Surrounding Earth is a powerful magnetic field created by swirling liquid iron in the planet’s core. Earth’s magnetic field may be nearly as old as the Earth itself – and stands in stark contrast to the Moon, which completely lacks a magnetic field today.

But did the Moon’s core generate a magnetic field in the past?

In the 1980s, geophysicists studying rocks brought back by Apollo astronauts concluded the Moon once had a magnetic field that was as strong as Earth’s. But a robust magnetic field requires a power source, and the Moon’s core is relatively small. For decades, scientists have struggled to resolve this conundrum: how could such a small core create a strong magnetic field?

I’m a professor of geophysics and have been studying Earth’s magnetic field for more than 30 years. I recently assembled a team to use new scientific techniques to reexamine the evidence for lunar magnetization. We found that the Moon did not in fact have a long-lived magnetic field. Not only does this finding change the modern understanding of the Moon’s geologic history, it also has major implications for the presence of resources on the Moon that could be critical to future human exploration.

Why a magnetic Moon?

Certain rocks have the extraordinary ability to preserve records of past magnetic fields when they contain minerals with iron atoms that align with a magnetic field as the rock cools and solidifies. The best magnetic minerals at preserving evidence of a field are tiny – a thousand times smaller than the width of a human hair – because it takes a lot of energy to rearrange their atoms.

Geophysicists who study ancient magnetism recreate this process, reheating rock samples in the presence of known magnetic fields and comparing the new alignment of the iron atoms with the orientation of iron atoms before the rock was reheated. This allows researchers to learn about past magnetic fields.

Early researchers studying the first rocks brought back from the Moon by U.S. astronauts wanted to use this method to study the Moon’s magnetism. But they faced problems. Lunar rocks contain a certain type of iron – called native iron – that is easily altered by heat. Additionally, the native iron grains in lunar rocks are sometimes relatively large, making them less likely to reliably record past magnetic fields.

From the 1970s onward, geophysicists used alternative, nonheating methods to study the Moon’s magnetism. They found that some lunar samples had recorded strong magnetic fields, suggesting that the Moon had a magnetic field for over 2 billion years.

But this result only deepened the conundrum. The question of how the Moon’s core could produce a strong magnetic field remained unsolved.

An alternative theory

In the experiments, some Apollo samples showed evidence of strong magnetic fields but other samples did not. Some researchers attributed the missing magnetization to the presence of large native iron grains that were poor magnetic recorders. But many of the samples also contained small iron grains that should have recorded a field.

There have been long-standing doubts about the nonheating techniques researchers used on the Apollo samples. Some scientists have called them methods of “last resort” and conclude that the uncertainties in data collected in this way were so large that any interpretation must be viewed as speculation.

Alternatively, another group of scientists has suggested for decades that when meteorites strike the Moon, they create a dusty plasma – a gas of ions and electrons – that could generate a strong magnetic field and magnetize lunar rocks near the impact zone.

In 2008, geophysicist Kristin Lawrence decided to revisit the question of lunar magnetization using an improved reheating technique. In contrast to the researchers who originally studied the samples, she was unable to detect any definitive evidence for a past magnetic field. The approach Lawrence and her team used was better than the nonheating tests, but her results were still not conclusive. She felt she was on to something, though, and that is when she turned to me and my lab for help.

In 2011, Lawrence brought us a collection of lunar samples to test. We had been developing techniques to identify individual millimeter-size silicate crystals that contain only very small iron grains and have ideal recording properties. We then used an ultrasensitive superconducting magnetometer and a special carbon dioxide laser to rapidly heat those samples in a way that avoids altering their iron minerals. We found that nearly all the rocks had profoundly weak magnetic signals.

At the time of this first test we were still improving the method, so we couldn’t say with certainty whether the samples had formed on a Moon without a magnetic field. But we have been improving our testing methods, and last year we decided to revisit the Apollo samples.

We definitively found that some of the samples did indeed contain magnetic minerals capable of preserving high-fidelity signals of ancient magnetic fields. But the rocks had recorded no such signals. This suggests that the Moon lacked a magnetic field for nearly all of its history.

