

The study, which recently appeared in the journal Science Advances, was led by Saied Mighani, an experimental rock physicist with MIT’s Department of Earth, Atmospheric, and Planetary Sciences. He was joined by members of the Berkeley Geochronology Center at UC Berkeley and the China University of Geosciences, with additional support provided by famed EAPS professor, Dr. Benjamin Weiss.

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To recap, Earth’s magnetic field is essential to life as we know it. When incoming solar wind particles reach Earth, they are deflected by this field and form a bow shock in front of Earth and magnetotail behind it. The remaining particles are deposited on the magnetic poles where they interact with our atmosphere, which causes the Aurorae seen in the far northern and southern hemispheres.

Were it not for this magnetic field, Earth’s atmosphere would have been slowly stripped away by solar wind over the course of billions of years and rendered a cold, dry place. This is believed to be what happened on Mars, where a once-thicker atmosphere was depleted between 4.2 and 3.7 billion years ago and all of the liquid water on its surface was either lost or froze as a result.

Over the years, Weiss’ group has helped demonstrate through the study of lunar rocks that roughly 4 billion years ago, the Moon also had a strong magnetic field of about 100 microteslas in strength (whereas Earth’sis around 50 microteslas today). In 2017, they studied samples collected by the Apollo astronauts that were dated to about 2.5 billion years ago and found a much weaker field (less than 10 microteslas).

In other words, the Moon’s magnetic field weakened by a factor of five between 4 and 2.5 billion years ago, then disappeared entirely about 1 billion years ago. At the time, Weiss and his colleagues theorized that perhaps there were two dynamo mechanisms in the Moon’s interior that were responsible for this change.

Measurements of lunar rocks have demonstrated that the ancient moon generated a dynamo magnetic field in its liquid metallic core (innermost red shell). Credit: Hernán Cañellas/Benjamin Weiss

In short, they argued that a first dynamo effect could have generated a much stronger magnetic field around 4 billion years ago. Then, 2.5 billion years ago, it was replaced by a second dynamo that was more long-lived but sustained a much weaker magnetic field. As Dr. Weiss explained in an MIT News release:

“There are several ideas for what mechanisms powered the lunar dynamo, and the question is, how do you figure out which one did it? It turns out all these power sources have different lifetimes. So if you could figure out when the dynamo turned off, then you could distinguish between the mechanisms that have been proposed for the lunar dynamo. That was the purpose of this new paper.”

Until now, obtaining lunar rocks that are less than 3 billion years old has been a major challenge. The reason for this has to do with the fact that volcanic activity, which was common on the Moon 4 billion years ago, ceased roughly 3 billion years ago. Luckily, the MIT team was able to identify two samples of lunar rock obtained by the Apollo astronauts that were created by an impact 1 billion years ago.

While these rocks were melted by the impact and then resolidified, thus erasing their magnetic record in the process, the team was able to perform tests on them to reconstruct their magnetic signature. First, they analyzed the orientation of the rock’s electrons, which Weiss describes as “little compasses” since they would either align in the direction of an existing magnetic field or appear in random orientations in the absence of one.

Moon rocks from the Apollo 11 mission. Credit: NASA

In both samples, the team observed the latter, which suggested that the rocks formed in an extremely weak magnetic field of no more than 0.1 microteslas (possibly none at all). This was followed by a radiometric dating technique that was adapted for this study by Weiss and David L. Shuster (a Berkeley Geochronology Center researcher and co-author of the study). These results confirmed that the rocks were indeed 1 billion years old.

Finally, the team conducted heat tests on the samples to determine if they could provide a good magnetic record at the time of the impact. This consisted of placing both samples in an oven and exposing them to the kinds of high temperatures that would have been created by an impact. As they cooled, they exposed them to an artificially-generated magnetic field in the laboratory and confirmed that they were able to record it.

These results confirm that the magnetic strength initially measured by the team (0.1 microteslas) is accurate and that by 1 billion years ago, the dynamo powering the Moon’s magnetic field had likely ended. As Weiss expressed:

“The magnetic field is this nebulous thing that pervades space, like an invisible force field. We’ve shown that the dynamo that produced the moon’s magnetic field died somewhere between 1.5 and 1 billion years ago, and seems to have been powered in an Earth-like way.”

Lunar footprint from the Apollo missions. Credit: NASA

As noted, this study also helps to resolve the debate surrounding what drove the lunar dynamo in its later stages. While multiple theories have been suggested, these new findings are consistent with the theory that core crystallization is responsible. Basically, this theory states that the Moon’s inner core crystallized over time, slowing the flow of electrically-charged fluid and arresting the dynamo.

Weiss suggests that prior to this, precession may have been responsible for powering a much stronger (but short-lived) dynamo which would have produced the strong magnetic field. This is consistent with the fact that 4 billion years ago, the Moon is thought to have orbited much closer to Earth. This would have resulted in Earth’s gravity having a far greater effect on the Moon, causing its mantle to wobble and stirring up activity in the core.

As the Moon slowly migrated away from Earth, the effect of precession decreased and the magnetic field-producing dynamo would weaken. By about 2.5 billion years ago, crystallization became the dominant mechanism by which the lunar dynamo continued, producing a weaker magnetic field that persisted until the outer core finally crystallized a billion years ago.

Studies like this could also help resolve the mystery of why planets like Venus and Mars lost their magnetic fields (contributing to cataclysmic climate change) and how Earth could lose its own someday. Considering its importance to habitability, a greater understanding of dynamos and magnetic fields could also help in the search for habitable exoplanets.

