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Using ground-based and space-based observations, a team of researchers has been monitoring a difficult-to-see comet carefully. It’s called Comet 323P/SOHO, and it was discovered over 20 years ago in 1999. But it’s difficult to observe due to its proximity to the Sun.

They’ve found that the Sun is slowly tearing the comet to pieces.

Comets with the SOHO designation were discovered with the SOHO spacecraft. The Solar and Heliospheric Observatory (SOHO) is a joint ESA/NASA mission launched in 1995. Its mission is to study the Sun, and though the mission was scheduled to last two years, it’s been operating for over 26 years.

As a by-product of its solar observations, the spacecraft has discovered 4,000 comets. Most of these comets are Sungrazers, a class of comets very close to the Sun. Astronomers think most Sungrazers are chunks of a much larger comet that broke apart. 323P isn’t a Sungrazer; it’s a near-Sun comet. Small comets can completely evaporate in one close approach to the Sun, while larger ones can survive many. For most of them, their small perihelions spell their eventual doom.

Comet 323P/SOHO’s perihelion is only 0.04 astronomical units. Its orbital period is just over four years. In 2020, observations with the Subaru telescope showed that the comet had no cometary features as it approached perihelion. But that changed.

“However, in our post-perihelion observations, it developed a long, narrow tail mimicking a disintegrating cometary debris cloud,” the authors write in their paper.

The paper is titled “The Lingering Death of Periodic Near-Sun Comet 323P/SOHO.” The first author is Man-To Hui from the State Key Laboratory of Lunar and Planetary Science, Macau University of Science and Technology. The others are from institutions in the USA, Germany, Canada, and Taiwan.

Sungrazers have perihelions smaller than Mercury’s. Astronomers think they’re main-belt asteroids or short-period comets that were drawn closer to the Sun via the gravitational influence of giant planets or as a consequence of ancient impacts. Sungrazers usually don’t last very long. Their lifetimes seldom surpass 10 million years, according to astronomers, due to their orbit in the inner Solar System. Not only do they have to contend with the Sun’s gravitational power, they frequently cross the paths of the terrestrial planets.

According to the new paper, 323P/SOHO is flirting with destruction. The researchers identified two 20 meter diameter fragments coming from the comet shortly in March 2021. They also found that the comet lost between 0.1-10% of the mass of its nucleus. It looks like its end is near.

The Lowell Discovery Telescope captured this image of comet 323P/SOHO in February 2021. The debris tail is clearly visible. Image Credit: Hui et al. 2022.
The Lowell Discovery Telescope captured this image of comet 323P/SOHO in February 2021. The debris tail is visible. Image Credit: Hui et al. 2022.

The comet’s nucleus is only about 172 meters (560 ft) in diameter. It rotates quickly, at 0.522 hr., the most rapid rotation of every known comet in the Solar System. According to the authors of this paper, that means that the nucleus has high cohesive strength. That strength might help it survive more gravitational encounters with the Sun.

If it seems strange that the researchers only observed the comet’s debris tail after it left perihelion, that’s because of how difficult near-Sun comets are to watch. At perihelion, the Sun’s brightness renders the comets nearly unobservable. They’re observable in any detail outside of perihelion.

There are far fewer observed near-Sun objects than models show there should be. Part of the reason for that is the difficulty in observing them in the Sun’s glare. But the other reason is that astronomers expect them to disintegrate into millimetre-sized particles due to thermal destruction. Even so, observing them being turned to dust is difficult. There’s not much good-quality observational evidence of them breaking apart.

This study is among the first instances of comets like these being observed with ground-based observatories.

This Hubble Wide-Field Camera 3 image shows two 20m diameter fragments coming from Comet 323P/SOHO, marked A and B. Image Credit: Hui et al. 2022.Did you miss our previous article…
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Finally, an Explanation for the Moon’s Radically Different Hemispheres

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Pink Floyd was wrong, there is no dark side to the Moon. There is however, a far side. The tidal effects between the Earth and Moon have caused this captured or synchronous rotation. The two sides display very different geographical features; the near side with mare and ancient volcanic flows while the far side displaying craters within craters. New research suggests the Moon has turned itself inside out with heavy elements like titanium returning to the surface. It’s now thought that a giant impact on the far side pushed titanium to the surface, creating a thinner more active near side. 