So, what explains the previous findings of a magnetic Moon? The answer was in one of the samples: a small, dark piece of glass containing tiny iron-nickel particles.

The glass was made by a meteorite impact and showed clear evidence of a strong magnetic field. But it was formed only about 2 million years ago. Nearly all geophysicists agree the Moon did not have a magnetic field at that time, because after 4.5 billion years of cooling there was not enough heat left to power the churning of iron in the Moon’s core to generate a field. The magnetic signature of the glass matched simulations of magnetic fields that can be generated by meteor impacts. This showed that meteorite impacts alone can create strong magnetic fields that magnetize rocks nearby. This could explain the high values previously reported from some Apollo rocks.

Taken together, I believe these findings resolve the mystery of a seemingly magnetic Moon.

Magnetic shielding and lunar resources

This new view of lunar magnetism has huge implications for the potential presence of valuable resources as well as information about the ancient Sun and Earth that may be buried in lunar soils.

Magnetic fields act as shields that prevent solar particles from reaching a planet or moon. Without a magnetic field, solar wind can hit the surface of the Moon directly and implant elements like helium-3 and hydrogen into the soil.

Helium-3 has many applications, but importantly, it could be a fuel source for nuclear fusion and future planetary exploration. The value of hydrogen comes from the fact that it can combine with oxygen to form water, another crucial resource in space.

Since the Moon did not have a long-lived magnetic field, these elements could have been accumulating in soils for billions of years longer than previously thought.

There is also scientific value. Elements embedded by solar wind could shed light on the evolution of the Sun. And as the Moon passes through Earth’s magnetic field, elements from Earth’s atmosphere can be deposited on the lunar surface, and these may hold clues about the earliest Earth.

The absence of a long-lived magnetic field on the Moon might strike some as a loss, but I believe it may unlock a scientific bonanza and a valuable stash of potential resources.

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John Tarduno, Professor of Geophysics, University of Rochester

This article is republished from The Conversation under a Creative Commons license. Read the original article.

With the delta variant making up over 93% of COVID-19 cases in the U.S. at the end of July 2021, questions arise about how to stay protected against evolving forms of the SARS-CoV-2 virus. Here, pediatrician and infectious disease specialist Dr. Lilly Cheng Immergluck of Morehouse School of Medicine answers some common questions about variants and what you can do to best protect yourself.

1. What are variants and how do they emerge?

Viruses mutate over time to adapt to their environment and improve their survival. Over the course of the pandemic, SARS-CoV-2, the novel coronavirus that causes COVID-19, has mutated enough to change both its ability to spread through the population and its ability to infect people.

These new strains are called variants. The U.S. Centers for Disease Control and Prevention currently classifies variants into three categories, listed in order of least to most concerning:

• Variant of Interest (VOI): Have features that may reduce your immune system’s ability to prevent infection. For example, you might have heard of VOI eta, iota or kappa.

• Variant of Concern (VOC): Are less responsive to treatments or vaccines and more likely to evade diagnostic detection. They tend to be more transmissible, or contagious, and result in more severe infections. Alpha and delta are VOCs, for instance.

• Variant of High Consequence (VOHC): Are significantly less responsive to existing diagnostic, prevention and treatment options. They also result in more severe infections and hospitalizations. There have not been any VOHCs identified so far.

The World Health Organization uses similar classifications, but their definitions may differ from the CDC’s U.S.-based ones, as variant features and effects may differ by geographic location.

2. Are variants always more harmful?

A variant may be more or less dangerous than other strains depending on the mutations in its genetic code. Mutations can affect attributes like how contagious a viral variant is, how it interacts with the immune system or the severity of the symptoms it triggers.

For example, the alpha variant is more transmissible than the original form of SARS-CoV-2. Studies show it’s somewhere between 43% to 90% more contagious than the virus that was most common at the start of the pandemic. Alpha also is more likely to cause severe disease, as indicated by increased rates of hospitalization and death after infection.