Further Reading: MIT News, Science Advances

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Joe Biden Wants to Put a Japanese Astronaut on the Moon – Gizmodo



Gateway, illustrated here, will serve as a crucial part of the upcoming Artemis missions.
Illustration: NASA

President Joe Biden and Japanese Prime Minister Fumio Kishida further solidified their plans to send a Japanese astronaut to the upcoming lunar space station, while also affirming the possibility of having a Japanese astronaut walk on the Moon during future Artemis missions.

Biden and Kishida met in Tokyo on Monday to continue discussions around an Implementing Agreement that will potentially place a Japanese astronaut on the Gateway space station. The leaders also reaffirmed each country’s commitment to share data on climate change. The discussion around Gateway personnel is a part of ongoing conversations between the U.S. and Japan regarding NASA’s upcoming missions to the Moon.

Gateway is an integral component of NASA’s larger effort to return to the Moon, a series of upcoming missions known as the Artemis program. Once built, Gateway will serve as a Moon-orbiting outpost offering lunar-bound astronauts support for their visit. The lunar space station, in addition to serving as critical infrastructure for the Artemis missions, will also serve as a staging point for future crewed missions to Mars. The first pieces of the upcoming lunar station are set to launch no earlier than November 2024.

“In recent years, the alliance between Japan and the United States has grown stronger, deeper, and more capable as we work together to take on new challenges—just as important as the opportunities—of a rapidly changing world,” said President Biden in a NASA press release.

Japan and the U.S. are also interested in placing a Japanese astronaut on the surface of the Moon during a yet-to-be-determined Artemis mission, according to a White House fact sheet. NASA is looking to land astronauts on the lunar south pole by 2025, and Artemis will involve the first crewed Moon missions since Apollo 17 in 1972. NASA Administrator Bill Nelson said in the release: “Our shared ambition to see Japanese and American astronauts walk on the Moon together reflects our nations’ shared values to explore space responsibly and transparently for the benefit of humanity here on Earth.”

While the first pieces of Gateway are still a few years away from launch, having the U.S. and Japan team up is an opportunity to get more nations involved. The Artemis missions will be a global effort, and getting back to the Moon represents an exciting next step in space exploration and engineering.

More: This Tiny Moon-Bound Satellite Could Carve a Path For a Lunar Space Station.

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Crumbling comet could create meteor shower May 30 – Toronto Sun



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A crumbling comet could create a meteor shower on May 30.

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The ‘tau Herculids’ meteor display might be one of the most dramatic observed in over two decades, according to

Meteor showers occur when dust or particles from asteroids or comets enter Earth’s atmosphere at a very high speed, the U.K. Sun explained.

This one is expected to be the product of a comet named 73P/Schwassmann-Wachmann, also known as SW3.

SW3 was first discovered in 1930 but did not reappear again until the 1970s, Republic World reported.

In 1995, astronomers noticed that the comet’s nucleus split into four smaller chunks, according to CNET.

It has continued to disintegrate more in the ensuing years.

The display is expected to be very visible in the Northern Hemisphere as it is occurring on a Moon-less night.

A consensus of experts predicts that the shower will be visible starting from 1 a.m. EST on May 31.

It is suggested viewers will want to be outside at least an hour before this so your eyes have a chance to adjust to the dark.

“The southwestern USA and Mexico are favored locations as the radiant, the area of the sky where these meteors come from, will be located highest in a dark sky,” Robert Lunsford wrote for AMS.

“The outburst may be seen from southeastern Canada and the remainder of the (eastern) USA, but at a lower altitude.”

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Boeing capsule returns from space station after test flight with no crew – CBC News



Boeing’s crew taxi returned to Earth from the International Space Station on Wednesday, completing a repeat test flight before NASA astronauts climb aboard.

It was a quick trip back: the Starliner capsule parachuted into the New Mexico desert just four hours after leaving the orbiting lab, with airbags attached to cushion the landing. Only a mannequin was buckled in.

Aside from thruster failures and cooling system snags, Starliner appeared to clinch its high-stakes shakedown cruise, 2½ years after its botched first try. Flight controllers in Houston applauded and cheered the bull’s-eye touchdown.

NASA astronauts will strap in next for a trip to the space station. The space agency has long wanted two competing U.S. companies ferrying astronauts, giving it added insurance as it drastically reduced its reliance on Russia for rides to and from the space station.

Elon Musk’s SpaceX is already the established leader, launching astronauts since 2020 and even tourists. Its crew capsules splash down off the Florida coast; Boeing’s Starliner returns to the U.S. Army’s expansive White Sands Missile Range in New Mexico.

This image from NASA TV shows the Boeing Starliner approaching the International Space Station last Friday. (NASA/The Associated Press)

Boeing scrapped its first attempt to reach the space station in 2019, after software errors left the capsule in the wrong orbit and nearly doomed it. The company fixed the flaws and tried again last summer, but corroded valves halted the countdown. Following more repairs, Starliner finally lifted off from Cape Canaveral last Thursday and docked to the space station Friday.

Station astronauts tested Starliner’s communication and computer systems during its five days at the space station. They also unloaded hundreds of kilograms of groceries and other supplies that flew up in the Boeing capsule, then filled it with empty air tanks and other discarded gear.

A folded U.S. flag sent up by Boeing stayed behind, to be retrieved by the first Starliner crew.

“We’re a little sad to see her go,” station astronaut Bob Hines radioed as the capsule flew away.

Along for the ride was Starliner’s test dummy — Rosie the Rocketeer, a takeoff on the Second World War’s Rosie the Riveter.

The repairs and do-over cost Boeing nearly $600 million US.

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