There have been a number of theories for the formation of the Moon; the capture theory and the accretion theory to name two of them. Perhaps the most accepted theory now is the giant impact theory which suggests Earth was struck by a large object, causing a lot of debris to be ejected into orbit. This material eventually coalesced to form the Moon we know and love today.

In the decades that followed the Apollo missions, scientists studied the rocks returned by the astronauts. The studies revealed that many of the surface rocks contained unexpectedly high concentrations of titanium. More surprisingly was that satellite observations revealed these titanium rich minerals were far more common on the nearside and absent on the far-side. What is known is that the Moon formed fast and hot and would have been covered for a short period in an ocean of molten magma. The magma cooled and solidified forming the Moon’s crust but trapped below was the more dense material including titanium and iron. 

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Sample collection on the surface of the Moon. Apollo 16 astronaut Charles M. Duke Jr. is shown collecting samples with the Lunar Roving Vehicle in the left background. Image: NASA

The dense material should have sunk to greater depths inside the Moon however over the years that followed something strange seems to have happened. The denser material did indeed sink, mixed with mantle but melted and returned to the surface as titanium rich lava flows. Debates have been raging whether this is exactly what happened but a new piece of research by a team at the University of Arizona Lunar and Planetary Laboratory offer more details about the process and how the interior of the Moon evolved.

It has already been suggested that the Moon may have suffered a giant impact on the far side causing the heavier elements to be forced over to the near side but the new study highlighted supporting evidence from gravitational anomalies. The team measured tiny variations in the Moon’s gravitational field from data from the GRAIL mission. GRAIL – or Gravity Recovery and Interior Laboratory – orbited the Moon to create the most accurate gravitational map of the Moon to date. Using GRAIL data the team discovered that titanium-iron oxide minerals had migrated to the near side and sunk to the interior in sheetlike cascades. This was consistent with models suggesting the event occurred more than 4.22 billion years ago. 

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Global map of the Moon, as seen from the Clementine mission, showing the differences between the lunar near- and farside. Credit: NASA.

As paper co-author and LPL associate professor Jeff Andrews-Hanna said “The moon is fundamentally lopsided in every respect.” The near side feature known as Oceanus Procellarum is a great example. It is lower in elevation and has a lava flow covered thinner crust with high concentrations of titanium rich elements. This is very different on the far

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Wireless Power Transmission Could Enable Exploration of the Far Side of the Moon

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How can future lunar exploration communicate from the far side of the Moon despite never being inline with the Earth? This is what a recent study submitted to Instrumentation and Methods for Astrophysics hopes to address as a pair of researchers from the IEEE Polytechnique Montréal investigated the potential for a wireless power transmission method (WPT) comprised of anywhere from one to three satellites located at Earth-Moon Lagrange Point 2 (EMLP-2) and a solar-powered receiver on the far side of the Moon. This study holds the potential to help scientists and future lunar astronauts maintain constant communication between the Earth and Moon since the lunar far side of the Moon is always facing away from Earth from the Moon’s rotation being almost entirely synced with its orbit around the Earth.

Here, Universe Today discusses this research with Dr. Gunes Karabulut Kurt, who is an associate professor at IEEE Polytechnique Montréal and the study’s co-author, regarding the motivation behind the study, significant results, follow-up research, and implications for WPT. So, what was the motivation behind this study?

“This research is motivated by the objective of overcoming the logistical and technical challenges associated with using traditional cables on the Moon’s surface,” Dr. Kurt tells Universe Today. “Laying cables on the Moon’s rough, dusty surface would lead to ongoing maintenance and wear problems, as lunar dust is highly abrasive. On the other hand, transporting large quantities of cables to the Moon requires a significant amount of fuel, which adds considerably to the mission’s costs.”

