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Were Scientists Wrong About the Planet Mercury? Its Big Iron Core May Be Due to Magnetism! – SciTechDaily

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New research shows the sun’s magnetic field drew iron toward the center of our solar system as the planets formed. That explains why Mercury, which is closest to the sun has a bigger, denser, iron core relative to its outer layers than the other rocky planets like Earth and Mars. Credit: NASA’s Goddard Space Flight Center

New research from the University of Maryland shows that proximity to the sun’s magnetic field determines a planet’s interior composition.

A new study disputes the prevailing hypothesis on why Mercury has a big core relative to its mantle (the layer between a planet’s core and crust). For decades, scientists argued that hit-and-run collisions with other bodies during the formation of our solar system blew away much of Mercury’s rocky mantle and left the big, dense, metal core inside. But new research reveals that collisions are not to blame—the sun’s magnetism is.

William McDonough, a professor of geology at the University of Maryland, and Takashi Yoshizaki from Tohoku University developed a model showing that the density, mass and iron content of a rocky planet’s core are influenced by its distance from the sun’s magnetic field. The paper describing the model was published on July 2, 2021, in the journal Progress in Earth and Planetary Science.

“The four inner planets of our solar system—Mercury, Venus, Earth, and Mars—are made up of different proportions of metal and rock,” McDonough said. “There is a gradient in which the metal content in the core drops off as the planets get farther from the sun. Our paper explains how this happened by showing that the distribution of raw materials in the early forming solar system was controlled by the sun’s magnetic field.”

McDonough previously developed a model for Earth’s composition that is commonly used by planetary scientists to determine the composition of exoplanets. (His seminal paper on this work has been cited more than 8,000 times.)

McDonough’s new model shows that during the early formation of our solar system, when the young sun was surrounded by a swirling cloud of dust and gas, grains of iron were drawn toward the center by the sun’s magnetic field. When the planets began to form from clumps of that dust and gas, planets closer to the sun incorporated more iron into their cores than those farther away.

The researchers found that the density and proportion of iron in a rocky planet’s core correlates with the strength of the magnetic field around the sun during planetary formation. Their new study suggests that magnetism should be factored into future attempts to describe the composition of rocky planets, including those outside our solar system.

The composition of a planet’s core is important for its potential to support life. On Earth, for instance, a molten iron core creates a magnetosphere that protects the planet from cancer-causing cosmic rays. The core also contains the majority of the planet’s phosphorus, which is an important nutrient for sustaining carbon-based life.

Using existing models of planetary formation, McDonough determined the speed at which gas and dust was pulled into the center of our solar system during its formation. He factored in the magnetic field that would have been generated by the sun as it burst into being and calculated how that magnetic field would draw iron through the dust and gas cloud.

As the early solar system began to cool, dust and gas that were not drawn into the sun began to clump together. The clumps closer to the sun would have been exposed to a stronger magnetic field and thus would contain more iron than those farther away from the sun. As the clumps coalesced and cooled into spinning planets, gravitational forces drew the iron into their core.

When McDonough incorporated this model into calculations of planetary formation, it revealed a gradient in metal content and density that corresponds perfectly with what scientists know about the planets in our solar system. Mercury has a metallic core that makes up about three-quarters of its mass. The cores of Earth and Venus are only about one-third of their mass, and Mars, the outermost of the rocky planets, has a small core that is only about one-quarter of its mass.

This new understanding of the role magnetism plays in planetary formation creates a kink in the study of exoplanets, because there is currently no method to determine the magnetic properties of a star from Earth-based observations. Scientists infer the composition of an exoplanet based on the spectrum of light radiated from its sun. Different elements in a star emit radiation in different wavelengths, so measuring those wavelengths reveals what the star, and presumably the planets around it, are made of.

“You can no longer just say, ‘Oh, the composition of a star looks like this, so the planets around it must look like this,’” McDonough said. “Now you have to say, ‘Each planet could have more or less iron based on the magnetic properties of the star in the early growth of the solar system.’”

The next steps in this work will be for scientists to find another planetary system like ours—one with rocky planets spread over wide distances from their central sun. If the density of the planets drops as they radiate out from the sun the way it does in our solar system, researchers could confirm this new theory and infer that a magnetic field influenced planetary formation.

Reference: “Terrestrial planet compositions controlled by accretion disk magnetic field” by William F. McDonough and Takashi Yoshizaki, 2 July 2021, Progress in Earth and Planetary Science.
DOI: 10.1186/s40645-021-00429-4

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NASA discovers double crater on the moon – CTV News

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The moon has a new double crater after a rocket body collided with its surface on March 4.

New images shared by NASA’s Lunar Reconnaissance Orbiter, which has been circling the moon since 2009, have revealed the location of the unusual crater.

The impact created two craters that overlap, an eastern crater measuring 59 feet (18 metres) across and a western crater spanning 52.5 feet (16 metres). Together, they create a depression that is roughly 91.8 feet (28 metres) wide in the longest dimension.