Even more extreme, the delta variant is reported to be nearly twice as contagious as previous strains and may cause even more severe disease among those who are unvaccinated. The viral load of those infected with delta – meaning the amount of virus detected from the nasal passages of an infected person – is also reported to be over 1,000 times higher than in those infected with the original form of SARS-CoV-2. Recent evidence also suggests that both unvaccinated and vaccinated people carry similar viral loads, further contributing to the especially contagious nature of this variant.

3. Which variants are most common in the US?

Over the course of a few months, the delta variant has become the predominant strain in the U.S., accounting for the vast majority of COVID-19 cases at the end of July 2021.

But there are regional variations across the country. As of July 31, the CDC estimated that the alpha variant represented over 3% of cases identified in a region of eight states that includes Georgia, Florida and Tennessee, compared with less than 1% in the region that includes Iowa, Kansas, Missouri and Nebraska. The CDC tracks variants in cooperation with state health departments and other public health agencies. COVID-19 infection samples from across the country are genetically sequenced each week to identify existing and new variants.

And new variants will likely continue to appear as the virus evolves. Delta plus, for instance, is a sub-lineage of delta. The effects of this subvariant are yet to be determined.

4. How are vaccines holding up against variants?

Researchers are working to figure out how effective the three COVID-19 vaccines currently authorized for emergency use in the U.S. are at preventing infection from variants in “real-world” conditions where variant distribution and frequency constantly change. Several preliminary studies that have not yet been peer-reviewed suggest that these vaccines are still effective in preventing COVID-19-related serious infections and death.

No vaccine is perfect, however, and breakthrough COVID-19 infections are possible in those who are vaccinated. Older adults and those with immunocompromising conditions may be at increased risk to have these breakthrough infections.

Thankfully, fully vaccinated individuals generally experience milder COVID-19 infections. For example, a study analyzing COVID-19 cases in England estimated that two doses of the Pfizer BioNTech vaccine are 93.7% effective in preventing symptomatic disease from the alpha variant and 88% effective from delta. A different study in Ontario, Canada, that is not yet peer-reviewed reported that the Moderna vaccine is 92% effective in preventing symptomatic disease from alpha.

5. How can I stay safe?

How cautious you should be depends on a number of individual and external factors.

One factor is whether you’re fully vaccinated. Nearly all - 99.5% - of COVID-19 deaths in the U.S. over the past few months were among unvaccinated people.

The most recent CDC guidelines recommend that everyone wear a mask in areas of substantial or high transmission, regardless of whether or not they’re vaccinated. More caution should especially be taken if you aren’t fully vaccinated or have a weakened immune system.

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Another factor to consider is the level of community transmission and the proportion of unvaccinated people in your local community. For example, someone who lives in an area that is below the national average for COVID-19 vaccinations may have a higher chance of encountering someone who is unvaccinated – and so more likely to spread the coronavirus – than someone in an area with higher vaccination rates.

Finally, there are still a significant number of people who are at high risk of COVID-19, including children. As of Aug. 3, 2021, only 29.1% of children ages 12 to 15, and 40.4% of those ages 16 and 17, had been fully vaccinated. The American Academy of Pediatrics and the Children’s Hospital Association note that 4,292,120 total child COVID-19 cases had been reported as of Aug. 5. Children make up 14.3% of reported COVID-19 cases. If your child is unvaccinated, the best way you can protect them and other unvaccinated members of your household is to get yourself vaccinated and have everyone wear a mask in indoor public spaces.

Guidelines provided by public health agencies are simply that – general guidelines. They are not tailored to be prescriptive for each individual and their personal risk assessments.

Vaccines remain the best protection against every strain of the novel coronavirus. But masking, social distancing and avoiding crowds and poorly ventilated indoor spaces add extra layers of protection against breakthrough infections and lower your risk of inadvertently spreading the virus.

Lilly Cheng Immergluck, Professor of Microbiology, Biochemistry and Immunology, Morehouse School of Medicine

This article is republished from The Conversation under a Creative Commons license. Read the original article.