For the study, the researchers used a myriad of calculations and computer models to ascertain if one, two, or three satellites are sufficient within an EMLP-2 halo orbit to maintain both constant coverage of the lunar far side (LFS) and line of sight with the Earth. For context, EMLP-2 is located on the far side of the Moon with the halo orbit being perpendicular—or sideways—to the Moon’s orbit. The calculations involved in the study included the distances between each satellite, the antenna angles between the satellites and surface receiver, the amount of LFS surface coverage, and the amount of transmitted power between the satellites and LFS surface antennae. So, what were the most significant results from this study?

Dr. Kurt tells Universe Today their models concluded that three satellites in an EMLP-2 halo orbit and operating at equal distances from each other could “achieve continuous power beaming to a receiver optical antenna anywhere on the lunar far side” while maintaining 100 percent LFS coverage and line of sight with the Earth. “Aside triple satellite scheme that provides continuous LFS full coverage, even a two-satellite configuration provides full coverage during 88.60% of a full cycle around the EMLP-2 halo orbit,” Dr. Kurt adds.

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Schematic from Figure 1 of the study displaying the wireless power transmission and receiver on the lunar far side with three satellites (SPS-1, SPS-2, and SPS-3) in a halo orbit at the Earth-Moon Lagrange Point 2. (Credit: Donmez & Kurt (2024))

Regarding follow-up research, Dr. Kurt tells Universe Today, “Our future studies will focus on more complex harvesting and transmission models to get closer to reality. On the other hand, an approach that takes into account the irregular nature of lunar dust and the variation in its density due to environmental factors such as subsolar angle and others. In the future, if research in this field continues, explore this experimentally with lunar dust simulants and lasers.”

This study comes as NASA is preparing to send astronauts to the Moon for the first time since 1972 with the Artemis program, whose goal will be to land the first woman and person of color on the lunar surface. With the success of the Artemis 1 mission in November 2022 that consisted of an uncrewed Orion capsule orbiting the Moon, NASA is currently targeting September 2025 for their Artemis 2 mission, which is scheduled to be a 10-day, 4-person crewed mission using the Orion capsule for a lunar flyby, whose goal will be to conduct a full systems checkout of the Orion capsule. Therefore, what implications can this study have for the upcoming Artemis missions, or any future human exploration of the Moon?

“The findings have implications for the design of energy transmission systems on the Moon,” Dr.
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The Best Base Layers, Shorts and Socks for Hiking and Running

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By Michael Lanza

Let’s admit it: We don’t always take our base layers as seriously and we do our outerwear and insulation—or packs, tents, boots and other gear, for that matter. But this under-appreciated first stage in a layering system for the outdoors really sets the table for how comfortable you’ll be. Base layers that don’t perform well probably won’t kill you, but misery isn’t a good companion. This is what we wear against our skin. It matters.

After much testing from the trails to the mountains to the gym year-round, the long-sleeve tops, T-shirts, shorts, underwear, and socks reviewed here are the best I’ve found for dayhiking, backpacking, trail running, climbing, and training. And over the course of a quarter-century of testing and reviewing gear, including the 10 years I spent as the lead gear reviewer for Backpacker magazine and even longer running this blog, I’ve learned how to distinguish the mediocre from the excellent.

Light- and medium-weight T-shirts and long-sleeve tops are the most versatile because you can layer them in a wider range of temperatures to keep you drier and cooler, but fabrics and design features of tops and shorts also affect their temperature range and the activities for which they’re comfortable.

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Hi, I’m Michael Lanza, creator of The Big Outside. Click here to sign up for my FREE email newsletter. Join The Big Outside to get full access to all of my blog’s stories. Click here for my e-books to classic backpacking trips. Click here to learn how I can help you plan your next trip.

A backpacker above Oldman Lake along the Dawson Pass Trail in Glacier National Park.
” data-image-caption=”Jeff Wilhelm high above Oldman Lake along the Dawson Pass Trail in Glacier National Park. Click photo to see all e-books describing classic backpacking trips in Glacier and other national parks.
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