Although astronomers expected the impact after discovering that the rocket part was on track to collide with the moon, the double crater it created was a surprise.

Typically, spent rockets have the most mass at the motor end because the rest of the rocket is largely just an empty fuel tank. But the double crater suggests that this object had large masses at both ends when it hit the moon.

The exact origin of the rocket body, a piece of space junk that had been careening around for years, is unclear, so the double crater could help astronomers determine what it was.

The moon lacks a protective atmosphere, so it’s littered with craters created when objects like asteroids regularly slam into the surface.

This was the first time a piece of space junk unintentionally hit the lunar surface that experts know of. But craters have resulted from spacecraft being deliberately crashed into the moon.

For example, four large moon craters attributed to the Apollo 13, 14, 15 and 17 missions are all much larger than each of the overlapping craters created during the March 4 impact. However, the maximum width of the new double crater is similar to the Apollo craters.

UNCLEAR ORIGIN

Bill Gray, an independent researcher focused on orbital dynamics and the developer of astronomical software, was first to spot the trajectory of the rocket booster.

Gray had initially identified it as the SpaceX Falcon rocket stage that launched the US Deep Space Climate Observatory, or DSCOVR, in 2015 but later said he’d gotten that wrong and it was likely from a 2014 Chinese lunar mission — an assessment NASA agreed with.

However, China’s Ministry of Foreign Affairs denied the booster was from its Chang’e-5 moon mission, saying that the rocket in question burned up on reentry to Earth’s atmosphere.

No agencies systematically track space debris so far away from Earth, and the confusion over the origin of the rocket stage has underscored the need for official agencies to monitor deep-space junk more closely, rather than relying on the limited resources of private individuals and academics.

However, experts say that the bigger challenge is the space debris in low-Earth orbit, an area where it can collide with functioning satellites, create more junk and threaten human life on crewed spacecraft.

There are at least 26,000 pieces of space junk orbiting Earth that are the size of a softball or larger and could destroy a satellite on impact; over 500,000 objects the size of a marble — big enough to cause damage to spacecraft or satellites; and over 100 million pieces the size of a grain of salt, tiny debris that could nonetheless puncture a spacesuit, according to a NASA report issued last year.

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7 Amazing Dark Sky National Parks – AARP

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James Ronan/Getty Images/Steve Burns

Great Basin, Arches, and Voyageurs National Park

Can’t afford to join a commercial space mission offered by Jeff Bezos or Richard Branson? Consider the next best thing: seeing a starry, starry night in a sea of darkness, unimpeded by artificial light, at one of the International Dark Sky Parks in the U.S. It’s a rare treat, since light pollution prevents nearly 80 percent of Americans from seeing the Milky Way from their homes.

The International Dark-Sky Association (IDSA) has certified 14 of the nation’s 63 national parks as dark sky destinations. So visitors can take full advantage of such visibility, many of them offer specialized after-dark programs, from astronomy festivals and ranger-led full-moon walks to star parties and astrophotography workshops. If you prefer to stargaze on your own at a park, the National Park Service recommends bringing a pair of 7-by-50 binoculars, a red flashlight, which enhances night vision, and a star chart, which shows the arrangement of stars in the sky.

Here are seven of the IDSA-certified parks where you can appreciate how the heavens looked from the Earth before the dawn of electric light.




AARP Membership -Join AARP for just $9 per year when you sign up for a 5-year term

Join today and save 43% off the standard annual rate. Get instant access to discounts, programs, services, and the information you need to benefit every area of your life. 



Award-winning travel writer Veronica Stoddart is the former travel editor of USA Today. She has written for dozens of travel publications and websites.​​

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A Mystery Rocket Left A Crater On The Moon – Forbes

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While we think of the moon as a static place, sometimes an event happens that reminds us that things can change quickly.

On March 4, a human-made object (a rocket stage) slammed into the moon and left behind a double crater, as seen by NASA’s Lunar Reconnaissance Orbiter (LRO) mission.

Officials announced June 23 that they spotted a double crater associated with the event. But what’s really interesting is there’s no consensus about what kind of rocket caused it.

China has denied claims that the rocket was part of a Long March 3 rocket that launched the country’s Chang’e-5 T1 mission in October 2014, although the orbit appeared to match. Previous speculation suggested it might be from a SpaceX rocket launching the DISCOVR mission, but newer analysis has mostly discredited that.

On a broader scale, the value of LRO observations like this is showing how the moon can change even over a small span of time. The spacecraft has been in orbit there since 2009 and has spotted numerous new craters since its arrival.

It’s also a great spacecraft scout, having hunted down the Apollo landing sites from orbit and also having tracked down a few craters from other missions that slammed into the moon since the dawn of space exploration.

It may be that humans return to the moon for a closer-up look in the coming decade, as NASA is developing an Artemis program to send people to the surface no earlier than 2025.

LRO will also be a valuable scout for that set of missions, as the spacecraft’s maps will be used to develop plans for lunar bases or to help scout safe landing sites for astronauts.

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